Part 3: Hull Construction and Equipment

RULES FOR BUILDING AND CLASSING

STEEL VESSELS UNDER 90 METERS (295 FEET) IN

LENGTH
2018

PART 3
HULL CONSTRUCTION AND EQUIPMENT

American Bureau of Shipping

Incorporated by Act of Legislature of
the State of New York 1862

 2017 American Bureau of Shipping. All rights reserved.

ABS Plaza
16855 Northchase Drive
Houston, TX 77060 USA
R u l e C h a n g e N o t i c e ( 2 0 1 8 )

Rule Change Notice (2018)

The effective date of each technical change since 1993 is shown in parenthesis at the end of the
subsection/paragraph titles within the text of each Part. Unless a particular date and month are shown, the
years in parentheses refer to the following effective dates:
(2000) and after 1 January 2000 (and subsequent years) (1996) 9 May 1996
(1999) 12 May 1999 (1995) 15 May 1995
(1998) 13 May 1998 (1994) 9 May 1994
(1997) 19 May 1997 (1993) 11 May 1993

Listing by Effective Dates of Changes from the 2017 Rules

Notice No. 1 (effective on 1 July 2017) to the 2017 Rules, which is incorporated in the 2018 Rules, is summarized
below.

EFFECTIVE DATE 1 July 2017 – shown as (1 July 2017)

(based on the contract date for new construction between builder and Owner)
Part/Para. No. Title/Subject Status/Remarks
3-2-11/17.1 Strength To reflect current practice for cover plates and address vortex shedding
for spade rudders with embedded trunks. (Incorporates Notice No. 1)
3-2-11/Figure 5 <No Title> To reflect current practice for cover plates and address vortex shedding
(New) for spade rudders with embedded trunks. (Incorporates Notice No. 1)
3-2-11/Figure 6 <No Title> To reflect current practice for cover plates and address vortex shedding
(New) for spade rudders with embedded trunks. (Incorporates Notice No. 1)
3-2-11/Figure 7 <No Title> To reflect current practice for cover plates and address vortex shedding
(New) for spade rudders with embedded trunks. (Incorporates Notice No. 1)
3-2-11/17.1.2 In way of Cutouts To reflect current practice for cover plates and address vortex shedding
for spade rudders with embedded trunks. (Incorporates Notice No. 1)

EFFECTIVE DATE 1 January 2018 – shown as (2018)

(based on the contract date for new construction between builder and Owner)
Part/Para. No. Title/Subject Status/Remarks
3-1-1/3.1 Scantling Length (L) To align the requirements with ICLL 1966/Reg. 3 & IACS UR S2.
3-1-1/3.3 Freeboard Length (Lf) To align the requirements with ICLL 1966/Reg. 3 & IACS UR S2.
3-1-1/13.1 Freeboard Deck To align the requirements with ICLL 1966/Reg. 3 & IACS UR S2.
3-1-1/15 Deadweight (DWT) and Lightship To incorporate interpretation made in IACS UI SC273 and MPC128.
Weight
3-2-5/7.5 Proportions To specify a limitation of the maximum required thickness for girders
and webs, in line with other ABS Rules.
3-2-6/5.3 Permissible Load To modify the permissible load to consider material yield strength.
3-2-8/5.7 Girders and Web To specify a limitation of the maximum required thickness for girders
and webs, in line with other ABS Rules.
3-2-9/11.3.7 Bolted Connections To specify requirements for bolted connections on helidecks.
(New)
3-2-9/11.7 Aluminum Decks To clarify the requirements for aluminum helideck escape stairs and
intermediate platforms.
3-2-9/11.9 Means of Escape and Access To clarify the requirements for aluminum helideck escape stairs and
(New) intermediate platforms.
3-2-11/7.3 Lower Rudder Stocks To make the stress units consistent with the allowable stress.

ii ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
 Part/Para. No. Title/Subject Status/Remarks
3-2-11/Figure 4 Tapered Couplings To be consistent with the requirements of 3-2-11/11.7.
3-2-11/17.5 Diaphragm Plates To allow larger openings on diaphragm plates when the effects of
openings are considered in the strength assessment.
3-2-12/5.3.1 Cargo Hatch Covers in Position 1 To align the requirements with IACS UR S21, S21A, and 3-2-15/3.3.1
of the Steel Vessel Rules for less than 100 m.
3-2-16/1.3.2 Overlapped Seams To prohibit use of lapped connections on the watertight envelope and
provide guidance for use elsewhere on vessels.
3-3-A2 (Title) Computer Software for Onboard To align the Rules with IACS UR L5, Revision 3.
Stability Calculations
3-3-A2/5 Types of Stability Software To align the Rules with IACS UR L5, Revision 3.
3-3-A2/7.1 Calculation Program To align the Rules with IACS UR L5, Revision 3.
3-3-A2/7.5 Warning To align the Rules with IACS UR L5, Revision 3.
3-3-A2/7.15 Computer Model To align the Rules with IACS UR L5, Revision 3.
(New)
3-3-A2/7.17 Further Requirements for Type 4 To align the Rules with IACS UR L5, Revision 3.
(New) Stability Software
3-3-A2/Table 1 Acceptable Tolerances To align the Rules with IACS UR L5, Revision 3.
3-3-A2/11.1 Conditions of Approval of the To align the Rules with IACS UR L5, Revision 3.
Onboard Software for Stability
Calculations
3-3-A2/11.5 Specific Approval To align the Rules with IACS UR L5, Revision 3.
3-3-A2/15 Installation Testing To align the Rules with IACS UR L5, Revision 3.
3-4-A1/1.1 <No Title> To align the requirements with ASTM F3059-15, in line with IACS,
IMO, and USCG policy.
3-4-A1/5 Fire Test Requirements To align the requirements with ASTM F3059-15, in line with IACS,
IMO, and USCG policy.
3-4-A1/7 Structural Fire Integrity Test To align the requirements with ASTM F3059-15, in line with IACS,
Procedures IMO, and USCG policy.
3-4-A1/Table 1 Structural Fire Integrity Matrix To align the requirements with ASTM F3059-15, in line with IACS,
IMO, and USCG policy.
3-7-1 Tank, Bulkhead and Rudder To reflect the comments from Administrations, Industry Organizations
Tightness Testing and IMO considered during review of the proposed Testing Guidelines
associated with SOLAS Chapter II-1, Regulation 11, reflected in
IACS UR S14 (Rev.6, Sept 2016).

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 iii
PART Table of Contents

3
Hull Construction and Equipment

CONTENTS
CHAPTER 1 General .................................................................................................... 1
Section 1 Definitions ..............................................................................3
Section 2 General Requirements ...........................................................6

CHAPTER 2 Hull Structures and Arrangements ..................................................... 16

Section 1 Longitudinal Strength ...........................................................31
Section 2 Shell Plating .........................................................................43
Section 3 Deck Plating .........................................................................48
Section 4 Bottom Structure ..................................................................53
Section 5 Side Frames, Webs and Stringers .......................................65
Section 6 Beams, Deck Girders, Deck Transverses and Pillars ..........71
Section 7 Watertight Bulkheads and Doors .........................................81
Section 8 Deep Tanks ..........................................................................89
Section 9 Superstructures and Deckhouses ........................................93
Section 10 Keels, Stems, Stern Frames, Shaft Struts, and Propeller
Nozzles ..............................................................................102
Section 11 Rudders..............................................................................112
Section 12 Protection of Deck Openings .............................................160
Section 13 Protection of Shell Openings .............................................176
Section 14 Bulwarks, Rails, Freeing Ports, Portlights, Windows,
Ventilators, Tank Vents and Overflows..............................190
Section 15 Ceiling, Sparring and Protection of Steel ...........................201
Section 16 Weld Design .......................................................................203

Appendix 1 Loading Manuals and Loading Instruments .........................39

Appendix 2 Guidelines for Calculating Bending Moment and Shear
Force in Rudders and Rudder Stocks................................150
Appendix 3 Portable Beams and Hatch Cover Stiffeners of Variable
Cross Section .....................................................................174

CHAPTER 3 Subdivision and Stability ................................................................... 212

Section 1 General Requirements .......................................................214

Appendix 1 Intact Stability of Tankers During Liquid Transfer

Operations .........................................................................217
Appendix 2 Onboard Computers for Stability Calculations ...................220

iv ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
 CHAPTER 4 Fire Safety Measures ......................................................................... 230
Section 1 Structural Fire Protection ................................................... 231

Appendix 1 Fiber Reinforced Plastic (FRP) Gratings ........................... 233

CHAPTER 5 Equipment........................................................................................... 236

Section 1 Anchoring, Mooring and Towing Equipment ...................... 237

CHAPTER 6 Navigation ........................................................................................... 253

Section 1 Visibility .............................................................................. 254

CHAPTER 7 Testing, Trials and Surveys During Construction – Hull ................ 259
Section 1 Tank, Bulkhead and Rudder Tightness Testing ................ 260
Section 2 Trials .................................................................................. 269
Section 3 Surveys .............................................................................. 270

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 v
This Page Intentionally Left Blank
PART Chapter 1: General

3
CHAPTER 1 General

CONTENTS
SECTION 1 Definitions............................................................................................... 3
1 Application .......................................................................................... 3
3 Length ................................................................................................. 3
3.1 Scantling Length (L) ........................................................................ 3
3.3 Freeboard Length (Lf) ...................................................................... 3
5 Breadth (B) .......................................................................................... 3
7 Depth................................................................................................... 4
7.1 Molded Depth (D) ............................................................................ 4
7.3 Scantling Depth (Ds) ........................................................................ 4
9 Draft for Scantlings (d) ........................................................................ 4
11 Molded Displacement and Block Coefficient ...................................... 4
11.1 Molded Displacement (∆) ................................................................ 4
11.3 Block Coefficient (Cb) ....................................................................... 4
13 Decks .................................................................................................. 4
13.1 Freeboard Deck ............................................................................... 4
13.3 Bulkhead Deck ................................................................................ 4
13.5 Strength Deck .................................................................................. 5
13.7 Superstructure Deck ........................................................................ 5
13.9 Deckhouses..................................................................................... 5
15 Deadweight and Lightship Weight ...................................................... 5
17 Gross Tonnage ................................................................................... 5
17.1 International Tonnage ..................................................................... 5
17.3 National Tonnage ............................................................................ 5
19 Units .................................................................................................... 5

FIGURE 1......................................................................................................... 3

SECTION 2 General Requirements ........................................................................... 6

1 Materials.............................................................................................. 6
1.1 General............................................................................................ 6
1.3 Selection of Material Grade ............................................................. 6
1.5 Note for the Users ........................................................................... 6
1.7 Structures Exposed to Low Air Temperatures ................................. 8
1.9 Design Temperature tD .................................................................... 9
3 Workmanship .................................................................................... 10

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 1
 5 Design ...............................................................................................10
5.1 Continuity ....................................................................................... 10
5.3 Openings ....................................................................................... 11
5.5 Brackets ......................................................................................... 11
7 Structural Sections ............................................................................12
7.1 Deep Supporting Members ............................................................ 12
7.3 Frames, Beams and Stiffeners ...................................................... 12
7.5 Hold Frames of Single Side Skin Bulk Carriers ............................. 13
9 Structural Design Details ..................................................................13
9.1 General .......................................................................................... 13
9.3 Termination of Structural Members................................................ 13
9.5 Fabrication ..................................................................................... 14

TABLE 1 Material Grades.........................................................................7

TABLE 2 Material Class of Structural Members .......................................7
TABLE 3 Application of Material Classes and Grades – Structures
Exposed at Low Temperatures .................................................8
TABLE 4 Material Grade Requirements for Classes I, II and III at Low
Temperatures ............................................................................9
TABLE 5 Brackets ..................................................................................11
TABLE 6 Hull Components and Equipment List for Steel Vessels
Under 90 Meters .....................................................................15

FIGURE 1 Commonly Used Definitions of Temperatures ........................10

FIGURE 2 Bracket ....................................................................................12

2 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Section 1: Definitions

3
CHAPTER 1 General

SECTION 1 Definitions

1 Application
The following definitions apply throughout these Rules.

3 Length

3.1 Scantling Length (L) (2018)

L is the distance in meters (feet) on the summer load line from the fore side of the stem to the centerline of
the rudder stock. For use with the Rules, L is not to be less than 96% and need not be greater than 97% of
the extreme length on the summer load line. The forward end of L is to coincide with the fore side of the
stem on the waterline on which L is measured.

3.3 Freeboard Length (Lf) (2018)

Lf is the distance in meters (feet) on a waterline at 85% of the least molded depth measured from the top of
the keel from the fore side of the stem to the centerline of the rudder stock or 96% of the length on that
waterline, whichever is greater. Where the stem is a fair concave curve above the waterline at 85% of the
least molded depth and where the aftmost point of the stem is above the waterline, the forward end of the
length, Lf, is to be taken at the aftmost point of the stem above that waterline. See 3-1-1/Figure 1.
In ships designed with a raked keel, the waterline on which this length is measured is to be parallel to the
designed waterline.

FIGURE 1

FBD Deck

D
∆ 0.85D

Lf
F.P.

5 Breadth (B)
B is the greatest molded breadth in meters (feet).

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 3
Part 3 Hull Construction and Equipment
Chapter 1 General
Section 1 Definitions 3-1-1

7 Depth

7.1 Molded Depth (D)

D is the molded depth at side in meters (feet) measured at the middle of L from the molded base line to the
top of the freeboard-deck beams. In vessels having rounded gunwales, D is to be measured to the point of
intersection of the molded lines of the deck and side shell plating. In cases where watertight bulkheads
extend to a deck above the freeboard deck and are to be recorded in the Record as effective to that deck, D
is to be measured to the bulkhead deck.

7.3 Scantling Depth (Ds)

The depth, Ds, for use with scantling requirements is measured to the strength deck, as defined in 3-1-1/13.5.

9 Draft for Scantlings (d)

d is the draft in meters (feet) measured at the middle of the length, L, from the molded keel or the rabbet
line at its lowest point to the estimated summer load waterline, the design load waterline or 0.66D, whichever
is greater.

11 Molded Displacement and Block Coefficient

11.1 Molded Displacement (∆)

∆ is the molded displacement of the vessel in metric tons (long tons), excluding appendages, taken at the
summer load line.

11.3 Block Coefficient (Cb)

Cb is the block coefficient obtained from the following equation:

Cb = ∆/1.025LBwld (SI & MKS units)

Cb = 35∆/LBwld (US units)

where
∆ = molded displacement, as defined in 3-1-1/11.1
L = scantling length, as defined in 3-1-1/3.1
d = draft, as defined in 3-1-1/9
Bwl = the greatest molded breadth at summer load line

13 Decks

13.1 Freeboard Deck (2018)

The freeboard deck is normally the uppermost complete deck exposed to weather and sea, which has permanent
means of closing all openings in the weather part thereof, and below which all openings in the vessel’s side
are equipped with permanent means for watertight closure. In cases where a vessel is designed for a special
draft considerably less than that corresponding to the least freeboard obtainable under the International
Load Line Regulations, the freeboard deck for the purpose of the Rules may be taken as the lowest actual
deck from which the draft can be obtained under those regulations.

13.3 Bulkhead Deck

The bulkhead deck is the highest deck to which watertight bulkheads extend and are made effective.

4 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 1 General
Section 1 Definitions 3-1-1

13.5 Strength Deck

The strength deck is the deck which forms the top of the effective hull girder at any part of its length. See
Section 3-2-1.

13.7 Superstructure Deck

A superstructure deck is a deck above the freeboard deck to which the side shell plating extends. Except
where otherwise specified, the term superstructure deck, where used in the Rules, refers to the first such
deck above the freeboard deck.

13.9 Deckhouses
A deckhouse is an enclosed structure above the freeboard deck having side plating set inboard of the hull’s
side-shell plating more than 4% of the breadth, B, of the vessel.

15 Deadweight and Lightship Weight (2018)

For the purpose of these Rules, the deadweight, DWT, is the difference in metric tons (long tons) between
the displacement of the vessel in water having a specific gravity of 1.025 at the summer load line and the
lightship weight. For the purpose of these Rules, lightship weight is the displacement of a vessel in metric tons
(long tons) without cargo, fuel, lubricating oil, ballast water, fresh water and feed water in tanks, consumable
stores, and passengers and crews and their effects. The weight of mediums on board for the fixed fire-
fighting systems (e.g., freshwater, CO2, dry chemical powder, foam concentrate, etc.) are to be included in
the lightweight and lightship condition.

17 Gross Tonnage

17.1 International Tonnage

For the purpose of application of these Rules to vessels intended for unrestricted service (see 1-1-3/1 of the
ABS Rules for Conditions of Classification (Part 1)), the referenced gross tonnage throughout the Rules is
the measure of the internal volume of spaces within the vessel as determined in accordance with the provisions
of the “International Convention on Tonnage Measurement of Ships, 1969”.

17.3 National Tonnage

As an alternative to 3-1-1/17.1 above, requirements applicable on the basis of National Tonnage measurement
and National Regulations will be considered for vessels whose operation is intended to be restricted
exclusively to domestic service. (See 1-1-3/7 of the ABS Rules for Conditions of Classification (Part 1)).

19 Units
These Rules are written in three systems of units, i.e., SI units, MKS units and US customary units. Each
system is to be used independently of any other system.
Unless indicated otherwise, the format of presentation in the Rules of the three systems of units is as follows:
SI units (MKS units, US customary units).

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 5
PART Section 2: General Requirements

3
CHAPTER 1 General

SECTION 2 General Requirements

1 Materials

1.1 General
These Rules are intended for vessels of welded construction using steels complying with the requirements
in Chapter 1 of the ABS Rules for Materials and Welding (Part 2).
1.1.1 Steel
Use of steels other than Grade A and AH in Chapter 1 of the ABS Rules for Materials and Welding
(Part 2) and plate over 20 mm (0.79 in.) in important locations will be specially considered.
1.1.2 Aluminum Alloys
The use of aluminum alloys in hull structures will be considered upon submission of proposed
specification for the alloy and the method of fabrication.
1.1.3 Design Consideration
Where scantlings are reduced in connection with the use of higher-strength steel or where aluminum
alloys are used, adequate buckling strength is to be provided. Where it is intended to use material
of cold flanging quality for important longitudinal strength members, this steel is to be indicated
on the plans.
1.1.4 Guidance for Repair
Where special welding procedures are required for the special steels used in the construction, including
any low temperature steel and those materials not in Chapter 1 of the ABS Rules for Materials and
Welding (Part 2), a set of plans showing the following information for each steel should be placed
aboard the vessel:
• Material Specification
• Welding Procedure
• Location and extent of application
These plans are in addition to those normally placed aboard which are to show all material applications.

1.3 Selection of Material Grade

For vessels 61 m (200 ft) and over in length, steel materials for particular locations are not to be lower grades
than those required by 3-1-2/Table 1 for the material class given in 3-1-2/Table 2.

1.5 Note for the Users

The attention of users is drawn to the fact that when fatigue loading is present, the effective strength of
higher-strength steel in a welded construction may not be greater than that of ordinary-strength steel.
Precautions against corrosion fatigue may also be necessary.

6 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 1 General
Section 2 General Requirements 3-1-2

TABLE 1
Material Grades (2017)
Plate Thickness t Material Class
mm (in.) I II
t ≤ 15 (t ≤ 0.60) A(1), AH A, AH
15 < t ≤ 20 (0.60 < t ≤ 0.79) A, AH A, AH
20 < t ≤ 25 (0.79 < t ≤ 0.98) A, AH B, AH
25 < t ≤ 30 (0.98 < t ≤ 1.18) A, AH D, DH
30 < t ≤ 35 (1.18 < t ≤ 1.38) B, AH D, DH
35 < t ≤ 40 (1.38 < t ≤ 1.57) B, AH D, DH
40 < t ≤ 100 (1.57 < t ≤ 4.0) D, DH E, EH
Note:
1 (2017) ASTM A36 steel otherwise manufactured by an ABS approved steel mill, tested and certified to
the satisfaction of ABS may be used in lieu of Grade A for a thickness up to and including 12.5 mm (0.5 in.)
for plate and 15 mm (0.6 in.) for sections.

TABLE 2
Material Class of Structural Members (2017)
Material Class (1)
Structural Member
Within 0.4L Amidships Outside 0.4L Amidships
Shell
Bottom plating including keel plate II A(4)/AH
Bilge strake II A(4)/AH
Side plating I A(4)/AH
Sheer strake at strength deck (2) II A(4)/AH
Decks
Strength deck plating (3) II A(4)/AH
Stringer plate in strength deck (2) II A(4)/AH
Strength deck plating within line of hatches and exposed to I A(4)/AH
weather, in general
Strength deck strake on tankers at longitudinal bulkhead II A(4)/AH
Longitudinal Bulkheads
Lowest strake in single bottom vessels I A(4)/AH
Uppermost strake including that of the top wing tank II A(4)/AH
Other Structures in General
External continuous longitudinal members and bilge keels II A(4)/AH
(1 July 2015) Plating materials for stern frames supporting — I
rudder and propeller boss, rudders, rudder horns, steering
equipment (5), propeller nozzles, and shaft brackets
Strength members not referred to in above categories and A(4)/AH A(4)/AH
above local structures
Notes:
1 Special consideration will be given to vessels in restricted service.
2 A radius gunwale plate may be considered to meet the requirements for both the stringer plate and the
sheer strake, provided it extends suitable distances inboard and vertically. For formed material, see
2-4-1/3.13.
3 Plating at the corners of large hatch openings are to be specially considered.
4 (2017) ASTM A36 steel otherwise manufactured by an ABS approved steel mill, tested and certified to
the satisfaction of ABS may be used in lieu of Grade A for a thickness up to and including 12.5 mm (0.5 in.)
for plate and up to and including 19 mm (0.75 in.) for sections.
5 (1 July 2015) Steering equipment components other than rudders, as described in Section 3-2-11.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 7
Part 3 Hull Construction and Equipment
Chapter 1 General
Section 2 General Requirements 3-1-2

1.7 Structures Exposed to Low Air Temperatures (2017)

For ships intended to operate in areas with low air temperatures [below and including –20°C (–4°F)], the
materials in exposed structures are to be selected based on the design temperature tD, to be taken as defined
in 3-1-2/1.9.
Materials in the various strength members above the lowest ballast water line (BWL) exposed to air are not to
be of lower grades than those corresponding to Classes I, II and III, as given in 3-1-2/Table 3, depending
on the categories of structural members (secondary, primary and special). For non-exposed structures (except
as indicated in Note 5 of 3-1-2/Table 3) and structures below the lowest ballast water line, see 3-1-2/1.3.

TABLE 3
Application of Material Classes and Grades – Structures Exposed at Low
Temperatures (2017)
Structural Member Category Material Class
Within 0.4L Amidships Outside 0.4L Amidships
Secondary
Deck plating exposed to weather, in general
I I
Side plating above BWL
Transverse bulkheads above BWL (5)
Primary
Strength deck plating (1)
Continuous longitudinal members above
strength deck, excluding longitudinal hatch II I
coamings
Longitudinal bulkhead above BWL (5)
Top wing tank bulkhead above BWL (5)
Special
Sheer strake at strength deck (2)
Stringer plate in strength deck (2) III II
Deck strake at longitudinal bulkhead (3)
Continuous longitudinal hatch coamings (4)
Notes:
1 Plating at corners of large hatch openings to be specially considered. Class III or Grade E/EH
to be applied in positions where high local stresses may occur.
2 Not to be less than Grade E/EH within 0.4L amidships in ships with length exceeding 250 meters
(820 feet).
3 In ships with breadth exceeding 70 meters (230 feet) at least three deck strakes to be Class III.
4 Not to be less than Grade D/DH.
5 (2017) Applicable to plating attached to hull envelope plating exposed to low air temperature.
At least one strake is to be considered in the same way as exposed plating and the strake width
is to be at least 600 mm (24 in.).

The material grade requirements for hull members of each class depending on thickness and design
temperature are defined in 3-1-2/Table 4. For design temperatures tD < –55°C (–67°F), materials are to be
specially considered.

8 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 1 General
Section 2 General Requirements 3-1-2

TABLE 4
Material Grade Requirements for Classes I, II and III at Low Temperatures (2015)
Class I
Thickness, in mm (in.) –20 to –25°C –26 to –35°C –36 to –45°C –46 to –55°C
(–4 to –13°F) (–14 to –31°F) (–32 to –49°F) (–50 to –68°F)
t ≤ 10 (t ≤ 0.39) A, AH B, AH D, DH D, DH
10 < t ≤ 15 (0.39 < t ≤ 0.60) B, AH D, DH D, DH D, DH
15 < t ≤ 20 (0.60 < t ≤ 0.79) B, AH D, DH D, DH E, EH
20 < t ≤ 25 (0.79 < t ≤ 0.98) D, DH D, DH D, DH E, EH
25 < t ≤ 30 (0.98 < t ≤ 1.18) D, DH D, DH E, EH E, EH
30 < t ≤ 35 (1.18 < t ≤ 1.38) D, DH D, DH E, EH E, EH
35 < t ≤ 45 (1.38 < t ≤ 1.80) D, DH E, EH E, EH -, FH
45 < t ≤ 50 (1.80 < t ≤ 1.97) E, EH E, EH -, FH -, FH

Class II
Thickness, in mm (in.) –20 to –25°C –26 to –35°C –36 to –45°C –46 to –55°C
(–4 to –13°F) (–14 to –31°F) (–32 to –49°F) (–50 to –68°F)
t ≤ 10 (t ≤ 0.39) B, AH D, DH D, DH E, EH
10 < t ≤ 20 (0.39 < t ≤ 0.79) D, DH D, DH E, EH E, EH
20 < t ≤ 30 (0.79 < t ≤ 1.18) D, DH E, EH E, EH -, FH
30 < t ≤ 40 (1.18 < t ≤ 1.57) E, EH E, EH -, FH -, FH
40 < t ≤ 45 (1.57 < t ≤ 1.80) E, EH -, FH -, FH -, -
45 < t ≤ 50 (1.80 < t ≤ 1.97) E, EH -, FH -, FH -, -

Class III
Thickness, in mm (in.) –20 to –25°C –26 to –35°C –36 to –45°C –46 to –55°C
(–4 to –13°F) (–14 to –31°F) (–32 to –49°F) (–50 to –68°F)
t ≤ 10 (t ≤ 0.39) D, DH D, DH E, EH E, EH
10 < t ≤ 20 (0.39 < t ≤ 0.79) D, DH E, EH E, EH -, FH
20 < t ≤ 25 (0.79 < t ≤ 0.98) E, EH E, EH E, FH -, FH
25 < t ≤ 30 (0.98 < t ≤ 1.18) E, EH E, EH -, FH -, FH
30 < t ≤ 35 (1.18 < t ≤ 1.38) E, EH -, FH -, FH -, -
35 < t ≤ 40 (1.38 < t ≤ 1.57) E, EH -, FH -, FH -, -
40 < t ≤ 50 (1.57 < t ≤ 1.97) -, FH -, FH -, - -, -

Single strakes required to be of Class III or of Grade E/EH or FH are to have breadths not less than
800 + 5L mm, maximum 1800 mm.
Plating materials for sternframes, rudder horns, rudders and shaft brackets are not to be of lower grades
than those corresponding to the material classes given in 3-1-2/1.3.

1.9 Design Temperature tD (2017)

The design temperature tD is to be taken as the lowest mean daily average air temperature in the area of
operation.
• Mean: Statistical mean over observation period
• Average: Average during one day and night
• Lowest: Lowest during year

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 9
Part 3 Hull Construction and Equipment
Chapter 1 General
Section 2 General Requirements 3-1-2

For seasonally restricted service the lowest value within the period of operation applies.
For the purpose of issuing a Polar Ship Certificate in accordance with the Polar Code, the design temperature
tD shall be no more than 13°C (23.6°F) higher than the Polar Service Temperature (PST) of the ship.
In the Polar Regions, the statistical mean over observation period is to be determined for a period of at
least 10 years.
3-1-2/Figure 1 illustrates the temperature definition.

FIGURE 1
Commonly Used Definitions of Temperatures (2017)

MDHT

MDAT
Air Temp

MDLT

Lowest mean daily average temperature

Lowest mean daily low temperature

J F M A M J J A S O N D J
Month
MDHT = Mean Daily High (or maximum) Temperature
MDAT = Mean Daily Average Temperature
MDLT = Mean Daily Low (or minimum) Temperature

3 Workmanship
All workmanship is to be of commercial marine quality and acceptable to the Surveyor. Welding is to be in
accordance with the requirements of Chapter 4 of the Rules for Materials and Welding (Part 2) and
Section 3-2-16 of these Rules. Plates which have been subjected to excessive furnacing are to undergo a
satisfactory heat treatment before being worked into a hull.

5 Design

5.1 Continuity
Care is to be taken to provide structural continuity. Changes in scantlings are to be gradual. Strength members
are not to change direction abruptly. Where major longitudinal members end at transverse structural members,
tapering may be required forward or aft of the transverses. Stanchions and bulkheads are to be aligned to
provide support and to minimize eccentric loading. Major appendages outside the hull and strength bulkheads in
superstructures are to be aligned with major structural members within the hull.

10 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 1 General
Section 2 General Requirements 3-1-2

5.3 Openings
In general, major openings such as doors, hatches, and large vent ducts are to be avoided in the sheer strake
and stringer plate within the amidships three-fifths length. Corners of openings in strength structures are to
have generous radii. Compensation may be required for openings.

5.5 Brackets
Where brackets are fitted having thicknesses as required by 3-1-2/Table 5 and faces at approximately 45
degrees with the bulkhead deck or shell and the bracket is supported by a bulkhead, deck or shell and the
bracket is supported by a bulkhead, deck or shell structural member, the length of each member, , may be
measured at a point 25% of the extent of the bracket beyond the toe of the bracket, as shown in
3-1-2/Figure 2, when a reduction of the span is so permitted in each section. The minimum overlap of the
bracket arm along the stiffener is not to be less than obtained from the following equation:
x = 1.4y + 30 mm x = 1.4y + 1.2 in.
where
x = length of overlap along stiffener, in mm (in.)
y = depth of stiffener, in mm (in.)
Where a bracket laps a member, the amount of overlap generally is to be 25.5 mm (1 in.).

TABLE 5
Brackets
Metric

Thickness, mm
Length of Face f, mm Width of Flange, mm
Plain Flanged
Not exceeding 305 5.0 — —
Over 305 to 455 6.5 5.0 38
Over 455 to 660 8.0 6.5 50
Over 660 to 915 9.5 8.0 63
Over 915 to 1370 11.0 9.5 75

Inch

Thickness, in.
Length of Face f, in. Width of Flange, in.
Plain Flanged
Not exceeding 12 3/16 — —
Over 12 to 18 1/4 3/16 11/2
Over 18 to 26 5/16 1/4 2
Over 26 to 36 3/8 5/16 21/2
Over 36 to 54 7/16 3/8 3

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 11
Part 3 Hull Construction and Equipment
Chapter 1 General
Section 2 General Requirements 3-1-2

FIGURE 2
Bracket

e x y

0.25(e + x)

7 Structural Sections
The scantling requirements of these Rules are applicable to structural angles, channels, bars, rolled or built-
up sections.

7.1 Deep Supporting Members

The required section modulus of members, such as girders, webs, etc., supporting frames, beams and
stiffeners, is to be obtained on an effective width of plating basis, in accordance with this subsection. The
section is to include the structural member in association with an effective width of plating not exceeding
one-half the sum of spacing on each side of the member or 33% of the unsupported span , whichever is
less. For girders and webs along hatch openings, an effective breadth of plating not exceeding one-half the
spacing or 16.5% of the unsupported span, , whichever is less, is to be used. The section modulus of a
shape, bar or fabricated section not attached to plating is that of the member only.

7.3 Frames, Beams and Stiffeners

7.3.1 Section Modulus
The required section modulus is assumed to be provided by the stiffener and a maximum of one
frame space of the plating to which it is attached.
7.3.2 Web Thickness
The ratio of depth to thickness of the web portion of members is not to exceed the following:
Members with flange 50C1C2
Members without flange 15C1C2
C1 = 0.95 (horizontal web within tank)
= 1.0 (all other cases)
C2 = 1.0 (ordinary strength steel)
= 0.92 (HT32)
= 0.90 (HT36)

12 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 1 General
Section 2 General Requirements 3-1-2

7.5 Hold Frames of Single Side Skin Bulk Carriers (1998)

The hold frames of dry cargo vessels with typical bulk carrier configuration (sloping upper and lower wing
tanks with a transversely framed side shell in way of the hold), in addition to the requirements of Section
3-2-5, are to comply insofar as is practical with the requirements for hold frames given in the following
sections of the Rules.
• 5C-4-2/11.1, “Strength of Frame and Supporting Structure,” of the ABS Rules for Building and Classing
Steel Vessels (Steel Vessel Rules)
• 3-2-16/Table 1, “Welding Requirements,” of these Rules

9 Structural Design Details

9.1 General
The designer is to give consideration to the following:
i) The thickness of internals in locations susceptible to rapid corrosion.
ii) The proportions of built-up members to comply with established standards for buckling strength.
iii) The design of structural details such as noted below against the harmful effects of stress concentrations
and notches:
• Details of the ends, the intersections of members and associated brackets.
• Shape and location of air, drainage or lightening holes.
• Shape and reinforcement of slots or cut-outs for internals.
• Elimination or closing of weld scallops in way of butts, “softening” of bracket toes, reducing
abrupt changes of section or structural discontinuities.
iv) Proportions and thickness of structural members to reduce fatigue response due to engine, propeller
or wave-induced cyclic stresses, particularly for higher-strength steels.
Standard construction details based on the above considerations are to be indicated on the plans or in a
booklet submitted for review and comment.

9.3 Termination of Structural Members (1998)

Unless permitted elsewhere in the Rules, structural members are to be effectively connected to the adjacent
structure in such a manner as to avoid hard spots, notches and other harmful stress concentrations.
Where load bearing members are not required to be attached at their ends, special attention is to be given to
the end taper by using a sniped end of not more than 30°.
The end brackets of large primary load-bearing members are to be soft-toed. Where any end bracket has a
face bar, it is to be sniped and tapered not more than 30°.
Bracket toes and sniped end members are to be kept within 25 mm (1.0 in.) of the adjacent member, unless
the bracket or member is supported by another member on the opposite side of the plating. The depth of
toe or sniped end is generally not to exceed 15 mm (0.60 in.).
Where a strength deck or shell longitudinal terminates without end attachment, it is to extend into the
adjacent transversely framed structure or stop at a local transverse member fitted at about one transverse
frame space, see 3-2-5/1.3, beyond the last floor or web that supports the longitudinal.
The end attachments of non-load bearing members may, in general, be snipe ended. The snipe end is to be
not more than 30° and is to be kept generally within 40 mm (1.57 in.) of the adjacent member unless it is
supported by a member on the opposite side of the plating. The depth of the toe is generally not to exceed
15 mm (0.6 in.).

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 13
Part 3 Hull Construction and Equipment
Chapter 1 General
Section 2 General Requirements 3-1-2

9.5 Fabrication (1 July 2011)

Structural fabrication is to be carried out in accordance with a recognized standard to the satisfaction of the
attending Surveyor. If a recognized national standard or an appropriate shipbuilding and repair standard is
not available, the latest version of IACS Recommendation No. 47 “Shipbuilding and Repair Quality Standard”
may be used. These standards are for conventional ship types and hull structures and they are not
applicable to critical and highly stressed areas of the structure, which are to be reviewed and verified on an
individual basis.

14 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 1 General
Section 2 General Requirements 3-1-2

TABLE 6
Hull Components and Equipment List for Steel Vessels Under 90 Meters (2012)
This components and equipment list has been annotated to agree with ABS Rules for Building and Classing Steel
Vessels Under 90 meters (295 feet) in Length. This list is not to be considered exhaustive: should additional
equipment not listed to be fitted on board, the same will be specially considered for compliance with the Rules. In
case of conflict between the content of this list and the applicable Rules and regulations, the latter are to be
considered applicable.
Notes:
1 Please refer to the specific Rule requirement for the applicable latest revision.
2 ABS Surveyor may require additional certification on any equipment as considered necessary on a case-by-case
basis.

Symbol Meaning
d DESIGN REVIEW – (Design Review Required)
m MATERIAL TESTING – (Material Testing is to be witnessed by an ABS Surveyor)
s MANUFACTURING SURVEYS – (Product is to be inspected during fabrication by an ABS Surveyor)
t TYPE/PROTOTYPE – (Testing conducted on an actual sample or a prototype model is required, as applicable)
obs ON BOARD SURVEYS – Operational, hydrostatic non-destructive testing, or other required tests are to be
witnessed by an ABS surveyor after installation on board vessel
g MANUFACTURER'S DOCUMENTATION – (Manufacturer should supply documentation to guarantee that the
material or the equipment complies with an acceptable Standard, (e.g., Standard tests reports, Ex Certification, etc.)

No. Equipment d m s t obs g Remarks

1 Hull Steels of Grade A, B, D and E, F X
2 Higher Strength Hull Steel AH/DH/EH 32, 36 & 40 X
3 Aluminum Hull Materials X
4 Hull Steel Castings and Forgings X X X
5 Stern Frame Castings X X X
6 Neck and Pintle Bush Bearing X X
7 Rudder Stock X X X
8 Rudder Pintles X X X
9 Rudder Coupling Bolts and Keys X X X
10 Upper and Lower Rudder Casting X X X
11 Rudder Carrier Casting X X X
12 Rudder Carrier Bearing X X X
Fixed Propeller Nozzles with Inner Diameter of
13 X X
5 meters (16.4 feet) or Less
Fixed Propeller Nozzles With Inner Diameter
14 X X X
Greater than 5 meters (16.4 feet)
15 Anchor Windlass X X X
16 Anchor – Á X X X
17 Anchor Chain – Á X X X
Anchor and Anchor Chain – EN Less than 205
18 X
or Tow
19 Bollard, Fairlead and Chocks X X
20 Structural Fire Protection (If Applicable) X X X X
21 Onboard Computer for Stability (If Applicable) X X X X
22 Loading Manual X
23 Portlights and Windows X X X X X Confirm the recognized standards
24 Watertight Doors X X X

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 15
PART Chapter 2: Hull Structures and Arrangements

3
CHAPTER 2 Hull Structures and Arrangements

CONTENTS
SECTION 1 Longitudinal Strength .......................................................................... 31
1 General .............................................................................................31
3 Longitudinal Hull Girder Strength ......................................................31
3.1 Minimum Section Modulus ............................................................. 31
3.3 Vessels 61 m (200 ft) in Length and Over ..................................... 32
3.5 Hull Girder Moment of Inertia ......................................................... 35
5 Decks ................................................................................................36
5.1 Strength Decks .............................................................................. 36
5.3 Effective Lower Decks ................................................................... 36
7 Longitudinal Strength with Higher-Strength Materials ......................36
7.1 General .......................................................................................... 36
7.3 Hull Girder Moment of Inertia ......................................................... 36
7.5 Hull Girder Section Modulus .......................................................... 36
9 Loading Guidance .............................................................................37
9.1 Loading Manual and Loading Instrument....................................... 37
9.3 Allowable Stresses ........................................................................ 37
11 Section Modulus Calculation.............................................................37
11.1 Items Included in the Calculation ................................................... 37
11.3 Effective Areas Included in the Calculation .................................... 37
11.5 Section Modulus to the Deck or Bottom ......................................... 37
11.7 Section Modulus to the Top of Hatch Coamings ............................ 38
13 Continuous Longitudinal Hatch Coamings and Above-Deck
Girders ..............................................................................................38

FIGURE 1 Sign Convention ......................................................................32

FIGURE 2 Distribution Factor M ...............................................................33
FIGURE 3 Distribution Factor F1...............................................................34
FIGURE 4 Distribution Factor F2...............................................................34

SECTION 2 Shell Plating .......................................................................................... 43

1 General .............................................................................................43
3 Bottom Shell Plating..........................................................................43
3.1 Extent of Bottom Plating ................................................................ 43
3.3 Bottom Shell Plating ...................................................................... 43
3.5 Bottom Forward ............................................................................. 44
5 Side Shell Plating ..............................................................................44
5.1 General .......................................................................................... 44
5.3 Side Shell for Vessels Subject to Impact Loadings ........................ 45

16 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
 5.5 Side Shell Plating at Ends ............................................................. 45
5.7 Forecastle and Poop Side Plating ................................................. 45
7 Bow and Stern Thruster Tunnels ...................................................... 45
9 Local Strengthening for Research Vessels....................................... 46
11 Compensation ................................................................................... 46
13 Breaks ............................................................................................... 46
15 Bilge Keels ........................................................................................ 46
16 Bilge Plating ...................................................................................... 46
17 Higher-strength Materials.................................................................. 47
17.1 General.......................................................................................... 47
17.3 Bottom Plating of Higher-strength Material .................................... 47
17.5 Side Plating of Higher-strength Material ........................................ 47
17.7 End Plating .................................................................................... 47

SECTION 3 Deck Plating .......................................................................................... 48

1 General ............................................................................................. 48
3 Deck Plating ...................................................................................... 48
3.1 All Decks ....................................................................................... 48
3.3 Strength Decks within the Midship 0.8L......................................... 49
3.5 All Strength Deck Plating Outside the Line of Openings and
Other Effective Deck Plating.......................................................... 49
5 Compensation ................................................................................... 49
7 Wheel Loading .................................................................................. 50
9 Higher-strength Material ................................................................... 51
9.1 Thickness ...................................................................................... 51
9.3 Wheel Loading .............................................................................. 51

FIGURE 1 Wheel Loading Curves of K .................................................... 51

SECTION 4 Bottom Structure .................................................................................. 53

1 Double Bottoms ................................................................................ 53
1.1 General.......................................................................................... 53
1.3 Center Girder................................................................................. 53
1.5 Side Girders .................................................................................. 54
1.7 Floors ............................................................................................ 54
1.9 Frames .......................................................................................... 54
1.11 Struts ............................................................................................. 55
1.13 Inner-bottom Plating ...................................................................... 55
1.15 Sea Chests .................................................................................... 56
1.17 Access, Lightening, Air, and Drainage Holes ................................ 56
3 Single Bottoms with Floors and Keelsons ........................................ 56
3.1 General.......................................................................................... 56
3.3 Center Keelsons ............................................................................ 56
3.5 Side Keelsons ............................................................................... 57
3.7 Floors ............................................................................................ 57

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 17
 5 Single Bottoms with Longitudinal or Transverse Frames .................59
5.1 General .......................................................................................... 59
5.3 Bottom Girders and Transverses ................................................... 60
5.5 Center Girder ................................................................................. 61
5.7 Frames .......................................................................................... 61
7 Fore-end Strengthening ....................................................................62
7.1 General .......................................................................................... 62
7.3 Extent of Strengthening ................................................................. 62
7.5 Longitudinal Framing ..................................................................... 62
7.7 Transverse Framing....................................................................... 63
9 Higher-strength Materials..................................................................63
9.1 General .......................................................................................... 63
9.3 Inner-bottom Plating ...................................................................... 63
9.5 Bottom and Inner-bottom Longitudinals ......................................... 64
9.7 Center Girders, Side Girders and Floors ....................................... 64
11 Machinery Space ..............................................................................64
11.1 General .......................................................................................... 64
11.3 Engine Foundations ....................................................................... 64
11.5 Thrust Foundations ........................................................................ 64
11.7 Shaft Stools and Auxiliary Foundations ......................................... 64

TABLE 1 Location of Flat of Bottom Forward .........................................62

TABLE 2 Spacing of Floors ....................................................................63

FIGURE 1 Plate Floors .............................................................................58

FIGURE 2 Round Bottom Floors with Deadrise .......................................59
FIGURE 3 Transverse Bottom Frames with Longitudinal Side
Girders ....................................................................................59
FIGURE 4 Longitudinal Frames with Transverse Webs ...........................60

SECTION 5 Side Frames, Webs, and Stringers...................................................... 65

1 General .............................................................................................65
1.1 Basic Considerations ..................................................................... 65
1.3 End Connections ........................................................................... 65
3 Longitudinal Side Frames .................................................................65
3.1 Section Modulus ............................................................................ 65
5 Transverse Side Frames...................................................................66
5.1 Section Modulus ............................................................................ 66
5.3 Tween-deck Frames ...................................................................... 68
5.5 Peak Frames ................................................................................. 68
7 Side Web Frames .............................................................................69
7.1 Section Modulus ............................................................................ 69
7.3 Tween-deck Web Frames .............................................................. 69
7.5 Proportions .................................................................................... 69
7.7 Tripping Brackets and Stiffeners .................................................... 69
9 Vessel Side Frames Subject to Impact Loads ..................................70

18 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
 11 Side Stringers ................................................................................... 70
11.1 Section Modulus ............................................................................ 70
11.3 Proportions .................................................................................... 70
11.5 Tripping Brackets and Stiffeners ................................................... 70

FIGURE 1 Transverse Side Frame .......................................................... 67

FIGURE 2 Transverse Side Frame .......................................................... 67
FIGURE 3 Hold and Tween Deck Frames ............................................... 67

SECTION 6 Beams, Deck Girders, Deck Transverses, and Pillars....................... 71

1 Beams ............................................................................................... 71
1.1 Spacing ......................................................................................... 71
1.3 Section Modulus ............................................................................ 71
1.5 Special Heavy Beams ................................................................... 72
1.6 Deck Fittings.................................................................................. 73
1.7 Container Loading ......................................................................... 75
3 Deck Girders and Deck Transverses ................................................ 75
3.1 General.......................................................................................... 75
3.3 Deck Girders and Transverses Clear of Tanks.............................. 75
3.5 Proportions .................................................................................... 76
3.7 Tripping Brackets and Stiffeners ................................................... 76
3.9 Deck Girders and Transverses in Tanks ....................................... 76
3.11 Hatch Side Girders ........................................................................ 76
3.13 Container Loading ......................................................................... 76
3.15 End Attachments ........................................................................... 76
3.17 Hatch-end Beams .......................................................................... 77
5 Stanchions and Pillars ...................................................................... 78
5.1 General.......................................................................................... 78
5.3 Permissible Load ........................................................................... 78
5.5 Calculated Load ............................................................................ 79
5.7 Stanchions in Double Bottoms and Under Tank Tops ................... 79
5.9 Bulkheads...................................................................................... 80
5.11 Attachments .................................................................................. 80
7 Higher-strength Materials.................................................................. 80
7.1 General.......................................................................................... 80
7.3 Beams, Girders and Transverses of Higher-strength Materials ..... 80

TABLE 1 Values of f ............................................................................... 75

FIGURE 1 Application of Design Loads ................................................... 74

FIGURE 2 Hatch-end Beams ................................................................... 78

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 19
 SECTION 7 Watertight Bulkheads and Doors ........................................................ 81
1 General .............................................................................................81
1.1 Openings and Penetrations ........................................................... 81
3 Arrangement of Watertight Bulkheads ..............................................81
3.1 Collision Bulkheads ....................................................................... 81
3.3 Engine Room ................................................................................. 82
3.5 Chain Lockers ................................................................................ 82
3.7 Hold Bulkheads ............................................................................. 83
5 Construction of Watertight Bulkheads ..............................................83
5.1 Plating............................................................................................ 83
5.3 Stiffeners ....................................................................................... 84
5.5 Girders and Webs .......................................................................... 85
5.7 Corrugated Bulkheads ................................................................... 86
7 Watertight Doors ...............................................................................87
7.1 Vessels Requiring Subdivision and Damage Stability.................... 87
7.3 Other Vessels ................................................................................ 88
7.5 Construction .................................................................................. 88
9 Testing ..............................................................................................88

FIGURE 1 Reference Point of Vessels with Bulbous Bow .......................82

FIGURE 1A ....................................................................................................83
FIGURE 1B ....................................................................................................83
FIGURE 2 Corrugated Bulkhead ..............................................................86
FIGURE 3 Corrugated Bulkhead End Connections..................................87

SECTION 8 Deep Tanks ........................................................................................... 89

1 General Arrangement .......................................................................89
3 Construction ......................................................................................89
5 Construction of Deep-tank Bulkheads ..............................................89
5.1 Plating............................................................................................ 89
5.3 Stiffeners ....................................................................................... 90
5.5 Corrugated Bulkheads ................................................................... 91
5.7 Girders and Webs .......................................................................... 91
7 Tank Top Plating ...............................................................................91
9 Higher-strength Materials..................................................................91
9.1 General .......................................................................................... 91
9.3 Plating............................................................................................ 91
9.5 Stiffeners ....................................................................................... 92
11 Drainage and Air Escape ..................................................................92
13 Testing ..............................................................................................92

SECTION 9 Superstructures and Deckhouses ...................................................... 93

1 Superstructure Scantlings .................................................................93
1.1 Side and Top Plating ..................................................................... 93
1.3 Framing and Internal Bulkheads .................................................... 93
1.5 Breaks in Continuity ....................................................................... 93
1.7 Structural Support .......................................................................... 93

20 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
 3 Exposed Bulkheads of Superstructures and Deckhouses................ 93
3.1 General.......................................................................................... 93
3.3 Stiffeners ....................................................................................... 94
3.5 Plating ........................................................................................... 95
3.7 End Attachments ........................................................................... 96
3.9 Raised-quarter-deck Bulkheads .................................................... 96
5 Enclosed Superstructures ................................................................. 96
5.1 Closing Appliances ........................................................................ 96
5.3 Sills of Access Openings ............................................................... 96
5.5 Means of Access ........................................................................... 96
7 Open Superstructures ....................................................................... 97
9 Deckhouses ...................................................................................... 97
10 Aluminum Deckhouses ..................................................................... 97
10.1 Scantling Correction ...................................................................... 97
10.3 Material Factors ............................................................................. 98
10.5 Attachments .................................................................................. 98
11 Helicopter Decks ............................................................................... 99
11.1 General.......................................................................................... 99
11.3 Structure ........................................................................................ 99
11.5 Safety Net.................................................................................... 100
11.7 Aluminum Decks ......................................................................... 100
11.9 Means of Escape and Access ..................................................... 100

TABLE 1 Values of a .............................................................................. 95

TABLE 2 Values of f ............................................................................... 95
TABLE 3 Allowable Factors of Safety Based on Y for Helicopter
Decks .................................................................................... 101

SECTION 10 Keels, Stems, Stern Frames, Shaft Struts, and Propeller

Nozzles ................................................................................................ 102
1 Keels ............................................................................................... 102
1.1 Bar Keels ..................................................................................... 102
1.3 Plate Keels .................................................................................. 102
3 Stems .............................................................................................. 102
3.1 Bar Stems.................................................................................... 102
3.3 Cast or Forged Stems ................................................................. 103
3.5 Plate Stems ................................................................................. 103
5 Sternposts ....................................................................................... 103
5.1 Bar Sternposts ............................................................................. 103
5.3 Cast, Forged, or Fabricated Sternposts....................................... 103
7 Stern Frames .................................................................................. 103
7.1 Below the Boss............................................................................ 103
7.3 Above the Boss ........................................................................... 104
7.5 Secondary Members ................................................................... 104
9 Stern Frames with Shoepieces ....................................................... 105

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 21
 11 Shoepieces .....................................................................................105
11.1 General ........................................................................................ 105
11.3 Design Stress .............................................................................. 105
11.5 Minimum Scantlings..................................................................... 106
13 Rudder Horns ..................................................................................106
15 Rudder Gudgeons ...........................................................................107
17 Shaft Struts .....................................................................................107
17.1 General ........................................................................................ 107
17.3 V Strut.......................................................................................... 107
17.5 I Strut ........................................................................................... 107
17.7 Strut Length ................................................................................. 108
19 Propeller Nozzles ............................................................................108
19.1 Application ................................................................................... 108
19.3 Design Pressure .......................................................................... 108
19.5 Nozzle Cylinder............................................................................ 109
19.7 Nozzle Section Modulus .............................................................. 109
19.9 Welding Requirement .................................................................. 111
21 Propulsion Improvement Devices (PID) as Hull Appendages ........111
21.1 Application Scope ........................................................................ 111
21.3 Plans and Documentation ............................................................ 111
21.5 Design and Arrangement ............................................................. 111
21.7 Structural End Connection ........................................................... 111
23 Inspection of Castings.....................................................................111

TABLE 1 Coefficient c...........................................................................108

TABLE 2 Coefficient ε...........................................................................108
TABLE 3 Coefficient cn .........................................................................109
TABLE 4 Corrosion Allowance tc ..........................................................109

FIGURE 1 Stern Frame ..........................................................................105

FIGURE 2 Shoepiece .............................................................................106
FIGURE 3 Propeller Nozzle Section View ..............................................110

SECTION 11 Rudders and Steering Equipment ..................................................... 112

1 General ...........................................................................................112
1.1 Application ................................................................................... 112
1.3 Materials for Rudder, Rudder Stock and Steering Equipment ..... 112
1.5 Expected Torque ......................................................................... 113
1.7 Rudder Stops ............................................................................... 113
3 Rudder Design Force ......................................................................113
3.1 Rudder Blades without Cutouts ................................................... 113
3.3 Rudder Blades with Cutouts ........................................................ 114
3.5 Rudders Blades with Twisted Leading-Edge ............................... 114
5 Rudder Design Torque....................................................................117
5.1 General ........................................................................................ 117
5.3 Rudder Blades without Cutouts ................................................... 117

22 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
 5.5 Rudders Blades with Cutouts ...................................................... 118
5.7 Rudders with Twisted Leading Edge ........................................... 118
5.9 Trial Conditions ........................................................................... 118
7 Rudder Stocks ................................................................................ 118
7.1 Upper Rudder Stocks .................................................................. 118
7.3 Lower Rudder Stocks .................................................................. 118
7.4 Rudder Trunk and Rudder Stock Sealing .................................... 119
7.5 Bending Moments ....................................................................... 121
9 Flange Couplings ............................................................................ 122
9.1 General........................................................................................ 122
9.3 Horizontal Couplings ................................................................... 122
9.5 Vertical Couplings ....................................................................... 123
11 Tapered Stock Couplings................................................................ 124
11.1 Coupling Taper ............................................................................ 124
11.3 Keyed Fitting ............................................................................... 125
11.5 Keyless Fitting ............................................................................. 126
11.7 Locking Nut ................................................................................. 127
13 Pintles ............................................................................................. 127
13.1 General........................................................................................ 127
13.3 Diameter ...................................................................................... 128
13.4 Push-up Pressure and Push-up Length ...................................... 128
13.5 Shear and Bearing Forces........................................................... 129
15 Supporting and Anti-Lifting Arrangements ...................................... 130
15.1 Bearings ...................................................................................... 130
15.3 Rudder Carrier ............................................................................. 131
15.5 Anti-Lifting Devices ...................................................................... 131
17 Double Plate Rudder....................................................................... 132
17.1 Strength ....................................................................................... 132
17.3 Side, Top and Bottom Plating ...................................................... 135
17.5 Diaphragm Plates ........................................................................ 135
17.7 Connections of Rudder Blade Structure with Solid Parts ............ 135
17.9 Welding and Design Details ........................................................ 138
17.11 Watertightness ............................................................................ 138
19 Single Plate Rudders ...................................................................... 138
19.1 Mainpiece Diameter .................................................................... 138
19.3 Blade Thickness .......................................................................... 139
19.5 Arms ............................................................................................ 139
21 Steering Nozzles ............................................................................. 139
21.1 Application Scope ........................................................................ 139
21.3 Design Force ............................................................................... 140
21.5 Design Torque ............................................................................. 141
21.7 Nozzle Stock ............................................................................... 141
21.9 Design Pressure .......................................................................... 142
21.11 Plate Thickness ........................................................................... 143
21.13 Section Modulus .......................................................................... 143
21.15 Locking Device ............................................................................ 143
21.17 Welding Requirement .................................................................. 143

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 23
 23 Azimuthal Thruster ..........................................................................143
23.1 Application Scope ........................................................................ 143
23.3 Plans and Documents.................................................................. 144
23.5 Locking Device ............................................................................ 144
23.7 Design Force ............................................................................... 144
23.9 Design Torque ............................................................................. 146
23.11 Design Pressure .......................................................................... 146
23.13 Nozzle Scantlings ........................................................................ 146
23.15 Steering Tube .............................................................................. 147
23.17 Section Modulus .......................................................................... 147
23.19 Thruster Nozzle Top Connections ............................................... 147
23.21 Nozzle Strut ................................................................................. 147
23.23 Direct Analysis ............................................................................. 148
23.25 Welding and NDT Testing ............................................................ 149

TABLE 1A Coefficient kc for Ordinary Rudders .......................................115

TABLE 1B Coefficient kc for High-Lift/Performance Rudders .................115
TABLE 2 Coefficient kl ..........................................................................117
TABLE 3 Coefficient α ..........................................................................117
TABLE 4 Minimum Bearing Force Bmin .................................................128
TABLE 5 Bearing Reaction Force ........................................................131
TABLE 6 Allowable Bearing Surface Pressure ....................................131
TABLE 7 Thickness of Side Plating and Vertical Diaphragm Plates ....138
TABLE 8 Coefficient cm .........................................................................142

FIGURE 1A Rudder Blade without Cutouts ..............................................116

FIGURE 1B Rudder Blade with Cutouts ...................................................116
FIGURE 2 Fillet Shoulder Radius ...........................................................120
FIGURE 3 Welded Joint Between Rudder Stock and Coupling
Flange ...................................................................................123
FIGURE 4 Tapered Couplings ................................................................124
FIGURE 5.....................................................................................................132
FIGURE 6.....................................................................................................133
FIGURE 7.....................................................................................................133
FIGURE 8.....................................................................................................134
FIGURE 9 Cross-section of the Connection Between Rudder Blade
Structure and Rudder Stock Housing ...................................137
FIGURE 10 Nozzle Geometry ..................................................................141
FIGURE 11 An Illustration of Azimuthal Thruster .....................................145

SECTION 12 Protection of Deck Openings ............................................................ 160

1 General ...........................................................................................160
3 Additional Requirements for Bulk Carriers, Ore Carriers and
Combination Carriers ......................................................................160

24 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
 5 Positions and Design Pressures ..................................................... 160
5.1 Positions of Deck Openings ........................................................ 160
5.3 Design Pressures ........................................................................ 160
7 Hatchway Coamings, Companionway Sills and Access Sills ......... 161
7.1 Coaming and Sill Heights ............................................................ 161
7.3 Coaming Plates ........................................................................... 162
7.5 Coaming Stiffeners ...................................................................... 162
7.7 Continuous Longitudinal Hatch Coamings................................... 162
9 Hatchways Closed by Portable Covers and Secured
Weathertight by Tarpaulins and Battening Devices ........................ 163
9.1 Pontoon Covers........................................................................... 163
9.3 Wooden Hatch Covers ................................................................ 163
9.5 Steel Hatch Covers ..................................................................... 164
9.7 Bearing Surface ........................................................................... 164
9.9 Materials Other Than Steel.......................................................... 164
11 Hatchways Closed by Covers of Steel Fitted with Gaskets and
Clamping Devices ........................................................................... 165
11.1 Strength of Covers ...................................................................... 165
11.3 Means for Securing Weathertightness ........................................ 165
13 Hatchways Closed by Portable Covers in Lower Decks or within
Fully Enclosed Superstructures ...................................................... 167
13.1 General........................................................................................ 167
13.3 Portable Beams and Wood Covers ............................................. 167
13.5 Steel Covers ................................................................................ 167
13.7 Wheel Loading ............................................................................ 168
14 Small Hatches on the Exposed Fore Deck ..................................... 168
14.1 Application ................................................................................... 168
14.3 Strength ....................................................................................... 168
14.5 Primary Securing Devices ........................................................... 168
14.7 Requirements for Primary Securing ............................................ 168
14.9 Secondary Devices ..................................................................... 169
15 Hatchways within Open Superstructures ........................................ 171
17 Hatchways within Deckhouses ....................................................... 171
19 Container Loading........................................................................... 172
21 Machinery Casings ......................................................................... 172
21.1 Arrangement ................................................................................ 172
21.3 Exposed Casings on Freeboard or Raised Quarter Decks .......... 172
21.5 Exposed Casings on Superstructure Decks ................................ 172
21.7 Casings within Open Superstructures ......................................... 173
21.9 Casings within Enclosed Superstructures, Deckhouses, or
below Freeboard Decks............................................................... 173
23 Miscellaneous Openings in Freeboard and Superstructure
Decks .............................................................................................. 173
23.1 Manholes and Scuttles ................................................................ 173
23.3 Other Openings ........................................................................... 173
23.5 Escape Openings ........................................................................ 173
23.7 Chain Pipe Opening .................................................................... 173

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 25
 TABLE 1 Coaming and Sill Heights ......................................................161
TABLE 2 Scantlings for Small Steel Hatch Covers on the Fore
Deck ......................................................................................169

FIGURE 1 Arrangement of Stiffeners .....................................................170

FIGURE 2 Example of Primary Securing Method ..................................171

SECTION 13 Protection of Shell Openings ............................................................ 176

1 Cargo, Gangway, or Fueling Ports .................................................176
1.1 Construction ................................................................................ 176
1.3 Location ....................................................................................... 176
3 Bow Doors, Inner Doors, Side Shell Doors and Stern Doors .........176
3.1 General ........................................................................................ 176
3.3 Arrangement ................................................................................ 177
5 Securing, Locking and Supporting of Doors ...................................177
5.1 Definitions .................................................................................... 177
7 Securing and Supporting Devices ..................................................177
7.1 Bow Doors ................................................................................... 177
7.3 Side Shell and Stern Doors ......................................................... 178
9 Securing and Locking Arrangement ...............................................178
9.1 General ........................................................................................ 178
9.3 Operation ..................................................................................... 178
9.5 Indication/Monitoring.................................................................... 178
11 Watertightness ................................................................................180
11.1 Bow Doors ................................................................................... 180
11.3 Inner Doors .................................................................................. 180
11.5 Side Shell and Stern Doors ......................................................... 180
11.7 Testing at Watertight Door Manufacturer ..................................... 180
13 Bow Door Scantlings.......................................................................180
13.1 General ........................................................................................ 180
13.3 Primary Structure ......................................................................... 180
13.5 Secondary Stiffeners ................................................................... 180
13.7 Plating.......................................................................................... 180
13.9 Securing and Supporting Devices ............................................... 181
13.11 Visor Door Lifting Arms and Supports.......................................... 181
15 Inner Door Scantlings .....................................................................181
15.1 General ........................................................................................ 181
15.3 Primary Structure ......................................................................... 181
15.5 Securing and Supporting Devices ............................................... 182
17 Side Shell Door and Stern Door Scantlings ....................................182
17.1 General ........................................................................................ 182
17.3 Primary Structure ......................................................................... 182
17.5 Secondary Stiffeners ................................................................... 182
17.7 Plating.......................................................................................... 182
17.9 Securing and Supporting Devices ............................................... 182

26 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
 19 Bow Door Design Loads ................................................................. 183
19.1 External Pressure ........................................................................ 183
19.3 External Forces ........................................................................... 184
19.5 Visor Door Forces, Moments and Load Cases ............................ 185
19.7 Side-Opening Door Load Cases .................................................. 187
21 Inner Door Design Loads ................................................................ 187
21.1 External Pressure ........................................................................ 187
21.3 Internal Pressure ......................................................................... 187
23 Side Shell and Stern Doors............................................................. 187
23.1 Design Forces for Primary Members ........................................... 187
23.3 Design Forces for Securing or Supporting Devices of Doors
Opening Inwards ......................................................................... 187
23.5 Design Forces for Securing or Supporting Devices of Doors
Opening Outwards ...................................................................... 187
25 Allowable Stresses.......................................................................... 188
25.1 Primary Structure and Securing and Supporting Devices ........... 188
25.3 Steel Securing and Supporting Devices Bearing Stress .............. 188
25.5 Tensile Stress on Threaded Bolts ............................................... 188
27 Operating and Maintenance Manual............................................... 189
27.1 Manual......................................................................................... 189
27.3 Operating Procedures ................................................................. 189

FIGURE 1 Entry and Flare Angles ......................................................... 183

FIGURE 2 Definition of αm and βm .......................................................... 185
FIGURE 3 Visor Type Bow Door ............................................................ 186

SECTION 14 Bulwarks, Rails, Freeing Ports, Portlights, Windows, Ventilators,

Tank Vents, and Overflows ............................................................... 190
1 Bulwarks and Guard Rails .............................................................. 190
1.1 Height .......................................................................................... 190
1.3 Strength of Bulwarks ................................................................... 190
1.5 Guard Rails ................................................................................. 190
3 Access and Crew Protection ........................................................... 191
3.1 General........................................................................................ 191
3.3 Access to Bow on Tankers .......................................................... 191
5 Freeing Ports .................................................................................. 194
5.1 Basic Area ................................................................................... 194
5.3 Trunks, Deckhouses, and Hatchway Coamings .......................... 194
5.5 Superstructure Decks .................................................................. 194
5.7 Open Superstructures ................................................................. 194
5.9 Details of Freeing Ports ............................................................... 194
7 Portlights ......................................................................................... 195
7.1 Application ................................................................................... 195
7.3 Location ....................................................................................... 195
7.5 Construction ................................................................................ 195

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 27
 9 Windows..........................................................................................195
9.1 Construction ................................................................................ 195
9.3 Testing ......................................................................................... 197
11 Ventilators, Tank Vents, and Overflows..........................................197
11.1 General ........................................................................................ 197
11.3 Ventilators .................................................................................... 197
11.5 Tank Vents and Overflows ........................................................... 197
11.7 Ventilators, Tank Vents and Overflows on the Fore Deck ........... 198

TABLE 1 Acceptable Arrangement for Access.....................................192

TABLE 2 .......................................................................................................196
TABLE 3 .......................................................................................................196
TABLE 4 760 mm (30 in.) High Tank Vents and Overflows
Thickness and Bracket Standards ........................................199
TABLE 5 900 mm (35.4 in.) High Ventilator Thickness and Bracket
Standards ..............................................................................200
FIGURE 1 Guardrail Stanchion....................................................................191

SECTION 15 Ceiling, Sparring, and Protection of Steel ........................................ 201

1 Ceiling .............................................................................................201
3 Sparring...........................................................................................201
5 Protection of Steel Work .................................................................201
5.1 All Spaces .................................................................................... 201
5.3 Salt Water Ballast Space ............................................................. 201
5.5 Oil Spaces ................................................................................... 201
5.7 Cargo Holds on Bulk Carriers (including Combination
Carriers) ....................................................................................... 202

FIGURE 1 Extent of Coatings ......................................................................202

SECTION 16 Weld Design ........................................................................................ 203

1 Fillet Welds......................................................................................203
1.1 General ........................................................................................ 203
1.3 Tee Connections.......................................................................... 203
1.5 Tee Type End Connections ......................................................... 204
1.7 Tee Joints at Boundary Connections ........................................... 204
1.9 Ends of Unbracketed Stiffeners ................................................... 204
1.11 Reduced Weld Size ..................................................................... 204
1.13 Lapped Joints .............................................................................. 204
1.15 Plug Welds or Slot Welds ............................................................ 205
3 Full or Partial Penetration Corner or Tee Joints .............................205
5 Alternatives .....................................................................................205

TABLE 1 Weld Sizes and Spacing – Millimeters ..................................206

TABLE 1 Weld Sizes and Spacing – Inches ........................................209

28 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
 APPENDIX 1 Loading Manuals and Loading Instruments ...................................... 39
1 General ............................................................................................. 39
1.1 Application ..................................................................................... 39
3 Definitions ......................................................................................... 39
3.1 Loading Guidance ......................................................................... 39
3.3 Category I Vessels ........................................................................ 39
3.5 Category II Vessels ....................................................................... 40
5 Required Loading Guidance ............................................................. 40
5.1 Loading Manual ............................................................................. 40
5.3 Modifications ................................................................................. 40
7 Loading Manual ................................................................................ 40
7.1 Required Information ..................................................................... 40
7.3 Loading Conditions ........................................................................ 40
7.5 Language ...................................................................................... 41
9 Loading Instrument ........................................................................... 41
9.1 Type .............................................................................................. 41
9.3 Required Verifications ................................................................... 41
9.5 Language ...................................................................................... 41
11 Annual Surveys ................................................................................. 41

TABLE 1 Loading Conditions in the Loading Manual............................. 42

APPENDIX 2 Guidelines for Calculating Bending Moment and Shear Force in

Rudders and Rudder Stocks ............................................................. 150
1 Application ...................................................................................... 150
3 Spade Rudders ............................................................................... 150
3.1 Rudder......................................................................................... 150
3.3 Lower Stock................................................................................. 151
3.5 Moment at Top of Upper Stock Taper ......................................... 152
3.7 Bearing Reaction Forces ............................................................. 152
5 Rudders Supported by Shoepiece .................................................. 155
5.1 Shear Force, Bending Moment and Reaction Forces .................. 155
7 Rudders Supported by a Horn with One Pintle ............................... 156
7.1 Shear Force, Bending Moment and Reaction Forces .................. 156
9 Rudders Supported by a Horn Arranged with Two Pintles
(Supports) ....................................................................................... 157
9.1 Shear Force, Bending Moment and Reaction Forces .................. 157

FIGURE 1 Spade Rudder ....................................................................... 154

FIGURE 2 Rudder Supported by Shoepiece .......................................... 155
FIGURE 3 Rudder Supported by a Horn with One Pintle....................... 157
FIGURE 4 Rudder Supported by a Horn Arranged with Two Pintles
(Supports) ............................................................................. 159

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 29
 APPENDIX 3 Portable Beams and Hatch Cover Stiffeners of Variable Cross
Section ................................................................................................ 174
1 Application.......................................................................................174

FIGURE 1 SM and I of Construction Elements .......................................175

30 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Section 1: Longitudinal Strength

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 1 Longitudinal Strength

1 General
Vessels are to have longitudinal hull girder section modulus in accordance with the requirements of this
section. The equation in this section is, in general, valid for all vessels having breadths, B, which do not
exceed two times their depths, D, as defined in Section 3-1-1. Vessels whose proportions exceed these
limits will be subject to special consideration.

3 Longitudinal Hull Girder Strength

3.1 Minimum Section Modulus

The minimum required hull girder section modulus, SM, at amidships, is to be determined in accordance
with the following equation:
SM = C1C2L2B (Cb + 0.7) m-cm2 (ft-in2)
where
C1 = 30.67 – 0.98L 12 ≤ L < 18 m

= 22.40 – 0.52L 18 ≤ L < 24 m

= 15.20 – 0.22L 24 ≤ L < 35 m
= 11.35 – 0.11L 35 ≤ L < 45 m
= 6.40 45 ≤ L < 61 m
= 0.0451L + 3.65 61 ≤ L < 90 m
C1 = 30.67 – 0.299L 40 ≤ L < 59 ft

= 22.40 – 0.158L 59 ≤ L < 79 ft

= 15.20 – 0.067L 79 ≤ L < 115 ft
= 11.35 – 0.033L 115 ≤ L < 150 ft
= 6.40 150 ≤ L < 200 ft
= 0.0137L + 3.65 200 ≤ L < 295 ft
C2 = 0.01 (0.01, 0.000144)
L = length of vessel, as defined in 3-1-1/3, in m (ft)
B = breadth of vessel, as defined in 3-1-1/5, in m (ft)
Cb = block coefficient at design draft, based on the length, L, measured on the design load
waterline. Cb is not to be taken as less than 0.60.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 31
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 1 Longitudinal Strength 3-2-1

3.3 Vessels 61 m (200 ft) in Length and Over

In addition to meeting the above criteria in 3-2-1/3.1, vessels of 61 m (200 ft) in length or greater are to
comply with the following requirements.
3.3.1 Sign Convention of Bending Moment and Shear
The sign convention bending moment and shear force is as shown in 3-2-1/Figure 1.

FIGURE 1
Sign Convention

(+)
FSW, FW

Aft Fore

MSW, MW (+)

3.3.2 Still-water Bending Moment and Shear Force

Still-water bending moment and shear force calculations showing hull girder shear force and bending
moment values along the entire vessel length for the anticipated loaded, transitional and ballasted
conditions are to be submitted together with the distribution of lightship weights.
3.3.3 Wave Loads
3.3.3(a) Wave Bending Moment Amidships. The wave bending moment, expressed in kN-m
(tf-m, Ltf-ft), may be obtained from the following equations:
Mws = −k1C1L2B(Cb + 0.7) × 10−3 Sagging Moment

Mwh = +k2C1L2BCb × 10−3 Hogging Moment

where
k1 = 110 (11.22, 1.026)
k2 = 190 (19.37, 1.772)
C1 = 0.044L + 3.75 SI/MKS units (0.0134L + 3.75 US customary units)
L = length of vessel, as defined in 3-1-1/3, in m (ft)
B = breadth of vessel, as defined in 3-1-1/5, in m (ft)
Cb = block coefficient at summer load waterline, based on L, as defined in 3-1-1/3
3.3.3(b) Envelope Curve of Wave Bending Moment. The wave bending moment along the length
of the vessel L may be obtained by multiplying the midship value by the distribution factor M
given in 3-2-1/Figure 2.

32 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 1 Longitudinal Strength 3-2-1

3.3.3(c) Wave Shear Force. The envelopes of maximum shearing forces induced by waves, Fw,
as shown in 3-2-1/Figure 3 and 3-2-1/Figure 4, may be obtained from the following equations:
Fwp = +kF1C1LB(Cb + 0.7) × 10−2 For positive shear force

Fwn = −kF2C1LB(Cb + 0.7) × 10−2 For negative shear force

where
Fwp, Fwn = maximum shearing force induced by wave, in kN (tf, Ltf)
C1 = as defined in 3-2-1/3.3.3(a)
L = length of vessel, as defined in 3-1-1/3, in m (ft)
B = breadth of vessel, as defined in 3-1-1/5, in m (ft)
Cb = block coefficient at summer load waterline, based on L, as defined in 3-1-1/3
k = 30 (3.059, 0.2797)
F1 = distribution factor, as shown in 3-2-1/Figure 3
F2 = distribution factor, as shown in 3-2-1/Figure 4

FIGURE 2
Distribution Factor M

1.0

0 0.0 0.4 0.65 1.0

Aft Forward
end of L Distance from the aft end of L in terms of L end of L

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 33
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 1 Longitudinal Strength 3-2-1

FIGURE 3
Distribution Factor F1

1.0

0.92 X 190 Cb
110 (Cb + 0.7)

F1 0.7

0
0.0 0.2 0.3 0.4 0.6 0.7 0.85 1.0
Aft Forward
end of L Distance from the aft end of L in terms of L end of L

FIGURE 4
Distribution Factor F2

0.92

190 Cb
110 (Cb + 0.7)

F2 0.7

0
0.0 0.2 0.3 0.4 0.6 0.7 0.85 1.0
Aft Forward
end of L Distance from the aft end of L in terms of L end of L

3.3.4 Section Modulus

The required hull girder section modulus for 0.4L amidships is to be obtained from the following
equation, or 3-2-1/3.1, whichever is greater.
SM = Mt/fp m-cm2 (ft-in2)
where
Mt = total bending moment to be obtained as the maximum algebraic sum (see
sign convention in 3-2-1/3.3.1) of still-water bending moment and wave-
induced bending moment, as follows.
Mt = Msw + Mw
Msw = still water bending moment, in accordance with 3-2-1/3.3.2

34 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 1 Longitudinal Strength 3-2-1

Mw = maximum wave-induced bending moment, in accordance with 3-2-1/3.3.3(a)

fp = nominal permissible bending stress

= 17.5 kN/cm2 (1.784 tf/cm2, 11.33 Ltf/in2)

3.3.5 Shearing Strength
In calculating the nominal total shear stresses due to still-water and wave-induced loads, the
maximum algebraic sum of the shearing force in still-water, Fsw, and that induced by wave, Fw, at
the station examined is to be used. The thicknesses of the side shell and longitudinal bulkhead,
where fitted, are to be such that the nominal total shear stresses, as obtained from 3-2-1/3.3.5(a) or
3-2-1/3.3.5(c), are not greater than 11.0 kN/cm2 (1.122 tf/cm2, 7.122 Ltf/in2). Where the side shell
or longitudinal bulkhead is constructed of higher strength material, the permissible shear stresses
may be increased by the factor, 1/Q.
3.3.5(a) Shearing Strength for Vessels without Effective Longitudinal Bulkheads. For vessels
without continuous longitudinal bulkheads, the nominal total shear stress, fs, in the side shell
plating may be obtained from the following equation:
fs = (Fsw + Fw)m/2tsI kN/cm2 (tf/cm2, Ltf/in2)
where
I = moment of inertia of the hull girder section, in cm4 (in4), at the section under
consideration
m = first moment, in cm3 (in3), about the neutral axis, of the area of the effective
longitudinal material between the horizontal level at which the shear stress is
being determined and the vertical extremity of effective longitudinal material,
taken at the section under consideration.
ts = thickness of the side shell plating, in cm (in.), at the position under
consideration.
Fsw = hull girder shearing force in still-water, in kN (tf, Ltf)
Fw = Fwp or Fwn, as specified by 3-2-1/3.3.3(c), depending upon loading
3.3.5(b) Modification of Hull Girder Shearing Force for Vessels Carrying Cargo in Alternate
Holds or with Other Non-Uniform Loading. Where cargo is carried in alternate holds, the hull
girder shearing force in still water, Fsw, to be used for calculating shear stresses in the side shell
plating may be modified to account for the shear loads transmitted through the double bottom
structure to the traverse bulkhead.
3.3.5(c) Shearing Strength for Vessels with Two or Three Longitudinal Bulkheads. For vessels
having continuous longitudinal bulkheads, the total shear stresses in the side shell and longitudinal
bulkhead plating are to be calculated by an acceptable method. In determining the still-water shear
force, consideration is to be given to the effects of non-uniform athwartship distribution of loads.
The method described in Appendix 3-2-A1 of the Steel Vessel Rules may be used as a guide in
calculating the nominal total shear stress, fs, related to the shear flow in the side shell or
longitudinal bulkhead plating. Alternative methods of calculation will also be considered. One
acceptable method is shown in Appendix 5C-2-A1 of the Steel Vessel Rules.

3.5 Hull Girder Moment of Inertia

The hull-girder moment of inertia of the vessel amidships, I, is to be not less than obtained from the
following equation:
I = L(SM)/33.3 m2-cm2 (ft2-in2)
where
L = length of vessel, as defined in 3-1-1/3, in m (ft)
SM = hull girder section modulus required for the vessel in 3-2-1/3.1 or 3-2-1/3.3.4

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 35
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 1 Longitudinal Strength 3-2-1

5 Decks

5.1 Strength Decks

The uppermost deck to which the side shell plating extends for any part of the length of the vessel is to be
considered the strength deck for that portion of the length, except in way of comparatively short superstructures.
In such a case, the deck on which the superstructures are located is to be considered the strength deck in
way of the superstructure. In general, the effective sectional area of the deck for use in calculating the section
modulus is to exclude hatchways and other large openings through the deck but may include seam overlaps.
The deck sectional areas used in the section modulus calculations are to be maintained throughout the
midship 0.4L in vessels. They may be reduced to one-half the normal requirement at 0.15L from the ends.
In way of a superstructure beyond the midship 0.4L, the strength deck area may be reduced to approximately
70% of the normal requirement at that location.

5.3 Effective Lower Decks

To be considered effective for use in calculating the hull girder section modulus, the thickness of the deck
plating is to comply with the requirements of Section 3-2-3. The sectional areas of lower decks used in
calculating the section modulus are to be obtained as described in 3-2-1/5.1. These areas are to be maintained
throughout the midship 0.4L and may be gradually reduced to one-half their midship value at 0.15L from
the ends.

7 Longitudinal Strength with Higher-Strength Materials

7.1 General
Vessels in which the effective longitudinal material of either the upper or lower flanges of the main hull
girder, or both, are constructed of materials having mechanical properties greater than those of ordinary
strength hull structural steel [see Section 2-1-2 of the ABS Rules for Materials and Welding (Part 2)], are
to have longitudinal strength generally in accordance with the preceding paragraphs of this section, but the
value of the hull girder section modulus may be modified as permitted by the following paragraphs.
Applications of higher-strength material are to be continuous over the length of the vessel to locations
where the stress levels will be suitable for the adjacent mild steel structure. Higher strength steel is to be
extended to suitable locations below the strength deck and above the bottom, so that the stress levels will
be satisfactory for the remaining ordinary strength steel structure. The strength deck and bottom structure
are to be longitudinally framed. The longitudinal framing members are to be essentially of the same
material as the plating they support and are to be continuous throughout the required extent of higher
strength steel. Calculations showing that adequate strength has been provided against buckling are to be
submitted for review and care is to be exercised against the adoption of reduced thicknesses of materials
which may be subject to damage during normal operations.

7.3 Hull Girder Moment of Inertia (2012)

The hull-girder moment of inertia is to be not less than required by 3-2-1/3.5 using the mild steel section
modulus obtained from 3-2-1/3.3.4.

7.5 Hull Girder Section Modulus

When either the top or the bottom flange of the hull girder, or both, is constructed of higher-strength
material, the section modulus, as obtained from 3-2-1/3.1 or 3-2-1/3.3.4, may be reduced by the factor Q.
SMhts = Q(SM)
where
Q = 0.78 for Grade H32
Q = 0.72 for Grade H36
H32, H36 are as specified in Section 2-1-3 of the ABS Rules for Materials and Welding (Part 2).
Q factor for steels having other yield point or yield strength will be specially considered.

36 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 1 Longitudinal Strength 3-2-1

9 Loading Guidance (1 July 1998)

9.1 Loading Manual and Loading Instrument (2009)

All vessels that are contracted for construction on or after July 1998 are to be provided with a loading
manual. Loading instruments are not required by these Rules. However, when fitted, a loading instrument
is to be in accordance with Appendix 3-2-A1.

9.3 Allowable Stresses

9.3.1 At Sea
See 3-2-1/3.3.4 for bending stress and 3-2-1/3.3.5 for shear stress for vessels with ordinary strength
steel material. For higher strength steel, the allowable stress may be increased by a factor of 1/Q
where Q is as defined in 3-2-1/7.5.
9.3.2 In Port
The allowable in-port stress is 13.13 kN/cm2 (1.34 tf/cm2, 8.5 Ltf/in2) for bending and 10 kN/cm2
(1.025 tf/cm2, 6.5 Ltf/in2) for shear. For higher strength steel, the allowable stress may be
increased by a factor of 1/Q where Q is as defined in 3-2-1/7.5.

11 Section Modulus Calculation

11.1 Items Included in the Calculation

In general, the following items may be included in the calculation of the section modulus, provided they
are continuous or effectively developed within midship, 0.4L, and gradually tapered beyond the midship,
0.4L. Where the scantlings are based on the still-water bending moment envelope curves, items included in
the hull girder section modulus amidships are to be extended as necessary to meet the hull girder section
modulus required at the location being considered.
• Deck plating (strength deck and other effective decks)
• Shell and inner bottom plating
• Deck and bottom girders
• Plating and longitudinal stiffeners of longitudinal bulkheads
• All longitudinals of deck, sides, bottom and inner bottom
• Continuous longitudinal hatch coamings. See 3-2-1/13.

11.3 Effective Areas Included in the Calculation

In general, the net sectional areas of longitudinal strength members are to be used in the hull girder section
modulus calculations, except that small isolated openings need not be deducted, provided the openings and
the shadow area breadths of the other openings in any one transverse section do not reduce the section
modulus by more than 3%. The breadth or depth of such openings is not to be greater than 1200 mm (47 in.)
or 25% of the breadth or depth of the member in which it is located, whichever is less, with a maximum of
75 mm (3 in.) for scallops. The length of small isolated openings not required to be deducted is generally
not to be greater than 2500 mm (100 in.) The shadow area of an opening is the area forward and aft of the
opening enclosed by the lines tangential to the corners of the opening intersecting each other to form an
included angle of 30 degrees.

11.5 Section Modulus to the Deck or Bottom

The section modulus to the deck or bottom is obtained by dividing the moment of inertia by the distance
from the neutral axis to the molded deck at side amidships or baseline, respectively.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 37
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 1 Longitudinal Strength 3-2-1

11.7 Section Modulus to the Top of Hatch Coamings

For continuous longitudinal hatch coamings, in accordance with 3-2-1/13, the section modulus to the top of
the coaming is to be obtained by dividing the moment of inertia by the distance from the neutral axis to the
deck at side plus the coaming height. This distance need not exceed yt, as given by the following equation,
provided yt is not less than the distance to the molded deck line at side.
yt = y (0.9 + 0.2x/B) m (ft)
where
y = distance, in m (ft), from the neutral axis to the top of the continuous coaming
x = distance, in m (ft), from the top of the continuous coaming to the centerline of the
vessel
B = breadth of the vessel, as defined in 3-1-1/5, in m (ft). x and y are to be measured to
the point giving the largest value of yt
Section modulus to the top of longitudinal hatch coamings between multi-hatchways will be subject to
special consideration.

13 Continuous Longitudinal Hatch Coamings and Above-Deck Girders

Where strength deck longitudinal coamings of length greater than 0.14L are effectively supported by
longitudinal bulkheads or deep girders, the coamings are to be longitudinally stiffened, in accordance with
3-2-12/7.7. The section modulus amidships to the top of the coaming is to be as required by 3-2-1/3.1,
3-2-1/3.3, and 3-2-1/11.7, but the section modulus to the deck at side, excluding the coaming, need not be
determined in way of such coaming.
Continuous longitudinal girders on top of the strength deck are to be similarly considered. Their scantlings
are also to be in accordance with Section 3-2-6.

38 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Appendix 1: Loading Manuals and Loading Instruments

3
CHAPTER 2 Hull Structures and Arrangements

APPENDIX 1 Loading Manuals and Loading Instruments

(1 July 1998)
Note: These requirements are intended to satisfy Regulation 10(1) of the International Convention on Load Lines, 1966.

1 General

1.1 Application
The requirements in Appendix 3-2-A1 apply to all classed vessels 65 m (213 ft) and above in length (Lf)
that are contracted for construction on or after 1 July 1998.

3 Definitions

3.1 Loading Guidance

Loading guidance is a generic term covering both loading manual and loading instrument as defined below.
3.1.1 Loading Manual
A loading manual is a document with sufficient information to enable the master of the vessel to
arrange for the loading and ballasting of the vessel in such a way as to avoid the creation of any
unacceptable stresses in the vessel’s structure.
3.1.2 Loading Instrument
A loading instrument is an instrument by means of which it can be easily and quickly ascertained
that the still water bending moments, shear forces and, where applicable, the still water torsional
moments and lateral loads at the specified points along the length of the vessel will not exceed the
specified values in any loaded or ballast condition.

3.3 Category I Vessels

Category I vessels are any one of the following vessels.
3.3.1
Vessels with large deck openings where combined stresses due to vertical and horizontal hull
girder bending and torsional and lateral loads need to be considered.
3.3.2
Vessels designed for non-homogeneous loading where the cargo and/or ballast may be unevenly
distributed, except those belonging to 3-2-A1/3.5.3.
3.3.3
Chemical carriers and gas carriers.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 39
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Appendix 1 Loading Manuals and Loading Instruments 3-2-A1

3.5 Category II Vessels

Category II vessels are any one of the following vessels.
3.5.1
Vessels with such arrangement as will result in small possibilities for variation in the distribution
of cargo and ballast.
3.5.2
Vessels on regular and fixed trading pattern where the loading manual gives sufficient guidance.
3.5.3
Vessels of which the design takes into account the uneven distribution of cargo or ballast.

5 Required Loading Guidance (2003)

5.1 Loading Manual

All vessels are to be provided with a loading manual reviewed and stamped by ABS, in accordance with
3-2-A1/7, with the exception that a loading manual is not required for Category II vessels where the
deadweight does not exceed 30% of the displacement at the summer load line.

5.3 Modifications
Where the modifications to the vessel or to the loading/trading pattern result in changes to the input
information, a revised or new loading manual is to be submitted and a stamped copy to be placed aboard to
replace the existing manual. The loading instrument is to be re-verified in accordance with 3-2-A1/9.3 or
newly installed and verified in such cases.
Where the changes due to modification of the vessel are such that the still water bending moments and
shear forces corresponding to the new loading conditions are within ±2% of the existing allowable values,
the existing allowable values need not be modified.

7 Loading Manual

7.1 Required Information (2017)

The loading manual is to be based on the final data of the vessel and is to include at least the following
information:
i) The loading conditions based on which the design of the vessel is approved.
ii) The results of the calculations of still water bending moments, shear forces.
iii) Permissible limits of still water bending moment and shear force and, where applicable, limitations
due to torsional and lateral loads.
iv) Maximum allowable tank top loading.
v) If cargoes other than bulk cargoes are contemplated, such cargoes are to be listed together with
any specific instructions for loading.
vi) Maximum allowable load on deck and hatch covers. If the vessel is not approved to carry load on
deck or hatch covers, that fact is to be clearly stated in the loading manual.
vii) Information on the heavy ballast draft forward used for the fore-end strengthening required in
3-2-4/7.

7.3 Loading Conditions

The above information is to be based on the intended service conditions. See 3-2-A1/Table 1 for the
selection of loading conditions.

40 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Appendix 1 Loading Manuals and Loading Instruments 3-2-A1

7.5 Language
The loading manual is to be prepared in, or include, a language understood by the user. English may be
considered as a language understood by the user.

9 Loading Instrument

9.1 Type
A loading instrument is to be digital. Single point loading instrument is not acceptable.

9.3 Required Verifications

Before a loading instrument is accepted for the vessel, all relevant aspects of the instrument, including but
not limited to the following, are to be demonstrated to the Surveyor for the Surveyor’s personal verification:
i) That the instrument is type approved, where applicable
ii) That the instrument is based on the final data of the vessel
iii) That the number and position of read-out points are satisfactory
iv) That the relevant limits for all read-out points are satisfactory
v) That the operation of the instrument after installation onboard, in accordance with the approved
test conditions has been satisfactory
vi) That approved test conditions are available onboard
vii) That an operational manual, which does not require approval, is available onboard for the instrument

9.5 Language
The operation manual and the instrument output are to be prepared in, or include, a language understood
by the user. English may be considered to be a language understood by the user.

11 Annual Surveys
The requirements in 7-3-2/1.1.5 of the Rules for Survey After Construction (Part 7) are to be complied
with as follows: At each Annual Survey, loading manual is to be verified onboard and, where applicable,
loading instrument is to be verified in working order. The operation manual for loading instrument is also
to be verified onboard.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 41
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Appendix 1 Loading Manuals and Loading Instruments 3-2-A1

TABLE 1
Loading Conditions in the Loading Manual
1. The loading manual is to include at least
1.1 full load conditions, subdivided into departure and arrival conditions,
1.2 ballast conditions, subdivided into departure and arrival conditions (see also 1.5)
1.3 critical loading conditions on which the design of the vessel is based.
1.4 in-port conditions (see also 1.5.3)
1.5 Intermediate conditions, including but not limited to
1.5.1 before and after any ballasting/deballasting during the voyage.
1.5.2 ballast exchange and its sequence, where intended,
1.5.3 during loading/unloading (for vessels in 2.1, 2.2 and, where applicable, 2.5)
2. The following conditions are to be considered for the particular type of vessel. The list does not preclude any loading
conditions that are necessary for the particular service intended:
2.1 Oil Carriers:
2.1.1 homogeneous cargo if consistent with the service of the vessel
2.1.2 cargoes of typical densities within the expected range
2.1.3 part loaded conditions
2.1.4 short voyages (e.g., half bunker)
2.1.5 tank cleaning conditions
2.1.6 docking conditions afloat
2.2 Bulk Carriers, Ore Carriers, Container Carriers, Dry Cargo Vessels, Other Specialized Carriers:
2.2.1 homogeneous cargo if consistent with the service of the vessel
2.2.2 cargoes of typical densities within the expected range
2.2.3 heavy cargo with empty holds or non-homogeneous conditions
2.2.4 short voyages (e.g., half bunker)
2.2.5 deck cargoes
2.2.6 docking conditions afloat
2.3 Liquefied Gas Carriers:
2.3.1 homogeneous loading for all approved cargoes
2.3.2 with empty or partially filled tank(s)
2.3.3 docking conditions afloat
2.4 Chemical Carriers:
2.4.1 conditions for oil carriers
2.4.2 all approved high density cargoes
2.5 Combination Carriers
2.5.1 conditions as specified in 2.1 and 2.2 above.

42 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Section 2: Shell Plating

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 2 Shell Plating

1 General
Shell plating is to be of not less thickness than is required by the equations for thickness of side and bottom
plating as required by this section, nor less than required by Section 3-2-1 for longitudinal strength and
Section 3-2-8 for deep tank plating with h not less than the vertical distance to the freeboard deck at side.

3 Bottom Shell Plating

3.1 Extent of Bottom Plating

The term “bottom plating” refers to the plating from the keel to the upper turn of the bilge or upper chine.

3.3 Bottom Shell Plating

The thickness of the bottom shell plating throughout is not to be less than that obtained from the following
equations:
3.3.1
s h
t= + 2.5 mm
254

s h
t= + 0.10 in.
460
where
t = thickness of bottom shell plating, in mm (in.)
s = frame spacing, in mm (in.)
h = depth, D, in m (ft), as defined in 3-1-1/7.1, but not less than 0.1L or 1.18d,
whichever is greater
d = draft for scantlings, as defined in 3-1-1/9, or 0.066L, whichever is greater
L = length of vessel, in m (ft), as defined in 3-1-1/3
3.3.2
s SM R 1
t= ⋅ mm (in.)
R SM A Q

where
t and s are as defined above.
R = 45 with transverse framing
= 55 with longitudinal framing

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 43
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 2 Shell Plating 3-2-2

SMR = hull girder section modulus required by 3-2-1/3, in cm2-m (in2-ft)

SMA = bottom hull girder section modulus, in cm2-m (in2-ft)

Q = as defined in 3-2-1/7.5

3.5 Bottom Forward

For vessels of 61 m (200 ft) in length and above, where the heavy weather ballast draft or operating draft
forward is less than 0.04L, the plating on the flat of bottom forward, forward of the location given in
3-2-4/Table 1 is to be not less than required by the following equation:

t = 0.0046s (0.005L2 − 1.3d 2f ) / d f mm

t = 0.0026s (0.005L2 − 1.3d 2f ) / d f in.

where
s = frame spacing, in mm (in.)
L = length of vessel, as defined in 3-1-1/3
df = heavy weather ballast draft at the forward perpendicular, in m (ft)

5 Side Shell Plating

5.1 General (1998)

The side shell plating is not to be less in thickness than that obtained from the following equation:

s h
t= + 2.5 mm
268

s h
t= + 0.10 in.
485
where
t = thickness, in mm (in.)
s = spacing of transverse frames or longitudinals, in mm (in.)
h = depth, in m (ft), as defined in 3-1-1/7, but not less than 0.1L or 1.18d, whichever is
greater
d = draft for scantlings, as defined in 3-1-1/9, or 0.066L, whichever is greater
L = length of the vessel, as defined in 3-1-1/3
t is not to be taken less than 8.5 mm (0.33 in.) for offshore support vessels.
The side shell plating in way of hold frames of dry cargo vessels with typical bulk carrier configuration
(sloping upper and lower wing tanks with a transversely framed side shell in way of the hold) is also not to
be less than that obtained from the following equation:

t= L mm

t = 0.0218 L in.
with L as defined above.

44 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 2 Shell Plating 3-2-2

5.3 Side Shell for Vessels Subject to Impact Loadings (2014)

For vessels subject to impact loadings during routine operations, the side shell is to be 25% greater in thickness
than that obtained from the equation in 3-2-2/5.1.

5.5 Side Shell Plating at Ends

The minimum side shell plating thickness, t, at ends is to be obtained from the following equations and is
not to extend for more than 0.1L from the ends. Between the midship 0.4L and the end 0.1L, the thickness
of the plating may be gradually tapered.
t = 0.0455L + 0.009s mm
t = 0.000545L + 0.009s in.
where
s = frame spacing, in mm (in.)
L = length of vessel, as defined in 3-1-1/3, in m (ft)
Where the strength deck at the ends is above the freeboard deck, the thickness of the side plating above the
freeboard deck may be reduced to the thickness given for forecastle and poop sides at the forward and after
ends, respectively.

5.7 Forecastle and Poop Side Plating

5.7.1 Forecastle Side Plating
The thickness, t, of the plating is to be not less than that obtained from the following equation:
t = 0.038(L + 30.8) + 0.006s mm
t = 0.00045(L + 103.3) + 0.006s in.
5.7.2 Poop Side Plating
The thickness, t, of the plating is to be not less than that obtained from the following equation:
t = 0.0296(L + 39.5) + 0.006s mm
t = 0.00035(L + 132.9) + 0.006s in.
where
s = spacing of frames, in mm (in.)
L = length of vessel, as defined in 3-1-1/3, in m (ft)

7 Bow and Stern Thruster Tunnels

The thickness of the tunnel plating is to be not less than that required by 3-2-2/5.5, nor is the thickness to
be less than that obtained from the following equation:
t = 0.008d + 3.3 mm
t = 0.008d + 0.13 in.
where
d = inside diameter of the tunnel, in mm (in.), but is to be taken as not less than 968 mm
(38 in.)
Where the outboard ends of the tunnel are provided with bars or grids, the bars or grids are to be effectively
secured.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 45
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 2 Shell Plating 3-2-2

9 Local Strengthening for Research Vessels

In vessels used for research, wear plates or rollers are recommended at all places where research methods
or gear will subject the shell plating to accelerated wear. Special strengthening may be required in areas
where small boats are regularly launched, retrieved or stowed. Special strengthening may also be required
in areas where the vessel makes contact with another vessel when pursing, hauling, brailing, pumping, loading,
unloading or running together.

11 Compensation
Compensation is to be provided for openings in the shell plating where required to maintain the longitudinal
and transverse strength of the hull. All openings are to have well-rounded corners. Those in the upper side
shell are to be located a suitable distance below the deck edge. Cargo and gangway openings are to be kept
well clear of other discontinuities in the hull girder. Local provision is to be made to maintain the longitudinal
and transverse strength of the hull.
Thick plating or doublers of sufficient breadth to prevent damage from the flukes of stockless anchors are
to be fitted around the hawse pipes.

13 Breaks
Breaks in vessels having partial superstructures are to be specially strengthened to limit the local increases
in stresses at these points. The stringer plates and sheer strakes at the lower level are to be increased in
thickness well beyond the break in both directions. The thickness is to be increased 25% in way of breaks
of superstructures. The side plating of the superstructure is to be increased in thickness and the side plating
is to extend well beyond the end of the superstructure in such fashion as to provide a long gradual taper.
Where the breaks of the forecastle or poop are appreciably beyond the midship 0.5L, these requirements
may be modified. Gangways, large freeing ports, side shell doors, and other openings in the shell or
bulwarks are to be kept well clear of the breaks, and any holes which must unavoidably be cut in the plating
are to be kept as small as possible and are to be circular or oval in form.

15 Bilge Keels
Bilge keels, where fitted, are to be attached to the shell by a doubler. In general, both the bilge keel and the
doubler are to be continuous. The connection of the bilge keel to the doubler, and the doubler to the shell,
are to be by double continuous fillet welds.
Butt welds in the bilge keel and doubler are to be full penetration and are to be kept clear of master erection
butts. In general, shell butts are to be flush in way of the doubler. Doubler butts are to be flush in way of
the bilge keel. In general, scallops and cutouts are not to be used. Where desired, a crack-arresting hole at
least 25 mm (1 in.) in diameter may be drilled in the bilge keel butt weld as close as practicable to the doubler.
The ends of the bilge keel are to be suitably tapered and are to terminate on an internal stiffening member.
The material tensile properties of bilge keels and doublers are to be as required for bottom shell plating.

16 Bilge Plating (2016)

For longitudinally stiffened bilge plate, the plate thickness is not to be less than required in 3-2-2/3 and 3-2-2/5,
adjusted for spacing of the bilge longitudinals or frames and the material factors. Where girth spacing of
bilge longitudinals is greater than that of the adjacent bottom plating, the spacing may be modified by the
following equation in calculations of minimum required thickness:
s = kr1 sg mm (in.) but not to be taken less than the spacing of the longitudinals of the
adjacent bottom plating
where
sg = girth spacing of bilge longitudinals, in mm (in.)

46 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 2 Shell Plating 3-2-2

kr1 = (1 – 0.5sg/R)2 but not less than 0.55

R = radius of bilge, in mm (in.)
Bilge keels are not to be considered as longitudinal stiffening members unless they are continuous and
effectively developed.
In no case is the thickness of the bilge plate to be less than that of the adjacent bottom plating.

17 Higher-strength Materials

17.1 General
In general, applications of higher-strength materials are to take into consideration the suitable extension of
the higher-strength material above and below the bottom and deck, respectively, as required by 3-2-1/7.1.
Care is to be taken against the adoption of reduced thickness of material that might be subject to damage
during normal operation. The thickness of bottom and side-shell plating, where constructed of higher-
strength materials, are to be not less than required for purposes of longitudinal hull girder strength; nor are
they to be less than required by the foregoing paragraphs of this section when modified as indicated by the
following paragraphs.

17.3 Bottom Plating of Higher-strength Material

Bottom shell plating, where constructed of higher-strength material and where longitudinally framed, is to
be not less in thickness than that obtained from the following equation:

thts = (tms – C) Q + C

where
thts = thickness of higher-strength material, in mm (in.)
tms = thickness, in mm (in.), of ordinary-strength steel, as required by preceding paragraphs
of this section, or from the requirements of other sections of the Rules, appropriate to
the vessel type.
C = 4.3 mm (0.17 in.)
Q = as defined in 3-2-1/7.5

17.5 Side Plating of Higher-strength Material

Side-shell plating, where constructed of higher-strength material, is to be not less in thickness than that
obtained from the following equation:

thts = [tms – C][(Q + 2 Q )/3] + C

where thts, tms, C and Q are as defined in 3-2-2/17.3 for bottom plating.

17.7 End Plating

End-plating thickness, including plating on the flat of bottom forward, where constructed of higher-strength
materials, will be subject to special consideration.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 47
PART Section 3: Deck Plating

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 3 Deck Plating

1 General
The thickness of the deck plating is not to be less than that required to obtain the hull-girder section
modulus given in Section 3-2-1, nor less than required by this section.

3 Deck Plating
The thickness of plating on each deck is to be not less than the greater of those obtained from the following
equations. The required thickness is not to be less than 5.0 mm (0.20 in.), except for platform decks in
enclosed passenger spaces where the thickness is not to be less than 4.5 mm (0.18 in.). Thickness of strength
deck inside line of openings may be reduced by 1.0 mm (0.04 in.) from t obtained by 3-2-3/3.3 below.

3.1 All Decks

s h
t= + 2.5 mm
254

s h
t= + 0.10 in.
460
where
t = thickness, in mm (in.)
s = beam or longitudinal spacing, in mm (in.)
h = height, in m (ft), as follows:
= for a deck or portion of deck forming a tank top, the greater of the following
distances:
• two-thirds of the distance from the tank top to the top of the overflow, or
• two-thirds of the distance from the tank top to the bulkhead deck or freeboard deck.
= for a lower deck on which cargo or stores are carried, the tween-deck height at side;
where the cargo weights are greater than normal [7010 N/m3 (715 kgf/m3, 45 lbf/ft3)],
h is to be suitably adjusted.
= for an exposed deck on which cargo is carried, 3.66 m (12 ft). Where it is intended to
carry deck cargoes in excess of 25850 N/m2 (2636 kgf/m2, 540 lbf/ft2), this head is to
be increased in proportion to the added loads which will be imposed on the structure
Elsewhere, the value of h is to be not less than that obtained from the appropriate equation below, where L
is the length of vessel in m (ft), as defined in 3-1-1/3.

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 3 Deck Plating 3-2-3

3.1.1 Exposed Freeboard Deck Having No Deck Below

h = 0.028L + 1.08 m
h = 0.028L + 3.57 ft
3.1.2 Exposed Freeboard Deck Having a Deck Below, Forecastle Deck, Superstructure Deck
Forward of Amidships 0.5L
h = 0.028L + 0.66 m
h = 0.028L + 2.14 ft
3.1.3 Freeboard Deck within Superstructure, Any Deck Below Freeboard Deck, Superstructure
Deck Between 0.25L Forward of and 0.20L Aft of Amidships
h = 0.014L + 0.87 m
h = 0.014L + 2.86 ft
3.1.4 All Other Locations
h = 0.014L + 0.43 m
h = 0.014L + 1.43 ft

3.3 Strength Decks within the Midship 0.8L (2002)

For vessels of length equal to or greater than 61 meters, the strength deck plating within the midship 0.8L
shall meet the following requirement:
t = 0.009s + 2.4 mm
t = 0.009s + 0.095 in.
where
s = beam or longitudinal spacing, in mm (in.)

3.5 All Strength Deck Plating Outside the Line of Openings and Other Effective Deck
Plating (2002)
For vessels of length equal to or greater than 61 meters, the strength deck plating within the midship 0.8L
shall meet the following requirement:

s SM R 1
t= ⋅ mm (in.)
R SM A Q

where
t = thickness, in mm (in.)
s = beam or longitudinal spacing, in mm (in.), not to be taken less than 610 mm (24 in.)
R = 60 for longitudinal framing, 45 for transverse framing
SMR = hull girder section modulus required in 3-2-1/3, in cm2-m (in2-ft)
SMA = hull girder section modulus, in cm2-m (in2-ft), measured to the deck in question
Q = material factor for the material used in determining SMR, as defined in 3-2-1/7.5

5 Compensation
Compensation is to be provided for openings in the strength deck and other effective decks to maintain the
longitudinal and transverse strength. Openings in the strength deck are to have a minimum corner radius of
0.125 times the width of the opening, but need not exceed a radius of 600 mm (24 in.). In other decks, the
radius is to be 0.09375 times the width of the opening, but need not exceed radius of 450 mm (18 in.).
Openings are to be a suitable distance from the deck edge, from cargo hatch covers, from superstructure
breaks and from other areas of structural discontinuity.

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 3 Deck Plating 3-2-3

7 Wheel Loading (2014)

Where provision is to be made for the operation or stowage of vehicles having rubber tires, and after all
other requirements are met, the thickness of deck plating is to be not less than that obtained from the following
equation:

t = kKn CW mm (in.)
where
k = 8.05 (25.2, 1)
K = [21.99 + 0.316(a/s)2 – 5.328(a/s) + 2.6(a/s)(b/s) – 0.895(b/s)2 – 7.624(b/s)]10-2,
derived from the curves indicated in 3-2-3/Figure 1
n = 1.0 where l/s > 2.0 and 0.85 where l/s = 1.0. For intermediate values of l/s, n is to be
obtained by interpolation
C = 1.5 for wheel loads of vehicles stowed at sea and 1.1 for vehicles operating in port
W = static wheel load, in kN (tf, Ltf)
a = wheel imprint dimension, in mm (in.), parallel to the longer edge, l, of the plate panel
b = wheel imprint dimension, in mm (in.), perpendicular to the longer edge, l, of the plate
panel
s = spacing of deck beams or deck longitudinals, in mm (in.)
l = length of the plate panel, in mm (in.)
For wheel loading, the strength deck plating thickness is to be not less than 110% of that required by the
above equation, and platform deck plating thickness is to be not less than 90% of that required by the
above equation.
Where the wheels are close together, special consideration will be given to the use of the combined imprint
and load. Where the intended operation is such that only the larger dimension of the wheel imprint is
perpendicular to the longer edge of the plate panel, b above may be taken as the larger wheel imprint
dimension, in which case, a is to be the lesser one.

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 3 Deck Plating 3-2-3

FIGURE 1
Wheel Loading Curves of K

9 Higher-strength Material

9.1 Thickness
In general, applications of higher strength materials are to take into consideration the suitable extension of
the higher strength material below the deck, forward and aft. Care is to be taken to avoid the adoption of
reduced thickness of material such as might be subject to damage during normal operation. The thickness
of deck plating for longitudinally framed decks, where constructed of higher-strength material, is to be not
less than required for longitudinal strength, nor is it to be less than that obtained from the following equation:

thts = (tms – C) Q + C

where
thts = thickness of higher-strength material, in mm (in.)
tms = thickness of ordinary-strength steel, in mm (in.), as required 3-2-3/3.1 and 3-2-3/3.3
C = 4.3 mm (0.17 in.)
Q = is as defined in 3-2-1/7.5
Where the deck plating is transversely framed, or where the Rules do not provide a specific thickness for
the deck plating, the thickness of the higher-strength material will be specially considered, taking into
consideration the size of the vessel, intended service and the foregoing Rule requirements.

9.3 Wheel Loading

Where deck or flats are constructed of higher strength material and provision is made for the operation or
stowage of vehicles having rubber tires, the thickness of plating is to be not less than that obtained from the
following equation:

thts = tms ( M / Y ) mm (in.)

where
thts = thickness of higher-strength material, in mm (in.)

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Part 3 Hull Construction and Equipment
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Section 3 Deck Plating 3-2-3

tms = thickness of ordinary-strength steel, as obtained from 3-2-3/7

Y = as defined in 3-2-7/5.1
M = 235 (24, 34000)

52 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Section 4: Bottom Structure

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 4 Bottom Structure

1 Double Bottoms

1.1 General
Inner bottoms are to be fitted fore and aft between the peaks or as near thereto as practicable in vessels of
ordinary design of 500 GT or over. Where, for special reasons, it may be desired to omit the inner bottom,
the arrangements are to be clearly indicated on the plans when first submitted for approval. A double
bottom need not be fitted in way of deep tanks, provided the safety of the vessel in the event of bottom
damage is not thereby impaired. It is recommended that the inner bottom be arranged to protect the bilges
as much as possible and that it be extended to the sides of the vessel.
Shell longitudinals and frames in way of deep tanks are to have not less strength than is required for stiffeners
on deep tank bulkheads.

1.3 Center Girder

(2017) A center girder is to be fitted extending as far forward and aft as practicable. The plates are to be
continuous within the midship three-quarters length; elsewhere, they may be intercostal between floors.
Manholes may be cut in every frame space outside the midships three-quarters length; they may be cut in
alternate frames spaces within the midships three-quarters length. For vessels which have a length more
than 61 m (200 ft) and the length of the cargo hold is greater than 1.2B, the thickness and depth of center
girder plates are to be specially considered based on the results of a direct structural calculation.
1.3.1 Thickness Amidships
The thickness of the center girder within the midship one-half length is not to be less than that
obtained from the following equation.
t = 0.056L + 5.5 mm
t = 0.00067L + 0.22 in.
where
t = thickness, in mm (in.)
L = length of vessel, in m (ft), as defined 3-1-1/3
1.3.2 Thickness at Ends
The thickness of the center girder forward and aft of the midship one-half length may be reduced
to 85% of the girder thickness amidships.

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Chapter 2 Hull Structures and Arrangements
Section 4 Bottom Structure 3-2-4

1.3.3 Depth
The depth of the center girder is not to be less than that obtained from the following equation:
hg = 32B + 190 d mm
hg = 0.384B + 4.13 d in.
where
hg = depth, in mm (in.)
B = breadth of vessel, in m (ft), as defined in 3-1-1/5
d = draft for scantlings, in m (ft), as defined in 3-1-1/9

1.5 Side Girders

Where the distance between the center girder and the side shell exceeds 4.57 m (15 ft), intercostal side
girders are to be fitted approximately midway between the center girder and the side shell. The minimum
thickness of the intercostal side girders is not to be less than obtained from the following equation.
t = 0.036L + c mm
t = 0.00043L + c in.
where
t = thickness, in mm (in.)
L = length of vessel, in m (ft), as defined in 3-1-1/3
c = 4.7 mm (0.18 in.)

1.7 Floors (2016)

Solid floors are to be fitted at every frame (600 mm to 800 mm) under machinery, under the outer ends of
bulkhead stiffener brackets, under transverse bulkheads and at the forward end (see 3-2-4/7.5 or 3-2-4/7.7,
as applicable). Elsewhere, the solid floors are to have a maximum spacing of 3.66 m (12 ft) in association
with intermediate open floors or longitudinal framing. The thickness of solid floors is to be equal to the
thickness of side girders obtained in 3-2-4/1.5, except that for widely spaced floors in association with
longitudinal framing, c is to be taken as 6.2 mm (0.24 in.).

1.9 Frames
In transversely framed vessels, open floors consisting of frames and reverse frames are to be fitted at all
frames where solid floors are not fitted. Center and side brackets are to overlap the frames and reverse
frames for a distance equal to 0.05B. They are to be of the thickness required for side girders in the same
location and are to be flanged on their outer edges. Alternatively, longitudinal framing is to be fitted in
association with widely spaced floors. The section modulus, SM, of each frame, reverse frame or bottom,
or inner bottom longitudinal in association with the plating to which it is attached is not to be less than that
obtained from the following equation.
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
s = frame spacing, in m (ft)
l = unsupported span between supporting members, in m (ft). Where brackets are fitted
in accordance with 3-1-2/5.5 and are supported by bulkheads, inner bottom, or side
shell, the length, l, may be measured as permitted therein.
h = vertical distance, in m (ft), from the middle of l to the deck at side. In way of a deep
tank, h is the greatest distance from the middle of l to a point located at two-thirds of
the distance from the top of the tank to the top of the overflow; a point located above
the top of the tank not less than 0.01L + 0.15 m or 0.46 m (0.01L + 0.5 ft or 1.5 ft),
whichever is greatest.

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Section 4 Bottom Structure 3-2-4

c for transverse frames and reverse frames:

= 0.8 clear of tanks
= 1.0 in way of tanks
= 0.5 with struts
c for longitudinal frames:
= 1.0 without struts
= 0.55 with struts
c for inner bottom longitudinals:
= 0.85 without struts
= 0.45 with struts
Frames and reverse frames in way of tanks are not to be less than that required clear of tanks if that be greater.

1.11 Struts (2015)

Struts fitted on open floor bottom structures are to comply with the following:
i) Struts are not to be of hollow sections in way of tanks;
ii) Struts are to be located at the mid-point of the spans of the bottom/inner bottom stiffeners, where
fitted;
iii) Struts, in general, are not to be fitted in way where cargo is discharged by grabs, or heavy liquid
cargoes are carried, or in the bottom forward slamming area;
The permissible load, Wa, for struts is to be determined in accordance with 3-2-6/5.3. The calculated load,
W, is to be determined by:
W = nphs kN (tf, Ltf)
where
n = 10.5 (1.07, 0.03)
p = sum of the half lengths, in m (ft), on each side of the strut, of the frames supported
h = as defined in 3-2-4/1.9
s = frame spacing, in m (ft)
Struts are to be positioned so as to divide the span into approximately equal intervals.

1.13 Inner-bottom Plating

The thickness of the inner-bottom plating throughout the length of the vessel is to be not less than that
obtained from the following equation. Where applicable, the plating is to meet deep tank requirements.
t = 0.037L + 0.009s + c mm
t = 0.000445L + 0.009s + c in.
where
t = thickness, in mm (in.)
L = length of vessel, in m (ft), as defined in 3-1-1/3
s = frame spacing, in mm (in.)
c = 1.5 mm (0.06 in.) in engine space
= −0.5 mm (−0.02 in.) elsewhere

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Section 4 Bottom Structure 3-2-4

Where no ceiling is fitted under cargo hatchways, except for vessels intended for the exclusive carriage of
containers on the inner bottom, the thickness of the inner-bottom plating is to be increased 2.0 mm
(0.08 in.). For vessels with longitudinally-framed inner bottoms, the minimum thickness of inner-bottom
plating may be reduced by 1 mm (0.04 in.).
For vessels regularly engaged in trades where the cargo is handled by grabs or similar mechanical appliances,
it is recommended that flush inner-bottom plating be adopted throughout the cargo space, and that the plating
be suitably increased, but the increase need not exceed 5 mm (0.20 in.). It is also recommended that the
minimum thickness be not less than 12.5 mm with 610 mm (0.50 in. with 24 in.) frame spacing and 19 mm
with 915 mm (0.74 in. with 36 in.) frame spacing. Intermediate thicknesses may be obtained by interpolation.
Where provision is to be made for the operation or stowage of vehicles having rubber tires, and after all
other requirements are met, the thickness of the inner bottom plating is to be not less than that obtained
from 3-2-3/7.
Margin plates which are approximately horizontal are to have thicknesses not less than the adjacent inner
bottom plating. Where they are nearly vertical, they are to be not less than the required inner bottom
plating in the engine space and are to extend the full depth of the inner bottom.

1.15 Sea Chests

Where the double bottom structure forms part of a sea chest, the thickness of the plating is to be not less
than the required thickness of the shell plating, using the approximate value of stiffener spacing, s.

1.17 Access, Lightening, Air, and Drainage Holes

Access holes in double bottom tank tops and lightening holes in nontight members are to be sufficient in
size and number to assure accessibility to all parts of the double bottom. The proposed locations and sizes
of the holes are to be indicated on the drawings submitted for approval. Tank top access hole covers are to
be of steel or equivalent material, and where no ceiling is fitted in a cargo hold, the covers are to be protected
against damage by the cargo. Air and drainage holes are to be cut in all nontight parts of the double bottom
structure to assure the free escape of gases to the vents and the free drainage of liquids to the suctions.

3 Single Bottoms with Floors and Keelsons

3.1 General
Where double bottom construction is not required by 3-2-4/1.1 or is not applied, single bottom construction is
to be in accordance with 3-2-4/3 or 3-2-4/5, as may be applicable.

3.3 Center Keelsons

Single-bottom vessels are to have center keelsons formed of continuous or intercostal center girder plates
with horizontal top plates. The thickness of the keelson and the area of the horizontal top plate are to be not
less than that obtained from the following equations. Vessels less than 30.5 m (100 ft) in length will be
subject to special consideration. Tapering of the horizontal top plate area at the ends is not normally
considered for vessels less than 30.5 m (100 ft) in length. The keelsons are to extend as far forward and aft
as practicable.
3.3.1 Center-girder Plate Thickness Amidships
t = 0.063L + 5 mm
t = 0.00075L + 0.2 in.
3.3.2 Center-girder Plates Thickness at Ends
t = 85% of center keelson thickness amidships
3.3.3 Horizontal Top-plate Area Amidships
A = 0.168L3/2 – 8 cm2
A = 0.0044L3/2 – 1.25 in2

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 4 Bottom Structure 3-2-4

3.3.4 Horizontal Top-Plate Area at Ends [L ≥ 30.5 m (100 ft)]

A = 0.127L3/2 – 1 cm2
A = 0.0033L3/2 – 0.15 in2
where
t = thickness of center-girder plate, in mm (in.)
L = length of vessel, as defined in 3-1-1/3, in m (ft)
A = area of horizontal top plate, in cm2 (in2)

3.5 Side Keelsons

Side keelsons are to be arranged so that there are not more than 2.13 m (7 ft) from the center keelson to the
inner side keelson, from keelson to keelson and from the outer keelson to the lower turn of bilge. Forward
of the midship one-half length, the spacing of keelsons on the flat of floor is not to exceed 915 mm (36 in.).
Side keelsons are to be formed of continuous rider plates on top of the floors. They are to be connected to
the shell plating by intercostal plates. The intercostal plates are to be attached to the floor plates. In the engine
space, the intercostal plates are to be of not less thickness than the center girder plates. The scantlings of the
side keelsons are to be obtained from the following equations but need not exceed 3-2-4/3.3, if that be less.
3.5.1 Side Keelson and Intercostal Thickness Amidships
t = 0.063L + 4 mm
t = 0.00075L + 0.16 in.
3.5.2 Side Keelson and Intercostal Thickness at Ends
t = 85% of center thickness amidships
3.5.3 Side Keelson and Intercostal, Horizontal Top Plate Area Amidships
A = 0.038L3/2 + 17 cm2
A = 0.001L3/2 + 2.6 in2
3.5.4 Side Keelson and Intercostal, Horizontal Top Plate Area at Ends
A = 0.025L3/2 + 20 cm2
A = 0.00065L3/2 + 3.1 in2
t, L and A are as defined in 3-2-4/3.3.

3.7 Floors
3.7.1 Section Modulus
With transverse framing, a floor as shown in 3-2-4/Figure 1 is to be fitted on every frame and is to
be of the scantlings necessary to obtain a section modulus, SM, not less than that obtained from
the following equation:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 0.55
h = draft, d, in m (ft), as defined in section 3-1-1/9, but not to be less than 0.66D
or 0.066L, whichever is greater.
s = floor spacing, in m (ft)
l = span, in m (ft). Where brackets are fitted in accordance with 3-1-2/5.5 and
are supported by bulkheads, inner bottom or side shell, the length, l, may be
measured as permitted therein.

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Chapter 2 Hull Structures and Arrangements
Section 4 Bottom Structure 3-2-4

The section modulus may be calculated at the centerline of the vessel, provided the rise of floor is
such that the depth at the toe of brackets is not less than one-half of the depth at the centerline.
The above requirements are limited to cargo holds where cargoes of specific gravity 0.715 or less
are uniformly loaded. In way of engine room and in the forward 0.2L, the floor face bar area is to
be doubled.
3.7.2 Depth
The minimum depth of floors at centerline is not to be less than that obtained from the following
equation:
hf = 62.5l mm
hf = 0.75l in.
where
hf = floor depth, in mm (in.)
l = unsupported span of floors, in m (ft). Where brackets are fitted in accordance
with 3-1-2/5.5, the length, l, may be measured as permitted therein.
3.7.3 Thickness
The minimum thickness of floors is not to be less than that obtained from the following equation:
t = 0.01hf + 3 mm
t = 0.01hf + 0.12 in.
where
t = floor thickness, in mm (in.)
hf = floor depth, in mm (in.)
Floors under engine girders are to be not less in thickness than the thickness required for keelsons.

FIGURE 1
Plate Floors

l/2 for floors

side keelson
keelson

CL

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 4 Bottom Structure 3-2-4

5 Single Bottoms with Longitudinal or Transverse Frames

5.1 General
Where longitudinal frames supported by bottom transverses or transverse frames supported by longitudinal
girders and bottom transverses are proposed in lieu of keelsons referred to in 3-2-4/3, the construction is to
be in accordance with this subsection. Frames are not to have less strength than is required for watertight
bulkhead stiffeners or girders in the same location in association with head to the bulkhead deck. In way of
deep tanks, frames are not to have less strength than is required for stiffeners or girders on deep tank
bulkheads. See 3-2-4/Figure 2, 3-2-4/Figure 3 and 3-2-4/Figure 4.

FIGURE 2
Round Bottom Floors with Deadrise
deck at side

h for bottom
frames

CVK θ ≤ 150° θ ≤ 150°

d
1.5d

l /2

l for bottom frames

CL

FIGURE 3
Transverse Bottom Frames with Longitudinal Side Girders
deck at side

h for lb

θ ≤ 150°
h for la
la
plate floor lb h for bottom girder
l a/2
l b/2

θ ≤ 150°
s for bottom girder
CL

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Section 4 Bottom Structure 3-2-4

FIGURE 4
Longitudinal Frames with Transverse Webs
deck at side

h for bottom
longitudinals
h for bottom
transverse

l for bottom
transverse θ ≤ 150°

s for longitudinals
l/2
θ ≤ 150°
CL

5.3 Bottom Girders and Transverses

5.3.1 Section Modulus
The section modulus, SM, of each bottom girder and transverse, where intended as a primary
supporting member, in association with the plating to which it is attached, is not to be less than
that obtained from the following equation:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 0.915
h = vertical distance, in m (ft), from the center of area supported to the deck at
side
s = spacing, in m (ft)
l = unsupported span, in m (ft). Where brackets are fitted in accordance with
3-1-2/5.5 and are supported by bulkheads, inner bottom or side shell, the
length, l, may be measured as permitted therein.
Tripping brackets are to be fitted at intervals of about 3 m (10 ft) and stiffeners are to be fitted as
may be required.

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Section 4 Bottom Structure 3-2-4

5.3.2 Depth
The minimum depth of the girder or transverse is to be not less than 2.5 times the depth of the
cutouts for bottom frames, unless effective compensation for cutouts is provided, nor less than that
obtained from the following equation:
hw = 145l mm
hw = 1.75l in.
where
hw = girder or transverse depth, in mm (in.)
l is defined in 3-2-4/5.3.1.
5.3.3 Thickness
The minimum thickness of the web is to be not less than that obtained from the following equation:
t = 0.01hw + 3 mm
t = 0.01hw + 0.12 in.
where
t = floor thickness, in mm (in.)
hw is as given in 3-2-4/5.3.2.
5.3.4 Non-prismatic Members
Where the cross sectional properties of the member is not constant throughout the length of the
girders or transverses, the above requirements will be specially considered with particular attention
being paid to the shearing forces at the ends.

5.5 Center Girder

In general, a center girder is to be fitted, complying with 3-2-4/5.3; however, alternative arrangements that
provide suitable support for docking will be considered.

5.7 Frames
The section modulus, SM, of each bottom frame to the chine or upper turn of bilge, in association with the
plating to which it is attached, is not to be less than that obtained from the following equation:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 0.80 for transverse frames clear of tanks
= 1.00 for longitudinal frames clear of tanks, and in way of tanks
= 1.00 for transverse frames in way of tanks
s = frame spacing in, m (ft)
l = unsupported span, in m (ft), Where brackets are fitted in accordance with 3-1-2/5.5
and are supported by bulkheads, inner bottom or side shell, the length, l, may be
measured as permitted therein.
h = vertical distance, in m (ft), from the middle of l to the deck at side. In way of a deep
tank, h is the greatest of the distances, in m (ft), from the middle of l to a point located
at two-thirds of the distance from the top of the tank to the top of the overflow, a
point located above the top of the tank not less than 0.01L + 0.15 m (0.01L + 0.5 ft)
or 0.46 m (1.5 ft), whichever is greatest.
L is as defined in 3-1-1/3.

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Chapter 2 Hull Structures and Arrangements
Section 4 Bottom Structure 3-2-4

7 Fore-end Strengthening

7.1 General
For vessels 61 m (200 ft) in length and over, where the heavy weather ballast draft forward is less than 0.04L,
strengthening of the flat of bottom forward is to be in accordance with 3-2-4/7.3, 3-2-4/7.5, 3-2-4/7.7 and
3-2-2/3.5. Information on the heavy weather ballast draft forward used for the required fore-end strengthening
is to be furnished to the master for guidance. The heavy weather ballast draft is also to be indicated on the
shell expansion plan.

7.3 Extent of Strengthening

The flat of bottom forward is defined as being forward of the locations indicated in 3-2-4/Table 1. For
intermediate values of Cb, the locations are to be obtained by interpolation. Aft of these locations, a
suitable transition is to be provided between the increased scantlings and structural arrangements of the flat
of bottom forward and the structure aft of the locations given in 3-2-4/Table 1.

TABLE 1
Location of Flat of Bottom Forward
Cb is the block coefficient at the summer load waterline, based
on L, as defined in 3-1-1/3.
Cb Location Forward of Amidships
0.6 or less 0.25L
0.8 or more 0.30L

7.5 Longitudinal Framing

When longitudinal framing is used for the bottom and inner bottom, longitudinals and side girders are to be
continued as far forward as practicable at not more than their amidship spacing. The section modulus of
flat of bottom longitudinals forward of the location indicated in 3-2-4/Table 1 is to be not less than
required by the following equation, nor less than required by 3-2-4/5.7.
SM = 8.47(0.005L2 − 1.3df2)sl2/df cm3

SM = 0.0044(0.005L2 − 1.3df2)sl2/df in3

where
df = heavy weather ballast draft at the forward perpendicular, in m (ft)
L = length of vessel, as defined in 3-1-1/3
s = spacing of longitudinals, in m (ft)
l = distance between floors, in m (ft)
The spacing of floors forward of 0.25L forward of amidships is to be not greater than that given in
3-2-4/Table 2, nor greater than the spacing amidships.

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 4 Bottom Structure 3-2-4

TABLE 2
Spacing of Floors
df Cb From 0.25L to 0.3L from amidships Forward of 0.3L from amidships
0.60 or less 3s 2s
0.02L or less
> 0.60 3s 3s
0.035L all values 3s 3s
0.04L and more all values As required elsewhere in the Rules
Notes:
df is the heavy weather ballast draft at the forward perpendicular and Cb is the block coefficient at the summer load
waterline, based on L as defined in 3-1-1/3.
s is the spacing of the transverse side frames, or s = 2.08L + 438 (mm) [0.025L + 17.25 (in.)], where the side shell
is longitudinally framed.
For values of df between 0.02L, 0.035L and 0.04L m (ft), the required floor spacing may be obtained by interpolation.

7.7 Transverse Framing

Where the heavy weather ballast draft forward is less than 0.04L, solid floors are to be fitted on every
frame and additional full-depth and half-depth side girders are to be introduced so that the spacing of full-
depth girders forward of the locations in 3-2-4/Table 1 does not exceed 2.13 m (7 ft) and so that the spacing
of alternating half- and full-depth girders forward of the location in 3-2-4/Table 1 does not exceed 1.07 m
(3.5 ft). Where the heavy weather ballast draft forward is 0.04L or more, the arrangement of solid floors
and side girders may be in accordance with 3-2-4/1.7 and 3-2-4/1.5.

9 Higher-strength Materials

9.1 General
In general, applications of higher-strength materials for bottom structures are to meet the requirements of
this section, but may be modified as permitted by the following paragraphs. Care is to be exercised to
avoid the adoption of reduced thickness of material such as might be subject to damage during normal
operation, and calculations are to be submitted to show adequate provision against buckling. Longitudinal
framing members are to be of essentially the same material as the plating they support.

9.3 Inner-bottom Plating

Inner-bottom plating, where constructed of higher-strength material and where longitudinally framed, is to be
not less in thickness than required by 3-2-4/1.13 or for tank top plating as modified by the following equation:

thts = [tms – C][(Q + 2 Q )/3] + C

where
thts = thickness of higher-strength material, in mm (in.)
tms = thickness of mild steel, as required by 3-2-4/1.13, in mm (in.), increased where
required for no ceiling
C = 3 mm (0.12 in.) or 5 mm (0.20 in.) where the plating is required by 3-2-4/1.13 to be
increased for no ceiling
Q = as defined in 3-2-1/7.5
The thickness of inner-bottom plating, where transversely framed, will be specially considered.
Where cargo is handled by grabs, or similar mechanical appliances, the recommendations of 3-2-4/1.13 are
applicable to thts.

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 4 Bottom Structure 3-2-4

9.5 Bottom and Inner-bottom Longitudinals

The section modulus of bottom and inner-bottom longitudinals, where constructed of higher-strength material
and in association with the higher-strength plating to which they are attached, are to be determined as indicated
in 3-2-4/1.9, except that the value may be reduced by the factor Q, as defined in 3-2-1/7.5.

9.7 Center Girders, Side Girders and Floors

Center girders, side girders and floors, where constructed of higher-strength materials, are generally to comply
with the requirements of 3-2-4/1.3, 3-2-4/1.5 or 3-2-4/1.7, but may be modified as permitted by the following
equation:

thts = [tms – C][(Q + 2 Q )/3] + C

where
thts, tms and C are defined in 3-2-4/9.3.
Q is as defined in 3-2-1/7.5.

11 Machinery Space

11.1 General
Special attention is directed to arranging for the provision of plated through beams and such casing and
pillar supports as are required to secure structural efficiency. All parts of the machinery, shafting, etc., are
to be efficiently supported and the adjacent structure is to be adequately stiffened.
Consideration is to be given to the submittal of plans of the foundations for main propulsion units, reduction
gears and thrust bearings and of the structure supporting those foundations to the machinery manufacturer
for review. (See also 4-3-1/21.)

11.3 Engine Foundations

11.3.1 Single Bottom Vessels
In vessels with single bottoms, the engines are to be seated on thick plates laid across the top of
deep floors or upon heavy foundation girders efficiently bracketed and stiffened. Intercostal plates
are to be fitted between the floors beneath the lines of bolting to distribute the weight effectively
through the bottom structure to the shell. Seat plates are to be of thickness and width appropriate
to the holding-down bolts and are to be effectively attached to girders and intercostals.
11.3.2 Double Bottom Vessels
On vessels with double bottoms, the engines are to be seated directly upon thick inner-bottom plating
or upon thick seat plates on top of heavy foundations arranged to distribute the weight effectively.
Additional intercostal girders are to be fitted within the double bottom to ensure the satisfactory
distribution of the weight and the rigidity of the structure.

11.5 Thrust Foundations

Thrust blocks are to be bolted to efficient foundations extending well beyond the thrust blocks and arranged
to distribute the loads effectively into the adjacent structure. Extra intercostal girders, effectively attached,
are to be fitted in way of the foundations, as may be required.

11.7 Shaft Stools and Auxiliary Foundations

Shaft stools and auxiliary foundations are to be of ample strength and stiffness in proportion to the weight
supported.

64 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Section 5: Side Frames, Webs, and Stringers

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 5 Side Frames, Webs, and Stringers

1 General

1.1 Basic Considerations

Frames or webs and stringers are not to have less strength than is required for watertight bulkhead
stiffeners, or girders, in the same location in association with heads to the bulkhead deck. In way of deep
tanks, frames or webs and stringers are not to have less strength than is required for stiffeners or girders on
deep-tank bulkheads. The calculated section modulus is based upon the intact sections being used. Where a
hole is cut in the flange of any member or a large opening is made in the web of the member, the net
section is to be used in determining the section modulus of the member in association with the plating to
which it is attached.

1.3 End Connections

At the ends of unbracketed frames, both the web and the flange are to be welded to the supporting member.
At bracketed end connections, continuity of strength is to be maintained at the connection to the bracket
and at the connection of the bracket to the supporting member. Welding is to be in accordance with
3-2-16/Table 1. Where longitudinal frames are not continuous at bulkheads, end connections are to effectively
develop their sectional area and resistance to bending. Where a structural member is terminated, structural
continuity is to be maintained by suitable back-up structure, fitted in way of the end connection of frames,
or the end connection is to be effectively extended by a bracket or flat bar to an adjacent beam, stiffener, etc.

3 Longitudinal Side Frames

3.1 Section Modulus

The section modulus, SM, of each longitudinal side frame above the chine or upper turn of bilge is to be
not less than that obtained from the following equation:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 0.915
h = vertical distance, in m (ft), from the frame to the freeboard deck at side, but not less
than 0.02L + 0.46 m (0.02L + 1.5 ft)
s = frame spacing, in m (ft)
l = straight-line unsupported span, in m (ft). Where brackets are fitted in accordance with
3-1-2/5.5 and are supported by bulkheads, the length, l, may be measured as permitted
therein.

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Chapter 2 Hull Structures and Arrangements
Section 5 Side Frames, Webs and Stringers 3-2-5

5 Transverse Side Frames

5.1 Section Modulus

The section modulus, SM, of each transverse side frame other than tween deck frames above the chine or
upper turn of bilge, in association with the plating to which the frame is attached, is not to be less than that
obtained from the following equation. See 3-2-5/Figure 1, 3-2-5/Figure 2 and 3-2-5/Figure 3.
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 0.915 for frames having no tween decks above
= 0.90 + 5.8/l3 (0.90 + 205/l3) for frames having tween decks above
s = frame spacing, in m (ft)
l = straight-line unsupported span, in m (ft). Where brackets are fitted in accordance with
3-1-2/5.5 and are supported by decks or inner bottoms, the length l may be measured
as permitted therein. Where tween decks are located above the frame, l is to be taken
as the length between the toes of the brackets, except where beam knees are fitted on
alternate frames, l is to be increased by one half the depth of the beam knees. l is not
to be taken less than 2.1 m (7.0 ft).
h = on frames having no tween decks above, the vertical distance, in m (ft), from the mid
length of the frame to the freeboard deck at side, but not less than 0.02L + 0.46 m
(0.02L + 1.5 ft).
= on frames having tween decks above, the vertical distance, in m (ft), from the middle
of l to the load line or 0.4l, whichever is greater, plus bh1/33 (bh1/100).
b = horizontal distance, in m (ft), from the outside of the frames to the first row of deck
beam supports.
h1 = vertical distance, in m (ft), from the deck at the top of the frame to the bulkhead or
freeboard deck plus the height of all cargo tween deck spaces above the bulkhead or
freeboard deck plus one-half the height of all passenger spaces above the bulkhead or
freeboard deck, or plus 2.44 m (8 ft), if that is greater. Where the cargo load differs
from 715 kgf/m3 (45 lbf/ft3), h1 is to be adjusted accordingly.

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Section 5 Side Frames, Webs and Stringers 3-2-5

FIGURE 1 FIGURE 2
Transverse Side Frame Transverse Side Frame
deck at side deck at side

h for side
l/2 frames
h for side frames
middle of l
l θ middle of l
l

θ knuckle is not credited

as a point of support
when θ > 150º

knuckle is credited
as a point of support
when θ ≤ 150°

CL CL

FIGURE 3
Hold and Tween Deck Frames

Minimum Type A
2.44m
(8 ft)
Bhd deck

Type B
h1

h
Type C

l Minimum 0.5 l
2.10 m (7 ft)

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 5 Side Frames, Webs and Stringers 3-2-5

5.3 Tween-deck Frames

The section modulus, SM, of each transverse side frame above the chine or upper turn of bilge, in association
with the plating to which the frame is attached, is not to be less than obtained from the following equation:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 0.90
h = 0.032L – 0.68 m (0.032L – 2.23 ft) type A frame
= 0.049L – 0.81 m (0.049L – 2.66 ft) type B frame
= 0.052L – 0.13 m (0.052L – 0.43 ft) type C frame
= in no case less than the vertical distance, in m (ft), from the mid-length of the frame
to the freeboard deck, but not less than 0.02L + 0.46 m (0.02L + 1.5 ft)
s = frame spacing, in m (ft)
l = tween deck height or unsupported length along frame, whichever is greater, in m (ft),
not to be taken less than 2.13 m (7.0 ft). For frame types, see 3-2-5/Figure 3. Forward
of 0.125L, frames above the bulkhead or freeboard deck are to be type B frames.
Longitudinal tween deck frames are to meet the requirements of 3-2-5/3. The section modulus of each
longitudinal tween deck frame forward of 0.125L from the stem is to be not less than required by 3-2-5/5.1
for transverse frames in the same location, taking l as the unsupported span along the frame length.

5.5 Peak Frames

5.5.1 General
For vessels 61 m (200 ft) or greater in length, peak frames are to be efficiently connected to deep
floors of not less thickness than that obtained from 3-2-4/1.7 for floors in engine spaces. The floors
are to extend as high as necessary to give lateral stiffness to the structure and are to be properly
stiffened on their upper edges. Care is to be taken in arranging the framing and floors to assure no
wide areas of unsupported plating adjacent to the stem. Breast hooks are to be arranged at rectangular
intervals at and between the stringers above and below the waterline. In general, the frames above
the lowest deck are to be as required by 3-2-5/5, but in vessels having large flare with unusually
long frames, stringers and webs above the lowest deck or suitably increased frames may be required.
5.5.2 Section Modulus
For vessels 61 m (200 ft) or greater in length, the section modulus of each peak frame is to be not
less than that obtained from the following equation:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 1.13 for forepeak frames
= 0.90 for aftpeak frames
h = 0.110L – 1.990 m (0.110L – 6.53 ft) for forepeak frames
= 0.062L – 1.122 m (0.062L – 3.68 ft) for aftpeak frames
s = frame spacing, in m (ft)
l = straight line unsupported span, in m (ft), not to be taken less than 2.1 m (7.0 ft)
L = length as defined in 3-1-1/3, but is not to be taken less than 30 m (98.5 ft)

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 5 Side Frames, Webs and Stringers 3-2-5

7 Side Web Frames

7.1 Section Modulus

The section modulus, SM, of each side web frame supporting longitudinal framing or shell stringers above
the chine or upper turn of bilge, in association with the plating to which the web frame is attached, is not to
be less than that obtained from the following equation:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 0.915 aft of the forepeak
= 1.13 in the forepeak of vessel 61 m (200 ft) or greater in length.
s = frame spacing, in m (ft)
l = straight-line unsupported span, in m (ft). Where brackets are fitted in accordance with
3-1-2/5.5 and are supported by decks or inner bottoms, the length, l, may be measured
as permitted therein
h = on frames having no tween decks above, the vertical distance, in m (ft), from the mid
length of the frame to the freeboard deck at side, but not less than 0.02L + 0.46 m
(0.02L + 1.5 ft).
= on frames having tween decks above, the vertical distance, in m (ft), from the middle
of l to the load line or 0.5l, whichever is greater, plus bh1/45K (bh1/150K).
b = horizontal distance, in m (ft), from the outside of the frames to the first row of deck
beams supports.
h1 = vertical distance, in m (ft), from the deck at the top of the web frame to the bulkhead
or freeboard deck plus the height of all cargo tween deck spaces above the bulkhead
or freeboard deck plus one-half the height of all passenger spaces above the bulkhead
or freeboard deck, or plus 2.44 m (8 ft), if that is greater. Where the cargo load differs
from 715 kgf/m3 (45 lbf/ft3), h1 is to be adjusted accordingly.
K = 1.0 where the deck is longitudinally framed and a deck transverse is fitted in way of
each web frame.
= the number of transverse frame spaces between web frames where the deck is
transversely framed.

7.3 Tween-deck Web Frames

Tween-deck web frames are to be fitted below the bulkhead deck over the hold web frames, as may be
required to provide continuity of transverse strength above the main web frames in holds and machinery space.

7.5 Proportions (2018)

The depth of each web frame is to be not less than 125l mm (1.5l in.) or, unless effective compensation is
provided for cutouts, 2.5 times the cutout for frame or longitudinal if greater. The thickness of the web of
web frame or stringer is to be not less than 0.01 times the depth plus 3 mm (0.12 in.) but need not exceed
11.5 mm (0.46 in.), l is as defined in 3-2-5/7.1.

7.7 Tripping Brackets and Stiffeners

7.7.1 Stiffeners
Where the shell is longitudinally framed, stiffeners attached to the longitudinal frames and extending
to the full depth of the web frame are to be fitted at least at alternate longitudinal frames. Other
stiffening arrangements may be considered based on the structural stability of the web plates.

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 5 Side Frames, Webs and Stringers 3-2-5

7.7.2 Tripping Brackets

Tripping brackets are to be fitted at intervals of about 3 m (10 ft) and near the change of section.
Where the breadth of the flanges on either side of the web exceeds 200 mm (8 in.), tripping brackets
are to be arranged to support the flange.

9 Vessel Side Frames Subject to Impact Loads (2014)

For vessels subject to impact loads during routine operations, side frames in the impact region are to have a
section modulus 25% greater than that obtained from 3-2-5/7.1. All side structural members in the impact
region are to have end connections with brackets and adequate double continuous fillet welds at the end.
Scallop welds are not to be used in connections between side frames and shell plating.

11 Side Stringers

11.1 Section Modulus

The section modulus, SM, of each side stringer in association with the plating to which the side stringer is
attached is not to be less than that obtained from the following equation:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 0.915
= 1.13 in the forepeak of vessel 61 m (200 ft) or greater in length.
h = vertical distance, in m (ft), from the middle of s to the freeboard deck at side, but not
less than 0.02L + 0.46 m (0.02L + 1.5 ft).
= for stringers above the lowest deck or at a similar height in relation to the design
draft, not less than given in 3-2-5/5.3 appropriate to the tween deck location.
= for stringers in the peaks of vessels 61 m (200 ft) or greater in length, not less than
given in 3-2-5/5.5.
s = sum of the half lengths, in m (ft), (on each side of the stringer) of the frames
supported.
l = span, in m (ft), between web frames, or between web frame and bulkhead. Where
brackets are fitted in accordance with 3-1-2/5.5 and are supported by transverse
bulkheads, the length, l, may be measured as permitted therein.

11.3 Proportions
Side stringers are to have a depth of not less than 0.125l (1.5 in per ft of span l) plus one-quarter of the
depth of the slot for the frames, but need not exceed the depth of the web frames to which they are attached.
In general, the depth is not to be less than 2.5 times the depth of the slots, or the slots are to be fitted with
filler plates. The thickness of each stringer is to be not less than 0.014L + 7.2 mm (0.00017L + 0.28 in.)
where L is as defined in 3-1-1/3.

11.5 Tripping Brackets and Stiffeners

11.5.1 Stiffeners
Stiffeners attached to the frame and extending to the full depth of the stringer are to be fitted at
least at alternate transverse frames. Other stiffening arrangements may be considered based on the
structural stability of the web plates.
11.5.2 Tripping Brackets
The arrangements of tripping brackets are to be in accordance with 3-2-5/7.7.2.

70 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Section 6: Beams, Deck Girders, Deck Transverses, and Pillars

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 6 Beams, Deck Girders, Deck Transverses, and

Pillars

1 Beams

1.1 Spacing
Beams may be fitted either transversely or longitudinally. Transverse beams, where provided, are to be
fitted at each transverse side frame at the tops of tanks, tunnel tops, and bulkhead recesses. Elsewhere,
these beams are not to be more than two frame spaces apart and those in different tiers are to be fitted on
the same frames.

1.3 Section Modulus

The section modulus, SM, of each transverse or longitudinal beam, in association with the plating to which
it is attached, is not to be less than that obtained from the following equations:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 1.00 for transverse or longitudinal beams at the tops of tank, with
deep tank h
= 1/(1.709 – 0.651k) for longitudinal beams of strength decks and effective lower decks
= 0.60 for all other transverse beams
= 0.70 for all other longitudinal beams
k = SMRY/IA

SMR = required hull-girder section modulus amidships from 3-2-1/3, in cm2-m (in2-ft)
Y = distance, in m (ft), from the neutral axis to the deck being considered, always taken as
positive
IA = hull girder moment of inertia of the vessel amidships, in cm2-m2 (in2-ft2)
The values of IA and Y are to be those obtained using the area of the longitudinal beams given by the above
equation.
s = beam spacing, in m (ft)
l = unsupported span, in m (ft). At the tops of tanks and bulkhead recesses, the maximum
span permissible between supports is 4.57 m (15 ft). Where brackets are fitted in
accordance with 3-1-2/5.5, the length, l, may be measured as permitted therein.

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Section 6 Beams, Deck Girders, Deck Transverses and Pillars 3-2-6

h = height, in m (ft), as follows:

= for a deep tank top, is the greatest of the following: two-thirds of the distance from
the top of the tank to the top of the overflow, or
• two-thirds of the distance from the top of the tank to the bulkhead deck or freeboard
deck, or
• the height to the load line, or
• 0.01L + 0.15 m (0.01L + 0.5 ft)
= for a lower deck on which cargo or stores are carried, the tween-deck height at side.
Where the cargo weights differ from 7010 N/m3 (715 kgf/m3, 45 lbf/ft3), h is to be
proportionately adjusted.
= for an exposed deck on which cargo is carried, 3.66 m (12 ft). Where it is intended to
carry deck cargoes in excess of 25850 N/m2 (2636 kgf/m2, 540 lbf/ft2), this head is to
be increased in proportion to the added loads which will be imposed on the structure.
Elsewhere, the value of h is obtained from the appropriate equation below, where L = length of the vessel,
in m (ft), as defined in 3-1-1/3.
1.3.1 Exposed Freeboard Deck Having no Deck Below
h = 0.02L + 0.76 m
h = 0.02L + 2.5 ft
1.3.2 Exposed Freeboard Deck Having a Deck Below, Forecastle Deck, Superstructure Deck
Forward of Amidships 0.5L
h = 0.02L + 0.46 m
h = 0.02L + 1.5 ft
1.3.3 Freeboard Deck within Superstructure, any Deck Below Freeboard Deck, Superstructure
Deck Between 0.25L Forward of and 0.30L Aft of Amidships
h = 0.01L + 0.61 m
h = 0.01L + 2.0 ft
1.3.4 All Other First Tier Above Freeboard Deck Locations
h = 0.01L + 0.30 m
h = 0.01L + 1.0 ft
1.3.5 Second Tier Above Freeboard Deck; Deckhouse Top or Short Superstructure*
h = 0.01L + 0.15 m
h = 0.01L + 0.5 ft
* Where used only as weather covering, may be used as 3-2-6/1.3.6, but L need not be taken greater than
45.70 m (150 ft).

1.3.6 Third Tier Above Freeboard Deck Deckhouse Top or Short Superstructure*
h = 0.01L m
h = 0.01L ft
* Where used only as weather covering, may be used as 3-2-6/1.3.6, but L need not be taken greater than
45.70 m (150 ft).

1.5 Special Heavy Beams

Special reinforced beams are to be fitted under concentrated loads such as the ends of deckhouses, masts,
winches, auxiliary machinery, etc. Beams at the heads of web frames are to be suitably increased in strength
and stiffness.

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Part 3 Hull Construction and Equipment
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Section 6 Beams, Deck Girders, Deck Transverses and Pillars 3-2-6

1.6 Deck Fittings (2007)

1.6.1 General
The strength of supporting hull structures used for mooring operations and/or normal towing
operations at bow, sides and stern are to comply with the requirements of this section.
Deck fittings for mooring and/or towing are to be located on longitudinals, beams and/or girders,
which are part of the deck construction so as to facilitate efficient distribution of the mooring
and/or towing load. The same attention is to be paid to recessed bitts, if fitted, of their structural
arrangements and strength of supporting structures.
1.6.2 Design Loads
Unless greater safe working load (SWL) of deck fittings is specified by the applicant, the minimum
design load to be used is the greater values obtained from 3-2-6/1.6.2(a) or 3-2-6/1.6.2(b), whichever
is applicable:
1.6.2(a) Mooring Operations. The minimum design load for deck fittings for mooring operations
is the applicable value obtained from 3-2-6/1.6.2(a)i) or 3-2-6/1.6.2(a)ii):
i) Mooring Line Force. 1.25 times the breaking strength of the mooring line according to
3-5-1/Table 2 for each equipment number (EN). EN is the corresponding value used for
determination of the vessel’s equipment. (See Note)
Notes:
1 Side projected area including maximum stacks of deck cargoes is to be taken into
account for assessment of lateral wind forces, arrangements of tug boats and selection
of mooring lines.
2 Where the tabular breaking strength exceeds 490 kN (50,000 kgf, 110,200 lbf), the
breaking strength of individual mooring line may be reduced with corresponding
increase of number of the mooring lines, provided that the total breaking load of all
lines aboard the vessel is not less than the total loads as specified in 3-5-1/Table 2.
The number of mooring lines is not less than 6 and no one line is to have a strength
less than 490 kN. (See also 3-5-1/17 and 3-5-1/19.7)
ii) Mooring Winch Force. The design load applied to supporting hull structures for winches,
etc. is to be 1.25 times the intended maximum brake holding load and, for capstans, 1.25
times the maximum hauling-in force.
1.6.2(b) Towing Operations. The minimum design load for deck fittings for towing operations is
the applicable value obtained from 3-2-6/1.6.2(b)i or 3-2-6/1.6.2(b)ii):
i) Normal towing operations (e.g., harbor/maneuvering). 1.25 times the intended maximum
towing load (e.g., static bollard pull) as indicated on the towing and mooring arrangements
plan.
ii) Other towing service (e.g., escort). The nominal breaking strength of the tow line according
to the 3-5-1/Table 2 for each equipment number (EN). EN is the corresponding value
used for determination of the vessel’s equipment. (See Note)
Note: Side projected area including maximum stacks of deck cargoes is to be taken into account for
assessment of lateral wind forces, arrangements of tug boats and selection of mooring lines.
1.6.2(c) Application of Design Loads. The design load is to be applied through the mooring line
or tow line, whichever is applicable, according to the arrangement shown on the mooring and
towing arrangements plan.
The method of application of the design load to the supporting hull structures is to be taken into
account such that the total load need not be more than twice the design load specified in
3-2-6/1.6.2(b) above, i.e., no more than one turn of one line (see 3-2-6/Figure 1 below).

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Section 6 Beams, Deck Girders, Deck Transverses and Pillars 3-2-6

FIGURE 1
Application of Design Loads (2007)

Line
on
ng
itti es

oad
F
on tim

ign L
oad an 2 ne)
n L th n li
sig ore ad o

Des
e
D ot m lo
(N esign
d

Design Load
on Line
Fitting

When a specific SWL is applied for a deck fitting at the request of the applicant, by which the
design load will be greater than the above minimum values, the strength of the supporting hull
structures is to be designed using this specific design load.
1.6.3 Supporting Structures
1.6.3(a) Arrangement. The reinforced structural members (e.g., carling) are to be arranged
beneath the deck where deck fittings are located and effectively distribute the loads from deck
fittings for any variation of direction (horizontally and vertically).
1.6.3(b) Line Forces. The acting point of the mooring and/or towing force on deck fittings is to
be taken at the attachment point of a mooring line or a towing line, as applicable.
1.6.3(c) Allowable Stresses. Allowable stresses under the design load conditions as specified in
3-2-6/1.6.2 are as follows:
• Normal stress: 100% of the specified minimum yield point of the material;
• Shearing stress: 60% of the specified minimum yield point of the material;
No stress concentration factors being taken into account. Normal stress is the sum of bending stress
and axial stress with the corresponding shearing stress acting perpendicular to the normal stress.
1.6.4 Scantlings
1.6.4(a) Net Scantlings. The net minimum scantlings of the supporting hull structure are to
comply with the requirements given in 3-2-6/1.6.3. The net thicknesses, tnet, are the member
thicknesses necessary to obtain the above required minimum net scantlings. The required gross
thicknesses are obtained by adding the total corrosion additions, tc, given in 3-2-6/1.6.4(b), to tnet.
1.6.4(b) Corrosion Addition. The total corrosion addition, tc, in mm (in.), for both sides of the
hull supporting structure is not to be less than the following values:
• Ships covered by Common Structural Rules (CSR) for bulk carriers and CSR for double hull
oil tankers: Total corrosion additions defined in these Rules
• Other ships: 2.0 (0.08)

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Section 6 Beams, Deck Girders, Deck Transverses and Pillars 3-2-6

1.7 Container Loading

Where it is intended to carry containers, the exact locations of the container pads and the maximum total
static load on the pads are to be indicated on the plans. Where the pads are not in line with the supporting
structures, headers are to be provided to transmit the loads to these members.
Each member intended to support containers is to have a section modulus, SM, in cm3 (in3), not less than
that obtained from the following equation:
SM = M/f
where
M = maximum bending moment due to maximum static container loading in kN-cm
(kgf-cm, Ltf-in)
f = permissible maximum bending stress, as given in 3-2-6/Table 1.
In determining the maximum bending moment, members may be considered fixed-ended, provided the
member is continuous over the adjacent spans or is effectively attached to a bulkhead stiffener or frame or
has suitable end connections. Where this is not the case, the member is to be considered simply-supported.
Where weather deck containers are supported by pedestals, the section modulus required by 3-2-6/1.3, with
h equal to the distance between the deck and the underside of the container, but not greater than 50% of the
value given in 3-2-1/1.3.1 through 3-2-1/1.3.6, is to be added to the above required section modulus.

TABLE 1
Values of f
kN/cm2 kgf/cm2 Ltf/in2
Effective longitudinal members 12.36 1262 8
Transverse members and longitudinal members 13.90 1420 9
inside the line of openings

The net sectional area of the web of the member in cm2 (in2), including effective brackets, where
applicable, is to be not less than that obtained from the following equation:
A = F/q
where
F = shearing force at the point under consideration, kN (kgf, Ltf)
q = allowable average shear stress in the web, not to exceed 10.35 kN/cm2
(1057 kgf/cm2, 6.7 Ltf/in2)

3 Deck Girders and Deck Transverses

3.1 General
Girders and transverses are to be fitted as required to support beams and longitudinals. Additional girders
are to be fitted as required under masts, king posts, deck machinery or other heavy concentrated loads.

3.3 Deck Girders and Transverses Clear of Tanks

Section modulus, SM, of each longitudinal deck girder and deck transverse clear of tanks is not to be less
than that obtained from the following equation:
SM = 7.8cbhl2 cm3
SM = 0.0041cbhl2 in3

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where
c = 0.60
b = mean breadth of area of deck supported (for girders), or spacing of deck transverses
(for transverses), in m (ft)
h = height, in m (ft), as required by 3-2-6/1.3 for the beams supported
l = unsupported span, in m (ft). Where brackets are fitted at bulkhead supports, in
accordance with 3-1-2/5.5, the length, l, may be measured as permitted therein.

3.5 Proportions
The minimum depth of a deck girder or transverse supporting member is to be 58.3l mm (0.7l in.), where
l is as defined in 3-2-6/3.3; the depth is also not to be less than 2.5 times the cutout for the beam or
longitudinal unless effective compensation is provided for the cutouts. The minimum thickness is to be 1
mm per 100 millimeters (0.01 in. per inch) of depth plus 4 mm (0.16 in.).

3.7 Tripping Brackets and Stiffeners

Tripping brackets are to be fitted on girders and transverses at a spacing of about 3 m (10 ft). Stiffeners are
to be fitted as may be required.

3.9 Deck Girders and Transverses in Tanks

The requirements for deck girders or transverse supporting members in tanks may be obtained in the same
manner as given in 3-2-6/3.3, 3-2-6/3.5 and 3-2-6/3.7, except that c is equal to 0.915. The minimum depth
of a girder or transverse supporting member is to be 83.3l mm (1.0l in.), where l is as defined in 3-2-6/3.3.

3.11 Hatch Side Girders

Scantlings for hatch side girders supporting athwartship shifting beams or supporting hatch covers are to
be obtained in the same manner as deck girders (3-2-6/3.3 and 3-2-6/3.9). Such girders along lower deck
hatches under trunks in which covers are omitted are to be increased in proportion to the extra load which
may be required to be carried due to the loading up into the trunks. The structure on which the hatch covers
are seated is to be effectively supported.
Where deep coamings are fitted above decks, such as at weather decks, the girder below deck may be modified
so as to obtain a section modulus in cm3 (in3), when taken in conjunction with the coaming up to and
including the horizontal coaming stiffener, of not less than 35% more than the required girder value, as
derived from 3-2-6/3.3. Where hatch side girders are not continuous under deck beyond the hatchways to
the bulkheads, brackets extending for at least two frame spaces beyond the ends of the hatchways are to be
fitted.
Where hatch side girders are continuous beyond the hatchways, care is to be taken in proportioning their
scantlings beyond the hatchway. Gusset plates are to be fitted at hatchway corners, arranged so as to tie
effectively the flanges of the side coamings and extension pieces or continuous girders and the hatch-end
beam flanges both beyond and in the hatchway.

3.13 Container Loading

Where it is intended to carry containers, the structure is to comply with 3-2-6/1.7.

3.15 End Attachments

The ends of deck girders and transverses are to be effectively attached by welding.

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Section 6 Beams, Deck Girders, Deck Transverses and Pillars 3-2-6

3.17 Hatch-end Beams

Each hatch-end beam, similar to that shown in 3-2-6/Figure 2, which is supported by a centerline pillar
without a pillar at the corner of the hatchway, is to have a section modulus, SM, not less than that obtained
from the following equations:
3.17.1 Where Deck Hatch-side Girders are Fitted Fore and Aft Beyond the Hatchways
SM = K(AB + CD)hl cm3
SM = 0.000527K(AB + CD)hl in3
3.17.2 Where Girders are not Fitted on the Line of the Hatch Side Beyond the Hatchway
SM = KABhl cm3
SM = 0.000527KABhl in3
where
A = length of the hatchway, in m (ft)
B = distance from the centerline to the midpoint between the hatch side and the
line of the toes of the beam knees, in m (ft)
C = distance from a point midway between the centerline and the line of the hatch
side to the midpoint between the hatch side and the line of the toes of the
beam knees, in m (ft). Where no girder is fitted on the centerline beyond the
hatchway, C is equal to B
D = distance from the hatch-end beam to the adjacent hold bulkhead, in m (ft)
h = height for the beams of the deck under consideration, as given in 3-2-6/1.3,
in m (ft)
l = distance from the toe of the beam knee to the centerline plus 0.305 m (1 ft),
in m (ft)
K = 2.20 + 1.29(F/N) when F/N ≤ 0.6
= 4.28 – 2.17 (F/N) when F/N > 0.6
N = one-half the breadth of the vessel in way of the hatch-end beam
F = distance from the side of the vessel to the hatch-side girder
Weather deck hatch-end beams which have deep coamings above deck for the width of the hatch may have
the flange area reduced from a point well within the line of the hatch side girder to approximately 50% of
the required area at centerline; in such cases, it is recommended that athwartships brackets be fitted above
deck at the ends of the hatch-end coaming.
Brackets at the end of hatch-end beams are to be generally as described in 3-1-2/5.5. Where brackets are
not fitted, the length, l, is to be measured to the side of the vessel and the face plates or flanges on the
beams are to be attached to the shell by heavy horizontal brackets extending to the adjacent frame.

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FIGURE 2
Hatch-end Beams
L
C
305 mm (1 ft)

305 mm (1 ft)

Mid-distance between
girder and knee

B N C

Girder

A
Mid-distance between
supports
D
Center Support
L
C

5 Stanchions and Pillars

5.1 General
Supports under pillars are to be sufficient strength to distribute the loads effectively. Tween-deck pillars
are to be arranged directly above those below, or effective means are to be provided for transmitting their
loads to supports below. Tripping brackets are to be fitted on members in way of pillars, both when the
pillar is over and under the member.

5.3 Permissible Load (2018)

The permissible load a pillar can carry is to be equal to or greater than the pillar load, W, as determined in
3-2-6/5.5. The permissible load may be obtained from the following equation:
Wa = (k – nl/r)A
where
Wa = load, in kN (tf, Ltf)
k = 12.09 (1.232, 7.83) ordinary strength steel
= 16.11 (1.643, 10.43) HT32 strength steel
= 18.12 (1.848, 11.73) HT36 strength steel

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n = 0.0444 (0.00452, 0.345) ordinary strength steel

= 0.0747 (0.00762, 0.581) HT32 strength steel
= 0.0900 (0.00918, 0.699) HT36 strength steel
l = unsupported length of the pillar, in cm (ft)
r = least radius of gyration of pillar, in cm (in.)
A = area of pillar, in cm2 (in2)

5.5 Calculated Load

The load on a pillar is to be obtained from the following equation:
W = nbhs
where
W = load, in kN (tf, Ltf)
n = 7.04 (0.715, 0.02)
b = mean breadth, in m (ft), of area supported
h = height, in m (ft), above the deck supported, as defined below
s = mean length, in m (ft), of area supported
For a pillar below an exposed deck on which cargo is carried, h is the distance from the deck supported to a
point 3.66 m (12 ft) above the exposed deck. Where it is intended to carry deck cargoes in excess of 2636
kilograms per square meter (540 pounds per square foot), this head is to be increased in proportion to the
added loads which will be imposed on the structure.
For a pillar below the freeboard deck, h is to be measured to a point not less than 0.02L + 0.76 m (0.02L + 2.5 ft)
above the freeboard deck.
For a pillar below the superstructure deck, h is to be measured to a point not less than 0.02L + 0.46 m
(0.02L + 1.5 ft) above the superstructure deck.
The height, h, for any pillar is not to be less than the given height in 3-2-6/1.3 for the beams at the top of
the pillar plus the sum of the heights given in the same paragraphs for the beams of all complete cargo
decks and one-half the heights given for all partial superstructure decks above.
L is the length of vessel, in m (ft), as defined in 3-1-1/3.

5.7 Stanchions in Double Bottoms and Under Tank Tops

Stanchions in double bottoms and under the tops of deep tanks are to be solid in cross section. Stanchions
under the tops of deep tanks are not to be less than required by 3-2-6/5.3 and 3-2-6/5.5, nor are they to
have less section area than cW cm2 (in2) where W is to be obtained from the following equation:
W = nbhs
where
W = load, in kN (tf, Ltf)
n = 10.5 (1.07, 0.03)
b = breadth, in m (ft), of the area of the top of the tank supported by the stanchion
h = height, in m (ft), as required by 3-2-6/1.3, for the tank-top beams
s = length, in m (ft), of the area of the top of the tank supported by the stanchion
c = 0.1035 (1.015, 0.16)

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5.9 Bulkheads
Bulkheads supporting girders or bulkheads fitted in lieu of girders are to be stiffened to provide supports
not less effective than required for pillars.

5.11 Attachments
Wide-spaced tubular or solid pillars are to bear solidly at head and heel and are to be attached by welding,
properly proportioned to the size of the pillar. The attachments of stanchions or pillars under bulkhead
recesses, tunnel tops or deep-tank tops which may be subjected to tension loads are to be specially developed
to provide sufficient welding to withstand the tension load.

7 Higher-strength Materials

7.1 General
In general, applications of higher-strength materials for deck beams, girders and transverses are to meet the
requirements of this section, but may be modified as permitted by the following paragraph.
Calculations are to be submitted to show adequate provision against buckling. Longitudinal members are
to be of essentially the same material as the plating they support.

7.3 Beams, Girders and Transverses of Higher-strength Materials

Each beam, girder and transverse of higher-strength material, in association with the higher-strength plating
to which it is attached, is generally to comply with the requirements of the appropriate preceding paragraphs
of this section and is to have a section modulus, SMhts, not less than obtained from the following equation:
SMhts = SM(Q)
where
SM = required section modulus in ordinary-strength material, as determined elsewhere in
this section.
Q = as defined in 3-2-1/7.5

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PART Section 7: Watertight Bulkheads and Doors

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 7 Watertight Bulkheads and Doors

1 General
All vessels having lengths, L, equal to or exceeding 15 m (50 ft) are to be provided with watertight bulkheads
in accordance with this section. The plans submitted are to clearly show the location and extent of each
watertight bulkhead. Watertight bulkheads constructed in accordance with the Rules will be recorded in the
Record as WT (watertight), the symbols being prefixed in each case by the number of such bulkheads.

1.1 Openings and Penetrations (2006)

The number of openings in watertight subdivisions is to be kept to a minimum, compatible with the design
and proper working of the vessel. Where penetrations of watertight bulkheads and internal deck are necessary
for access, piping, ventilation, electrical cables, etc., arrangements are to be made to maintain the watertight
integrity. Relaxation in the watertightness of openings above the freeboard deck may be considered, provided
it is demonstrated that any progressive flooding can be easily controlled and that the safety of the vessel is
not impaired.
Ventilation penetrations through watertight subdivision bulkheads are to be avoided. Where penetrations
are unavoidable, the ventilation ducting is to satisfy watertight bulkhead requirements or watertight closing
appliances are to be installed at the bulkhead penetrations. For ventilation penetrations below the bulkhead
deck or below damage equilibrium waterlines, the closing appliances are to be operable from the bridge.
Otherwise, local, manual controls may be provided.

3 Arrangement of Watertight Bulkheads

3.1 Collision Bulkheads

3.1.1 General
A collision bulkhead is to be fitted on all vessels. It is to be intact, that is, without openings,
except as permitted in 4-4-1/9.11. It is to extend, preferably in one plane, to the freeboard deck. In
the case of vessels having long superstructures at the fore end, it is to be extended weathertight to
the superstructure deck. The extension need not be fitted directly over the bulkheads below,
provided the location of the extension meets the following requirements and the part of the deck
which forms the step is made effectively weathertight.
On vessels with bow-doors, that part of their sloping loading ramps that form part of the extension
of a collision bulkhead and are more than 2.3 m (7.5 ft) above the freeboard deck may extend
forward of the limit below.
Collision bulkhead requirements for passenger vessels are as indicated in Part 5C, Chapter 7 of the
Steel Vessel Rules.
3.1.2 Location (1 July 2010)
The collision bulkhead is to be located at any point not less than 0.05Lf abaft the reference point.
At no point on vessels having 500 or more gross tonnage, except as specially permitted, is it to be
further than 0.08Lf or 0.05Lf + 3 m (9.84 ft), whichever is greater, from the reference point.

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3.1.3 Reference Point

The reference point in determining the location of the collision bulkhead is the forward end of Lf,
except that in the case of vessels having any part of the underwater body, such as the bulbous bow,
extending forward of the forward end of Lf, the required distances are to be measured from a
reference point located a distance forward of the forward end of Lf. This distance, x, is the lesser of
the following (see 3-2-7/Figure 1):
i) Half the distance between the forward end of Lf and the extreme forward end of the
extension, p/2 or
ii) 0.015Lf
iii) 3 m (9.84 ft)
where Lf is as defined in 3-1-1/3.3.
The forward end of Lf is to coincide with the fore side of the stem on the waterline at which Lf is
measured.

FIGURE 1
Reference Point of Vessels with Bulbous Bow

R.P.

x = p/2
x 0.015Lr or
3m (9.84 ft)
whichever is least

FP

3.3 Engine Room

The engine room is to be enclosed by watertight bulkheads extending to the freeboard deck.

3.5 Chain Lockers (2012)

For vessels with freeboard length, Lf, (as defined in 3-1-1/3.3) greater than 24 meters (79 feet), chain
lockers and chain pipes are to be made watertight up to the weather deck. The arrangements are to be such
that accidental flooding of the chain locker cannot result in damage to auxiliaries or equipment necessary
for the proper operation of the vessel nor in successive flooding into other spaces. Bulkheads between
separate chain lockers not forming a part of subdivision bulkhead (* see 3-2-7/Figure 1A below), or
bulkheads which form a common boundary of chain lockers (see 3-2-7/Figure 1B below), need not be
watertight.
Where means of access into chain lockers are provided, they are to be closed by a substantial cover secured
by closely spaced bolts. Doors are not permitted.
Where a means of access to chain lockers is located below the weather deck, the access cover and its securing
arrangements are to be in accordance with recognized standards (such as ISO 5894-1999), or equivalent for
watertight manhole covers. Butterfly nuts and/or hinged bolts are prohibited as the securing mechanism for
the access cover.

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For closure of chain pipes, see 3-2-12/23.7.

The arrangements on vessels that are not subject to the International Convention on Load Lines or its
Protocol may be specially considered.

FIGURE 1A (2007) FIGURE 1B (2007)

Void/Access Space
Collision Bulkhead
* *
** **
Chain Chain Chain Chain
Locker Locker Locker Locker
A * B A B

** WT Cover

3.7 Hold Bulkheads (1 July 1998)

In addition to the above required bulkheads, for vessels of applicable type and size, the number and arrangement
of hold bulkheads are to satisfy the subdivision and damage requirements in 3-3-1/3.3. Review procedures
for this requirement are indicated in 3-3-1/5.

5 Construction of Watertight Bulkheads

5.1 Plating (1998)

Watertight bulkhead plating thickness is to be obtained from the following equation:

t = sk qh /c + 1.5 mm but not less than 6 mm or s/200 + 2.5 mm, whichever is greater

t = sk qh /c + 0.06 in. but not less than 0.24 in. or s/200 + 0.10 in., whichever is greater

where
t = thickness, in mm (in.)
s = spacing of stiffeners, in mm (in.)

k = (3.075 α − 2.077)/(α + 0.272) (1 ≤ α ≤ 2)

= 1.0 (α > 2)
α = aspect ratio of the panel (longer edge/shorter edge)
q = 235/Y N/mm2 (24/Y kgf/mm2, 34,000/Y psi)
Y = specified minimum yield point or yield strength, in N/mm2 (kgf/mm2, psi), as defined
in 2-1-1/13, for the higher strength material or 72% of the specified minimum tensile
strength, whichever is less
h = distance from the lower edge of the plate to the deepest equilibrium waterline in the
one compartment damaged condition, in m (ft)
• For passenger vessels, h is to be taken as not less than the distance to the margin
line.
• For cargo vessels, h is to be not less than the distance to the bulkhead deck at
center unless a deck lower than the uppermost continuous deck is designated as
the freeboard deck, as allowed in 3-1-1/13.1, in which case, h is to be not less
than the distance to the designated freeboard deck at center.

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c = 254 (460) for collision bulkhead

= 290 (525) for other watertight bulkheads
For vessels under 30.5 m (100 ft) in length, the following deductions may be made to the thicknesses obtained
from the above equation for mild steel only.
L Deduction L Deduction
meters mm feet in.
24.40 to 30.50 0.25 80 to 100 0.01
21.35 to 24.40 0.50 70 to 80 0.02
18.30 to 21.35 0.75 60 to 70 0.03
Under 18.30 1.00 Under 60 0.04

In general, main non-tight transverse strength bulkhead plating is to be similar to that required for watertight
bulkheads. Other non-tight strength bulkheads plating is to be not less than s/150, or 4 mm (0.16 in.),
whichever is greater. The section modulus of non-watertight bulkhead stiffeners is to be not less than one-
half of that required by 3-2-7/5.3.

5.3 Stiffeners (2016)

The section modulus, SM of each bulkhead stiffener, in association with the plating to which it is attached,
is to be not less than that obtained from the following equation:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 0.30 for a stiffener with effective brackets at both ends of its span. An effective
bracket for the application of this value of c is to have scantlings not less than
shown in 3-1-2/Table 5 and is to extend onto the stiffener for a distance at
least one-eighth of the length, l, of the stiffener.
= 0.43 for a stiffener with an effective bracket at one end and a clip connection or
horizontal girder at the other end. An effective bracket for the application of
this value of c is to have scantlings not less than shown in 3-1-2/Table 5 and
is to extend onto the stiffener for a distance at least one-eighth of the length,
l, of the stiffener.
= 0.56 for a stiffener with clip connections at both ends or a clip connection at one
end and a horizontal girder at the other end.
= 0.60 for a stiffener between horizontal girders or for a stiffener with no end
attachments.
h = distance from the middle of l to the deepest equilibrium waterline in the one
compartment damaged condition, in m (ft)
• For passenger vessels, h is to be taken as not less than the distance to the margin
line.
• For cargo vessels, h is to be taken as not less than the distance to the bulkhead
deck at center unless a deck lower than the uppermost continuous deck is designated
as the freeboard deck, as allowed in 3-1-1/13.1, in which case, h is to be not less
than the distance to the designated freeboard deck at center.
• For all vessels, where this distance is less than 6.10 m (20 ft), h is to be taken as
0.8 times the distance plus 1.22 m (4 ft).
s = spacing of stiffeners, in m (ft)
l = distance, in m (ft), between the heels of the end attachments. Where horizontal girders
are fitted, l is the distance from the heel of the end attachment to the first girder, or
the distance between the horizontal girders.

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 7 Watertight Bulkheads and Doors 3-2-7

In vessels under 46 meters (150 ft) in length, the above values for c may be 0.29, 0.38, 0.46 and 0.58,
respectively, and h may be taken as the distance in meters or in feet from the middle of l to the bulkhead
deck at center in every case. For vessels between 46 and 65.5 meters (150 and 215 feet), intermediate values
for c may be obtained by interpolation.
The section modulus of stiffeners on collision bulkheads is to be increased by 25% over the section modulus
of stiffeners on ordinary watertight bulkheads.
For higher-strength steel stiffeners attached to the higher-strength steel plating, its section modulus (SMhs)
is not to be less than obtained from the following equation, provided that all other strength criteria are satisfied:
SMhs = Q(SM) cm3 (in3)
where
SM = stiffener section modulus as defined in the above
Q = as defined in 3-2-1/7.5

5.5 Girders and Webs (1998)

Each horizontal girder or vertical web supporting bulkhead stiffeners is to have a section modulus, SM, not
less than that obtained from the following equation:
SM = 4.74chsl2 cm3
SM = 0.0025chsl2 in3
where
c = 1.0
h = vertical distance, in m (ft), to the deepest equilibrium waterline in the one compartment
damaged condition from the middle of s in the case of a horizontal girder or from the
middle of l in the case of a vertical web.
• For passenger vessels, h is to be taken as not less than the distance to the margin
line.
• For cargo vessels, h is to be not less than the distance to the bulkhead deck at
center unless a deck lower than the uppermost continuous deck is designated as
the freeboard deck, as allowed in 3-1-1/13.1, in which case, h is to be not less
than the distance to the designated freeboard deck at center.
• For all vessels, where this distance is less than 6.10 m (20 ft), h is to be taken as
0.8 times the distance plus 1.22 m (4 ft).
s = sum of half lengths, in m (ft), (on each side of the girder or web) of the stiffeners
supported by the girder or web
l = unsupported span of girder or web, in m (ft). Where brackets are fitted in accordance
with 3-1-2/5.5, the length, l, may be measured as permitted therein.
The required section modulus of girders or webs on collision bulkheads are to be increased by 25% over
the required section modulus of girders or webs on ordinary bulkheads. The depth of a girder or web is not
to be less than twice the depth of the cutout unless effective compensation is provided for stiffener cutouts.
Tripping brackets are to be fitted at intervals of about 3 m (10 ft), and stiffeners are to be fitted as may be
required.
Lower brackets to inner bottoms are to extend over the floor adjacent to the bulkhead. Where stiffeners
cross horizontal girders, they are to be effectively attached.

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Chapter 2 Hull Structures and Arrangements
Section 7 Watertight Bulkheads and Doors 3-2-7

5.7 Corrugated Bulkheads

5.7.1 Plating
The plating of corrugated bulkheads is to be of the thickness required by 3-2-7/5.1 with the
following modification. The spacing to be used is the greater of dimensions a or c, as indicated in
3-2-7/Figure 2. The angle φ is to be 45 degrees or more.
5.7.2 Stiffeners
The section modulus, SM, for a corrugated bulkhead is to be not less than that obtained from the
following equation:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
l = distance between supporting members, in m (ft)
s = a + b, where a and b are as defined in 3-2-7/Figure 2, in m (ft)
c = 0.56
h = as defined in 3-2-7/5.3
The developed section modulus, SM, may be obtained from the following equation, where a, t, and
d are as indicated in 3-2-7/Figure 2, in cm (in.).
SM = td2/6 + (adt/2) cm3 (in3)

FIGURE 2
Corrugated Bulkhead

b a b

d t
φ
c

5.7.3 End Connections (2017)

The structural arrangements and size of welding at the ends of corrugations are to be designed to
develop the required strength of corrugation stiffeners. Joints within 10% of the depth of
corrugation from the outer surface of corrugation, d1, are to have double continuous welds with
fillet size, w, not less than 0.7 times the thickness of the bulkhead plating or penetration welds of
equal strength (3-2-7/Figure 3). See also 3-2-16/3.
Where no stools are fitted for the vertically corrugated bulkhead, the following requirements are to
be complied with:
i) The corrugation webs are to be supported by brackets, beams, diaphragms or girders.
ii) The corrugation flanges are to be in line with the supporting floors. Scallops and cut-outs
in the supporting members aligned with corrugation flanges and webs are to be closed by
insert collar plates. Alternatives to closing the scallops and cut-outs may be accepted
provided that adequate strength to the supporting members is verified by special review.
iii) The thickness and material properties of the floors in line with the corrugation flanges are
to be at least equal to those provided for the corrugation flanges.
iv) Reinforcement may be required for access openings in supporting floors, girders, beams,
and transverses.

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 7 Watertight Bulkheads and Doors 3-2-7

v) Calculations or Finite Element analysis may be submitted for review to justify the design
of the supporting structure in way of the connection. Finite Element Analysis shall comply
with the ABS Guidance Notes on SafeHull Finite Element Analysis of Hull Structures.

FIGURE 3
Corrugated Bulkhead End Connections
t

0.1d1
d1

0.7t

7 Watertight Doors

7.1 Vessels Requiring Subdivision and Damage Stability

7.1.1 Doors Used While at Sea (2002)
Doors which are used while at sea are to be sliding watertight doors capable of being remotely
closed from the bridge and are also to be operable locally from each side of the bulkhead.
Indicators are to be provided at the control position showing whether the doors are open or closed,
and an audible alarm is to be provided which is to sound whenever the door is closed remotely by
power. The power-operated doors, control systems and indicators are to be functional in the event
of main power failure. Particular attention is to be paid to minimize the effect of control system
failure. Each power-operated sliding watertight door is to be provided with an individual hand-
operated mechanism. It is to be possible to open and close the door by hand at the door itself from
each side. For vessels less than 80 m (262.4 ft) in length (Lf as defined in 3-1-1/3.3), hinged quick-
acting doors, operable from both sides of the door, are permitted above a deck, the molded line of
which at its lowest point at side, is at least 2.14 m (7 ft) above the deepest load line. Hinged quick-
acting doors, operable from both sides, are also permitted for vessels less than 80 m (262.4 ft) in
length, Lf, in way of inboard compartments that are not within the assumed extent of damage that
may be applicable to the vessel.
7.1.2 Access Doors Normally Closed at Sea
Access doors and access hatch covers normally closed at sea may be substantially constructed
hinged type, fitted with gaskets and dogs, spaced and designed to ensure that the opening may be
closed thoroughly watertight. These closing appliances are to be provided with means of
indicating locally and on the bridge whether they are open or closed. A notice is to be affixed to
each closing appliance to the effect that it is not to be left open.
7.1.3 Doors or Ramps Dividing Large Cargo Spaces
Watertight doors or ramps of satisfactory construction may be fitted to internally subdivide large
cargo spaces, provided it is demonstrated to ABS that such doors or ramps are essential.

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Section 7 Watertight Bulkheads and Doors 3-2-7

These doors or ramps may be hinged, rolling, or sliding doors or ramps, but are not to be remotely
controlled. Such doors or ramps may be approved on condition that they be closed by the shipboard
personnel before the voyage commences and kept closed during navigation and that the time of
opening such doors or ramps in port and of closing them before the vessel leaves port is to be
entered in the log book.
Doors or ramps accessible during the voyage are to be fitted with a device which prevents
unauthorized opening.
7.1.4 Other Openings Closed at Sea
Closing appliances which are kept permanently closed at sea to ensure the watertight integrity of
internal openings in watertight bulkheads and decks and are not fitted with a device which prevents
unauthorized opening are to be provided with a notice affixed to each such closing appliance to the
effect that it is to be kept closed. Manholes fitted with closely bolted covers need not be so marked.

7.3 Other Vessels

Watertight doors may be installed in all watertight bulkheads, except collision bulkheads.

7.5 Construction
Watertight doors are to be of ample strength for the water pressure to which they may be subjected. Door
frames are to be carefully fitted to the bulkheads; where liners are required, the material is to be not readily
injured by heat or by deterioration. Sliding doors are to be carefully fitted to the frames and are to be tested
at the maker’s works.
Where stiffeners are cut in way of watertight doors, the openings are to be framed and bracketed to maintain
the full strength of the bulkheads without taking the strength of the door frames into consideration.

9 Testing (2014)
Watertight doors are to be tested for operation at the manufacturer’s plant. Watertightness of doors which
become immersed by an equilibrium or intermediate waterplane at any stage of assumed flooding is to be
confirmed by prototype hydrostatic testing at the manufacturer’s plant. The head of water used for the test
shall correspond at least to the head measured from the lower edge of the door opening, at the location in
which the door is to be fitted in the vessel, to:
i) The bulkhead deck or freeboard deck, as applicable, or
ii) The most unfavorable damage waterplane, if that be greater
Tests are to be carried out in the presence of the Surveyor and a test certificate is to be issued.
For large doors intended for use in the watertight subdivision boundaries of cargo spaces, structural analysis
may be accepted in lieu of pressure testing subject to ABS review. Where gasket seals are utilized for such
doors, a prototype pressure test is be carried out to verify that the gasket material under the compression is
capable of withstanding any deflection indicated in the structural analysis.
Doors above freeboard or bulkhead deck, which are not immersed by an equilibrium or intermediate waterplane
but become intermittently immersed at angles of heel in the required range of positive stability beyond the
equilibrium position, are to be hose tested after installation onboard.

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PART Section 8: Deep Tanks

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 8 Deep Tanks

1 General Arrangement
The arrangement of all deep tanks, their intended service, and the heights of the overflow pipes are to be
clearly indicated on the drawings submitted for approval. Tanks forward of the collision bulkhead are not
to be arranged for the carriage of oil or other flammable or combustible substances.

3 Construction
Boundary bulkheads and tight divisions of all deep tanks are to be constructed in accordance with the
requirements of this section where they exceed those of Section 3-2-7. Where the specific gravity of the
liquid exceeds 1.05, the design head, h, in this section is to be increased by the ratio of the specific gravity
of 1.05.

5 Construction of Deep-tank Bulkheads

5.1 Plating (2017)

The minimum thickness of deep-tank boundary bulkheads and tight divisions is to be obtained from the
following equation:

t = (sk qh /254) + 2.5 mm but not less than 6.5 mm or s/150 + 2.5 mm, whichever is greater

t = (sk qh /460) + 0.10 in. but not less than 0.25 in. or s/150 + 0.10 in., whichever is greater

where
t = thickness, in mm (in.)
s = stiffener spacing, in mm (in.)

k = (3.075 α − 2.077)/(α + 0.272) (1 ≤ α ≤ 2)

= 1.0 (α > 2)
α = aspect ratio of the panel (longer edge/shorter edge)
q = 235/Y N/mm2 (24/Y kgf/mm2, 34,000/Y psi)
Y = as defined in 3-2-7/5.1
h = the greatest of the following distances, in m (ft), from the lower edge of the plate to:
• A point located at two-thirds of the distance to the bulkhead or freeboard deck, or
• A point located at two-thirds the distance from the top of the tank to the top of
the overflow, or
• The load line, or
• A point located above the top of the tank, not less than the greater of the following:
• 0.01L + 0.15 m (0.5 ft), where L is as defined in 3-1-1/3, or 0.46 m (1.5 ft)

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Section 8 Deep Tanks 3-2-8

h is also not to be less than h1 or h0 where rupture disks or spill valves are fitted, as obtained below:

h1 = ρht + ha m (ft)

h0 = (2/3)(ρhs + 9.95Ps) m (Ps in bar)

= (2/3)(ρhs + 9.75Ps) m (Ps in kgf/cm2)

= (2/3)(ρhs + 2.25Ps) ft (Ps in lbf/in2)

where
ρ = 1.0 where the specific gravity of liquid is 1.05 or less
= specific gravity of liquid where it is in excess of 1.05
(The provisions under 3-2-8/5 need not be applied in addition hereto)
ht = head from the center of the supported area or lower edge of the plating to the deck at
side or, where such is fitted, to the top of the trunk deck at side for tanks within trunk
ha = 9.95pv (9.75pv, 2.25pv)

pv = pressure/vacuum valve pressure setting, in bar (kgf/cm2, lbf/in2)

hs = head to the spill valve or rupture disc, where fitted, in m (ft)

Ps = relieving pressure of spill valve or rupture disc, where fitted, in bar (kgf/cm2, lbf/in2)

5.3 Stiffeners
The section modulus, SM, of each deep-tank stiffener, in association with the plating to which it is attached,
is not to be less than that obtained from the following equation:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 0.594 for stiffeners having effective bracket attachments at both ends. An effective
bracket for the application of this value of c is to have scantlings not less
than shown in 3-1-2/Table 2 and is to extend onto the stiffener for a distance
at least one-eighth of the length, l, of the stiffener.
= 0.747 for stiffeners having an effective bracket attachment at one end and a clip
connection or horizontal girder at the other end. An effective bracket for the
application of this value of c is to have scantlings not less than shown in
3-1-2/Table 2 and is to extend onto the stiffener for a distance at least one-
eighth of the length, l, of the stiffener.
= 0.90 for stiffeners having clip connections at both ends or having such
attachments at one end and horizontal girders at the other end.
= 1.00 for stiffeners having horizontal girders at both ends.
l = the distance, in m (ft), between the heels of the end attachments. Where horizontal
girders are fitted, l is the distance from the heel of the end attachment to the first
girder or the distance between the horizontal girders.
s = stiffener spacing, in m (ft)
h = the greatest of the following distances, in m (ft), from the middle of l to:
• A point located at two-thirds of the distance from the middle of l to the bulkhead
or freeboard deck, or

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Chapter 2 Hull Structures and Arrangements
Section 8 Deep Tanks 3-2-8

• A point located at two-thirds of the distance from the top of the tank to the top of
the overflow, or
• The load line, or
• A point located above the top of the tank, not less than the greater of the following:
• 0.01L + 0.15 m (0.5 ft), where L is the length of a vessel as defined in 3-1-1/3, or
0.46 m (1.5 ft)

5.5 Corrugated Bulkheads

Where corrugated bulkheads are used as deep-tank boundaries, the scantlings may be developed from
3-2-7/5.7. The plating thickness, t, and value of SM are to be as required by 3-2-8/5.1 and 3-2-8/5.3,
respectively, with c = 0.90.

5.7 Girders and Webs (2018)

Horizontal girders or vertical webs supporting bulkhead stiffeners in deep tanks are to have a section
modulus as required by this paragraph. Girders or webs supporting frames or beams in deep tanks are to have
section modulus as required by Sections 3-2-5 and 3-2-6, respectively, or as required by this paragraph,
whichever is the greater. The section modulus, SM, of each girder or web is not to be less than that
obtained from the following equation:
SM = 4.74chsl2 cm3
SM = 0.0025chsl2 in3
where
c = 1.5
h = vertical distance, in m (ft), from the middle of s in the case of a girder or from the
middle of l in the case of a web to the same heights to which h for the stiffeners is
measured (see 3-2-8/5.3)
s = sum of half lengths, in m (ft) (on each side of the girder or web), of the frames or
stiffeners supported by the girder or web.
l = unsupported length of girder or web, in m (ft). Where brackets are fitted in
accordance with 3-1-2/5.5, the length, l, may be measured as permitted therein.
The depth of a girder or web is not to be less than 2.5 times the depth of the cutout unless effective
compensation is provided for stiffener cutouts. The thickness is to be not less than 1 mm per 100 millimeters
(0.01 inch per inch) of depth plus 3 mm (0.12 in.) but need not exceed 11.5 mm (0.46 in.). Tripping
brackets are to be fitted at intervals of about 3 m (10 ft) and stiffeners are to be fitted as may be required.

7 Tank Top Plating

Tops of tanks are to have plating 1 mm (0.04 in.) thicker than would be required for vertical plating at the
same level. The thickness is not to be less than required for deck plating. Beams, girders and pillars are to
be as required by Section 3-2-6.

9 Higher-strength Materials

9.1 General
In general, applications of higher-strength materials for deep-tank plating are to meet the requirements of
this section, but may be modified as permitted by the following paragraphs. Calculations are to be submitted
to show adequate provision to resist buckling.

9.3 Plating
Deep-tank plating of higher-strength material is to be of not less thickness than that obtained by 3-2-8/5.1.

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Section 8 Deep Tanks 3-2-8

9.5 Stiffeners
Each stiffener of higher-strength material, in association with the higher-strength plating to which it is
attached, is to have section modulus, SMhts, not less than that obtained from the following equation:

SMhts = 7.8chsl2Q cm3

SMhts = 0.0041chsl2Q in3

c, h, s and l are as defined in 3-2-8/5.3 and Q is as defined in 3-2-1/7.5.

11 Drainage and Air Escape (2011)

Limber and air holes are to be cut, as required, in non-tight parts of the tanks to permit the free flow of
liquids to the suction pipes and the escape of air to the vents. Vent pipes are to be arranged to prevent over
pressuring of tanks. (See 4-4-3/9.1) Arrangements are to be made for draining the tops of the tanks.

13 Testing
Requirements for testing are contained in Section 3-7-1.

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PART Section 9: Superstructures and Deckhouses

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 9 Superstructures and Deckhouses

1 Superstructure Scantlings

1.1 Side and Top Plating

The thickness of superstructure side plating is to be not less than that obtained from the requirements of
3-2-2/5. The thickness is also not to be less than that required by 3-2-9/3.5 for exposed aft-end bulkheads.
Superstructure top plating is to be in accordance with Section 3-2-3.

1.3 Framing and Internal Bulkheads

Superstructure side frames are to be in accordance with 3-2-5/5.3. Bulkheads, partial bulkheads or web
frames are to be fitted in the superstructure over the main hull bulkheads and elsewhere, as may be
required to give effective transverse rigidity.

1.5 Breaks in Continuity

Breaks in the continuity of superstructures are to be specially strengthened (See 3-2-2/13). The arrangements
in this area are to be clearly shown on the plans submitted for approval. Openings and changes in the scantlings
of the decks and shell are to be kept well clear of the breaks.

1.7 Structural Support

Main bulkheads in the hull are to be arranged to provide support under the ends of the superstructures.

3 Exposed Bulkheads of Superstructures and Deckhouses

3.1 General
The scantlings of the exposed bulkheads of superstructures and deckhouses are to be in accordance with
the following paragraphs, except that the requirements for house side stiffeners need not exceed the
requirements of Section 3-2-5 for the side frames directly below the deck on which the house is located.
Special consideration may be given to the bulkhead scantlings of deckhouses which do not protect openings
in the freeboard deck, superstructure deck or in the top of a lowest tier deckhouse or which do not protect
machinery casings, provided they do not contain accommodation or do not protect equipment essential to
the operation or safety of the vessel.
Superstructures or deckhouses located within the midship 0.4L that have lengths greater than 0.1L are to
have effective longitudinal scantlings to give a hull-girder section modulus through the superstructure or
deckhouse meeting the requirements for the main hull-girder. The superstructure scantlings are to be in
accordance with 3-2-9/1 and the house top and side plating of long deckhouses are to be not less than
0.009s + 0.8 mm (0.009s + 0.032 in.) where s is the spacing of the deck beams in mm (in.).
Partial bulkheads, deep webs, etc. are to be fitted at the ends and sides of large superstructures or deckhouses
to provide resistance to racking.
In general, the first or lowest tier is that located on the freeboard deck. Where the depth to the uppermost
continuous weather deck is such that the freeboard to this deck exceeds tabular freeboard by at least one
standard superstructure height, deckhouses and superstructures on this weather deck may be considered
second tier. Watertight bulkheads are to extend to this weather deck. This consideration of excess
freeboard may be followed in a similar manner to determine third tier deckhouses or superstructures.

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Section 9 Superstructures and Deckhouses 3-2-9

3.3 Stiffeners
Each stiffener, in association with the plating to which it is attached, is to have section modulus, SM, not
less than that obtained from the following equation:
SM = 3.5sl2h cm3
SM = 0.00185sl2h in3
where
s = stiffener spacing, in m (ft)
l = tween deck height or unsupported length, in m (ft)
h = a[(bf) – y]c, design head in m (ft). For unprotected front bulkheads on the lowest tier,
h is to be taken as not less than 9.9 m (32.5 ft), and for sides and ends of first tier, h is
to be taken as not less than 3.3 m (10.8 ft). For all other bulkheads the minimum
value of h is to be not less than 1.25 + L/200 m (4.1 + L/200 ft).
a = coefficient given in 3-2-9/Table 1.
2
 ( x / L) − 0.45 
b = 1.0 +   where (x/L) ≤ 0.45
 C b + 0.2 
2
 ( x / L) − 0.45 
b = 1.0 + 1.5   where (x/L) > 0.45
 C b + 0.2 
Cb = block coefficient at summer load waterline, based on the vessel’s length, L, as
defined in 3-1-1/3, not to be taken less than 0.60 nor greater than 0.80. For aft end
bulkheads forward of amidships, Cb need not be taken as less than 0.80.
x = distance, in m (ft), between the after perpendicular and the bulkhead being considered.
Deckhouse side bulkheads are to be divided into equal parts not exceeding 0.15L in
length, and x is to be measured from the after perpendicular to the center of each part
considered.
L = length of vessel, as defined in 3-1-1/3, in m (ft)
f = (L/10)(e–L/300) – [1 – (L/150)2] for L, in m, see also 3-2-9/Table 2
–L/984 2
(L/10)(e ) – [3.28 – L/272) ] for L, in ft, see also 3-2-9/Table 2
y = vertical distance, in m (ft), from the summer load waterline to the midpoint of the
stiffener span.
c = (0.3 + 0.7b1/B1), but is not to be taken as less than 1.0 for exposed machinery casing
bulkheads. In no case is b1/B1 to be taken as less than 0.25.
b1 = breadth of deckhouse at position being considered, in m (ft)
B1 = actual breadth of vessel at the freeboard deck at the position being considered, in m (ft)
Where windows are fitted in bulkheads, the spacing, s, is to be the spacing of the mullion stiffeners. The
mullion stiffeners are to extend continuously from deck to deck.

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 9 Superstructures and Deckhouses 3-2-9

TABLE 1
Values of a
Bulkhead Location Metric Units US Units
Unprotected front Lowest tier 2.0 + L/120 2.0 + L/393.6
Unprotected front Second tier 1.0 + L/120 1.0 + L/393.6
Unprotected front Third tiers 0.5 + L/150 0.5 + L/492
Protected front All tiers 0.5 + L/150 0.5 + L/492
Sides, All tiers 0.5 + L/150 0.5 + L/492
Aft ends, aft of amidships, All tiers 0.7 + (L/1000) – 0.8x/L 0.7 + (L/3280) – 0.8x/L
Aft ends, forward of amidships, All tiers 0.5 + (L/1000) – 0.4x/L 0.5 + (L/3280) – 0.4x/L

TABLE 2
Values of f
Intermediate values of f may be obtained by interpolation

SI and MKS Units US Units

L, m f L, ft f
24 1.24 79 4.09
40 2.57 130 8.34
60 4.07 200 13.6
80 5.41 250 17.0
90 6.00 295 19.8

3.5 Plating
The plating is to be not less in thickness than that obtained from the following equation:

t = 3s h mm

t = s h /50 in.
where
s and h are as defined in 3-2-9/3.3 above. When determining h, y is to be measured to the middle of the panel.
In no case is the thickness for bulkheads, other than the lowest tier, to be less than 5.0 mm (0.20 in.).
In addition, the thicknesses are to be not less than the following:
For the lowest tier and for deckhouses on the forecastle deck:
For front bulkheads:
t = (s/0.60)(6 + 0.02L) mm
t = (s/1.97)(0.24 + 0.00024L) in.
For side and end bulkheads:
t = (s/0.60)(5 + 0.02L) mm
t = (s/1.97)(0.20 + 0.00024L) in.
Where L is as defined in 3-2-9/3.3 and s is as defined in 3-2-9/3.3, but is not to be taken less than 0.60 m
(1.97 ft).

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Section 9 Superstructures and Deckhouses 3-2-9

3.7 End Attachments (2016)

The upper and lower ends of all lowest tier bulkhead stiffener webs and the 2nd tier unprotected front bulkhead
stiffener webs are to be efficiently welded. The end attachments are to be formed by end brackets, by welding
the webs all around to the deck plating or by lapping the stiffener onto the deck beam to prevent stress
concentration.
The ends of all transverse webs in way of girders or transverses are to be welded.
Where only the webs are welded, the flange or face bar is to be sniped not more than 30°.
The webs of all the bulkhead stiffeners may be sniped, having due regard to their scantlings and the depth
of the web.

3.9 Raised-quarter-deck Bulkheads

Raised-quarter-deck bulkheads are to have plating of not less thickness than required for unprotected front
bulkheads.
The sizes of stiffeners are to be specially considered on the basis of the length of the vessel, the actual
height of the raised quarter deck and the arrangement of the structure.

5 Enclosed Superstructures

5.1 Closing Appliances (2017)

All openings in the bulkheads of enclosed superstructures are to be provided with efficient means of
closing, so that in any sea conditions, water will not penetrate the vessel. Opening and closing appliances are
to be framed and stiffened so that the whole structure, when closed, is equivalent to the unpierced bulkhead.
Doors for access openings into enclosed superstructures are to be of steel or other equivalent material,
permanently and strongly attached to the bulkhead. Scantlings for door panels and stiffeners are to be
obtained from 3-2-9/3.3 and 3-2-9/3.5 based on the design head of the bulkhead where the door is located.
Minimum thickness requirements in 3-2-9/3.3 for exposed bulkheads are to be applied to panels of doors
located on exposed bulkheads of superstructure and deckhouses at and below Position 2 and to doors
located on the exposed front bulkhead at all levels. The doors are to be provided with gaskets and clamping
devices, or other equivalent arrangements, permanently attached to the bulkhead or to the doors themselves,
and the doors are to be so arranged that they can be operated from both sides of the bulkhead. Doors located
above Position 2 (refer to 3-2-12/5.1) of superstructure and deckhouses are to have strength compatible to
adjacent bulkheads and may be of joiner-type construction (e.g., thin gauge steel sheeting surrounding a
mineral wool core), provided they are verified to be weathertight to the satisfaction of the attending Surveyor.
Marine doors rated for the same design head as the bulkhead where they are located and which are designed
and built to industry standards (the current versions of ASTM F1069, JIS F 2318, and BSI Standards
BSMA 39) are considered acceptable as meeting requirements in this Section
Portlights in the end bulkheads of enclosed superstructures are to be of substantial construction and provided
with efficient inside deadlights. Also see 3-2-14/7 and 3-2-14/9.
The location and means of the closing appliances for windows are to be in accordance with 3-2-14/9.

5.3 Sills of Access Openings

Except as otherwise provided in these Rules, the height of the sills of access openings in bulkheads at the
ends of enclosed superstructures is to be at least 380 mm (15 in.) above the deck. See 3-2-12/Table 1 for
required sill heights.

5.5 Means of Access

Superstructures are not to be regarded as enclosed unless access is provided for the crew to reach
machinery and other working spaces inside these superstructures by alternate means which are available at
all times when bulkhead openings are closed.

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Section 9 Superstructures and Deckhouses 3-2-9

7 Open Superstructures
Superstructures with openings which do not fully comply with 3-2-9/5 are to be considered as open
superstructures. See also 3-2-14/5.7.

9 Deckhouses (2017)
Deckhouses are to comply with 3-2-9/3. Bulkheads are to be arranged as necessary in the main hull to
support deckhouses.
The closing appliances for the openings in deckhouse bulkheads are to comply with 3-2-9/5.1.
Doors for access openings into deckhouses are to be of steel or other equivalent material, permanently and
strongly attached to the bulkhead. Scantlings for door panels and stiffeners are to be obtained from 3-2-9/3.3
and 3-2-9/3.5 based on the design head of the bulkhead where the door is located. Minimum thickness
requirements in 3-2-11/3.3 for exposed bulkheads are to be applied to panels of doors located on exposed
bulkheads of superstructure and deckhouses at and below position two and to doors located on the exposed
front bulkhead at all levels. The doors are to be provided with gaskets and clamping devices, or other
equivalent arrangements, permanently attached to the bulkhead or to the doors themselves, and the doors are to
be arranged so that they can be operated from both sides of the bulkhead. Doors located above Position 2
of superstructure and deckhouses are to have strength compatible to adjacent bulkheads and may be of
joiner-type construction (e.g., thin gauge steel sheeting surrounding a mineral wool core), provided they
are verified to be weathertight to the satisfaction of the attending Surveyor.
Marine doors rated for the same design head as the bulkhead where they are located and which are designed
and built to industry standards (the current versions of ASTM F1069, JIS F 2318, and BSI Standards
BSMA 39) are considered acceptable as meeting requirements in this Section

10 Aluminum Deckhouses (2002)

10.1 Scantling Correction

Where deckhouses are constructed of aluminum alloys, the required plate thickness and stiffener section
modulus, SM, are first to be determined as required for steel deckhouses, and are then to be increased by
the material factor, Q0, as indicated below.
For all deck and bulkhead plating and stiffeners, the required thickness and section modulus for aluminum
alloy plate and shapes are obtained from the following equations:
Deck plating:

0.9(Q + Q )
t al = ts
2
Bulkhead plating:
tal = 0.9Q0ts
Deck and bulkhead stiffeners:
SMal = 0.9Q0SMs
where
tal = minimum thickness of aluminum plate
ts = required plate thickness for steel obtained from 3-2-3/3 for decks and 3-2-9/3.5 for
side and end bulkheads
SMal = minimum section modulus of aluminum stiffeners
SMs = minimum section modulus of steel stiffeners, as determined from 3-2-6/1 and 3-2-6/3
for deck stiffeners and 3.2.9/3.3 for bulkhead stiffeners

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Q = material factor, as determined from 3-2-9/10.3 below

Q0 = material factor, as determined from 3-2-9/10.3 below

10.3 Material Factors

The material factor, Q, is obtained from the following equation:
Q = 0.9 + (120/Yal) SI Units
Q = 0.9 + (12/Yal) MKS Units
Q = 0.9 + (17000/Yal) U.S. Units
but is not to be taken as less than Q0 below.
The material factor, Q0, is obtained from the following equation:

Q0 = 635/(σy +σu) SI Units

Q0 = 65/(σy +σu) MKS Units

Q0 = 92000/(σy +σu) U.S. Units

Yal = minimum yield strength of the welded aluminum alloy under consideration at 2%
offset in a 254 mm (10 in.) gauge length, in N/mm2 (kgf/mm2, psi), in accordance
with the requirements of the table below
σu = minimum ultimate strength of the welded aluminum alloy under consideration, in
N/mm2 (kgf/mm2, psi), in accordance with the table below
σy = minimum yield strength of the welded aluminum alloy under consideration, in
N/mm2 (kgf/mm2, psi), in accordance with the table below

Minimum Mechanical Properties for Butt-Welded Aluminum Alloys (2011)

Alloy Ultimate Tensile Strength (σu) Yield Strength (σy) (3)
N/mm2 (kgf/mm2, psi) N/mm2 (kgf/mm2, psi)
5083 (1) 275 (28.1, 40000) 125 (12.7, 18000)
(1)
5086 240 (24.6, 35000) 95 (9.85, 14000)
5454 (1) 215 (21.8, 31000) 85 (8.45, 12000)
(1)
5456 290 (29.5, 42000) 130 (13.4, 19000)
6061-T6 (2) 165 (16.9, 24000) 105 (10.6, 15000)
Notes:
1 (2011) For other tempers, refer to 2-5-A1/Table 2 of the ABS Rules for Materials and Welding (Part 2) –
Aluminum and Fiber Reinforced Plastics (FRP).
2 Values when welded with 4043, 5183, 5356 or 5556 filler wire.
3 Yield strength is not required for weld procedure qualification. Values shown apply to the yield
strength values of 3-2-9/10.3.
For other alloys, refer to Table 4 of Section 3 of the Aluminum Association’s
Aluminum Construction Manual.

10.5 Attachments
Stiffeners on bulkheads are to be attached to the deck plating at their upper and lower ends by welding all
around, for which cladding metal is to be inserted between stiffeners and steel deck plate. Suitable means
are to be taken to avoid direct contact of faying surfaces of aluminum to steel.

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Section 9 Superstructures and Deckhouses 3-2-9

11 Helicopter Decks

11.1 General
Helicopter landing facilities, where provided, are to meet the following structural and safety requirements.
The attention of owners, builders and designers is directed to various international and governmental
regulations and guides regarding the operational and other design requirements for helicopters landing on
ships. See also Section 1-1-5 of the ABS Rules for Conditions of Classification (Part 1) and 4-5-1/7 of
these Rules. Plans showing the arrangement, scantlings and details of the helicopter deck are to be
submitted. The arrangement plan is to show the overall size of the helicopter deck and the designated
landing area. If the arrangement provides for the securing of a helicopter or helicopters to the deck, the
predetermined position(s) selected to accommodate the secured helicopter, in addition to the locations of
deck fittings for securing the helicopter, are to be shown. The type of helicopter to be considered is to be
specified and calculations for appropriate loading conditions are to be submitted.

11.3 Structure
Scantlings of helicopter decks and supporting structure are to be determined on the basis of the following
loading conditions, whichever is greater, in association with the allowable factors of safety shown in
3-2-9/Table 3. Plastic design considerations may be applied for deck plating and stiffeners.
11.3.1 Overall Distributed Loading
A minimum distributed loading of 2010 N/m2 (205 kgf/m2, 42 lbf/ft2) is to be taken over the entire
helicopter deck.
11.3.2 Helicopter Landing Impact Loading
A load of not less than 75% of the helicopter maximum take-off weight is to be taken on each of
two square areas, 0.3 m × 0.3 m (1 ft × 1 ft). Alternatively, the manufacturer’s recommended wheel
impact loading will be considered. The deck is to be considered for helicopter landings at any
location within the designated landing area. The structural weight of the helicopter deck is to be
added to the helicopter impact loading when considering girders, stanchions, truss supports, etc.
Where the upper deck of the superstructure or deckhouse is used as a helicopter deck and the
spaces below are normally manned (quarters, bridge, control room, etc.), the impact loading is to
be multiplied by a factor of 1.15.
11.3.3 Stowed Helicopter Loading
If provisions are made to accommodate helicopters secured to the deck in a predetermined position,
the structure is to be considered for a local loading equal to the manufacturer’s recommended
wheel loadings at maximum take-off weight, multiplied by a dynamic amplification factor based
on the predicted motions of the vessel for this condition, as may be applicable for the vessel under
consideration.
In addition to the helicopter load, a uniformly distributed loading of 490 N/m2 (50 kgf/m2, 10.5 lbf/ft2)
representing wet snow or ice is to be considered, if applicable. For the girders, stanchions, truss
supports, etc., the structural weight of the helicopter deck is also to be considered.
11.3.4 Loading due to Motions of Vessel
The structure supporting helicopter decks is to withstand the loads resulting from the motions of
the vessel.
11.3.5 Special Landing Gear
Helicopters fitted with landing gear other than wheels will be specially considered.
11.3.6 Environmental Loading
Calculations are to consider anticipated wind and wave impact loadings on helicopter decks and
their supporting structures.

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11.3.7 Bolted Connections (2018)

Where bolted connections are used, calculations are to be carried out in accordance with a recognized
standard and submitted for review. Metallic isolation arrangement is to be provided where galvanic
potential exists between different materials. The degree of fixity of structural components incorporating
bolted connections is to be properly considered in the helideck structural assessment. Where fully
fixed connection is considered, the bolted connection is to be designed with enough stiffness to
account for the full transfer of moment and prevent relative rotation of the structural components.

11.5 Safety Net

The unprotected perimeter of the helicopter landing deck is to be provided with safety netting or equivalent.

11.7 Aluminum Decks (2018)

For requirements on aluminum helicopter decks, refer to 3-2-11/11.5 of the ABS Rules for Building and
Classing Offshore Support Vessels.

11.9 Means of Escape and Access (2018)

The helicopter deck is to be provided with both a main and an emergency means of escape and access for
fire fighting and rescue personnel. These means are to be located as far apart from each other as is practicable
and preferably on opposite sides of the helicopter deck.
Aluminum access/egress platforms and stairways leading to and from the aluminum helideck are acceptable,
provided the following conditions are satisfied:
i) Conditions in 3-2-11/11.5 of the ABS Rules for Building and Classing Offshore Support Vessels
are complied with.
ii) Acceptance from the flag Administration.
iii) The firefighting equipment, which includes the hose reel, portable fire extinguishers, fixed foam
system, is to provide coverage for the access/egress platforms and stairways. The capacity of the
fixed foam system is to be increased to include the additional areas of protection for the aluminum
access/egress platforms and stairways
iii) Where the helideck is also used as a firefighting station, the aluminum access/egress platforms and
stairways are to meet the L3 fire integrity test, or equivalent as per 3-4-A1/Table 1 of the Steel
Vessel Rules.
iv) Where alternative means of fire protection (such as deluge system) are provided (typically along
stairways or access under the helideck), and the arrangement and locations of the firefighting
equipment, required in i) above are also available at or cover the access/egress route, the L3
performance test will not be necessary.
vi) Where the helideck is fitted with a refueling station, there is to be sufficient distance from the
refueling station to at least one of the stairs, such that the aluminum stairs are not impacted by the
fire at the refueling station.
In case of a fire outside the helideck area, access platforms and stairways are not to be considered part of
an escape route.

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Section 9 Superstructures and Deckhouses 3-2-9

TABLE 3
Allowable Factors of Safety Based on Y for Helicopter Decks
Y = specified minimum yield point or yield strength of the material

Plating Beams Girders, Stanchions

Truss Supports, etc.
(See Note 3)
Overall Distributed Loading 1.67 1.67 1.67
Helicopter Landing Impact Loading (See Note 1) 1.00 1.10
1.00 (2)
Stowed Helicopter Loading 1.00 1.10 1.25
Notes:
1 The minimum plate thickness, t, is generally not to be less than that obtained from the following:

Beam Spacing t Beam Spacing t

460 mm 4.0 mm 18 in. 0.16 in.
610 mm 5.0 mm 24 in. 0.20 in.
760 mm 6.0 mm 30 in. 0.24 in.

2 Alternatively, ultimate state limit methods may be considered.

3 For members subjected to axial compression, the factor of safety is to be based on the yield stress or critical buckling
stress, whichever is less.

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PART Section 10: Keels, Stems, Stern Frames, Shaft Struts and Propeller Nozzles

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 10 Keels, Stems, Stern Frames, Shaft Struts, and

Propeller Nozzles

1 Keels

1.1 Bar Keels

Bar keels are to have thicknesses and depths not less than that obtained from the following equations:
t = 0.625L + 12.5 mm t = 0.0075L + 0.50 in.
h = 1.46L + 100 mm h = 0.0175L + 4 in.
where
t = thickness, in mm (in.)
h = depth, in mm (in.)
L = length of vessel, in m (ft), as defined in Section 3-1-1
Thicknesses and widths other than given above are acceptable, provided the section moduli and moments
of inertia about the transverse horizontal axis are not less than given above, nor is h/t more than 4.5.

1.3 Plate Keels

The thickness of the plate keel throughout the length of the vessel is to be not less than the bottom shell
required in 3-2-2/3.3.

3 Stems

3.1 Bar Stems

Bar stems are to have thicknesses and widths not less than that obtained from the following equations:
t = 0.625L + 6.35 mm t = 0.0075L + 0.25 in.
w = 1.25L + 90 mm w = 0.015L + 3.5 in.
where
t = thickness, in mm (in.)
w = width, in mm (in.)
L = length of vessel, in m (ft), as defined in Section 3-1-1
This thickness and width is to be maintained between the keel and design load waterline. Above the design
load waterline, they may be gradually reduced until the area at the head is 70% of that obtained from the
equations.
Thicknesses and widths other than given above are acceptable, provided the section moduli and moments
of inertia about the longitudinal axis are not less than above, nor w/t more than 5.5. The thickness of the
bar stem, in general, should also not be less than twice the shell thickness.

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Section 10 Keels, Stems, Stern Frames, Shaft Struts, and Propeller Nozzles 3-2-10

3.3 Cast or Forged Stems

Cast or forged stems of special shape are to be proportioned to provide strengths at least equivalent to
those of bar stems, as obtained in 3-2-10/3.1, and all joints and connections are to be at least as effective as
would be required on equivalent bar stems.

3.5 Plate Stems

Where plate stems are used, they are not to be less in thickness than the bottom shell plating required in
3-2-2/1 and 3-2-2/3, where s is the frame spacing, or 610 mm (24 in.), if greater.

5 Sternposts

5.1 Bar Sternposts

Bar sternposts without propeller bosses are to have thicknesses and widths not less than that obtained from
the following equations:
t = 0.73L + 10 mm t = 0.0088L + 0.39 in.
b = 1.283L + 87.4 mm b = 0.0154L + 3.44 in.
where
t = thickness, in mm (in.)
b = width, in mm (in.)
L = length of vessel, in m (ft), as defined in Section 3-1-1
Above the bottom shell plating, sternposts may be gradually reduced until the areas at their heads are half
the areas obtained from the above equations.
Thickness or width less than given above are acceptable, provided the section modulus and moment of
inertia about the longitudinal axis are not less than those of a plate having the minimum thickness and
width given above, and with b/t not more than 4.0.

5.3 Cast, Forged, or Fabricated Sternposts

Cast, forged or fabricated sternposts of special shape are to be so proportioned as to provide strengths at least
equivalent to those of bar posts, as obtained from 3-2-10/5.1, and all joints and connections are to be at
least as effective as would be required on equivalent bar posts.

7 Stern Frames
Except as modified in 3-2-10/9, the scantlings of stern frames of single screw vessels are to be in accordance
with the following, as applicable.

7.1 Below the Boss

7.1.1 Fabricated Stern Frame
The thickness, t, width, w, and length, l, are not to be less than given by the following equations:

t = 0.225 L cm t = 0.049 L in.

w = 5 L cm w = 1.09 L in.

l = 4 L cm l = 0.87 L in.
Widths and lengths other than given above are acceptable, provided the section modulus, SM, about
the longitudinal axis is not less than:
SM = 1.60L1.5 cm3 SM = 0.0164L1.5 in3

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where
t = thickness of side plating, in cm (in.) (See 3-2-10/Figure 1)
w = width of stern frame, in cm (in.) (See 3-2-10/Figure 1)
l = length of stern frame, in cm (in.) (See 3-2-10/Figure 1)
L = length of vessel, in m (ft), as defined in Section 3-1-1
7.1.2 Cast Stern Frame
The thicknesses, t1, t2, width, w, and length, l, are not to be less than given by the following equations:

t1 = 0.3 L cm t1 = 0.065 L in.

but not less than 2.5 cm (1.0 in.)
t2 = 1.25t1

w = 5 L cm w = 1.09 L in.

l = 4 L cm l = 0.87 L in.
Widths and lengths other than given above are acceptable, provided the section modulus, SM, about
the longitudinal axis is not less than:
SM = 1.60L1.5Kg cm3 SM = 0.0164L1.5Kg in3
where
t1 = thickness of casting at end. (See 3-2-10/Figure 1)
t2 = thickness of casting at mid-length. (See 3-2-10/Figure 1)
Kg = material factor defined in 3-2-11/1.3

w, l, L are as defined in 3-2-10/7.1.1.

The thickness in way of butt welding to shell plating may be tapered below t1. The length of taper
is to be at least three times the offset.
The castings are to be cored out to avoid large masses of thick material likely to contain defects
and to maintain a relatively uniform section throughout. Suitable radii are to be provided in way of
changes in section.

7.3 Above the Boss

Above the propeller boss, the scantlings are to be in accordance with 3-2-10/7.1, except that in the upper
part of the propeller aperture where the hull form is full and centerline supports are provided, the thickness
may be reduced to 80% of the requirements in 3-2-10/7.1, subject to the same minimum for cast steel stern
frames.

7.5 Secondary Members

Where round bars are used at the after edge of stern frames, their scantlings and connection details are to
be such as to facilitate welding.
Ribs or horizontal brackets of thickness not less than 0.8t or 0.8t1 are to be provided at suitable intervals,
extended forward and attached to the adjacent floor. Where t or t1 is reduced in accordance with 3-2-10/7.3, a
proportionate reduction in the thickness of ribs or horizontal brackets may be made.

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Section 10 Keels, Stems, Stern Frames, Shaft Struts, and Propeller Nozzles 3-2-10

FIGURE 1
Stern Frame

t
w

a. Fabricated

l/2

t1

t2
w

l
b. Cast

9 Stern Frames with Shoepieces

The scantlings below the boss of stern frames with shoepieces are to be gradually increased to provide
strength and stiffness in proportion to those of the shoepieces.

11 Shoepieces

11.1 General
The shoepiece is to be sloped to avoid pressure from the keel blocks when docking and is to extend at least
two frame spaces forward of the forward edge of the propeller boss.

11.3 Design Stress

The equivalent stress, σe, in the shoepiece at any section is not to exceed 115/Kg N/mm2 (11.7/Kg kgf/mm2,
16700/Kg psi) and is to be obtained from the following equation:

σ e = n σ b2 + 3τ 2
where
n = 1000 (1000, 2240)
Kg = K, as defined in 3-2-11/1.3 for castings and forgings
= 1.0 for ordinary strength hull steel plate

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σb = bending stress = 0.5CRl/Zv

CR = rudder force, as defined in 3-2-11/3.
l = horizontal distance between centerline of rudder stock and the particular section of
the stern frame shoe, in m (in.) (see 3-2-10/Figure 2)
Zv = section modulus of shoepiece about the vertical axis at the particular section under
consideration, in cm3 (in3)
τ = shear stress = 0.5CR/As
As = sectional area at the section of the shoepiece under consideration, in mm2 (in2)

11.5 Minimum Scantlings

In addition, shoepiece width is to be approximately twice the depth, and vertical and horizontal section
modulus and sectional area are in no case less than required by the following equations.
Zz = kzCRlKg cm3 (in3)

Zy = 0.5Zz cm3 (in3)

As′ = kaCRKg mm2 (in2)

where
Zz = minimum required section modulus of shoepiece about the vertical axis at the
particular section under consideration
Zy = minimum required section modulus of shoepiece about the transverse horizontal axis
at the particular section under consideration
As ′ = minimum required sectional area of shoepiece at the section under consideration
kz = 6.25 (61.3, 0.0967)
ka = 10.4 (102, 0.161)
CR, l and Kg are as defined in 3-2-10/11.3.

FIGURE 2
Shoepiece

13 Rudder Horns
Vessels that have rudder horns are to meet the requirements in 3-2-13/5 of the Steel Vessel Rules.

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Section 10 Keels, Stems, Stern Frames, Shaft Struts, and Propeller Nozzles 3-2-10

15 Rudder Gudgeons
Rudder gudgeons are to be an integral part of the stern frame. The bearing length of the pintle is to be
between 1.0 and 1.2 times the pintle diameter, and the thickness of the pintle housing is not to be less than
25% of the pintle diameter.

17 Shaft Struts

17.1 General
Tail-shaft (propeller-shaft) struts, where provided, may be of the V or I type. The thickness of the strut
barrel or boss is to be at least one-fourth the diameter of the tail shaft. The length of the strut barrel or boss
is to be adequate to accommodate the required length of propeller-end bearings. The following equations
are for struts having streamlined cross-sectional shapes.

17.3 V Strut
17.3.1 Inertia
The moment of inertia, Ix-x, of each strut arm is not to be less than that obtained from the following
equation:
Ix-x = 0.0044D4 mm4 (in4)
where
D = required diameter of ABS Grade 2 tail shaft, in mm (in.) (see Section 4-3-1)
17.3.2 Section Modulus
The section modulus, SMx-x, of each strut arm is not to be less than that obtained from the following
equation:
SMx-x = 0.024D3 mm3 (in3)
where
D = required diameter of ABS Grade 2 tail shaft, in mm (in.)
Where the included angle is less than 45 degrees, the foregoing scantlings are to be specially
considered.

17.5 I Strut
17.5.1 Inertia
The moment of inertia, Ix-x, of the strut arm is not to be less than that obtained from the following
equation:
Ix-x = 0.018D4 mm4 (in4)
where
D = required diameter of ABS Grade 2 tail shaft, in mm (in.)
17.5.2 Section Modulus
The section modulus, SMx-x, of the strut is not to be less than that obtained from the following
equation:
SMx-x = 0.068D3 mm3 (in3)
where
D = required diameter of ABS Grade 2 tail shaft, in mm (in.)

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Chapter 2 Hull Structures and Arrangements
Section 10 Keels, Stems, Stern Frames, Shaft Struts, and Propeller Nozzles 3-2-10

17.7 Strut Length

The length of the longer leg of a V strut or the leg of an I strut, measured from the outside perimeter of the
strut barrel or boss to the outside of the shell plating, is not to exceed 10.6 times the diameter of the tail
shaft. Where this length is exceeded, the width and thickness of the strut are to be increased, and the strut
design will be given special consideration.

19 Propeller Nozzles (2009)

19.1 Application
The requirements in this section are applicable for fixed propeller nozzles with inner diameter d of
5 meters (16.4 feet) or less. Nozzles of larger inner diameter are subject to special consideration with all
supporting documents and calculations submitted for review.

19.3 Design Pressure

The design pressure of the nozzle is to be obtained from the following:
 N 
p d = 10 −6 ⋅ c ⋅ ε ⋅   N/mm2 (kgf/mm2, psi)
 Ap 
 
where
c = coefficient as indicated in 3-2-10/Table 1
ε = coefficient as indicated in 3-2-10/Table 2, but not to be taken less than 10
N = maximum shaft power, in kW (hp)
Ap = propeller disc area
π
= D2 , in m2 (ft2)
4
D = propeller diameter, in m (ft)

TABLE 1
Coefficient c (2009)

Propeller Zone c
2
(see 3-2-10/Figure 3) pd in N/mm pd in kgf/mm2 pd in psi
2 10.0 1.02 11.62 × 103
1&3 5.0 0.51 5.81 × 103
4 3.5 0.36 4.067 × 103

TABLE 2
Coefficient ε (2009)
pd in N/mm2 pd in kgf/mm2 pd in psi
 N   N   N 
ε 21 − 2 × 10 − 2   21 − 2 × 10 − 2   21 − 16 × 10 − 2  
 Ap   Ap   Ap 
     

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Part 3 Hull Construction and Equipment
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Section 10 Keels, Stems, Stern Frames, Shaft Struts, and Propeller Nozzles 3-2-10

19.5 Nozzle Cylinder

19.5.1 Shell Plate Thickness
The thickness of the nozzle shell plating, in mm (in.), is not to be less than:
t = to + tc, but not to be taken less than 7.5 (0.3) mm (in.)
where
to = thickness obtained from the following formula:

= cn ⋅ Sp ⋅ p d Kn mm (in.)

cn = coefficient as indicated in 3-2-10/Table 3

Sp = spacing of ring webs in mm (in.)
pd = nozzle design pressure in N/mm2 (kgf/mm2, psi), as defined in 3-2-10/19.3
tc = corrosion allowance determined by 3-2-10/Table 4
Kn = nozzle material factor as defined in 3-2-11/1.3

TABLE 3
Coefficient cn (2009)
pd in N/mm2 pd in kgf/mm2 pd in psi
cn 1.58 × 10-1 4.95 × 10-1 1.32 × 10-2

TABLE 4
Corrosion Allowance tc (2009)
Value of to tc mm (in.)
If to ≤ 10.0 (0.4) 1.5 (0.06)
If to > 10.0 (0.4) the lesser of b1, b2
where
b1 = 3.0 (0.12) mm (in.)
 t   t 
b2 =  o
+ 5  × 10-1 mm or b2 =  o
+ 0.2  × 10-1 in.
 1/ K   1/ K 
 n   n 

19.5.2 Internal Diaphragm Thickness

Thickness of nozzle internal ring web is not to be less than the required nozzle shell plating for
Zone 3.

19.7 Nozzle Section Modulus

The minimum requirement for nozzle section modulus is obtained from the following formula:
SM = d2 b Vd2 Q n cm3 (in3)
where
d = nozzle inner diameter, in m (ft)
b = nozzle length, in m (ft)

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Section 10 Keels, Stems, Stern Frames, Shaft Struts, and Propeller Nozzles 3-2-10

Vd = design speed in ahead condition, in knots, as defined in 3-2-11/3.1

Q = reduction factor conditional on material type
= 1.0 for ordinary strength steel
= 0.78 for H32 strength steel
= 0.72 for H36 strength steel
= 0.68 for H40 strength steel
Q factor for steel having yield strength other than above is to be specially considered.
n = nozzle type coefficient taken equal to 0.7 (0.0012) for fixed nozzles

FIGURE 3
Propeller Nozzle Section View (2014)
Zone 2 Zone 2 Propeller disc
center plane center plane center plane
Zone 4 Zone 4

Zone 3 Zone 2 Zone 1 Zone 2 Zone 1

Zone 3

Z½ min
Z½ min

d
d
Propeller axis Propeller axis α

Nozzle axis
b b

(a) (b)

b = nozzle length
d = nozzle inner diameter
Zone 1 zone of nozzle inner skin from nozzle leading edge to the fore end of Zone 2
Zone 2 zone of nozzle inner skin in way of propeller tips with two ring webs
within the zone
z1/2 min = The minimum length on each side of Zone 2 center plane is to be:

b
= where Zone 2 center plane and propeller disc center plane
8 coincide as shown in 3-2-10/Figure 3(a);
b d
= cos α + tan α where α is the tilt angle between the Zone 2 and propeller
8 2 disc center planes, as shown in 3-2-10/Figure 3(b);
Zone 3 zone of nozzle inner and outer skin covering the tail vicinity, from aft end
of Zones 2 to the aft end of Zone 4
Zone 4 zone of nozzle outer skin from the leading edge to the fore end of Zone 3

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 10 Keels, Stems, Stern Frames, Shaft Struts, and Propeller Nozzles 3-2-10

19.9 Welding Requirement

The inner and outer nozzle shell plating is to be welded to the internal stiffening ring webs with double
continuous welds as far as practicable. Plug/slot welding is prohibited for the inner shell, but may be
accepted for the outer shell plating, provided that the nozzle ring web spacing is not greater than 350 mm
(13.8 in.).

21 Propulsion Improvement Devices (PID) as Hull Appendages (2017)

21.1 Application Scope

The requirements in this Subsection are applicable for Propulsion Improvement Devices (PID) hull appendages
including wake equalizing and flow separation alleviating devices (such as spoilers, wake equalizer, stern
tunnels, pre-swirl fins, stators, and pre-swirl ducts) and post swirl devices (such as rudder thrust fins, post
swirl stators, and rudder bulbs) that are permanently affixed to the hull structure.

21.3 Plans and Documentation

The following plans, details and calculations are to be submitted for approval:
i) Drawings and plans covering the detailed design of the structural components, including the end
connections and attachment to the hull structure;
ii) Information on material properties and welding details, such as scantlings of the welded connection
and welding detail and size;
iii) Calculations to validate the design of the PID and the supporting foundations interior to the vessel.
The calculations are to consider strength, fatigue and vibration in both the ahead and astern conditions.

21.5 Design and Arrangement

The following requirements are to be complied with for the propulsion improvement devices as outlined in
3-2-10/21.1. Devices of novel concept are to be specially considered with all the related drawings and
documents submitted:
i) The structural materials are to be compatible with the mechanical and chemical properties of the
hull strake to which it is attached. Examples of such design considerations are to have adequate
structural strength for load bearing/transferring and acceptable galvanic potential between
materials to reduce the risk of galvanic corrosion.
ii) PID end connections are to have a suitable transition for the particular application and to be
effectively terminated in way of internal stiffening members.

21.7 Structural End Connection

Welded end connections of device structural component to the hull are to be designed and constructed in
accordance with the following:
i) Welding at the connection is to be full penetration and is to be in accordance with Section 2-4-1 of
the ABS Rules for Materials and Welding (Part 2) and Section 3-2-16, as applicable.
ii) Nondestructive volumetric and surface examinations are to be performed on the welds of the
connection plates and the shell penetration. 100% Magnetic Testing (MT) and at least 10% Ultrasonic
Testing (UT) is to be carried out on the welds of the connection plates and the shell penetration.

23 Inspection of Castings
The location of radiographic or other subsurface inspections of large stern-frame and rudder-horn castings
is to be indicated on the approved plans. See applicable parts of Chapter 1 of the ABS Rules for Materials
and Welding (Part 2).

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PART Section 11: Rudders and Steering Equipment

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 11 Rudders and Steering Equipment (2009)

1 General

1.1 Application (1 July 2016)

Requirements specified in this section are applicable to:
i) Ordinary profile rudders described in 3-2-11/Table 1A;
ii) High-lift rudders described in 3-2-11/Table 1B;
iii) Other steering equipment other than rudders identified in Section 3-2-11.
Rudders not covered in 3-2-11/Table 1A or 3-2-11/Table 1B are subject to special consideration, provided
that all the required calculations are prepared and submitted for review in full compliance with the requirements
in this section. Where direct analyses adopted to justify an alternative design are to take into consideration
all relevant modes of failure, on a case by case basis. These failure modes may include, amongst others:
yielding, fatigue, buckling and fracture. Possible damages caused by cavitation are also to be considered.
Validation by laboratory tests or full scale tests may be required for alternative design approaches.
Rudders and other steering equipment provided on Ice Classed vessels, are subject to additional requirements
specified in 6-1-4/31 or 6-1-5/41 of the Steel Vessel Rules.

1.3 Materials for Rudder, Rudder Stock and Steering Equipment (1 July 2015)
Rudder stocks, pintles, coupling bolts, keys and other steering equipment components described in this
Section are to be made from material in accordance with the requirements of Chapter 1 of the ABS Rules
for Materials and Welding (Part 2), 3-1-2/Table 2, and particularly:
i) The Surveyor need not witness material tests for coupling bolts and keys.
ii) The surfaces of rudder stocks in way of exposed bearings are to be of noncorrosive material.
iii) Material properties of dissimilar parts and components in direct contact with each other are to be
submitted for review of compatibilities, such as galvanic potential.
iv) Material factors of castings and forgings used for the shoe piece (Kg), horn (Kh), stock (Ks), bolts (Kb),
coupling flange (Kf), pintles (Kp), and nozzles (Kn) are to be obtained for their respective material
from the following equation:
K = (ny/Y)e
where
ny = 235 N/mm2 (24 kgf/mm2, 34000 psi)
Y = specified minimum yield strength of the material, in N/mm2 (kgf/mm2, psi), but
is not to be taken as greater than 0.7U or 450 N/mm2 (46 kgf/mm2, 65000 psi),
whichever is less
U = minimum tensile strength of material used, in N/mm2 (kgf/mm2, psi)
e = 1.0 for Y ≤ 235 N/mm2 (24 kgf/mm2, 34000 psi)
= 0.75 for Y > 235 N/mm2 (24 kgf/mm2, 34000 psi)

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Section 11 Rudders and Steering Equipment 3-2-11

1.5 Expected Torque

The torque considered necessary to operate the rudder in accordance with 4-3-3/1.9 is to be indicated on
the submitted rudder or steering gear plan. See 4-3-3/1.5 and 3-2-11/5.7.
Note that this expected torque is not the design torque for rudder scantlings.

1.7 Rudder Stops

Strong and effective structural rudder stops are to be fitted. Where adequate positive mechanical stops are
provided within the steering gear in accordance with 4-3-3/5.1, structural stops will not be required.

3 Rudder Design Force

Rudder force, CR, upon which rudder scantlings are to be based, is to be obtained from equation described
either in 3-2-11/3.1 or 3-2-11/3.3 as applicable. Where for the ordinary rudders the rudder angle, φ, exceeds
35°, the rudder force, CR, is to be increased by a factor of 1.74 sin (φ).

3.1 Rudder Blades without Cutouts (2014)

Where the rudder profile can be defined by a single quadrilateral, the rudder force is to be obtained from
the following equation:
CR = n kRkcklAVR2 kN (tf, Ltf)
where
n = 0.132 (0.0135, 0.00123)
kR = (b2/At + 2)/3 but not taken more than 1.33
b = mean height of rudder area, in m (ft), as determined from 3-2-11/Figure 1A
At = sum of rudder blade area, A, and the area of rudder post or rudder horn within the
extension of rudder profile, in m2 (ft2)
A = total projected area of rudder as illustrated in 3-2-11/Figure 1A, in m2 (ft2)
For steering nozzles, A is not to be taken less than 1.35 times the projected area of the
nozzle.
kc = coefficient depending on rudder cross section (profile type) as indicated in
3-2-11/Table 1A and 1B. For profile types differing from those in 3-2-11/Table 1A
and 1B, kc is subject to special consideration.
kl = coefficient as specified in 3-2-11/Table 2
VR = vessel speed, in knots
= for ahead condition VR equals Vd or Vmin, whichever is greater
= for astern condition VR equals Va or 0.5Vd, or 0.5Vmin, whichever is greater
Vd = design speed in knots with the vessel running ahead at the maximum continuous rated
shaft rpm and at the summer load waterline
Va = maximum astern speed in knots
Vmin = (Vd + 20)/3
Where there are any appendages such as rudder bulb fitted on the rudder, its effective areas are to be included
in the area of the rudder blade if significant.

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Section 11 Rudders and Steering Equipment 3-2-11

3.3 Rudder Blades with Cutouts

This paragraph applies to rudders with cutouts (semi-spade rudders), such that the whole blade area cannot
be adequately defined by a single quadrilateral. See 3-2-11/Figure 1B. Equations derived in this paragraph
are based on a cutout blade with two quadrilaterals. Where more quadrilaterals are needed to define the
rudder shape, similar rules apply.
The total rudder force described in 3-2-11/3.1 is applicable for rudders with cutout(s), with A being the
summation of sub-quadrilaterals that make up the whole area of the rudder blade. Rudder force distribution
over each quadrilateral is to be obtained from the following equations:
CR1 = CRA1/A kN (tf, Ltf)
CR2 = CRA2/A kN (tf, Ltf)
where
CR and A are as defined in 3-2-11/3.1.
A1 and A2 are as described in 3-2-11/Figure 1B.

3.5 Rudders Blades with Twisted Leading-Edge (2014)

This kind of rudder has the leading edge twisted horizontally on the top and bottom of the section that is an
extension of the center of the propeller shaft. For the purpose of calculating design force, twisted rudders
may be distinguished in four categories:

Category Description
1 The projected leading edge of twisted upper and lower blades not lineup
to each other
2 The projected leading edge of twisted upper and lower blades form a
straight line
3 Rudder with twisted leading-edge combined with tail edge flap or fins
4 The twisted leading edge has a smooth continuous wavy contour (no
deflector) or the rudder has multiple section profile types

Design force for rudder with twisted leading edge is obtained according to the following criteria:
i) For Category 1 rudders as indicated in the above table, design force over upper and lower rudder
blades are obtained from the following equations respectively:
CR1 = nkRkcklA1VR2 kN (tf, Ltf) for twisted upper rudder blade;
CR2 = nkRkcklA2VR2 kN (tf, Ltf) for twisted lower rudder blade;
CR = CR1+ CR2 kN (tf, Ltf) overall design force;
ii) For Categories 2, 3, and 4, rudder design force indicated in 3-2-11/3.1 is applicable, that is:
CR = nkRkcklAVR2 kN (tf, Ltf)
where
n, kR, kc, kl, A, and VR are as defined in 3-2-11/3.1, (for rudder has multiple section profile types, A
is the whole projected areas).
A1 and A2 are the projected areas of upper and lower blades separated at the deflector cross section,
respectively. Where the effective projected area of rudder bulb (if present) forward of rudder
leading edge is significant and needs to be counted, the proportioned bulb effective areas are added
to A1 and A2 accordingly
Values of kc for ahead and astern conditions are determined from one of the methods below as
applicable, if the type of basic rudder profile is not provided:
a) kc is taken from 3-2-11/Table 1A for twisted rudders of Categories 1 & 2;
b) kc is taken from 3-2-11/Table 1B for twisted rudders of Category 3;

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Section 11 Rudders and Steering Equipment 3-2-11

c) kc is subjected to special considerations for twisted rudders of Category 4;

d) Shipyard/rudder manufacturers’ submitted kc obtained from testing data or calculations
may be accepted subject to ABS review of all the supporting documents;

TABLE 1A
Coefficient kc for Ordinary Rudders (2014)
kc
Profile Type
Ahead Condition Astern Condition
Single plate
1 1.0 1.0

NACA-OO
2 GÖttingen
1.1 0.80

Flat side
3 1.1 0.90

Mixed
(e.g., HSVA)
4 1.21 0.90

Hollow
5 1.35 0.90

Twisted rudder of
6 Cat. 1 & 2 1.21 0.90
(if not provided) (if not provided)

TABLE 1B
Coefficient kc for High-Lift/Performance Rudders (1 July 2016)
kc
Profile Type
Ahead Condition Astern Condition
Fish tail
(e.g., Schilling high-lift
1
rudder) 1.4 0.8

Flap rudder (or

Twisted rudder of Cat. 3) 1.3
2 1.7
(if not provided)

Rudder with steering nozzle

3 1.9 1.5

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Section 11 Rudders and Steering Equipment 3-2-11

FIGURE 1A
Rudder Blade without Cutouts (2009)
z3 + z4 - z2 - z1
b= 2
z (vert)
Rudder Stock x3 + x2 - x1 - x4
c= 2
Centerline

4 A (see 3-2-11/3.1)
Af (see 3-2-11/5.3)
3

b A
Af

2 x (fwd)
1

FIGURE 1B
Rudder Blade with Cutouts (2009)
z3 + z4 - z2 - z1
z (vert) Rudder Stock b= 2
Centerline x6 + x3 - x4 - x7
c1= 2
x2 + x5 - x1 - x7
c2= 2
4

A1 (see 3-2-11/3.3)
3
A2 (see 3-2-11/3.3)
A1f, A2f (see 3-2-11/5.5)
A1f
C1
A1

b
6
7 5

A2
A2f
C2

x (fwd)
1 2

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Section 11 Rudders and Steering Equipment 3-2-11

5 Rudder Design Torque

5.1 General
The rudder design torque, QR, for rudder scantling calculations is to be in accordance with 3-2-11/5.3 or
3-2-11/5.5 as applicable.

5.3 Rudder Blades without Cutouts (2014)

Rudder torque, QR, is to be determined from the following equation for both ahead and astern conditions.
QR = CRr kN-m (tf-m, Ltf-ft)
where
CR = rudder force, as calculated in 3-2-11/3

r = c(α − k) but not less than 0.1c for ahead condition

c = mean breadth of rudder area, as shown in 3-2-11/Figure 1A, in m (ft)
α = coefficient as indicated in 3-2-11/Table 3
k = Af /A
Af = area of rudder blade situated forward of the centerline of the rudder stock, in m2 (ft2),
as shown in 3-2-11/Figure 1A
A = whole rudder area as described in 3-2-11/3.1
Where there are any appendages such as rudder bulb fitted on the rudder, effective areas are to be included
in the area of the rudder blade if significant.

TABLE 2
Coefficient kl (2012)
Rudder/Propeller Layout kl
Rudders outside propeller jet 0.8
Rudders behind a fixed propeller nozzle 1.15
Steering nozzles and azimuthing thrusters 1.15
All others 1.0

TABLE 3
Coefficient α (2014)

Rudder Position α
or High-lift Ahead Condition Astern Condition
Located behind a fixed
structure, such as a rudder 0.25 0.55
horn
Located where no fixed 0.75 0.66
0.33
structure forward of it (hollow profile) (non-hollow)
High-Lift Rudders Special consideration
Special consideration
(see 3-2-11/Table 1B) (0.40 if unknown)

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Section 11 Rudders and Steering Equipment 3-2-11

5.5 Rudders Blades with Cutouts

This paragraph refers to rudder blades with cutouts (semi-spade rudders) as defined in 3-2-11/3.3. Equations
derived in this paragraph are based on a cutout blade with two quadrilaterals. Where more quadrilaterals
are needed to define the rudder shape, similar rules apply.
Total rudder torque, QR, in ahead and astern conditions is to be obtained from the following equation:
QR = CR1 r1 + CR2 r2 kN-m (tf-m, Ltf-ft)
but not to be taken less than QRmin in the ahead condition
where
QRmin = 0.1CR (A1c1 + A2c2)/A
r1 = c1(α − k1 ) m (ft)
r2 = c2(α − k2 ) m (ft)
c1, c2 = mean breadth of partial area A1, A2, from 3-2-11/Figure 1B
α = coefficient as indicated in 3-2-11/Table 3
k1, k2 = A1f /A1, A2f /A2 where A1f, A2f = area of rudder blade situated forward of the centerline
of the rudder stock for each part of the rudder, as shown in 3-2-11/Figure 1B
CR, CR1, CR2, A1, A2 are as defined in 3-2-11/3.3.

5.7 Rudders with Twisted Leading Edge (2014)

In general, rudder torque, QR, indicated in 3-2-11/5.3 is applicable for rudders with twisted leading edge,
where CR is obtained from 3-2-11/3.5.

5.9 Trial Conditions

The above equations for QR are intended for the design of rudders and should not be directly compared with
the torque expected during the trial (see 3-2-11/1.5) or the rated torque of steering gear (see 4-3-3/1.5).

7 Rudder Stocks

7.1 Upper Rudder Stocks (2012)

The upper rudder stock is that part of the rudder stock above the neck bearing or above the top pintle, as
applicable.
At the upper bearing or tiller, the upper stock diameter is not to be less than that obtained from the following
equation:

S = Nu 3 Q R K s mm (in.)

where
Nu = 42.0 (89.9, 2.39)
QR = total rudder torque, as defined in 3-2-11/5, in kN-m (tf-m, Ltf-ft)
Ks = material factor for upper rudder stock, as defined in 3-2-11/1.3

7.3 Lower Rudder Stocks (2018)

In determining lower rudder stock scantlings, values of rudder design force and torque calculated in 3-2-11/3
and 3-2-11/5 are to be used. Bending moments, shear forces, as well as the reaction forces are to be
determined from 3-2-11/7.5 and 3-2-11/13.5, and are to be submitted for review. For rudders supported by
shoe pieces or rudder horns, these structures are to be included in the calculation model to account for
support of the rudder body. Guidance for calculation of these values is given in Appendix 3-2-A2.

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Section 11 Rudders and Steering Equipment 3-2-11

The lower rudder stock diameter is not to be less than that obtained from the following equation:

Sl = S 6 1 + (4 / 3)( M / Q R ) 2 mm (in)

where
S = upper stock required diameter from 3-2-11/7.1, in mm (in.)
M = bending moment at the section of the rudder stock considered in kN-m (tf-m, Ltf-ft)
QR = rudder torque from 3-2-11/5, in kN-m (tf-m, Ltf-ft)
Above the neck bearing, a gradual transition is to be provided where there is a change in the diameter of
the rudder stock.
The equivalent stress of bending and torsion, σc to be assessed from the aforementioned direct calculation
in the transition is not to exceed 118 /K N/mm2 (12.0/K kgf/mm2, 17100/K lbs/in2).

σc = σ b 2 + 3τ 2 N/mm2 (kgf/mm2, lbs/in2)

where
K = material factor as defined in 3-2-11/1.3.

σb = 10.2 × 106 M/ S l3 for SI and MKS units

= 270 × 103 M/ S l3 for US units

τ = 5.1 × 106 QR/ S l3 for SI and MKS units

= 135 × 103 QR/ S l3 for US units

7.4 Rudder Trunk and Rudder Stock Sealing (1 July 2016)

i) In rudder trunks which are open to the sea, a seal or stuffing box is to be fitted above the deepest
load waterline, to prevent water from entering the steering gear compartment and the lubricant
from being washed away from the rudder carrier.
ii) Where the top of the rudder trunk is below the deepest waterline two separate stuffing boxes are to
be provided.
iii) Materials. The steel used for the rudder trunk is to be of weldable quality, with a carbon content
not exceeding 0.23% on ladle analysis and a carbon equivalent (Ceq) not exceeding 0.41. Plating
materials for rudder trunks are in general not to be of lower grades than corresponding to class II
as defined in 3-1-2/Table 1. Rudder trunks comprising of materials other than steel are to be specially
considered.
iv) Scantlings. Where the rudder stock is arranged in a trunk in such a way that the trunk is stressed
by forces due to rudder action, the scantlings of the trunk are to be such that the equivalent stress
due to bending and shear does not exceed 0.35σF, and the bending stress on welded rudder trunk is
to be in compliance with the following formula:
σ ≤ 80/k N/mm2
σ ≤ 8.17/k kgf/mm2
σ ≤ 11,600/k psi
where
σ = bending stress in the rudder trunk

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k = K as defined in 3-2-11/1.3 for castings

= 1.0 for ordinary strength hull steel plate
= Q as defined in 3-2-1/7.5 for higher strength steel plate
k is not to be taken less than 0.7
F = specified minimum yield strength of the material used, in N/mm2 (kgf/mm2, psi)
For calculation of bending stress, the span to be considered is the distance between the mid-height
of the lower rudder stock bearing and the point where the trunk is clamped into the shell or the
bottom of the skeg.
v) Welding at the Connection to the Hull. The weld at the connection between the rudder trunk and
the shell or the bottom of the skeg is to be full penetration and fillet shoulder is to be applied in
way of the weld. The fillet shoulder radius r, in mm (in.) (see 3-2-11/Figure 2) is to be as large as
practicable and to comply with the following:
r = 60 mm when   40/k N/mm2
60 mm when   4.09/k kgf/mm2
2.4 in. when   5800/k psi
r = 0.1S, without being less than 30 mm when  < 40/k N/mm2
= 0.1S, without being less than 30 mm when  < 4.09/k kgf/mm2
= 0.1S, without being less than 1.2 in. when  < 2900/k psi
where
S = rudder stock diameter axis defined in 3-2-11/7.3
 = bending stress in the rudder trunk in N/mm2 (kgf/mm2, psi)
k = material factor as defined in 3-2-11/7.4iv)
The radius may be obtained by grinding. If disk grinding is carried out, score marks are to be
avoided in the direction of the weld. The radius is to be checked with a template for accuracy.
Four profiles at least are to be checked. A report is to be submitted to the Surveyor.

FIGURE 2
Fillet Shoulder Radius (1 July 2016)

Radius to be considered

Radius to be considered

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Section 11 Rudders and Steering Equipment 3-2-11

7.5 Bending Moments

The bending moment on the rudder and rudder stock may be determined in accordance with Appendix 3-2-A2
or in accordance with the following equations.
7.5.1 Spade Rudders
M n = C R ln kN-m (Ltf-ft)

A1
Ms = C R lc kN-m (Ltf-ft)
A
where
Mn = bending moment at neck bearing
Ms = bending moment at section under consideration

ln = distance from center of neck bearing to the centroid of rudder area, m (ft)
lc = distance from section under consideration to the centroid of rudder area, A1,
m2 (ft2)
A1 = area below section under consideration, m2 (ft2)
CR and A are as defined in 3-2-11/3.

7.5.2 Balanced Rudders with Shoepiece Support

The bending moment at the neck bearing may be taken as indicated below. Bending moments at
other locations are to be determined by direct calculation and are to be submitted. See Appendix
3-2-A2 for guidance in calculating bending moments.
Mn = NCRlb kN-m (Ltf-ft)
where
Mn = bending moment at neck bearing
lb = distance between center of neck bearing and center of shoepiece pintle bearing,
m (ft)
 α 
 0.5 + 1 
N =  8 
  l I 
1 + α 1 1 + u b  
  l b I u  


l 3b I d
α1 =
l 3s I b
Id = mean moment of inertia of shoepiece about the vertical axis, cm4 (in4)
ls = distance between center of shoepiece pintle bearing and the effective support
point of the shoepiece in the hull, m (ft)
Ib = mean moment of inertia of the rudder, cm4 (in4), considering a width of
rudder plating twice the athwartship dimension of the rudder and excluding
welded or bolted cover plates for access to pintles, inc.
lu = distance between center of the neck bearing and the center of the rudder
carrier bearing, m (ft)
Iu = mean moment of inertia of rudder stock, between neck bearing and rudder
carrier bearing, cm4, (in4)
CR is as defined in 3-2-11/3.

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9 Flange Couplings

9.1 General
Rudder flange couplings are to comply with the following requirements:
i) Couplings are to be supported by an ample body of metal worked out from the rudder stock.
ii) The smallest distance from the edge of the bolt holes to the edge of the flange is not to be less than
two-thirds of the bolt diameter.
iii) Coupling bolts are to be fitted bolts.
iv) Suitable means are to be provided for locking the nuts in place.
In addition to the above, rudder flange couplings are to meet the type-specific requirements in 3-2-11/9.3
(horizontal couplings) or 3-2-11/9.5 (vertical couplings) as applicable.

9.3 Horizontal Couplings

9.3.1 Coupling Bolts
There are to be at least six coupling bolts in horizontal couplings, and the diameter, db, of each bolt is
not to be less than that obtained by the following equation:

db = 0.62 d s3 K b /(nrK s ) mm (in.)

where
ds = required rudder stock diameter, S (3-2-11/7.1) or Sl (3-2-11/7.3) as
applicable, in way of the coupling
n = total number of bolts in the horizontal coupling
r = mean distance, in mm (in.), of the bolt axes from the center of the bolt
system
Kb = material factor for bolts, as defined in 3-2-11/1.3
Ks = material factor for stock, as defined in 3-2-11/1.3

9.3.2 Coupling Flange

Coupling flange thickness is not to be less than the greater of the following equations:

tf = dbt K f /( K b ) mm (in.)

tf = 0.9dbt mm (in.)
where
dbt = calculated bolt diameter as per 3-2-11/9.3.1 based on a number of bolts not
exceeding 8
Kf = material factor for flange, as defined in 3-2-11/1.3
Kb = material factor of bolts, as defined in 3-2-11/1.3

9.3.3 Joint between Rudder Stock and Coupling Flange (1 July 2016)
The welded joint between the rudder stock and the flange is to be made in accordance with
3-2-11/Figure 3 or equivalent.

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FIGURE 3
Welded Joint Between Rudder Stock and Coupling Flange (1 July 2016)
D

R  100 mm

1/3 > a/b > 1/5

b

 8 mm
Final machining R  45 mm
after welding

 30°
a
R8 2 mm

9.5 Vertical Couplings

9.5.1 Coupling Bolts (1 July 2016)
There are to be at least eight coupling bolts in vertical couplings and the diameter, db, of each bolt
is not to be less than that obtained from the following equation:

db = 0.81ds K b /(nK s ) mm (in.)

where
n = total number of bolts in the vertical coupling, which is not to be less than 8
ds, Kb, Ks are as defined in 3-2-11/9.3.
In addition, the first moment of area, m, of the bolts about the center of the coupling is not to be
less than that given by the following equation:
m = 0.00043ds3 mm3 (in3)
where
ds = diameter, in mm (in.), as defined in 3-2-11/9.3

9.5.2 Coupling Flange

Coupling flange thickness is not to be less than db, as defined in 3-2-11/9.5.1.

9.5.3 Joint between Rudder Stock and Coupling Flange (1 July 2016)
The welded joint between the rudder stock and the flange is to be made in accordance with
3-2-11/Figure 3 or equivalent.

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11 Tapered Stock Couplings

11.1 Coupling Taper (1 July 2016)

Tapered stock couplings are to comply with the following general requirements in addition to type-specific
requirements given in 3-2-11/11.3 or 3-2-11/11.5 as applicable:
i) Tapered stocks, as shown in 3-2-11/Figure 4, are to be effectively secured to the rudder casting by
a nut on the end.
ii) The cone shapes are to fit exactly.
iii) Taper length () in the casting is generally not to be less than 1.5 times the stock diameter (do) as
shown in 3-2-11/Figure 4.
iv) The taper on diameter (c) is to be 1/12 to 1/8 for keyed taper couplings and 1/20 to 1/12 for
couplings with hydraulic mounting/dismounting arrangements, as shown in the following table.
v) Where mounting with an oil injection and hydraulic nut, the push-up oil pressure and the push-up
length are to be specially considered upon submission of calculations.
vi) Means of effective sealing are to be provided against sea water ingress.

do  du
Type of Coupling Assembly c= 

Without hydraulic mounting/dismounting 1/12  c  1/8

With hydraulic mounting/dismounting 1/20  c  1/12

FIGURE 4
Tapered Couplings (2018)

do do
  do  1.5

  do  1.5

du
du

hn
Locking
Nut Securing
dg dg
Flat Bar
dn dn

a) Keyed Fitting b) Keyless Fitting

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11.3 Keyed Fitting (1 July 2016)

Where the stock is keyed, the key is to be fitted in accordance with the following:
i) The top of the keyway is to be located well below the top of the rudder.
ii) Torsional strength of the key equivalent to that of the required upper stock is to be provided.
iii) For the couplings between stock and rudder the shear area* of the key is not to be less than:
17.55QF 27.20QF
as = cm2 as = in2
d k σ F1 d k σ F1

where
QF = design yield moment of rudder stock, in N-m (kg-m, lbf-ft)
3
dt
= 0.02664 N-m
k

dt 3
= 0.002717 kgf-m
k
3
dt
= 0.01965 lbf-ft
k
Where the actual rudder stock diameter dta is greater than the calculated diameter dt, the diameter
dta is to be used. However, dta applied to the above formula need not be taken greater than 1.145dt.
dt = stock diameter, in mm (in.), according to 3-2-11/7.1
k = material factor for stock as given in 3-2-11/1.3
dk = mean diameter of the conical part of the rudder stock, in mm (in.), at the key

σF1 = minimum yield stress of the key material, in N/mm2 (kgf/mm2, psi)
The effective surface area of the key (without rounded edges) between key and rudder stock or
cone coupling is not to be less than:
5QF 7.749QF
ak = cm2 ak = in2
dk σF 2 dk σF 2
where
σF2 = minimum yield stress of the key, stock or coupling material, in N/mm2
(kgf/mm2, psi), whichever is less.
iv) In general, the key material is to be at least of equal strength to the keyway material. For keys of
higher strength materials, shear and bearing areas of keys and keyways may be based on the
respective material properties of the keys and the keyways, provided that compatibilities in
mechanical properties of both components are fully considered. In no case, is the bearing stress of
the key on the keyway to exceed 90% of the specified minimum yield strength of the keyway
material.
v) Push up. It is to be proved that 50% of the design yield moment is solely transmitted by friction
in the cone couplings. This can be done by calculating the required push-up pressure and push-up
length according to 3-2-11/11.5v) and 3-2-11/11.5vi) for a torsional moment QF′ = 0.5QF.
Notwithstanding the requirements in 3-2-11/11.5iii) and 3-2-11/11.5v), where a key is fitted to the
coupling between stock and rudder and it is considered that the entire rudder torque is transmitted
by the key at the couplings.
* Note: The effective area is to be the gross area reduced by any area removed by saw cuts, set screw holes, chamfer, etc.,
and is to exclude the portion of the key in way of spooning of the key way.

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11.5 Keyless Fitting (1 July 2016)

Hydraulic and shrink fit keyless couplings are to be fitted in accordance with the following:
i) Detailed preloading stress calculations and fitting instructions are to be submitted;
ii) Preload stress is not to exceed 70% of the minimum yield strength of either the stock or the bore;
iii) Prior to applying hydraulic pressure, at least 75% of theoretical contact area of rudder stock and
rudder bore is to be achieved in an evenly distributed manner;
iv) The upper edge of the upper main piece bore is to have a slight radius;
v) Push-up Pressure. The push-up pressure is not to be less than the greater of the two following
values:
2QF 2.901QF 8
preq1 = 103 N/mm² (kgf/mm2) preq1 = 10 psi
d m lπµo
2
d m2 lπµo

6M b 8.702 M b 8
preq2 = 103 N/mm2 (kgf/mm2) preq2 = 10 psi
d ml 2d m d ml 2d m
where
QF = design yield moment of rudder stock, as defined in 3-2-11/11.3iii)
dm = mean cone diameter, in mm (in.)

l = cone length, in mm (in.)

µo = frictional coefficient, equal to 0.15
Mb = bending moment in the cone coupling (e.g., in case of spade rudders), in N-m
(kg-m, lbf-ft)
It has to be proved by the designer that the push-up pressure does not exceed the permissible
surface pressure in the cone. The permissible surface pressure is to be determined by the following
formula:

pperm =
(
0.8YG 1 − α 2 ) N/mm2 (kgf/mm2, psi)
3+α 4

where
YG = specified minimum yield strength of the material of the gudgeon, in N/mm2
(kgf/mm2, psi)
α = dm/da
dm = mean cone diameter, in mm (in.)
da = outer diameter of the gudgeon to be not less than 1.5dm, in mm (in.)

vi) Push-up Length. The push-up length ∆l, in mm (in.), ∆l is to comply with the following formula:
∆l1 ≤ ∆l ≤ ∆l2
where

 
 
preq d m 0.8Rtm  preq d m 0.8Rtm 
∆l1 = + mm (0.0394  +  in.)
 1-α 2  c  E  1 - α c
2 c 
E  c
   2  
 2     

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1.6YG d m 0.8Rtm  1.6YG d m 0.8 Rtm 

∆l2 = + mm (0.0394  + in.)
 
Ec 3 + α 4 c  Ec 3 + α 4 c 
Rtm = mean roughness, in mm (in.) taken equal to 0.01
c = taper on diameter according to 3-2-11/11.1iv)
YG = specified minimum yield strength of the material of the gudgeon, in N/mm2
(kgf/mm2, psi)
E = Young’s modulus of the material of the gudgeon, in N/mm2 (kgf/mm2, psi)
YG, α, and dm are as defined in 3-2-11/11.5v).
Notwithstanding the above, the push up length is not to be less than 2 mm (0.8 in.).
Note: In case of hydraulic pressure connections the required push-up force Pe for the cone may
be determined by the following formula:
c  c  c 
Pe = preqdmπl  + 0.02  N (0.102 preqdmπl  + 0.02  kgf, 0.225preqdmπl  + 0.02  lbf)
2  2  2 
The value 0.02 is a reference for the friction coefficient using oil pressure. It varies and depends
on the mechanical treatment and roughness of the details to be fixed. Where due to the fitting
procedure a partial push-up effect caused by the rudder weight is given, this may be taken into
account when fixing the required push-up length, subject to approval.
vii) Couplings with Special Arrangements for Mounting and Dismounting the Couplings. Where the
stock diameter exceeds 200 mm (8 in.), the press fit is recommended to be effected by a hydraulic
pressure connection. In such cases the cone is to be more slender, c ≈1:12 to ≈1:20. In case of
hydraulic pressure connections the nut is to be effectively secured against the rudder stock or the
pintle. For the safe transmission of the torsional moment by the coupling between rudder stock
and rudder body the push-up pressure and the push-up length are to be determined according to
3-2-11/11.5v) and 3-2-11/11.5vi), respectively.
viii) The locking nut is to be fitted in accordance with 3-2-11/11.7.

11.7 Locking Nut

Dimensions of the securing nut, as shown in 3-2-11/Figure 4, are to be proportioned in accordance with the
following and the nut is to be fitted with an effective locking device.
Height hn ≥ 0.6dg
Outer diameter of nut dn ≥ 1.2du or 1.5dg whichever is greater
External thread diameter dg ≥ 0.65do
In the case of a hydraulic pressure secured nut, a securing device such as a securing flat bar is to be
provided. Calculations proving the effectiveness of the securing device are to be submitted.

13 Pintles

13.1 General (1 July 2016)

Pintles are to have a conical attachment to the gudgeons with a taper on diameter of:
1/12 to 1/8 for keyed and other manually assembled pintles with locking nut.
1/20 to 1/12 for pintle mounted with oil injection and hydraulic nut.

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13.3 Diameter (1 July 2016)

The diameter of the pintles is not to be less than that obtained from the following equation.

dp = k1 BK p mm (in.)

where
k1 = 11.1 (34.7, 1.38)
B = bearing force, in kN (tf, Ltf), from 3-2-11/13.5 but not to be taken less than Bmin as
specified in 3-2-11/Table 4
Kp = material factor for the pintle, as defined in 3-2-11/1.3

TABLE 4
Minimum Bearing Force Bmin (2009)
Pintle Type Bmin
Conventional two pintle rudder 0.5 CR
3-2-A2/Figure 3 lower pintle 0.5 CR
3-2-A2/Figure 3 main pintle CRla/lp*

3-2-13/Figure 3 of the Steel main pintle CRla/lp*

Vessel Rules upper pintle 0.25 CR
* Bmin = CR where la/lp ≥ 1

la, lp as described in 3-2-13/Figure 3 of the Steel Vessel Rules

For rudders on horns with two pintles, as shown in 3-2-11/Figure 1B, calculations are to include pintle
bearing forces with the vessel running ahead at the maximum continuous rated shaft rpm and at the lightest
operating draft.
Threads and nuts are to be in accordance with 3-2-11/11.7.
The pintle and pintle boss are to comply with the following requirements:
i) The depth of the pintle boss is not to be less than dp.
ii) The bearing length of the pintle is to be between 1.0 and 1.2 times the pintle diameter, where dp is
measured on the outside of the liner.
iii) The bearing pressure is to be in accordance with 3-2-11/15.1.
iv) The thickness of the pintle housing is not to be less than 25% of the pintle diameter.

13.4 Push-up Pressure and Push-up Length (1 July 2016)

The required push-up pressure for pintle bearings, in N/mm2 (kgf/mm2, psi), is to be determined by the
following formula:
0.4 B1d o
preq = N/mm2
d m2 l
0.04079 B1d o
preq = kgf/mm²
d m2 l

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0.0001394 B1d o
preq = psi
d m2 l
where
B1 = supporting force in the pintle bearing, in N (kgf, lbf)
d0 = actual pintle diameter excluding the liner, in mm (in.)
dm = mean cone diameter, in mm (in.)

l = cone length, in mm (in.)

The push up length is to be calculated similarly as in 3-2-11/11.5vi), using required push-up pressure and
properties for the pintle bearing.

13.5 Shear and Bearing Forces

The shear and bearing forces may be determined in accordance with Appendix 3-2-A2 or by the equations
given below.
13.5.1 Spade Rudder
Mn
Bearing force at rudder carrier: Pu = kN (tf Ltf)
lu
Bearing force at neck bearing: Pn = C R + P u kN (tf Ltf)
Shear force at neck bearing: Fn = CR kN (tf Ltf)

where CR is as defined in 3-2-11/3 and lu is as defined in 3-2-11/7.5.2.

13.5.2 Balanced Rudder with Shoepiece Support

Mn
Bearing force at rudder carrier: Pu = kN (tf Ltf)
lu

 l  C l 
Bearing force at neck bearing: Pn = Pu 1 + u  + R  R + l p  kN (tf Ltf)
 lb  lb  2 
where
lb = distance between the center of neck bearing support and the center of
shoepiece support, as shown in 3-2-A2/Figure 2
= lp + lr + ll
lp = distance between bottom of rudder blade and center of support of neck
bearing
ll = distance between top of rudder blade and center of support of neck bearing
Bearing force at shoepiece: P p = C R + P u – Pn kN (tf, Ltf) but not less than 0.5CR
Shear force at neck bearing: Fn = Pn – Pu kN (tf, Ltf)
where CR is as defined in 3-2-11/3.

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15 Supporting and Anti-Lifting Arrangements

15.1 Bearings (2012)

15.1.1 Bearing Surfaces
Bearing surfaces for rudder stocks, shafts and pintles are to meet the following requirements:
i) The length/diameter ratio (lb/dl) of the bearing surface is not to be greater than 1.2*

ii) The projected area of the bearing surface (Ab = dl lb) is not to be less than Abmin,
where
dl = outer diameter of the liner, in mm (in.)

lb = bearing length, in mm (in.)

P
Abmin = k1 mm2 (in2)
qa
k1 = 1000 (2240)
P = bearing reaction force, in kN (tf, Ltf), as determined from 3-2-11/Table 5
pa = allowable surface pressure, as indicated in 3-2-11/Table 6 depending on
bearing material, in N/mm2 (kgf/mm2, psi)
* Request for bearing arrangement of length/diameter ratio greater than 1.2 is subject to special
consideration provided that calculations are submitted to show acceptable clearance at both ends of
the bearing.

15.1.2 Bearing Clearance

i) The clearance for metal bearings is not to be less than di /1000 + 1.0 mm (di /1000 + 0.04 in.)
on the diameter, where di is the inner diameter of the bushing, in mm (in.).
ii) The clearance for non-metallic bearings is to be specially determined considering the
material’s swelling and thermal expansion properties. This clearance in general is not to be
taken less than 1.5 mm (0.06 in.) on diameter*.
* Request of clearance less than 1.5 mm (0.06 in.) for non-metallic bearings is subject to special
considerations provided that documented evidence, such as manufacturer's recommendation on
acceptable clearance, expansion allowance and satisfactory service history with reduced clearances,
are submitted for review.

15.1.3 Bearing Pressure

Bearing pressure is to be accordance with 3-2-11/Table 6.
15.1.4 Bearing Material
Where stainless steel or wear-resistant steel is used for liners or bearings, the material properties
including chemical composition of both components are to be submitted for review for an approved
combination.
15.1.5 Liners and Bushes (1 July 2016)
i) Rudder Stock Bearings. Liners and bushes are to be fitted in way of bearings. The minimum
thickness of liners and bushes is to be equal to:
tmin = 8 mm (0.31 in.) for metallic materials and synthetic material
tmin = 22 mm (0.87 in.) for lignum material

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ii) Pintle Bearings

• The thickness of any liner or bush is neither to be less than:
t = k1 B mm (in.)
where
B = bearing force, in N (kgf, lbf)
k1 = 0.01 (0.0313, 0.000830)
nor than the minimum thickness defined in 3-2-11/15.1.5i).
• The bearing length Lp of the pintle is to be in accordance with 3-2-11/13.1.

15.3 Rudder Carrier (1 July 2016)

i) The weight of the rudder assembly is to be supported by a rudder carrier mounted on the hull
structure designed for that purpose.
ii) At least half of the rudder carrier’s holding-down bolts are to be fitted bolts. Alternative means of
preventing horizontal movement of the rudder carrier may be considered.
iii) The bearing part is to be well lubricated by dripping oil, automatic grease feeding, or a similar method.
iv) Hull structures in way of the rudder carrier are to be suitably strengthened.

15.5 Anti-Lifting Devices

Means are to be provided to prevent accidental unshipping or undue movement of the rudder which may
cause damage to the steering gear. There are to be at least two bolts in the joint of the anti-lifting ring.

TABLE 5
Bearing Reaction Force (2009)
P, Bearing Reaction Force
Bearing Type kN (tf, Ltf)
Pintle bearings P = B as defined in 3-2-11/13
Other bearings Calculation of P is to be submitted.
Guidelines for calculation can be
found in Appendix 3-2-A2

TABLE 6
Allowable Bearing Surface Pressure (1 July 2016)
pa
Bearing Material N/mm2 kgf/mm2 psi
lignum vitae 2.5 0.25 360
white metal, oil lubricated 4.5 0.46 650
synthetic material with hardness between 60 5.5(2) 0.56(2) 800(2)
and 70 Shore D(1)
steel(3) and bronze and hot-pressed 7.0 0.71 1000
bronze-graphite materials
Notes:
1 Indentation hardness test at 23°C (73.4°F) and with 50% moisture, according
to a recognized standard. Synthetic bearing materials to be of approved type.
2 Higher values than given in the table may be taken if they are verified by
tests, but in no case more than 10 N/mm2 (1.02 kgf/mm2, 1450 psi).
3 Stainless and wear-resistant steel in an approved combination with stock liner.

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17 Double Plate Rudder

17.1 Strength (1 July 2017)

The section modulus and web area of the rudder mainpiece are to be such that the stresses indicated in the
following Subparagraphs are not exceeded.
In calculating the section modulus of the rudder, the effective width of side plating is to be taken as not
greater than twice the athwartship dimension of the rudder. Bolted cover plates on access openings to pintles
are not to be considered effective in determining the section modulus of the rudder. In order for a cover
plate to be considered effective, it is to be closed using a full penetration weld and confirmed suitable by
non-destructive testing method. Generous radii are to be provided at abrupt changes in section where there
are stress concentrations, including in way of openings and cover plates. When inspection windows are
located in the panel below the rudder hub, the stress is to be as permitted in way of cutouts.
Moments, shear forces and reaction forces are to be as given in 3-2-11/7.5 and 3-2-11/13.5.
For spade rudders and rudders with horns, the section modulus at the bottom of the rudder is not to be less
than one-third the required section modulus of the rudder at the top of the rudder or at the center of the
lowest pintle.
Special attention is to be paid in design and construction of rudders with slender foil sections in the vicinity
of their trailing edge (e.g., hollow foil sections, fishtail foil sections). Where the width of the rudder blade
at the aftermost vertical diaphragm, w, is equal or less than 1/6 of the trailing edge length measured between
the diaphragm and the trailing edge, l, finite element vibration analysis of the rudder blade is also to be
submitted for review. See 3-2-11/Figure 5.

FIGURE 5 (1 July 2017)

w

Spade rudders with an embedded rudder trunk are to have a trailing edge with dimensions that satisfy the
following requirements:
i) For a rudder trailing edge having a monotonous transition to a rounded end with a finite thickness
or diameter (see 3-2-11/Figure 6), the vortex shedding frequency calculated using the equation
given below is to be higher than 35 Hz.
S tU
fs =
β D D + βT T
where
fs = vortex shedding frequency, in Hz
U = flow velocity, in m/s (ft/s), which is taken as vessel’s design speed with
vessel running ahead at the maximum continuous rated shaft rpm and at the
summer load waterline
St = nominal Strouhal number
= 0.18
βD = 0.27

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Section 11 Rudders and Steering Equipment 3-2-11

C = minimal chord length of rudder cross section profile, in m (ft)

D = nominal boundary layer thickness at trailing edge
= 0.01C
βT = 0.77
T = thickness or diameter of rounded end, in m (ft)

FIGURE 6 (1 July 2017)

Thickness or Diameter of Rounded End

ii) For a rudder trailing edge with a flat insert plate (see 3-2-11/Figure 7), the insert plate thickness,
t0, is to be no larger than 1.5Vd in mm, where Vd is the design speed in ahead condition, in knots,
as defined in 3-2-11/3.1. The extension beyond the weld to rudder plate, l, is to satisfy the following
3-2-11/Figure 7 and with consideration of possible local vibratory bending of the insert plate.

FIGURE 7 (1 July 2017)

Rudder Plate Thickness

t1
Insert Plate Thickness

t0

l
l ≥ (t0 + 2t1)

Alternatively, a vibration analysis is to be carried out to confirm that the natural frequency of the rudder is
to be at least ±20% away from the vortex shedding frequency preferably determined using either a detailed
numerical analysis method such as CFD or testing for ballast and full draft at 85% and 100% Vd as defined
in 3-2-11/3.1.
17.1.1 Clear of Cut-outs
Allowable stresses for determining the rudder strength clear of cutouts are as follows:
Bending stress σb = Kσ/Q N/mm2 (kgf/mm2, psi)
Shear stress τ = Kτ/Q N/mm2 (kgf/mm2, psi)

Equivalent stress σe = σ b 2 + 3τ 2 = Ke/Q N/mm2 (kgf/mm2, psi)

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where

SI units MKS units US units

Kσ 110 11.2 15,900
Kτ 50 5.1 7,300
Ke 120 12.2 17,400
Q = 1.0 for ordinary strength hull steel
= as defined in 3-2-1/7.5 for higher strength steel plate
17.1.2 In Way of Cutouts
Allowable stresses for determining the rudder strength in way of cutouts (see 3-2-11/Figure 8) are
as follows:
Bending stress b = K/Q N/mm2 (kgf /mm2, psi)
Shear stress  = K/Q N/mm2 (kgf /mm2, psi)

Equivalent stress e =  b 2  3 2 = Ke/Q N/mm2 (kgf/mm2, psi)

where

SI units MKS units US units

Kσ 75 7.65 10,900
Kτ 50 5.1 7,300
Ke 100 10.2 14,500
Q = 1.0 for ordinary strength hull steel
= as defined in 3-2-1/7.5 for higher strength steel plate

FIGURE 8 (2009)
Z
In way of cutouts

6r1
r1
6r1
6r2
r2
6r2

X
Note:
r1 = corner radius of rudder plate in way of
portable bolted inspection hole
r2 = corner radius of rudder plate

The mainpiece of the rudder is to be formed by the rudder side plating (but not more than the effective
width indicated above) and vertical diaphragms extending the length of the rudder or the extension of the
rudder stock or a combination of both.

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17.3 Side, Top and Bottom Plating (1 July 2016)

The plating thickness is not to be less than that obtained from the following equation:

t = 0.0055sβ k1 d + (k 2 C R / A) × Q + k3

where
Q = 1.0 for ordinary strength hull steel
= as defined in 3-2-1/7.5 for higher strength steel plate
k1 = 1.0 (1.0, 0.305)
k2 = 0.1 (0.981, 10.7)
k3 = 2.5 (2.5, 0.1)
d = summer load line draft of the vessel, in m (ft)
CR = rudder force according to 3-2-11/3, in kN (tf, Ltf)

A = rudder area, in m2 (ft2)

β = 1.1 − 0.5( s / b) 2 ; maximum 1.0 for b/s ≥ 2.5

s = smaller unsupported dimension of plating, in mm (in.)

b = greater unsupported dimension of plating, in mm (in.)
The thickness of the rudder side or bottom plating is to be at least 2 mm (0.08 in.) greater than that
required by 3-2-8/5 for deep tank plating in association with a head, h, measured to the summer load line.
The rudder side plating in way of the solid part is to be of increased thickness per 3-2-11/17.7.

17.5 Diaphragm Plates (2018)

Vertical and horizontal diaphragms are to be fitted within the rudder, effectively attached to each other and
to the side plating. Vertical diaphragms are to be spaced approximately 1.5 times the spacing of horizontal
diaphragms.
The thickness of diaphragm plates is not to be less than 70% of the required rudder side plate thickness or
8 mm (0.31 in.), whichever is greater. Openings in diaphragms are to have generous radii and the effects of
openings are to be considered in the strength assessment as required in 3-2-11/17.1.
The diaphragm plating in way of the solid part is to be of increased thickness for vertical and horizontal
diaphragm plates per 3-2-11/17.7.

17.7 Connections of Rudder Blade Structure with Solid Parts (1 July 2016)
Solid parts in forged or cast steel, which house the rudder stock or the pintle, are normally to be provided
with protrusions.
These protrusions are not required when the diaphragm plate thickness is less than:
• 10 mm (0.375 in.) for diaphragm plates welded to the solid part on which the lower pintle of a semi-
spade rudder is housed and for vertical diaphragm plates welded to the solid part of the rudder stock
coupling of spade rudders.
• 20 mm (0.75 in.) for other diaphragm plates.
The solid parts are in general to be connected to the rudder structure by means of two horizontal diaphragm
plates and two vertical diaphragm plates.
Minimum section modulus of the connection with the rudder stock housing.

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The section modulus of the cross-section of the structure of the rudder blade formed by vertical diaphragm
plates and rudder plating, which is connected with the solid part where the rudder stock is housed is to be
not less than:
 H − HX  Q  H − HX  Q
ws = cs S l3  E  10-4 cm3 ws = 6.1cs S l3  E  10-9 in3
 HE  s
K  HE  s
K

where
cs = coefficient, to be taken equal to:
= 1.0 if there is no opening in the rudder plating or if such openings are closed by a
full penetration welded plate
= 1.5 if there is an opening in the considered cross-section of the rudder
Sl = rudder stock diameter, in mm (in.)
HE = vertical distance between the lower edge of the rudder blade and the upper edge of
the solid part, in m (ft)
HX = vertical distance between the considered cross-section and the upper edge of the solid
part as indicated in 3-2-11/Figure 9, in m (ft)
Q = material factor for the rudder blade plating as given in 3-2-11/17.1
Ks = material factor for the rudder stock as given in 3-2-11/1.3
The actual section modulus of the cross-section of the structure of the rudder blade is to be calculated with
respect to the symmetrical axis of the rudder.
The breadth of the rudder plating to be considered for the calculation of section modulus is to be not greater
than:
b = sv + 2HX/3 m (ft)
where
sv = spacing between the two vertical diaphragm, in m (ft) (see 3-2-11/Figure 9)
Where openings for access to the rudder stock nut are not closed by a full penetration welded plate, they
are to be deducted.

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FIGURE 9
Cross-section of the Connection Between Rudder Blade Structure
and Rudder Stock Housing (1 July 2016)

Hx

x x

Access to the
rudder stock
nut, if any

Hx/3 Hx/3

x x

Sv
Section x-x

The thickness of the horizontal diaphragm plates connected to the solid parts, in mm (in.), as well as that of
the rudder blade plating between these diaphragms, is to be not less than the greater of the following
values:
tH = 1.2t mm (in.)
tH = 0.045dS2/sH mm (in.)
where
t = defined in 3-2-11/17.3
dS = diameter, in mm (in.), to be taken equal to:
= S as per 3-2-11/7.3, for the solid part housing the rudder stock
= dp as per 3-2-11/13.1, for the solid part housing the pintle
sH = spacing between the two horizontal diaphragm plates, in mm (in.)
The increased thickness of the horizontal diaphragms is to extend fore and aft of the solid part at least to
the next vertical diaphragm.
The thickness of the vertical diaphragm plates welded to the solid part where the rudder stock is housed as
well as the thickness of the rudder side plating under this solid part is to be not less than the values obtained,
in mm (in.), from 3-2-11/Table 7.

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The increased thickness of vertical diaphragm plates is to extend below the solid piece at least to the next
horizontal diaphragm.

TABLE 7
Thickness of Side Plating and Vertical Diaphragm Plates (1 July 2016)
Thickness of Vertical Diaphragm Plates, Thickness of Rudder Plating, in mm (in.)
in mm (in.)
Type of Rudder
Rudder Blade Rudder Blade with Rudder Blade Area with Opening
without Opening Opening without Opening
Rudder supported by sole piece 1.2t 1.6t 1.2t 1.4t
Semi-spade and spade rudders 1.4t 2.0t 1.3t 1.6t
t = thickness of the rudder plating, in mm (in.), as defined in 3-2-11/17.3

17.9 Welding and Design Details (1 July 2016)

i) Slot-welding is to be limited as far as possible. Slot welding is not to be used in areas with large
in-plane stresses transversely to the slots or in way of cut-out areas of semi-spade rudders.
ii) When slot welding is applied, the length of slots is to be minimum 75 mm (3 in.) with breadth of
2t, where t is the rudder plate thickness, in mm (in.). The distance between ends of slots is not to
be more than 125 mm (5 in.). The slots are to be fillet welded around the edges and filled with a
suitable compound (e.g., epoxy putty). Slots are not to be filled with weld.
iii) Grove welds with structural backing/backing bar (continuous type slot weld) may be used for
double-plate rudder welding. In that case, the root gap is to be between 6 to 10 mm (0.25 to 0.375 in.)
and the bevel angle is to be at least 15°.
iv) In way of the rudder horn recess of semi-spade rudders the radii in the rudder plating are not to be
less than 5 times the plate thickness, but in no case less than 100 mm (4 in.). Welding in side plate
are to be avoided in or at the end of the radii. Edges of side plate and weld adjacent to radii are to
be ground smooth.
v) Welds between plates and heavy pieces (solid parts in forged or cast steel or very thick plating)
are to be made as full penetration welds. In way of highly stressed areas (e.g., cut-out of semi-
spade rudder and upper part of spade rudder), cast or welding on ribs is to be arranged. Two sided
full penetration welding is normally to be arranged. Where back welding is impossible welding is
to be performed against ceramic backing bars or equivalent. Steel backing bars may be used and
are to be continuously welded on one side to the heavy piece.

17.11 Watertightness (1 July 2016)

The rudder is to be watertight and is to be tested in accordance with Section 3-7-1.

19 Single Plate Rudders

19.1 Mainpiece Diameter

The mainpiece diameter is calculated according to 3-2-11/7.3. For spade rudders, the lower third may be
tapered down to 0.75 times stock diameter at the bottom of the rudder.

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19.3 Blade Thickness

The blade thickness is not to be less than that obtained from the following equation:
tb = 0.0015sVR + 2.5 mm
tb = 0.0015sVR + 0.1 in.
where
s = spacing of stiffening arms, in mm (in.), not to exceed 1000 mm (39 in.)
VR = speed, as defined in 3-2-11/3

19.5 Arms
The thickness of the arms is not to be less than the blade thickness obtained in 3-2-11/19.3. The section
modulus of each set of arms about the axis of the rudder stock is not to be less than that obtained from the
following equation:
SM = 0.0005sC12VR2Q cm3
SM = 0.0000719sC12VR2Q in3
where
C1 = horizontal distance from the aft edge of the rudder to the centerline of the rudder
stock, in m (ft)
s and VR are as defined in 3-2-11/19.3.
Q is as defined in 3-2-11/17.3.

21 Steering Nozzles (2012)

21.1 Application Scope

Requirements in this Subsection are applicable to conventional steering nozzles, as illustrated in
3-2-11/Figure 10, with the following restrictions:
i) The inner diameter of 5 meters (16.4 feet) or less, and
ii) The operating angle ranging not more than –35° to +35° port and starboard
iii) Nozzles of above features but provided on the vessels for Ice Class are subject to additional
requirements specified in Part 6 of the Steel Vessel Rules, as applicable
Steering nozzles outside of the application scope are subject to special consideration with all supporting
documents and calculations submitted to ABS for review. The submitted documents and calculations are to
include, but not limited to, the items listed in the following:
i) The drawings and plans of steering nozzle with indications of design operating angles and the
torque considered necessary to operate the steering nozzle at the design operating angle
ii) The calculated steering nozzle section modulus
iii) The calculated maximum water induced pressure of the nozzle under design speed (both ahead
and astern conditions) and at the design operating angle, and
iv) The calculated maximum shear and bending of nozzle support structure under design speed (both
ahead and astern conditions) and at the design operating angle

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21.3 Design Force (2015)

The design force, CR, for steering nozzles is to be obtained from the following equation:

CR = nkRkckl AtVR2 = CR1 + CR2 kN (tf, Ltf)

CR1 = nkRkckl Aeq VR2 kN (tf, Ltf)

CR2 = nkRkckl (Apo + Amf)VR2 kN (tf, Ltf)

where
CR1 = design force associated with the turning movement of the nozzle
CR2 = design force associated with the turning movement of nozzle post, movable flap, if
present
kR = (dm2/At + 2)/3 but not taken more than 2
dm = mean external diameter of the nozzle, in m (ft)
= 0.5(df + da)
df , da = fore and aft nozzle external diameters as shown in 3-2-11/Figure 10, in m (ft)
At = Aeq+Apo+Amf, in m2 (ft2)
Aeq = nominal projected area of nozzle cylinder, not to be taken less than 1.35dmb
b = nozzle length in m (ft)
Apo = projected area of nozzle post or horn within the extension of nozzle profile as
applicable
Amf = projected area of movable flap if present
= da bmf

A = Aeq+ Amf, in m2 (ft2)

kc = 1.9 for ahead condition
= 1.5 for astern condition
kl = 1.15, as specified in 3-2-11/Table 2
n, VR are as defined in 3-2-11/3.1.

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Section 11 Rudders and Steering Equipment 3-2-11

FIGURE 10
Nozzle Geometry (2012)

da dc df

bmf ba bf
b

21.5 Design Torque

Design torque, QR, for steering nozzle is to be determined from the following equation for both ahead and
astern conditions:
QR = CR r kN-m (tf-m, Ltf-ft)
where
r = (α − k)l, but not less than 0.1 l for ahead condition
l = b without flap, in m (ft)
= b + bmf if flap present
k = Af /A

Af = Aeq bf /l, in m2 (ft2)

dc = nozzle diameter at the section intersecting with nozzle stock axis;
α is as defined in 3-2-11/Table 3.
A, CR are as defined in 3-2-11/21.3.

21.7 Nozzle Stock

21.7.1 Upper Stock
The upper stock is that part of the nozzle stock above the neck bearing.
At the upper bearing or tiller, the upper stock diameter is not to be less than obtained from the
following equation:

S = Nu 3 Q R K s mm (in.)

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where
Nu = 42.0 (823.9, 2.39)
QR = as defined in 3-2-11/21.5
Ks = material factor for nozzle stock, as defined in 3-2-11/1.3

21.7.2 Lower Stock

In determining lower stock diameters, values of nozzle design force and torque calculated in
3-2-11/21.3 and 3-2-11/21.5 are to be used. Bending moments and shear forces, as well as the
reaction forces are to be determined by direct calculation and are to be submitted for review. For
nozzles supported by shoe pieces, these structures are to be included in the calculation.
Calculation guidance for these values is given in Appendix 3-2-A2.
The lower nozzle stock diameter is not to be less than obtained from the following equation:

Sl = S 6 1 + 4 / 3 (M / QR ) 2 mm (in.)

where
S = required upper stock diameter from 3-2-11/21.7.1, in mm (in.)
M = bending moment at the cross section of the nozzle stock considered, in kN-m
(tf-m, Ltf-ft)
QR = design torque obtained from 3-2-11/21.5, in kN-m (tf-m, Ltf-ft)
Where there is a change in stock diameter above the neck bearing, a gradual transition is to be
provided.

21.9 Design Pressure (2015)

The design pressure of the nozzle is to be obtained from the following:
p = pd + ps N/mm2 (kgf/mm2, psi)
where
CR1
ps = cs cm N/mm2 (kgf/mm2, psi)
2 Aeq

cs = 0.001 (0.0001, 0.145)

cm = as indicated in 3-2-11/Table 8
CR1, Aeq as defined in 3-2-11/21.3
pd as defined in 3-2-10/19.3

TABLE 8
Coefficient cm (2015)

Propeller Zone cm
2
(see 3-2-10/Figure 3) ps in N/mm ps in kgf/mm2 ps in psi
2 0.35 3.6 × 10-2 4.067 × 102
1&3 0.5 5.1 × 10-2 5.81 × 102
4 1.0 1.02 × 10-1 11.62 × 102

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Section 11 Rudders and Steering Equipment 3-2-11

21.11 Plate Thickness

21.11.1 Nozzle Shell
The thickness of the nozzle shell plating, in mm (in.), is not to be less than:
t = to + tc mm (in.), but not to be taken less than 7.5 mm (0.3 in.)
where
to = thickness obtained from the following formula:

= cn⋅Sp⋅ pK n mm (in.)

cn = coefficient as indicated in 3-2-10/Table 3

Sp = spacing of ring webs, in mm (in.)
p = design pressure, in N/mm2 (kgf/mm2, psi), as defined in 3-2-11/21.9
tc = corrosion allowance determined by 3-2-10/Table 4
Kn = nozzle material factor as defined in 3-2-11/1.3
21.11.2 Internal Diaphragm
Thickness of nozzle internal ring web is not to be less than the required nozzle shell plating for
Zone 3 as illustrated in 3-2-10/Figure 3.
21.11.3 Movable Flap
Nozzle movable flap plate thickness, if present, is to comply with the following:
i) For double-plate movable flap, requirements in 3-2-11/17 are to be satisfied as applicable;
ii) For single-plate movable flap, requirements in 3-2-11/19 are to be satisfied as applicable;

21.13 Section Modulus

Steering nozzle is to have a section modulus at least equal to that specified in 3-2-10/19.7, where n is
replaced by 1.0 (0.0017).

21.15 Locking Device

A mechanical locking device is to be provided:
i) To prevent the steering nozzle from rotating beyond the maximum operating angle at design speed
ii) To prevent steering nozzle from rotating toward undesired directions in the event of accident or
damage

21.17 Welding Requirement

Steering nozzle welding procedures are to comply with 3-2-10/19.9.

23 Azimuthal Thruster (2012)

23.1 Application Scope (2017)

23.1.1 Extent of Coverage
Requirements in this Subsection are applicable to Azimuthal Thrusters (also referred as integrated
nozzle propellers), as illustrated in 3-2-11/Figure 11, with the following restrictions:
i) Azimuthal thrusters designed for propulsion and maneuvering
ii) The inner diameter of thruster’s nozzle is of 5 meters (16.5 feet) or less, and
iii) Azimuthal thrusters of above features but provided on the vessels for Ice Class are subject
to additional requirements specified in Part 6 of the Steel Vessel Rules, as applicable

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23.1.2 Special Review

Azimuthal thrusters outside of the above application scope are subject to special consideration
with all supporting documents and calculations submitted to ABS for review. The submitted
documents and calculations include, but are not limited to, the following items:
i) The drawings and plans of the thruster with indications of design operating angles and the
torque considered necessary to operate the thruster at the design operating angle
ii) The calculated thruster section modulus
iii) The calculated maximum water induced pressure of the thruster under design speed (both
ahead and astern conditions) and at the design operating angle, and
iv) The calculated maximum shear and bending of thruster support structure under design
speed (both ahead and astern conditions) and at the design operating angle

23.3 Plans and Documents (2017)

The following structural components related plans and documents are to be submitted to ABS as applicable:
i) Overall arrangement of the thruster unit
ii) Detailed nozzle drawing with nozzle profile type indicated
iii) Detailed plans of thruster connection, bolted or welded, to the hull
iv) Nozzle strut drawings including details of the connections to the propeller gear housing and the
nozzle duct
v) Material list and properties of all structure components
vi) Manufacturer specified/calculated maximum load on the unit for crash stop condition
Note: For specific requirements of machinery components, see Part 4 as applicable.

23.5 Locking Device

A locking device is to be provided to prevent the azimuthal thruster from rotating toward undesired directions
in the event of accident or damage.

23.7 Design Force (2017)

The design force, CR, for azimuthal thrusters is the maximum load for crash stop condition (3-2-11/23.1) or
as obtained from the following equation, whichever is greater:
CR = nkRkckl AVR2 = CR1 + CR2 kN (tf, Ltf)

CR1 = nkRkckl Aeq VR2 kN (tf, Ltf)

CR2 = nkRkckl Atb VR2 kN (tf, Ltf)

where
CR1 = Design force associated with the turning movement of the thruster nozzle
CR2 = Design force associated with the turning movement of other component of the
thruster
kR = (dm2/A + 2)/3 but not taken more than 1.33
dm = mean external diameter of the nozzle, in m (ft)
= 0.5(df + da)
df , da = fore and aft nozzle external diameters as shown in 3-2-11/Figure 11(a), in m (ft)
b = nozzle length as shown in 3-2-11/Figure 11(a), in m (ft)
A = Aeq+Atb, in m2 (ft2)

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Aeq = equivalent nominal area of nozzle cylinder, not to be taken less than 1.35dmb, in m2 (ft2)
Atb = effective projected areas of the azimuthal thruster components forward of the
nozzle*, in m2 (ft2)
do = outer diameter of steering tube as shown in 3-2-11/Figure 11(a), in m (ft)
kc = 1.9 for ahead condition
= 1.5 for astern condition.
k = 1.15, as specified in 3-2-11/Table 2
n, VR are as defined in 3-2-11/3.1.
*Note Effective projected areas forward of the azimuthal thruster nozzle are the parts that actually contribute to generate
lift force as the thruster turns. For example a torpedo shaped component, the projected profile area is to be
proportionally reduced in order to be taken as the effective projected area. If this resultant effective projected area
is too small to compare with the overall effective projected area, it may be discounted.

FIGURE 11
An Illustration of Azimuthal Thruster (2017)

do
Nozzle

Steering
Tube

Propeller
Housing

da df

Supporting
Strut

b c
a f


(a) Side View

L1

 
L2

(b) Looking Aft (c)

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Section 11 Rudders and Steering Equipment 3-2-11

23.9 Design Torque

Design torque, QR, for azimuthal thruster is to be determined from the following equation for both ahead
and astern conditions:
QR = CR r kN-m (tf-m, Ltf-ft)
where
r = (α − k)l, but not less than 0.1l for ahead condition
l = length of azimuthal thruster, in m (ft)
k = Af /A
Af = effective projected area of azimuthal thrust unit forward of steering centerline (within
the extent length of lf), not to be taken less than 0.5 Atb, in m2 (ft2)
α is as defined in 3-2-11/Table 3.
CR and A are as defined in 3-2-11/23.7.

23.11 Design Pressure (2015)

The design pressure of the nozzle is to be obtained from the following:
p = pd + ps N/mm2 (kgf/mm2, psi)
where
CR1
ps = cs cm N/mm2 (kgf/mm2, psi)
2 Aeq

pd, cs, and cm are as defined in 3-2-11/21.9.

CR1, Aeq are as defined in 3-2-11/23.7.

23.13 Nozzle Scantlings

23.13.1 Nozzle Shell
The thickness of the nozzle shell plating, in mm (in.), is not to be less than the following:
t = to + tc mm (in.), but not to be taken less than 7.5 mm (0.3 in.)
where
to = cn Sp⋅ pK n mm (in.)
cn = coefficient as indicated in 3-2-10/Table 3
Sp = nozzle ring web spacing, in mm (in.)
p = design pressure as defined in 3-2-11/23.11
tc = corrosion allowance determined by 3-2-10/Table 4
Kn = material factor of the nozzle, as defined in 3-2-11/1.3
23.13.2 Internal Diaphragm
Thickness of nozzle internal ring webs and diaphragms are not to be less than that required by
3-2-10/19.5.2.

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23.15 Steering Tube

The steering tube of the azimuthal thruster is to have scantlings of at least the same strength against bending
moment and shear force as an equivalent stock with diameter calculated in accordance with 3-2-11/7.
where
QR is replaced by the design torque as defined in 3-2-11/23.9
Ks is replaced by material factor of the steering tube
M is the bending moment calculated at the section of the steering tube under consideration

23.17 Section Modulus

Azimuthal thruster nozzle is to have a section modulus at least equal to that specified in 3-2-10/19.7, where
n is replaced by 1.1 (0.00187).

23.19 Thruster Nozzle Top Connections (2017)

The structure where nozzle top and the steering tub are connected is to comply with the following requirements
as the case may be.
23.19.1 Welded Connection
Refer to 3-2-11/23.25.2.
23.19.2 Bolted Connection
The following are to be complied with:
i) Flange couplings are to be supported by an ample bodies of metal worked out from both
sides, which provide the structural continuity to bear the anticipated loads. In certain
cases, stress analysis may be required to verify that the stress level within the flanges is
not greater than 80% of the yield strength.
ii) Flange thickness is to be comply with 3-2-11/9.3.2 or 3-2-11/9.5.2, as applicable.
iii) The coupling bolts are to be of fitted bolts and meet the scantling requirements specified
in 3-2-11/9.3.1 or 3-2-11/9.5.1, as applicable.
iv) Effective means are to be fitted for locking the nuts in place.
v) The smallest distance from the edge of the bolt holes to the edge of the flange is not to be
less than two-thirds of the bolt diameter.

23.21 Nozzle Strut (2017)

23.21.1 General
i) Structural transitions of strut connected to nozzle and propeller housing are to avoid
abrupt changes and the fillet radius is not to be less than 75 mm (3 in.) unless the stress in
the radius area is verified to be acceptable by direct analysis.
ii) The width and thickness of strut plating are to have a gradual transition for smooth load
carrying.
iii) Material properties of the nozzle strut and the structure components it is in direct contact
are to be compatible [see 3-2-11/1.3iii)].
23.21.2 Plate Thickness
The minimum plate thickness of the strut is not to be less than obtained from the following:
3Feqv Leqv
t= mm (in.), but not to be taken less than 7.5 mm (0.3 in.)
2bavg σ F

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where
Feqv = equivalent load perpendicular to strut applied at ½ L, in kN (tf, Ltf)

= pAstrut, where α is greater than 15° [see 3-2-11/Figure 11(b)]

= Wp weight of transmission shaft, gear, and bearings, in kN (tf, Ltf), where α
is less than or equal to 15° [see 3-2-11/Figure 11(c)]
Aeqv = equivalent area of nozzle supporting strut, in m2 (ft2)
= L1 bavg, as illustrated in 3-2-11/Figure 11(b)
= L2 bavg, as illustrated in 3-2-11/Figure 11(c)
Leqv = equivalent length of nozzle supporting strut, in m (ft)
= L1, as illustrated in 3-2-11/Figure 11(b)
= L2, as illustrated in 3-2-11/Figure 11(c)
bavg = average width of nozzle strut plate, in m (ft)

σF = minimum yield stress of the local material, in N/mm2 (kgf/mm2, psi)

p is as defined in 3-2-11/23.11.

23.23 Direct Analysis (2017)

Direct calculations may be accepted in lieu of applying prescriptive formulas presented in 3-2-11/23.7 to
3-2-11/23.21, provided that the following are complied with and satisfied:
23.23.1 Additional Information to Submit
Where the design is based on direct calculations such as FEM, the full analysis is to be submitted
for review including:
i) Software used;
ii) FE model;
iii) Loading conditions and load cases including but not limited to normal, heavy duty, and
crash stop;
iv) Applied loads and boundary conditions;
v) Stress and deflection results, and
vi) Any other data and information associated with the analysis;
23.23.2 Acceptance Criteria
The results of analysis verify the following:
i) The maximum nominal stress is not exceed 50% of the yield strength. For the crash stop
load case, the maximum local stress in the nozzle and its connection is not to exceed 80%
of the yield strength;
ii) The relative radial displacement, srel, between nozzle inner shell and propeller tip is not to
exceed the following:
srel = 0.1scl mm (in.)
where
scl = design clearance (the smallest distance) between nozzle inner shell
and propeller tip without any loads applied

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23.25 Welding and NDT Testing (2017)

The following general requirements are to be complied with:
i) Welding on azimuthal thruster is to be in accordance with Section 2-4-1 of the ABS Rules for
Materials and Welding (Part 2) and Section 3-2-16 as applicable.
ii) The required extent of NDE is to be indicated on the drawings and plans.
iii) NDE is to be performed in accordance with the ABS Guide for Nondestructive Inspection of Hull
Welds where applicable and any additional requirements specified by the manufacturer.
23.25.1 Nozzle Welding
i) Integrated nozzle welding details are to comply with 3-2-10/19.9
ii) Volumetric and surface examination are to be performed on weldments of the inner and
outer shell plating, as well as the internal ring web welds as appropriate.
23.25.2 Connection Welding
Where the connections between nozzle and the hull/steering tube, strut and nozzle/propeller
housing are welded (see figure below and 3-2-11/Figure 11), the following requirements are to be
complied with:
i) Scantlings of the welded connection and welding type/size are to be specially considered
and detailed stress analysis may be required to be submitted.
ii) Welding at the portion of the thruster assembly that penetrates the hull is to be of full
penetration and in accordance with Section 2-4-1 of the ABS Rules for Materials and
Welding (Part 2) and Section 3-2-16, as applicable.
iii) Volumetric or surface examination is to be performed on the welds of brackets and the
shell penetration.

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PART Appendix 2: Guidelines for Calculating Bending Moment and Shear Force in Rudders and Rudder Stocks

3
CHAPTER 2 Hull Structures and Arrangements

APPENDIX 2 Guidelines for Calculating Bending Moment and

Shear Force in Rudders and Rudder Stocks

1 Application
Bending moments, shear forces and reaction forces of rudders, stocks and bearings may be calculated according
to this Appendix for the types of rudders indicated. Moments and forces on rudders of different types or
shapes than those shown are to be calculated using alternative methods and will be specially considered.

3 Spade Rudders (2014)

3.1 Rudder
3.1.1 Shear Force
For regular spade rudders as shown in 3-2-A2/Figure 1(a), the shear force, V(z), at a horizontal section
of the rudder above baseline is given by the following equation:
 
V(z) =
zC R
c l +
z
(cu − cl ) kN (tf, Ltf )
A  2l R 
where
z = distance from the rudder baseline to the horizontal section under
consideration, in m (ft)
CR = rudder force, as defined in 3-2-11/3, in kN (tf, Ltf)

A = total projected area of rudder blade in m2 (ft2), as defined in 3-2-11/3

cl, cu and lR are dimensions as indicated in 3-2-A2/Figure 1(a), in m (ft).
For spade rudders with embedded rudder trunks let deep in the rudder blade, as shown in
3-2-A2/Figure 1(b), the shear forces at rudder horizontal sections above rudder baseline in areas
A1, and A2, are given by the following equations:

z′CR1  z′ 
V(z′)1 = cu − (cu − cb ) kN (tf, Ltf ), over area A1
A1  2l l 

zCR 2  
V(z)2 = cb +
z
(cb − cl ) kN (tf, Ltf ) , over area A2
A2  2l b 
where
z′ = lR – z
CR1 = rudder force over rudder area A1, in kN (tf, Ltf)
A1
= CR
A

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Appendix 2 Guidelines for Calculating Bending Moment & Shear Force in Rudders and Rudder Stocks 3-2-A2

CR2 = rudder force over rudder area A2, in kN (tf, Ltf)

A2
= CR
A
A1 = partial rudder blade area above neck bearing and below rudder top, in mm2 (ft2)
A2 = partial rudder blade area above rudder baseline and below neck bearing, in
mm2 (ft2)
z, A, and CR are as indicated in 3-2-A2/3.1.1.

cl, cb, cu, lu, and lb are dimensions as illustrated in 3-2-A2/Figure 1(b).

3.1.2 Bending Moment

For regular spade rudders, bending moment, M(z), at a horizontal section z meters (feet) above the
baseline of the rudder is given by the following equations:

z 2C R  
M(z) = c l +
z
(cu − cl ) kN-m, (tf-m, Ltf-ft)
2A  3l R 
For spade rudders with embedded rudder trunk, the bending moment at a horizontal section within
area A1 is obtained from the following:

( z ′) 2 C R1  z′ 
M(z′)1 = c u − (cu − cb ) kN-m, (tf-m, Ltf-ft)
2 A1  3l l 
With the maximum bending moment M1 over area A1 equals to:

 2c + cu 
M1 = C R1l l 1 − b  kN-m, (tf-m, Ltf-ft)
 3(cb + cu ) 
For spade rudders with embedded rudder trunk, the bending moment at a horizontal section within
area A2 is obtained from the following:

z 2C R 2  
M(z)2 = cl +
z
(cu − cl ) kN-m, (tf-m, Ltf-ft)
2 A2  3l b 
With the maximum bending moment M2 over area A2 equals to:
2cl + cb
M2 = C R 2 l b kN-m, (tf-m, Ltf-ft)
3(cl + cb )

where z, z′, CR1, CR2, A1, A2, cl, cu and lR are as defined in 3-2-A2/3.1.1.

3.3 Lower Stock

3.3.1 Shear Force
For regular spade rudder, the shear force, Vl, at any section of the lower stock between the top of
the rudder and the neck bearing is given by the following equation:
Vl = C R kN (tf, Ltf)
For spade rudder with embedded rudder trunk, the shear force at any section of the stock between
the top of the rudder and the neck bearing is given by the following equation:
M 2 − M1
Vl = kN (tf, Ltf)
lu + ll

where CR, ll, and lu are as defined in 3-2-A2/3.1.1.

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Appendix 2 Guidelines for Calculating Bending Moment & Shear Force in Rudders and Rudder Stocks 3-2-A2

3.3.2 Bending Moment at Neck Bearing (2017)

For regular spade rudder, the bending moment in the rudder stock at the neck bearing, Mn, is given
by the following equation:
 l (2cl + cu ) 
Mn = C R  l l + R  kN-m (tf-m, Ltf-ft)
 3 (c l + c u ) 

where
CR = rudder force as defined in 3-2-11/3
cl, cu, ll and lR are dimensions as indicated in 3-2-A2/Figure 1, in m (ft).
For spade rudder with embedded rudder trunk, the bending moment in the rudder stock at the neck
bearing is given by the following equation:
Mn = M2 – M1 kN-m (tf-m, Ltf-ft)
where M1and M2 are as defined in 3-2-A2/3.1.2.
Where partial submergence of the rudder leads to a higher bending moment in the rudder stock at
the neck bearing (compared with the fully submerged condition), Mn is to be calculated based on
the most severe partially submerged condition.

3.5 Moment at Top of Upper Stock Taper

For regular spade rudder, the bending moment in the upper rudder stock at the top of the taper, Mt, is given
by the following equation:
 l ( 2c l + c u )   ( l u + l R + l l − z t ) 
Mt = C R  l l + R ×  kN-m (tf-m, Ltf-ft)
 3 (c l + c u )   lu 
For spade rudder with embedded rudder trunk, the bending moment in the upper rudder stock at the top of
the taper is given by the following equation:
 ( l + l u − zt ) 
Mt = M R  R  kN-m (tf-m, Ltf-ft)
 lu 
where
zt = distance from the rudder baseline to the top of the upper rudder stock taper in m (ft)
CR = rudder force, as defined in 3-2-A2/3.1.1
MR = is the greater of M1 and M2, as defined in 3-2-A2/3.1.2
cl, cu, ll, lu and lR are dimensions as indicated in 3-2-A2/Figure 1, in m (ft).

3.7 Bearing Reaction Forces

For regular spade rudder, the reaction forces at the bearings are given by the following equations:
Pu = reaction force at the upper bearing
Mn
= − kN (tf, Ltf)
lu
Pn = reaction force at the neck bearing
Mn
= CR + kN (tf, Ltf)
lu

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Appendix 2 Guidelines for Calculating Bending Moment & Shear Force in Rudders and Rudder Stocks 3-2-A2

For spade rudder with embedded rudder trunk, the reaction forces at the bearings are given by the following
equations:
Mn
Pu = − kN (tf, Ltf)
lu + ll

Pn = CR + Pu kN (tf, Ltf)
where
Mn = bending moment at the neck bearing, as defined in 3-2-A2/3.3.2
CR = rudder force, as defined in 3-2-11/3
lu is as indicated in 3-2-A2/Figure 1, in m (ft).

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Appendix 2 Guidelines for Calculating Bending Moment & Shear Force in Rudders and Rudder Stocks 3-2-A2

FIGURE 1
Spade Rudder (2014)
Upper bearing

u

Neck bearing
l

cu

R

c
l

(a) Regular Spade Rudder

(b) Spade Rudder with Embedded Rudder Trunk

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Appendix 2 Guidelines for Calculating Bending Moment & Shear Force in Rudders and Rudder Stocks 3-2-A2

5 Rudders Supported by Shoepiece

5.1 Shear Force, Bending Moment and Reaction Forces

Shear force, bending moment and reaction forces may be calculated according to the model given in
3-2-A2/Figure 2.
wR = rudder load per unit length
CR
= kN/m (tf/m, Ltf/ft)
R
where
CR = rudder force, as defined in 3-2-11/3
ks = spring constant reflecting support of the shoepiece
ns I s
= kN/m (tf/m, Ltf/ft)
 3s

ns = 6.18 (0.630, 279)

Is = moment of inertia of shoepiece about the vertical axis, in cm4 (in4)
Iu = moment of inertia of the rudder stock above the neck bearing, in cm4 (in4)
I = moment of inertia of the rudder stock below the neck bearing, in cm4 (in4)
IR = moment of inertia of the rudder about the longitudinal axis, in cm4 (in4)
Ip = moment of inertia of the pintle, in cm4 (in4)
, s,R and u are dimensions as indicated in 3-2-A2/Figure 2, in m (ft).

FIGURE 2
Rudder Supported by Shoepiece

Upper bearing

u

Neck bearing


R wR

p

ks
s

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Appendix 2 Guidelines for Calculating Bending Moment & Shear Force in Rudders and Rudder Stocks 3-2-A2

7 Rudders Supported by a Horn with One Pintle (2009)

7.1 Shear Force, Bending Moment and Reaction Forces

Shear force, bending moment and reaction forces are to be assessed by the simplified beam model shown
in 3-2-A2/Figure 3.
wR1 = rudder load per unit length above pintle

C R1
= kN/m (tf/m, Ltf/ft)
l R1
wR2 = rudder load per unit length below pintle
CR2
= kN/m (tf/m, Ltf/ft)
l R2
where
CR1 = rudder force, as defined in 3-2-11/3.3
CR2 = rudder force, as defined in 3-2-11/3.3
kh = spring constant reflecting support of the horn
1
= kN/m (tf/m, Ltf/ft)
s 
3
Σ i  e 2 l h
lh  ti 
+
nb I h nt a 2
nb = 4.75 (0.485, 215)
nt = 3.17 (0.323, 143)

a = mean area enclosed by the outside lines of the rudder horn, in cm2 (in2)
si = the girth length of each segment of the horn of thickness ti, in cm (in.)
ti = the thickness of each segment of horn outer shell of length si, in cm (in.)

Ih = moment of inertia of horn section at lh about the longitudinal axis, in cm4 (in4)

e, lh, lR1 and lR2 are dimensions as indicated in 3-2-A2/Figure 3, in m (ft).

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Appendix 2 Guidelines for Calculating Bending Moment & Shear Force in Rudders and Rudder Stocks 3-2-A2

FIGURE 3
Rudder Supported by a Horn with One Pintle (2009)

Upper bearing

u

Neck bearing
l

R 1 wR1
h

h
2 kh
e
R2 wR 2

9 Rudders Supported by a Horn Arranged with Two Pintles (Supports)

(1 July 2016)

9.1 Shear Force, Bending Moment and Reaction Forces

Shear force, bending moment and reaction forces are to be assessed by the simplified beam model shown
in 3-2-A2/Figure 4.
wR1 = rudder load per unit length above lower rudder support/pintle

C R1
= kN/m (tf/m, Ltf/ft)
 R1
wR2 = rudder load per unit length below lower rudder support/pintle

CR 2
= kN/m (tf/m, Ltf/ft)
 R2
where
CR1 = rudder force, as defined in 3-2-11/3.3
CR2 = rudder force, as defined in 3-2-11/3.3

R1 and R2 are dimensions as indicated in 3-2-A2/Figure 4, in m (ft).

In 3-2-A2/Figure 4 the variables K11, K22, K12 are rudder horn compliance constants calculated for rudder
horn with 2-conjugate elastic supports. The 2-conjugate elastic supports are defined in terms of horizontal
displacements, yi, by the following equations:

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• At the lower rudder horn bearing:

y1 = –K12 B2 – K22 B1 m (ft)

• At the upper rudder horn bearing:

y2 = –K11 B2 – K12 B1 m (ft)
where
y1, y2 = horizontal displacement at lower and upper rudder horn bearings, respectively
B1, B2 = horizontal support force, in kN (tf, Ltf), at lower and upper rudder horn bearings,
respectively
K11, K22, K12 = spring constant of the rudder support obtained from the following:

 λ3 e2λ 
K11 = m 1.3 +  m/kN (m/tf, ft/Ltf)
 3EJ 1h GJ th 

  λ3 λ2 (d − λ )  e 2 λ 
K22 = m 1.3 + +  m/kN (m/tf, ft/Ltf)
  3EJ 1h 2 EJ 1h  GJ th 

  λ3 λ2 (d − λ ) λ(d − λ ) (d − λ )3  + e 2 d  m/kN (m/tf, ft/Ltf)

2
K12 = m 1.3 + + +  
  3EJ 1h EJ 1h EJ 1h 3EJ 2 h  GJ th 

m = 1.00 (9.8067, 32.691)

d = height of the rudder horn, in m (ft), defined in 3-2-A2/Figure 4. This value is
measured downwards from the upper rudder horn end, at the point of curvature
transition, to the mid-line of the lower rudder horn pintle.
λ = length, in m (ft), as defined in 3-2-A2/Figure 4. This length is measured downwards
from the upper rudder horn end, at the point of curvature transition, to the mid-line of
the upper rudder horn bearing. For λ = 0, the above formulae converge to those of
spring constant kh for a rudder horn with 1-pintle (elastic support), and assuming a
hollow cross section for this part.
e = rudder-horn torsion lever, in m (ft), as defined in 3-2-A2/Figure 4 (value taken at
vertical location lh/2).
E = Young’s modulus of the material of the rudder horn in kN/m2 (tf/m2, Ltf/in2)
G = modulus of rigidity of the material of the rudder horn in kN/m2 (tf/m2, Ltf/in2)
J1h = moment of inertia of rudder horn about the x axis, in m4 (ft4), for the region above the
upper rudder horn bearing. Note that J1h is an average value over the length λ (see
3-2-A2/Figure 4).
J2h = moment of inertia of rudder horn about the x axis, in m4 (ft4), for the region between
the upper and lower rudder horn bearings. Note that J2h is an average value over the
length d – λ (see 3-2-A2/Figure 4).
Jth = torsional stiffness factor of the rudder horn, in m4 (ft4)

4 FT2
= for any thin wall closed section, in m4 (ft4)
∑
ui
i
ti

Note that the Jth value is taken as an average value, valid over the rudder horn height.

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Appendix 2 Guidelines for Calculating Bending Moment & Shear Force in Rudders and Rudder Stocks 3-2-A2

FT = mean of areas enclosed by outer and inner boundaries of the thin walled section of
rudder horn, in m2 (ft2)
ui = length, in mm (in.), of the individual plates forming the mean horn sectional area
ti = thickness, in mm (in.), of the individual plates mentioned above

FIGURE 4
Rudder Supported by a Horn Arranged with Two Pintles (Supports) (1 July 2016)

u
J1h


Jth
h k11, k12
R1 wR1 k12, k22
J2h h/2

e
R2
wR2

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PART Section 12: Protection of Deck Openings

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 12 Protection of Deck Openings

1 General
All openings in decks are to be framed to provide efficient support and attachment for the ends of the deck
beams. The proposed arrangement and details for all hatchways are to be submitted for approval.

3 Additional Requirements for Bulk Carriers, Ore Carriers and

Combination Carriers (2004)
On all bulk carriers, ore carriers and combination carriers, in addition to all relevant requirements in this
Section, all cargo hold hatch covers, hatch coamings and closing arrangements for cargo hold hatches in
position 1, as defined in 3-2-12/5.1, are to meet the requirements in 5C-4-2/13.3 of the Steel Vessel Rules.

5 Positions and Design Pressures (1 January 2005)

5.1 Positions of Deck Openings (1 January 2005)

For the purpose of the Rules, two positions of deck openings are defined as follows.
Position 1 Upon exposed freeboard and raised quarter decks, and upon exposed superstructure decks
situated forward of a point located Lf /4 from the forward end of Lf.
Position 2 Upon exposed superstructure decks situated abaft Lf /4 from the forward end of Lf and located
at least one standard height of superstructure above the freeboard deck. Upon exposed
superstructures decks situated forward of a point located Lf /4 from the forward end of Lf and
located at least two standards heights of superstructure above the freeboard deck.

5.3 Design Pressures (1 January 2005)

The design pressures are not to be taken as less than the following. Values at intermediate lengths are to be
determined by interpolation.
5.3.1 Cargo Hatch Covers in Position 1 (2018)
p = R{15.8 + (Lf/N)[1 – (5/3)(x/Lf)] – 3.6x/Lf } kN/m2 (tf/m2, Ltf/ft2)
In no case is p to be less than:
p = 1.2897(0.15Lf + 11.6) kN/m2
= 0.1316(0.15Lf + 11.6) tf/m2
= 0.0121(0.0457Lf + 11.6) Ltf/ft2
For a position 1 hatchway located at least one superstructure standard height higher than the
freeboard deck:
p = 1.2897 (0.15Lf + 11.6) kN/m2
= 0.1316(0.15Lf + 11.6) tf/m2
= 0.0121(0.0457Lf + 11.6) Ltf/ft2

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Section 12 Protection of Deck Openings 3-2-12

where
Lf = freeboard length, in m (ft), as defined in 3-1-1/3.3
Lf1 = freeboard length, in m (ft), as defined in 3-1-1/3.3, but is not to be taken as
less than 24 m (80 ft)
x = distance, in m (ft), from the mid length of the hatch cover under examination
to the forward end of Lf, or 0.25Lf, whichever is less.
R = 1.0 (0.102, 0.00932)
N = 3 (3, 9.84)
5.3.2 Cargo Hatch Covers in Position 2
Where a position 2 hatchway is located at least one superstructure standard height higher than the
freeboard deck, the design pressures are as follows:
p = 25.5 – 0.142(100 – Lf) kN/m2

= 2.6 – 0.0145(100 – Lf) tf/m2

= 0.238 – 0.00041(328 – Lf) Ltf/ft2

7 Hatchway Coamings, Companionway Sills and Access Sills

7.1 Coaming and Sill Heights

The heights above deck of coamings of hatchways secured weathertight by tarpaulins and battening devices,
and sills of companionways and access openings, are to be not less than given in 3-2-12/Table 1. Where
hatch covers are made of steel or other equivalent material and made tight by means of gaskets and clamping
devices, these heights may be reduced or the coamings omitted entirely, provided that the safety of the
vessel is not thereby impaired in any sea conditions. Sealing arrangements are to be weathertight if coaming
is fitted, and watertight for flush covers.

TABLE 1
Coaming and Sill Heights
L equal to or over 24 meters (79 feet) in length

Position 1 Position 2
Hatch Coamings 600 mm (23.5 in.) 450 mm (17.5 in.)
Companionway Sills 600 mm (23.5 in.) 380 mm (15 in.)
Access Sills 380 mm (15 in.) 380 mm (15 in.)

L under 24 meters (79 feet) in length

Position 1 Position 2
Hatch Coamings and Companionways 450 mm (17.5 in.) 300 mm (12 in.)
Access Sills 380 mm (15 in.) 300 mm (12 in.)
Notes:
1 Coaming and sill heights may be reduced on vessels which have freeboard in excess of the minimum
geometric freeboard and/or a superstructure deck with height of deck in excess of the standard height of
a superstructure.
2 For vessels with L < 24 m (79 ft), the coaming/sill height should be as indicated above, unless otherwise
specifically requested by Flag Administration.

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Section 12 Protection of Deck Openings 3-2-12

7.3 Coaming Plates

Coaming plates are not to be less in thickness than that obtained from the following equation:
t = 0.05L + 7 mm
t = 0.0006L + 0.27 in.
where
t = thickness, in mm (in.)
L = length of vessel, in m (ft), as defined in 3-1-1/3, but need not exceed 76 m (250 ft)

7.5 Coaming Stiffeners (2016)

Except as noted below, coaming stiffening is to comply with the following:
i) Horizontal stiffeners are to be fitted on coamings 450 mm (17.5 in.) or greater in height.*
ii) The breadth of the stiffeners is not to be less than that obtained from the following equation:*
b = 1.67L + 50 mm
b = 0.02L + 2 in.
where
b = breadth, in mm (in.)
L = length of vessel, in m (ft), as defined in 3-1-1/3, but need not exceed 76 m
(250 ft)
iii) Efficient brackets or stays are to be fitted from the stiffeners to the deck at intervals of not more
than 3 m (10 ft).*
iv) Where exposed coamings are 760 mm (30 in.) or more in height, the arrangement of the stiffeners
and brackets or stays is to provide equivalent support.*
v) Where end coamings are protected, the arrangement of the stiffeners and brackets or stays may be
modified.
vi) Where chocks are provided on the coaming to limit the horizontal movement of hatch covers, the
strength of the coaming and deck structure is to be adequate to withstand the load on these chocks.
Similar consideration is to be given to pads supporting the weight from hatch covers.
* Note: Small hatches as specified in 3-2-12/14 need not comply with these requirements. (See the strength requirements
for small hatches in 3-2-12/14.3)

7.7 Continuous Longitudinal Hatch Coamings

Where strength deck longitudinal hatch coamings of length greater than 0.14L are effectively supported by
longitudinal bulkheads or deep girders, they are, in general, to be longitudinally stiffened. The coaming
thickness is to be not less than required by 3-2-3/3, and the longitudinal stiffeners not less than required by
3-2-6/1.3 for strength deck longitudinal beams where s is the stiffener spacing, l is the distance between
coaming brackets, and h is as given in 3-2-6/1.3.2. Special consideration will be given to the coaming
scantlings where adequate buckling strength is shown to be otherwise provided.

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Section 12 Protection of Deck Openings 3-2-12

9 Hatchways Closed by Portable Covers and Secured Weathertight by

Tarpaulins and Battening Devices

9.1 Pontoon Covers

9.1.1 Scantlings (1 January 2005)
Where steel pontoon covers are used, the maximum allowable stress and deflection under the
design pressures in 3-2-12/5.3, and the minimum required top plate thickness are as follows.
Maximum allowable stress 0.68Y
Maximum allowable deflection 0.0044 times the span
Top plate thickness 0.01s, but not less than 6 mm (0.24 in.)
where
Y = specified minimum upper yield point strength of the materials, in N/mm2
(kgf/mm2, psi)
s = stiffener spacing, in mm (in.)
Covers are to be assumed to be simply supported.
Where the cross section of hatch cover stiffeners is not constant along the span, Appendix 3-2-A3
may be used to determine required scantlings.
9.1.2 Cleats
Cleats are to be set to fit the taper of the wedges. They are to be at least 65 mm (2.5 in.) wide and
spaced not more than 600 mm (23.5 in.) center to center. The cleats along each side or end are to
be not more than 150 mm (6 in.) from the hatch corners.
9.1.3 Wedges
Wedges are to be of tough wood with a taper of not more than 1 in 6 and are to be not less than
13.0 mm (0.50 in.) thick at the toes.
9.1.4 Battening Bars
Battening bars are to be provided for properly securing the tarpaulins. They are to have a width of
64 mm (2.5 in.) and a thickness of not less than 9.5 mm (0.375 in.).
9.1.5 Tarpaulins
At least two thoroughly waterproofed tarpaulins of ample strength are to be provided for each
exposed hatchway. The material is to be guaranteed free from jute and is to be of an approved
type. Synthetic fabrics which have been demonstrated to be equivalent will be specially approved.
9.1.6 Security of Hatch Covers
For all hatchways in Position 1 or 2, steel bars or other equivalent means are to be provided in
order to efficiently and independently secure each section of hatch covers after the tarpaulins are
battened down. Hatch covers of more than 1.5 m (4.9 ft) in length are to be secured by at least two
such securing appliances.

9.3 Wooden Hatch Covers

9.3.1 Hatch Boards
Wood hatch covers on exposed hatchways are to have a finished thickness not less than 60 mm
(2.375 in.) where the span is not more than 1.5 m (4.9 ft); the wood is to be of satisfactory quality,
straight-grained, reasonably free from knots, sap and shakes, and is to be examined before being
coated. Hatch rests are to be beveled where necessary, so as to provide a solid bearing surface.

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Section 12 Protection of Deck Openings 3-2-12

9.3.2 Portable Beams (1 January 2005)

Where portable beams for supporting wooden hatch boards are made of steel, the maximum
allowable stress and deflection under the design loads in 3-2-12/5.3 are as follows:
Maximum allowable stress 0.68Y
Maximum allowable deflection 0.0044 times the span
Where Y is as defined in 3-2-12/9.1.1.
Where the cross section of portable beams is not constant along the span, Appendix 3-2-A3 may
be used to determine required beam scantlings.
9.3.3 Closing/Securing Arrangements
Closing arrangements are to be in accordance with 3-2-12/9.1.2 through 3-2-12/9.1.6.
9.3.4 Carriers and Sockets
Carriers or sockets for portable beams are to be of substantial construction, and are to provide
means for the efficient fitting and securing of the beams. Where rolling types of beams are used,
the arrangements are to ensure that the beams remain properly in position when the hatchway is
closed. The bearing surface is not to be less than 75 mm (3 in.) in width, measured along the axis
of the beam, unless the carriers are of an interlocking type with the beam ends. Carriers for beams
are to extend to the deck level or the coamings are to be fitted with stiffeners or external brackets
in way of each beam.

9.5 Steel Hatch Covers

9.5.1 Scantlings (1 January 2005)
Where steel hatch covers are fitted, the maximum allowable stress and deflection under the design
loads in 3-2-12/5.3 and the minimum top plate thickness are as follows:
Maximum allowable stress 0.8Y, and not exceed the critical buckling
strength in compression
Maximum allowable deflection 0.0056 times the span
Top plate thickness 0.01s, but not less than 6 mm (0.24 in.)
Where Y and s are as defined in 3-2-12/9.1.1.
Covers are to be assumed to be simply supported.
Where the cross section of hatch over stiffeners is not constant along the span, Appendix 3-2-A3
may be used to determine required scantlings.
9.5.2 Closing Arrangements
Closing arrangements are to be in accordance with 3-2-12/9.1.2 through 3-2-12/9.1.6.

9.7 Bearing Surface

The width of each bearing surface for hatchway covers is to be at least 65 mm (2.5 in.)

9.9 Materials Other Than Steel

The strength and stiffness of covers made of materials other than steel are to be equivalent to those of steel
and will be subject to special consideration.

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Section 12 Protection of Deck Openings 3-2-12

11 Hatchways Closed by Covers of Steel Fitted with Gaskets and

Clamping Devices

11.1 Strength of Covers (1 January 2005)

11.1.1 Scantlings
Where weathertight covers are steel, the maximum allowable stress and deflection under the
design loads in 3-2-12/5.3 and the minimum top plate thickness are as follows.
Maximum allowable stress 0.8Y, and not to exceed the critical buckling
strength in compression
Maximum allowable deflection 0.0056 times the span
Top plate thickness 0.01s, but not less than 6 mm (0.24 in.)
Where Y and s are as defined in 3-2-12/9.1.1.
The following corrosion margin is to be incorporated into each strength member of the hatch cover:
• Single skin hatch covers, a corrosion addition ts = 2.0 mm (*) for all plating and stiffeners.
• Double skin hatch covers, a corrosion addition ts = 1.5 mm (*) for top and bottom plating and
ts = 1.0 mm for the internal structure.
(*) Corrosion addition ts = 1.0 mm for the hatch covers in way of cellular cargo holds intended for containers.
The value for cargo hatch covers for bulk carriers, ore carriers and combination carriers is given in
5C-3-4/19.3.1(a) of the Steel Vessel Rules.
Where the cross section of hatch cover stiffeners is not constant along the span, Appendix 3-2-A3
may be used to determine required scantlings.

11.3 Means for Securing Weathertightness (1 January 2005)

11.3.1 General
The means for securing and maintaining weathertightness are to be such that the tightness can be
maintained in any sea conditions. The arrangements and the strength of these means of closing and
securing of the covers to the anticipated sea loads are to comply with the following requirements.
Where it is intended to carry cargoes on the covers, the securing means are also take into consideration
these loads, including dynamic effects. Strength calculations for the means of securing hatch covers
carrying cargoes are to be submitted for review. The covers are to be hose-tested in position under
a water pressure of at least 2.1 bar (2.1 kgf/cm2, 30 psi) at the time of construction and, if considered
necessary, at subsequent surveys.
11.3.2 Securing Arrangements
11.3.2(a) Securing Device. Hatch cover panels are to be secured by appropriate devices (bolts,
wedges or similar) suitably spaced alongside the coamings and between panels.
Arrangement and spacing are to be determined with due attention to the weather-tightness, the type
and the size of the hatch cover, as well as the stiffness of the cover edges between the securing devices.
Securing devices are to be of reliable construction and securely attached to the hatchway coamings,
decks or covers. Individual securing devices on each cover are to have approximately the same
stiffness characteristics.
Where rod cleats are fitted, resilient washers or cushions are to be incorporated.
Where hydraulic cleating is adopted, a positive means is to be provided to ensure that it remains
mechanically locked in the closed position in the event of failure of the hydraulic system.

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Section 12 Protection of Deck Openings 3-2-12

11.3.2(b) Sectional Area. Subject to 3-2-12/11.3.2(c), the net sectional area of each securing device
is not to be less than:
A = csd a/f cm2 (in2)
where
csd = 1.4 (1.4, 0.066)
a = spacing, in m (ft), of securing devices, not to be taken less than 2 m (6.6 ft)
f = (σY/Y)e
Y = 235 N/mm2 (24 kgf/mm2, 34,000 psi)
σY = specified minimum upper yield stress, in N/mm2 (kgf/mm2, psi), of the steel,
not to be taken greater than 70% of the ultimate tensile strength.
e = 0.75 for σY > 235 N/mm2 (24 kgf/mm2, 34,000 psi)
= 1.0 for σY < 235 N/mm2 (24 kgf/mm2, 34,000 psi)
Rods or bolts are to have a net diameter not less than 19 mm (0.75 in.) for hatchways exceeding 5 m2
(54 ft2) in area.
11.3.2(c) Packing Line Pressure. Between cover and coaming and at cross-joints, a packing line
pressure sufficient to obtain weathertightness is to be maintained by the securing devices.
For packing line pressures exceeding 5 N/mm2 (0.51 kgf/mm2, 28.6 psi), the cross section area of
the securing device is to be increased in direct proportion. The packing line pressure is to be specified.
11.3.2(d) Edge Stiffness. The cover edge stiffness is to be sufficient to maintain adequate sealing
pressure between securing devices. The moment of inertia, I, of edge elements is not to be less than:
I = ci p a4 cm4 (in4)
where
ci = 6 (58.8, 0.000218)
p = packing line pressure, in N/mm2 (kgf/mm2, psi), minimum 5 N/mm2 (0.51
kgf/mm2, 28.6 psi).
a = spacing, in m (ft), of securing devices.
11.3.3 Stoppers
11.3.3(a) Forces. All hatch covers are to be fitted with stoppers to limit horizontal movement of
the cover against the forces caused by the following pressures:
i) Longitudinal pressure on fore end of cover:
No. 1 hatch cover:
• Where a forecastle in accordance with 5C-3-1/7 of the Steel Vessel Rules is not fitted:
230 kN/m2 (23.5 tf/m2, 2.14 Ltf/ft2)
• Where a forecastle in accordance with 5C-3-1/7 of the Steel Vessel Rules is fitted:
175 kN/m2 (17.8 tf/m2, 1.63 Ltf/ft2)
Other hatch covers: 175 kN/m2 (17.8 tf/m2, 1.63 Ltf/ft2).
ii) Transverse pressure on side of cover:
All hatch covers: 175 kN/m2 (17.8 tf/m2, 1.63 Ltf/ft2).
11.3.3(b) Allowable Stresses. The equivalent stress:
i) In stoppers and their supporting structures, and
ii) Calculated in the throat of the stopper welds
is not to exceed 0.8σY under the above pressures.

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Section 12 Protection of Deck Openings 3-2-12

11.3.4 Materials and Welding

Stoppers and securing devices are to be manufactured of materials and corresponding welding
procedures and consumables, in accordance with applicable requirements of the ABS Rules for
Materials and Welding (Part 2).

13 Hatchways Closed by Portable Covers in Lower Decks or within Fully

Enclosed Superstructures

13.1 General
The following scantlings are intended for conventional type covers. Those for covers of special types are to
be specially considered.

13.3 Portable Beams and Wood Covers

Portable beams supporting lower deck hatch covers on which cargo is stowed are to have a section
modulus, SM, of not less than that obtained from the following equation:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 1.18
h = tween-deck height in m (ft). When a design load is specified, h is to be taken as p/n,
where p is the specified design pressure, in kN/m2 (kgf/m2, lbf/ft2), and n is defined
as 7.05 (715, 45).
s = spacing of the portable beams, in m (ft)
l = length of the portable beam, in m (ft)
The depth of the portable beam is not to be less than 4% of its unsupported span.
Wood covers are not to be less than 63.5 mm (2.5 in.) thick where the spacing of the portable beams does
not exceed 1.52 m (5 ft). Where the height to which the cargo may be loaded on top of the cover exceeds
2.59 m (8.5 ft), or where the spacing of the portable beams exceeds 1.52 m (5 ft), the thickness of the wood
covers is to be suitably increased.

13.5 Steel Covers

The thickness of the plating for steel covers is not to be less than required for platform decks in enclosed
cargo spaces, as obtained from 3-2-3/1. A stiffening bar is to be fitted around the edges, as required, to
provide the necessary rigidity to permit the covers being handled without deformation. The effective depth
of the framework is normally to be not less than 4% of its unsupported length. The stiffeners in association
with the plating to which they are attached are to have section modulus, SM, as determined by the following
equation:
SM = 7.8hsl2 cm3
SM = 0.0041hsl2 in3
where
h = tween-deck height, in m (ft). When a design load is specified, h is to be taken as p/n,
where p is the specified design pressure in kN/m2 (kgf/m2, lbf/ft2) and n is defined as
7.05 (715, 45).
s = spacing of the stiffeners, in m (ft)
l = length of the stiffener, in m (ft)

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Section 12 Protection of Deck Openings 3-2-12

13.7 Wheel Loading

Where provision is to be made for the operation or stowage of vehicles having rubber tires, the thickness of
the hatch cover plating is to be not less than that obtained from 3-2-3/3, for platform deck plating, except
that the thickness of plate panels adjacent to the edges of the covers is to be at least 15% greater than
obtained from 3-2-3/7.

14 Small Hatches on the Exposed Fore Deck (2004)

14.1 Application
This subsection is applicable to vessels with length, L, (as defined in 3-1-1/3.1) between 80 meters (263 feet)
and 90 meters (295 feet).
The requirements of this subsection apply to all small hatches [opening normally 2.5 m2 (27 ft2) or less]
located on the exposed fore deck within the forward 0.25L, where the deck in way of the hatch is less than
0.1L or 22 m (72.2 ft) above the summer load line, whichever is less.
Hatches designed for emergency escape need not comply with 3-2-12/14.5i), 3-2-12/14.5ii), the third paragraph
of 3-2-12/14.7 and 3-2-12/14.9.

14.3 Strength
For small rectangular steel hatch covers, the plate thickness, stiffener arrangement and scantlings are to be
in accordance with 3-2-12/Table 2 and 3-2-12/Figure 1. Stiffeners, where fitted, are to be aligned with the
metal-to-metal contact points required in 3-2-12/14.7 (see also 3-2-12/Figure 1). Primary stiffeners are to
be continuous. All stiffeners are to be welded to the inner edge stiffener (see 3-2-12/Figure 2).
The upper edge of the hatchway coaming is to be suitably reinforced by a horizontal section, normally not
more than 170 to 190 mm (6.9 to 7.5 in.) from the upper edge of the coaming.
For small hatch covers of circular or similar shape, the cover plate thickness and reinforcement is to provide
strength and stiffness equivalent to the requirements for small rectangular hatches.
For small hatch covers constructed of materials other than steel, the required scantlings are to provide strength
and stiffness equivalent to 235 N/mm2 (24 kgf/mm2, 34,000 psi) yield strength steel.

14.5 Primary Securing Devices

The primary securing devices are to be such that their hatch covers can be secured in place and made
weather-tight by means of a mechanism employing any one of the following methods:
i) Butterfly nuts tightening onto forks (clamps), or
ii) Quick acting cleats, or
iii) A central locking device.
Dogs (twist tightening handles) with wedges are not acceptable.

14.7 Requirements for Primary Securing

The hatch cover is to be fitted with a gasket of elastic material. This is to be designed to allow a metal-to-
metal contact at a designed compression and to prevent over compression of the gasket by green sea forces
that may cause the securing devices to be loosened or dislodged. The metal-to-metal contacts are to be
arranged close to each securing device, in accordance with 3-2-12/Figure 1, and of sufficient capacity to
withstand the bearing force.
The primary securing method is to be designed and manufactured such that the designed compression
pressure is achieved by one person without the need of any tools.
For a primary securing method using butterfly nuts, the forks (clamps) are to be of robust design. They are
to be designed by means of curving the forks upward and a raised surface on the free end or a similar method
to minimize the risk of butterfly nuts being dislodged while in use. The plate thickness of unstiffened steel
forks is not to be less than 16 mm (5/8 in.). An example arrangement is shown in 3-2-12/Figure 2.

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Section 12 Protection of Deck Openings 3-2-12

For small hatch covers located on the exposed deck forward of the fore-most cargo hatch, the hinges are to
be fitted such that the predominant direction of green sea will cause the cover to close, which means that
the hinges are normally to be located on the fore edge.
On small hatches located between the main hatches, for example, between Nos. 1 and 2, the hinges are to
be placed on the fore edge or outboard edge, whichever is practicable, for protection from green water in
beam sea and bow quartering conditions.

14.9 Secondary Devices

Small hatches on the fore deck are to be fitted with an independent secondary securing device, e.g., by
means of a sliding bolt, a hasp or a backing bar of slack fit, which is capable of keeping the hatch cover in
place, even in the event that the primary securing device became loosened or dislodged. It is to be fitted on
the side opposite to the hatch cover hinges.

TABLE 2
Scantlings for Small Steel Hatch Covers on the Fore Deck
Nominal Size Cover Plate Thickness Primary Stiffeners Secondary Stiffeners
(mm × mm) (mm) Flat Bar (mm × mm); number
630 × 630 8 --- ---
630 × 830 8 100 × 8; 1 ---
830 × 630 8 100 × 8; 1 ---
830 × 830 8 100 × 10; 1 ---
1030 × 1030 8 120 × 12; 1 80 × 8; 2
1330 × 1330 8 150 × 12; 2 100 × 10; 2

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Part 3 Hull Construction and Equipment
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Section 12 Protection of Deck Openings 3-2-12

FIGURE 1
Arrangement of Stiffeners

Nominal size 630 × 630 Nominal size 630 × 830

Nominal size 830 × 830 Nominal size 830 × 630

Nominal size 1030 × 1030 Nominal size 1330 × 1330

Hinge Primary stiffener

Securing device/metal to metal contact Secondary stiffener

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Chapter 2 Hull Structures and Arrangements
Section 12 Protection of Deck Openings 3-2-12

FIGURE 2
Example of Primary Securing Method
M20

5 (min. 16 mm)
1 6

9
2
7

10
20 8
3
4 11

1: butterfly nut (Note: Dimensions in millimeters)

2: bolt
3: pin
4: center of pin
5: fork (clamp) plate
6: hatch cover
7: gasket
8: hatch coaming
9: bearing pad welded on the bracket of a toggle bolt for metal to metal contact
10: stiffener
11: inner edge stiffener

15 Hatchways within Open Superstructures

Hatchways within open superstructures are to be considered as exposed.

17 Hatchways within Deckhouses

Hatchways within deckhouses are to have coamings and closing arrangements as required in relation to the
protection afforded by the deckhouse from the standpoint of its construction and the means provided for
the closing of all openings into the house.

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Section 12 Protection of Deck Openings 3-2-12

19 Container Loading (1 July 2016)

Where it is intended to carry containers on steel hatch covers, the exact locations of the container pads and
the maximum total static load on the pads are to be indicated on the plans. Where the pads are not in line
with the supporting structures, headers are to be provided to transmit the loads to these members. Each
member intended to support containers is to be designed for container loads in 3-2-15/9.11 of the Steel
Vessel Rules, applying the permissible stresses in 3-2-15/9.1.1 of the Steel Vessel Rules.

21 Machinery Casings

21.1 Arrangement
Machinery-space openings in Position 1 or 2 are to be framed and efficiently enclosed by steel casings of
ample strength, and, wherever practicable, those in freeboard decks are to be within superstructures or
deckhouses. Openings in exposed casings are to be fitted with doors complying with the requirements of
3-2-9/5.1. The sills are to be in accordance with 3-2-12/7.1 for companionways. Other openings in such
casings are to be fitted with equivalent covers, permanently attached. Stiffeners are to be spaced at not
more than 760 mm (30 in.)

21.3 Exposed Casings on Freeboard or Raised Quarter Decks

Exposed casings on freeboard or raised quarter decks are to have plating not less in thickness than that
obtained from 3-2-9/3 or the following equation, whichever is greater:
t = 0.0164L + 6 mm
t = 0.0002L + 0.24 in.
where
t = thickness, in mm (in.)
L = length of vessel, in m (ft), as defined in 3-1-1/3.
Stiffeners are to be at least as effective as those required for watertight bulkheads where l is the tween
deck height and h is l/2.

21.5 Exposed Casings on Superstructure Decks

Exposed casings on superstructure decks are to have plating not less in thickness than that obtained from
the following equation:
t = 0.033L + 3.5 mm
t = 0.0004L + 0.14 in.
where
t = thickness, in mm (in.)
L = length of vessel, in m (ft), as defined in 3-1-1/3, but is not to be taken as less than
30.5 m (100 ft).
Stiffeners in association with the plating to which they are attached are to have section modulus, SM, as
obtained from the following equation:
SM = 7.8chsl2 cm3
SM = 0.0041chsl2 in3
where
c = 0.25
s = spacing of stiffeners, in m (ft)
h = height of casing, in m (ft)
l = length, between supports, of the stiffeners, in m (ft)

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Section 12 Protection of Deck Openings 3-2-12

21.7 Casings within Open Superstructures

Casings within open superstructures are to be of similar scantlings to those obtained from 3-2-12/21.5 for
exposed casings on superstructure decks.

21.9 Casings within Enclosed Superstructures, Deckhouses, or below Freeboard Decks

Casings within enclosed superstructures or in decks below freeboard deck where cargo is carried are to have
plating not less in thickness than that obtained from the following equation:
t = 0.022L + 3.8 mm
t = 0.00027L + 0.15 in.
where
t = thickness, in mm (in.)
L = length of vessel, in m (ft), as defined in 3-1-1/3, but is not to be taken as less than
30.5 m (100 ft).
Stiffeners are to be fitted in line with the beams and are to have section modulus, SM, as required for
exposed casings by 3-2-12/21.5, but the coefficient in the formula may be 0.14 instead of 0.25 and h is the
tween-deck height.

23 Miscellaneous Openings in Freeboard and Superstructure Decks

23.1 Manholes and Scuttles

Manholes and flush scuttles in Position 1 or 2 within superstructures other than enclosed superstructures
are to be closed by substantial covers capable of being made watertight. Unless secured by closely spaced
bolts, the covers are to be permanently attached.

23.3 Other Openings

Openings in freeboard decks other than hatchways, machinery-space openings, manholes and flush scuttles
are to be protected by an enclosed superstructure, or by a deckhouse or companionway of equivalent strength
and weathertightness. Any such opening in an exposed superstructure deck or in the top of a deckhouse on
the freeboard deck which gives access to a space below the freeboard deck or a space within an enclosed
superstructure is to be protected by an efficient deckhouse or companionway. Doorways in such deckhouses
or companionways are to be fitted with doors complying with the requirements given in 3-2-9/5.1.

23.5 Escape Openings (1 July 2012)

i) The closing appliances of escape openings are to be of a type that is operable from each side.
ii) The maximum force needed to open the hatch cover is not to exceed 150 N (15.3 kgf, 33.7 lbf).
iii) The use of a spring equalizing, counterbalance or other suitable device on the hinge side to reduce
the force needed for opening is acceptable.

23.7 Chain Pipe Opening (1 July 2012)

Chain pipes through which anchor cables are led are to be provided with permanently attached closing
appliances to minimize the ingress of water. A canvas cover with appropriate lashing arrangement will be
acceptable* for this purpose. A cement and wire mesh arrangement is not permitted.
The arrangement on vessels that are not subject to the International Convention on Load Lines or its
Protocol may be specially considered.
* Note: Examples of acceptable arrangements are such as:
i) Steel plates with cutouts to accommodate chain links or
ii) Canvas hoods with a lashing arrangement that maintains the cover in the secured position.

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PART Appendix 3: Portable Beams and Hatch Cover Stiffeners of Variable Cross Section

3
CHAPTER 2 Hull Structures and Arrangements

APPENDIX 3 Portable Beams and Hatch Cover Stiffeners of

Variable Cross Section

1 Application
For portable beams and hatch cover stiffeners with free ends and varying cross section along their span, the
section modulus, SM, and inertia, I, at the midspan required by 3-2-12/9.3.2, 3-2-12/9.5.1 and 3-2-12/11.1.1
may be obtained from the following equations:

C1 K 1 ps l 2
SM = cm3 (in3)
σa
I = C2K2 psl3 cm4 (in4)
where
C1 = 125 (125, 1.5)

C2 = 2.87 (28.2, 2.85 × 10-5) for 3-2-12/9.1.1 and 3-2-12/9.3.2

= 2.26 (22.1, 2.24 × 10-5) for 3-2-12/9.5.1 and 3-2-12/11.1

3.2 α − γ − 0.8
K1 = 1+ , but not less than 1.0
7γ + 0.4

α = length ratio
= l1/l

γ = SM ratio
= SM1/SM

l1, l, SM1 and SM are as indicated in 3-2-A3/Figure 1

σa = allowable stress given in 3-2-12/9.1.1, 3-2-12/9.3.2, 3-2-12/9.5.1, and 3-2-12/11.1, in
kN/mm2 (kgf/mm2, psi)
(1 − β )
K2 = 1 + 8α3 , but not less than 1.0
(0.2 + 3 β )

β = ratio of the moments of inertia, I1 and I, at the locations indicated in 3-2-A3/Figure 1

= I1/I

p = design load given in 3-2-12/5.3, in kN/m2 (tf/m2, psi)

s = spacing of beams or stiffeners, in m (ft)
l = span of free ended constructional elements, in m (ft)

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Chapter 2 Hull Structures and Arrangements
Appendix 3 Portable Beams and Hatch Cover Stiffeners of Variable Cross Section 3-2-A3

FIGURE 1
SM and I of Construction Elements

SM1 I1
SM I

l1

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PART Section 13: Protection of Shell Openings

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 13 Protection of Shell Openings

1 Cargo, Gangway, or Fueling Ports

1.1 Construction
Cargo, gangway or fueling ports in the sides of vessels are to be strongly constructed and capable of being
made thoroughly watertight. Where frames are cut in way of such ports, web frames are to be fitted on the
sides of the openings, and suitable arrangements are to be provided for the support of the beams over the
openings. Thick shell plates or doublers are to be fitted, as required, to compensate for the openings. The
corners of the openings are to be well rounded. Waterway angles and scuppers are to be provided on the decks
in way of ports in cargo spaces below the freeboard deck or in cargo spaces within enclosed superstructures
to prevent the spread of any leakage water over the decks.
Indicators showing whether the ports in the side shell below the freeboard or superstructure deck are
secured closed or open are to be provided on the navigation bridge.
Where allowed by 3-2-13/1.3, cargo ports or similar openings located with their lower edge below the line
defined in 3-2-13/1.3 are to be fitted with a second door of equivalent strength and watertightness with a
leakage detection device for the compartment between the doors. The drain from this compartment is to be
led to the bilge with a screwdown valve operable from an accessible location.
In general, all outer doors are to open outwards.

1.3 Location
The lower edges of cargo, gangway or fueling-port openings are not to be below a line parallel to the freeboard
deck at side having as its lowest point the designed load waterline or upper edge of the uppermost load line.
Cargo ports or similar openings may be located with their lower edge below the line defined above, provided
they meet the additional construction requirements of 3-2-13/1.1.

3 Bow Doors, Inner Doors, Side Shell Doors and Stern Doors (1998)

3.1 General (2005)

Where bow doors of the visor or side-opening type are fitted leading to complete or long forward enclosed
superstructure or to long superstructures with closing appliances to the satisfaction of the Administration,
bow doors and inner doors are to meet the requirements of this Section. Hull supporting structure in way of
the bow doors is to be able to withstand the loads imposed by the bow door securing and supporting
devices without exceeding the allowable stresses for those devices, both given in this Section.
Side shell doors fitted abaft the collision bulkhead and stern doors leading into enclosed spaces are to meet
the requirements of this Section.

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Section 13 Protection of Shell Openings 3-2-13

3.3 Arrangement
As far as practicable, bow doors and inner doors are to be arranged so as to preclude the possibility of the
bow door causing structural damage to the inner door or to the collision bulkhead in the case of damage to
or detachment of the bow door.
3.3.1 Bow Doors
Bow doors are to be situated above the freeboard deck, except that where a watertight recess fitted
for arrangement of ramps or other related mechanical devices is located forward of the collision
bulkhead and above the deepest waterline, the bow doors may be situated above the recess.
3.3.2 Inner Doors
An inner door is to be fitted in the extension of the collision bulkhead required by 3-2-7/3.1.1. A
vehicle ramp made watertight and conforming to 3-2-7/3.1.1 in the closed position may be accepted
for this purpose.
3.3.3 Side Shell and Stern Doors (1998)
Stern doors for passenger vessels are to be situated above the freeboard deck. Stern doors for ro-ro
cargo vessels and all side shell doors need not be situated above the freeboard deck.

5 Securing, Locking and Supporting of Doors

5.1 Definitions
5.1.1 Securing Device
A device used to keep the door closed by preventing it from rotating about its hinges or its pivoted
attachments to the vessel.
5.1.2 Supporting Device
A device used to transmit external or internal loads from the door to a securing device and from
the securing device to the vessel’s structure, or a device other than a securing device, such as a hinge,
stopper or other fixed device that transmits loads from the door to the vessel’s structure.
5.1.3 Locking device
A device that locks a securing device in the closed position.

7 Securing and Supporting Devices

7.1 Bow Doors

Means are to be provided to prevent lateral or vertical movement of the bow doors when closed. Means are
also to be provided for mechanically fixing the door in the open position.
Means of securing and supporting the door are to maintain equivalent strength and stiffness of the adjacent
structure.
7.1.1 Clearance and Packing
The maximum design clearance between the door and securing/supporting devices is not to exceed
3 mm (0.12 in.). Where packing is fitted, it is to be of a comparatively soft type and the supporting
forces are to be carried by the steel structure only.
7.1.2 Visor Door Arrangement
The pivot arrangement is to be such that the visor is self-closing under external loads. The closing
moment, My, as defined in 3-2-13/19.5.1, is not to be less than Myo, as given by the following
equation:

Myo = Wc + 0.1 a 2 + b 2 Fx2 + Fz2

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Where W, a, b, c, Fx and Fz are as defined in 3-2-13/19. In addition, the arrangement of the door is
to be such that the reaction forces of pin or wedge supports at the base of the door do not act in the
forward direction when the door is loaded in accordance with 3-2-13/19.5.4.

7.3 Side Shell and Stern Doors (1998)

Means are to be provided to prevent lateral or vertical movement of the side shell or stern doors when
closed. Means are also to be provided for mechanically fixing the doors in the open position.
The means of securing and supporting the doors are to have strength and stiffness equivalent to the adjacent
structure.
Clearance and packing for side shell and stern doors are to be in accordance with 3-2-13/7.1.1.

9 Securing and Locking Arrangement

9.1 General
Securing devices are to be provided with a mechanical locking arrangement (self-locking or separate
arrangement), or are to be of the gravity type.

9.3 Operation
Securing devices are to be simple to operate and readily accessible. The opening and closing systems as
well as the securing and locking devices are to be interlocked in such a way that they can only operate in
the proper sequence.
9.3.1 Hydraulic Securing Devices
Where hydraulic securing devices are applied, the system is to be mechanically lockable in the
closed position. In the event of a loss of hydraulic fluid, the securing devices are to remain locked.
The hydraulic system for securing and locking devices is to be isolated from other hydraulic circuits
when in the closed position
9.3.2 Remote Control (1998)
Where bow doors and inner doors give access to a vehicle deck, or where side shell doors or stern
doors are located partially or totally below the freeboard deck with a clear opening area greater
than 6 m2 (65 ft2), an arrangement for remote control from a position above the freeboard deck is
to be provided, allowing closing and opening of the doors and associated securing and locking of
every door. The operating panels for doors are to be accessible to authorized persons only. A
notice plate giving instructions to the effect that all securing devices are to be closed and locked
before leaving harbor is to be placed at each operating panel and is to be supplemented by warning
indicator lights, as required by 3-2-13/9.5.1.

9.5 Indication/Monitoring (1998)

The following requirements for indicators, water leakage protection and door surveillance are required for
vessels fitted with bow doors and inner doors. The requirements also apply to vessels fitted with side shell
doors or stern doors in the boundary of special category spaces or ro-ro spaces through which such spaces
may be flooded.
The requirements are not applicable to ro-ro cargo vessels where no part of the side shell doors or stern
doors is located below the uppermost waterline and the area of the door opening is not greater than 6 m2
(65 ft2).
9.5.1 Indicators (2005)
The indicator system is to be designed on the fail safe principle and in accordance with the following.
See 3-2-13/9.5.1(e).
9.5.1(a) Location and Type (1998). Separate indicator lights are to be provided on the navigation
bridge and on each operating panel to show that the doors are closed and that their locking devices
are properly positioned.

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Section 13 Protection of Shell Openings 3-2-13

The indication panel on the navigation bridge is to be equipped with a mode selection function
“harbor/sea voyage”, arranged so that an audible and visible alarm is given on the navigation bridge
if, in the sea voyage condition, the doors are not closed, or any of the securing devices are not in
the correct position.
Indication of the open/closed position of every door and every securing and locking device is to be
provided at the operating panels.
9.5.1(b) Indicator Lights. Indicator lights are to be designed so that they cannot be manually
turned off. The indication panel is to be provided with a lamp test function.
9.5.1(c) Power Supply. The power supply for the indicator system is to be independent of the power
supply for operating and closing the doors and is to be provided with a backup power supply from
the emergency source of power or other secure power supply, e.g., UPS.
9.5.1(d) Protection of Sensors. Sensors are to be protected from water, ice formation and mechanical
damage.
9.5.1(e) Fail Safe Principle. The alarm/indicator system is considered designed on a fail-safe
principle when the following are provided, as applicable.
i) The indicator panel is provided with:
• A power failure alarm
• An earth failure alarm
• A lamp test
• Separate indication for door closed, door locked, door not closed and door not locked.
ii) Limit switches electrically closed when the door is closed (when more limit switches are
provided, they may be connected in series)
iii) Limit switches electrically closed when securing arrangements are in place (when more
limit switches are provided, they may be connected in series)
iv) Two electrical circuits (also in one multicore cable), one for the indication of door closed/
not closed and the other for door locked/not locked.
v) In the case of dislocation of limit switches, indication to show: not closed/not locked/
securing arrangements not in place, as appropriate.
9.5.2 Water Leakage Protection (2005)
A drainage system is to be arranged in the areas between the bow door and ramp or, where no
ramp is fitted, between the bow door and inner door. The system is to be equipped with an audible
alarm function to the navigation bridge being set off when the water levels in these areas exceed
0.5 m (1.6 ft) or the high water level alarm, whichever is the lesser. See 3-2-13/9.5.1(e).
For vessels fitted with bow and inner doors, a water leakage detection system with audible alarm
and television surveillance is to be arranged to provide an indication to the navigation bridge and
to the engine control room of leakage through the inner door. See 3-2-13/9.5.1(e).
For passenger vessels fitted with side shell or stern doors, a water leakage detection system with
audible alarm and television surveillance is to be arranged to provide an indication to the navigation
bridge and to the engine control room of leakage through any of the doors.
For cargo vessels fitted with side shell or stern doors, a water leakage detection system with audible
alarm is to be arranged to provide an indication to the navigation bridge of leakage through any of
the doors. See 3-2-13/9.5.1(e).
9.5.3 Door Surveillance (2005)
Between the bow door and the inner door, a television surveillance system is to be fitted with a monitor
on the navigation bridge and in the engine control room. The system is to monitor the position of
doors and a sufficient number of their securing devices. Special consideration is to be given for
the lighting and contrasting color of objects under surveillance.

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Section 13 Protection of Shell Openings 3-2-13

11 Watertightness

11.1 Bow Doors

Bow doors are to be so fitted as to ensure tightness consistent with operational conditions and to give effective
protection to the inner doors.

11.3 Inner Doors

Inner doors forming part of the extension of the collision bulkhead are to be weathertight over the full height
of the cargo space and arranged with fixed sealing supports on the aft side of the doors.

11.5 Side Shell and Stern Doors (1998)

Side shell doors and stern doors are to be so fitted as to ensure water tightness.

11.7 Testing at Watertight Door Manufacturer (2014)

To comply with relevant subdivision and damage stability regulations, doors which become immersed by
an equilibrium or intermediate waterplane at any stage of assumed flooding are to be hydrostatically tested
at the manufacturer’s plant. The head of water used for the test shall correspond at least to the head measured
from the lower edge of the door opening, at the location in which the door is to be fitted in the vessel, to
the most unfavorable damage waterplane.

13 Bow Door Scantlings

13.1 General
Bow doors are to be framed and stiffened so that the whole structure is equivalent to the unpierced bulkhead
when closed.

13.3 Primary Structure (2005)

Scantlings of primary members are to be designed so that the allowable stresses indicated in 3-2-13/25.1
are not exceeded when the structure is subjected to the design loads indicated in 3-2-13/19.1. Normally,
simple beam theory may be applied to determine the bending stresses. Members are to be considered to
have simply supported end connections.

13.5 Secondary Stiffeners

Secondary stiffeners are to be supported by primary members constituting the main stiffening of the door.
The section modulus, SM, of secondary stiffeners is to be as required by 3-2-5/1.1 and 3-2-5/5.3. In addition,
stiffener webs are to have a net sectional area not less than that obtained from the following equation:
A= VQ/10 cm2 (A = VQ cm2, A = VQ/6.5 in2)
where
V = shear force, in kN (tf, Ltf), in the stiffener calculated using the uniformly distributed
external pressure, Peb, given in 3-2-13/19.1
Q = as defined in 3-2-1/7.5

13.7 Plating
The thickness of bow door plating is to be not less than that required for side shell plating at the same location.

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Section 13 Protection of Shell Openings 3-2-13

13.9 Securing and Supporting Devices (2005)

Scantlings of securing and supporting devices are to be designed so that the allowable stresses indicated in
3-2-13/25.1 are not exceeded when the structure is subjected to the design loads indicated in 3-2-13/19.3.
All load transmitting elements in the design load path from the door through securing and supporting
devices into the vessel structure, including welded connections, are to meet the strength standards required
for securing and supporting devices. These elements include pins, support brackets and back-up brackets.
Where fitted, threaded bolts are not to carry support forces, and the maximum tensile stress in way of the
threads is not to exceed the allowable stress given in 3-2-13/25.5.
In determining the required scantlings, the door is to be assumed to be a rigid body. Only those active
supporting and securing devices having an effective stiffness in the relevant direction are to be included
and considered when calculating the reaction forces on the devices. Small or flexible devices, such as cleats,
intended to provide load compression of the packing material, are not to be included in the calculations.
13.9.1 Bearing Pressure
The bearing pressure on steel to steel bearings is to be calculated by dividing the design force by
the projected bearing area, and is not to exceed the allowable stress given in 3-2-13/25.3.
13.9.2 Redundancy
In addition to the above requirements, the arrangement of the securing and supporting devices is to
be designed with redundancy, such that in the event of failure of any single securing or supporting
device, the stresses in the remaining devices do not exceed the allowable stresses indicated in
3-2-13/25.1 by more than 20% under the above loads.
13.9.3 Visor Door Securing and Supporting Devices
Securing and supporting devices, excluding the hinges, are to be capable of resisting the vertical
design force given in 3-2-13/19.5.3 without stresses exceeding the allowable stresses in 3-2-13/25.1.
Two securing devices are to be provided at the lower part of the door, each capable of providing
the full reaction force required to prevent opening of the door without stresses exceeding the allowable
stresses indicated in 3-2-13/25.1. The opening moment, Mo, to be balanced by this force is as given
in 3-2-13/19.5.2.
13.9.4 Side-opening Door Thrust Bearing
A thrust bearing is to be provided in way of girder ends at the closing of the two doors, and is to
prevent one door from shifting towards the other one under the effect of unsymmetrical pressure.
Securing devices are to be fitted to secure sections of thrust bearing to one another.

13.11 Visor Door Lifting Arms and Supports

Where visor type bow doors are fitted, calculations are to be submitted, verifying that lifting arms and their
connections to the door and vessel structure are adequate to withstand the static and dynamic forces applied
during the lifting and lowering operations under a wind pressure of at least 1.5 kN/m2 (0.15 tf/m2, 0.014 Ltf/ft2).

15 Inner Door Scantlings

15.1 General
Scantlings of inner doors are to meet the requirements of this subsection. In addition, where inner doors are
used as vehicle ramps, scantlings are not to be less than that required for vehicle decks in Sections 3-2-6
and 3-2-3.

15.3 Primary Structure

Scantlings of primary members are to be designed so that the allowable stresses indicated in 3-2-13/25.1
are not exceeded when the structure is subjected to the design loads indicated in 3-2-13/21.1.

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Section 13 Protection of Shell Openings 3-2-13

15.5 Securing and Supporting Devices

Scantlings of securing and supporting devices are to be designed so that the allowable stresses indicated in
3-2-13/19 are not exceeded when the structure is subjected to the design loads indicated in 3-2-13/17.5.
Where fitted, threaded bolts are not to carry support forces, and the maximum tensile stress in way of the
threads is not to exceed the allowable stress given in 3-2-13/25.5.
The bearing pressure on steel to steel bearings is to be calculated by dividing the design force by the
projected bearing area, and is not to exceed the allowable stress given in 3-2-13/25.3.

17 Side Shell Door and Stern Door Scantlings (1998)

17.1 General
Scantlings of side shell doors or stern doors are to meet the requirements of this subsection. In addition,
where the doors are used as vehicle ramps, scantlings are not to be less than that required for vehicle decks
in Sections 3-2-6 and 3-2-3.

17.3 Primary Structure (2005)

Scantlings of primary members are to be designed so that the allowable stresses indicated in 3-2-13/25.1
are not exceeded when the structure is subjected to the design loads indicated in 3-2-13/23. Normally,
simple beam theory may be applied to determine the bending stresses. Members are to be considered to
have simply supported end connections.

17.5 Secondary Stiffeners

Secondary stiffeners are to be supported by primary members constituting the main stiffening of the door.
The section modulus, SM, of secondary stiffeners is to be not less than that required by Section 3-2-5 for
frames in the same location. In addition, the net sectional area of stiffener webs is to be in accordance with
3-2-13/13.5, using the external pressure, pe, given in 3-2-13/23.

17.7 Plating
The thickness of side or stern door plating is to be not less than that required for side shell plating at the
same location.

17.9 Securing and Supporting Devices

Scantlings of securing and supporting devices are to be designed so that the allowable stresses indicated in
3-2-13/25.1 are not exceeded when the structure is subjected to the design loads indicated in 3-2-13/23. All
load transmitting elements in the design load path from the door through securing and supporting devices
into the vessel structure, including welded connections, are to meet the strength standards required for securing
and supporting devices. Where fitted, threaded bolts are not to carry support forces, and the maximum
tensile stress in way of the threads is not to exceed the allowable stress given in 3-2-13/25.5.
In determining the required scantlings, the door is to be assumed to be a rigid body. Only those active
supporting and securing devices having an effective stiffness in the relevant direction are to be included
and considered when calculating the reaction forces on the devices. Small or flexible devices, such as cleats,
intended to provide compression load on the packing material are not to be included in the calculations.
17.9.1 Bearing Pressure
The bearing pressure on steel to steel bearings is to be calculated by dividing the design force by
the projected bearing area, and is not to exceed the allowable stress given in 3-2-13/25.3.
17.9.2 Redundancy
In addition to the above requirements, the arrangement of the securing and supporting devices is to
be designed with redundancy, such that in the event of a failure of any single securing or supporting
device, the stresses in the remaining devices do not exceed the allowable stresses indicated in
3-2-13/25.1 by more than 20% under the above loads.

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Section 13 Protection of Shell Openings 3-2-13

19 Bow Door Design Loads

19.1 External Pressure

The design external pressure, Peb, is to be taken as indicated by the following equation. Peb for vessels
engaged in restricted service will be specially considered.

Peb = nc(0.22 + 0.15 tan β)(0.4Vd sin α + 0.6 kL )2 kN/m2 (tf/m2, Ltf ft2)
where
n = 2.75 (0.280, 0.0256)
c = 0.0125L for L < 80 m
= 0.00385L for L < 260 ft
= 1.0 for L ≥ 80 m (260 ft)
L = length of vessel as defined in 3-1-1/3, in m (ft)
β = flare angle at the point to be considered, defined as the angle between a vertical line
and the tangent to the side shell plating measured in a vertical plane normal to the
horizon tangent to the shell plating. See 3-2-13/Figure 1.
α = entry angle at the point to be considered, defined as the angle between a longitudinal
line parallel to the centerline and the tangent to the shell plating in a horizontal plane.
See 3-2-13/Figure 1.
k = 1.0 (1.09, 0.305)
Vd = vessel design speed, as defined in 3-2-11/3

FIGURE 1
Entry and Flare Angles

A A

ß
B

Section B - B

α
B

Section A - A

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19.3 External Forces (2005)

The design external forces considered in determining scantlings of securing and supporting devices of bow
doors are not to be taken less than those given by the following equations:
Fx = Pem Ax
Fy = Pem Ay
Fz = Pem Az
where
Fx = design external force in the longitudinal direction, in kN (tf, Ltf)
Fy = design external force in the horizontal direction, in kN (tf, Ltf)
Fz = design external force in the vertical direction, in kN (tf, Ltf)
Ax = area, in m2 (ft2), of the transverse vertical projection of the door between the levels of
the bottom of the door and the top of the upper deck bulwark or between the bottom
of the door and the top of the door, whichever is the lesser. Where the flare angle of
the bulwark is at least 15° less than the flare of the adjacent shell plating, the bulwark
may be excluded and the distance may be measured from the bottom of the door to
the upper deck or to the top of the door, whichever is the lesser.
Ay = area, in m2 (ft2), of the longitudinal vertical projection of the door between the levels
of the bottom of the door and the top of the upper deck bulwark or between the
bottom of the door and the top of the door, whichever is the lesser. Where the flare
angle of the bulwark is at least 15º less than the flare of the adjacent shell plating, the
bulwark may be excluded and the distance may be measured from the bottom of the
door to the upper deck or to the top of the door, whichever is the lesser.
Az = area, in m2 (ft2), of the horizontal projection of the door between the levels of the
bottom of the door and the top of the upper deck bulwark or between the bottom of
the door and the top of the door, whichever is the lesser. Where the flare angle of the
bulwark is at least 15º less than the flare of the adjacent shell plating, the bulwark
may be excluded and the distance may be measured from the bottom of the door to
the upper deck or to the top of the door, whichever is the lesser.
Pem = bow door pressure, Pb, determined using αm and βm in place of α and β.
βm = flare angle measured at a point on the bow door l/2 aft of the stem line on a plane h/2
above the bottom of the door, as shown in 3-2-13/Figure 2.
αm = entry angle measured at the same point as βm. See 3-2-13/Figure 2.
h = height, in m (ft), of the door between the levels of the bottom of the door and the upper
deck or between the bottom of the door and the top of the door, whichever is less.
l = length, in m (ft), of the door at a height, h/2, above the bottom of the door.

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FIGURE 2
Definition of αm and βm

l /2 l/2

h/2
A A

h/2

ßm

B
Section B - B

αm
B

Section A - A

19.5 Visor Door Forces, Moments and Load Cases

19.5.1 Closing Moment
For visor doors, the closing moment, My, is to be taken as indicated by the following equation:
My = Fxa + Wc – Fzb kN-m (tf-m, Ltf-ft)
where Fx and Fz are defined in 3-2-13/19.3
W = weight of the visor door, in kN (tf, Ltf)
a = vertical distance, in m (ft), from the visor pivot to the centroid of the transverse
vertical projected area of the visor door. See 3-2-13/Figure 3.
b = horizontal distance, in m (ft), from visor pivot to the centroid of the horizontal
projected area of the visor door. See 3-2-13/Figure 3.
c = horizontal distance, in m (ft), from the visor pivot to the center of gravity of
the visor. See 3-2-13/Figure 3.

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FIGURE 3
Visor Type Bow Door
c

b
CL
X

a
W d

Ay Ax
CG

Elevation Front View

Az
CL

Plan View

19.5.2 Opening Moment

The opening moment, Mo, is to be taken as indicated by the following equation:
Mo = Wd + 5Axa kN-m (Mo = Wd + 0.5Axa tf-m, Mo = Wd + 0.047Axa Ltf-ft)
where
d = vertical distance, in m (ft), from the hinge axis to the center of gravity of the
door
W, Ax and a are as indicated above.
19.5.3 Vertical Design Force
The vertical design force is to be taken as Fz – W, where Fz is as defined in 3-2-13/19.3 and W is as
defined in 3-2-13/19.5.1.
19.5.4 Combined Load Case 1
The visor doors are to be evaluated under a load of Fx, Fz and W acting simultaneously with Fx and
Fz acting at the centroid of their respective projected areas.
19.5.5 Combined Load Case 2
The visor doors are to be evaluated under a load of 0.7Fy acting on each side separately, together
with 0.7Fx, 0.7Fz and W. Fx, Fy and Fz are to be taken as acting at the centroid of their respective
projected areas.

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19.7 Side-Opening Door Load Cases

19.7.1 Combined Load Case 1
Side opening doors are to be evaluated under a load of Fx, Fy, Fz and W acting simultaneously with
Fx, Fy and Fz acting at the centroid of their respective projected areas.
19.7.2 Combined Load Case 2
Side opening doors are to be evaluated under a load of 0.7Fx, 0.7Fz and W acting on both doors
simultaneously and 0.7Fy acting on each door separately.

21 Inner Door Design Loads

21.1 External Pressure

The design external pressure is to be taken as the greater of Pei or Ph, as given by the following equations:

Pei = 0.45L kN/m2 (0.046L tf/m2, 0042L Ltf/ft2)

Ph = 10h kN/m2 (1.0h tf/m2, 0.029h Ltf/ft2)
where
L is as defined in 3-1-1/3.
h = the distance, in m (ft), from the load point to the top of the cargo space.

21.3 Internal Pressure

The design internal pressure, Pi, is to be taken as not less than 25 kN/m2 (2.5 tf/m2, 0.23 Ltf/ft2).

23 Side Shell and Stern Doors (1998)

23.1 Design Forces for Primary Members

The design force, in kN (tf, Ltf), for primary members is to be the greater of the following:
External force: Fe = Ape
Internal force: Fi = Fo + W

23.3 Design Forces for Securing or Supporting Devices of Doors Opening Inwards
The design force, in kN (tf, Ltf), for securing or supporting devices of doors opening inwards is to be the
greater of the following:
External force: Fe = Ape + Fp
Internal force: Fi = Fo + W

23.5 Design Forces for Securing or Supporting Devices of Doors Opening Outwards
The design force, in kN (tf, Ltf), for securing or supporting devices of doors opening outwards is to be the
greater of the following:
External force: Fe = Ape
Internal force: Fi = Fo + W + F p
where
A = area, in m2 (ft2), of the door opening
W = weight of the door, in kN (tf, Ltf)
Fp = total packing force, in kN (tf, Ltf). Packing line pressure is normally not to be taken
less than 5.0 N/mm (0.51 kg/mm, 28.6 lbf/in).

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Fo = the greater of Fc and kA, in kN (tf, Ltf)

k = 5 (0.51, 0.047)
Fc = accidental force, in kN (tf. Ltf), due to loose cargo, etc., to be uniformly distributed
over the area A and not to be taken less than 300 kN (30.6 tf, 30.1 Ltf). For small
doors such as bunker doors and pilot doors, the value of Fc may be appropriately
reduced. However, the value of Fc may be taken as zero, provided an additional
structure such as an inner ramp is fitted which is capable of protecting the door from
accidental forces due to loose cargoes.
pe = external design pressure, in kN/m2 (tf/m2, Ltf/ft2), determined at the center of gravity
of the door opening and not taken less than:
pe = k1 for ZG ≥ d
pe = k2(d – ZG) + k1 for ZG < d
Moreover, for vessels fitted with bow doors, pe for stern doors is not to be taken less
than:
pe = nc(0.8 + 0.6(k3L)0.5)2
For vessels fitted with bow doors and operating in restricted service, the value of pe
for stern doors will be specially considered.
k1 = 25.0 (2.55, 0233)
k2 = 10.0 (1.02, 0.0284)
d = draft, in m (ft), as defined in 3-1-1/9
ZG = height of the center of area of the door, in m (ft), above the baseline.
n = 0.605 (0.0616, 0.00563)
k3 = 1.0 (1.0, 0.305)
c = 0.0125L for L < 80 m (260 ft)
= 1.0 for L ≥ 80 m (260 ft)
L = length of vessel, as defined in 3-1-1/3, in m (ft)

25 Allowable Stresses

25.1 Primary Structure and Securing and Supporting Devices

The following stresses are not to be exceeded under the loads indicated above.
Shear Stress: τ = 80/Q N/mm2 ( 8.2/Q kgf/mm2, 11600/Q psi)
Bending Stress: σ = 120/Q N/mm2 (12.2/Q kgf/mm2, 17400/Q psi)

Equivalent Stress ( σ 2 + 3τ 2 ): σe = 150/Q N/mm2 (15.3/Q kgf/mm2, 21770/Q psi)

where Q is defined in 3-2-1/7.5.

25.3 Steel Securing and Supporting Devices Bearing Stress

For steel to steel bearings in securing and supporting devices, the nominal bearing pressure is not to exceed
0.8σf, where σf is the yield stress of the bearing material.

25.5 Tensile Stress on Threaded Bolts

The tensile stress in threaded bolts is not to exceed 125/Q N/mm2 (12.7/Q kgf/mm2, 18000/Q psi).

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Section 13 Protection of Shell Openings 3-2-13

27 Operating and Maintenance Manual

The following information is to be submitted for review.

27.1 Manual (1998)

An operating and maintenance manual for the doors is to be provided onboard and is to contain at least the
following:
• Main particulars and design drawings
• Service conditions, e.g., service area restrictions, emergency operations, acceptable clearances for supports
• Maintenance and function testing
• Register of inspections and repairs

27.3 Operating Procedures (1998)

Documented operating procedures for closing and securing the doors are to be kept onboard and posted at
an appropriate location.

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PART Section 14: Bulwarks, Rails, Freeing Ports, Portlights, Windows, Ventilators, Tank Vents, and Overflows

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 14 Bulwarks, Rails, Freeing Ports, Portlights,

Windows, Ventilators, Tank Vents, and Overflows

1 Bulwarks and Guard Rails

1.1 Height (2017)

The height of bulwarks and guard rails on exposed freeboard and superstructure decks, at the boundary of
first tier deckhouses and at the ends of superstructures is to be at least 1 m (39.5 in.). Where this height
would interfere with the normal service or operation of a vessel, a lesser height may be approved if
adequate protection is provided. Where approval of a lesser height is requested, justifying information is to
be submitted.

1.3 Strength of Bulwarks

Bulwarks are to be of ample strength in proportion to their height and efficiently stiffened at the upper
edge. The bulwark plating is to be kept clear of the sheerstrake and the lower edge effectively stiffened.
For vessels under 61 m (200 ft) in length, the bulwark plating on freeboard decks is to be of a thickness
adequate for the intended service of the vessel. For vessels 61 m (200 ft) in length and over, the bulwark
plating on freeboard decks is not to be less than 6.5 mm (0.25 in.) in thickness. Bulwarks are to be
supported by efficient stays. Stays on freeboard decks are to be spaced not more than 1.83 m (6 ft) apart
and are to be efficiently attached to the bulwarks and deck plating. Where it is intended to carry timber
deck cargoes, the bulwark stays are to be not over 1.52 m (5 ft) apart and have increased attachment to
deck and bulwark. Gangways and other openings in bulwarks are to be kept well away from breaks of
superstructures, and heavy plates are to be fitted in way of mooring pipes.

1.5 Guard Rails (1998)

1.5.1
Fixed, removable or hinged stanchions are to be fitted at approximately 1.5 m (5 ft) apart. Removable
or hinged stanchions are to be capable of being locked in the upright position.
1.5.2 (2017)
At least every third stanchion is to be supported by a bracket or stay. Where the arrangements
would interfere with the safe traffic of persons on board, the following alternative arrangements of
stanchions may be acceptable:
i) At least every third stanchion is to be of increased breadth, kbs = 2.9bs at the attachment
of stanchion to the deck, or,
ii) At least every second stanchion is to be of increased breadth, kbs = 2.4bs at the attachment
of stanchion to the deck, or,
iii) Every stanchion is to be of increased breadth, kbs = 1.9bs at the attachment of stanchion to
the deck.
where, bs is the breadth of normal stanchion according to the recognized design standard.
(see 3-2-14/Figure 1)

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In any arrangement of i), ii) or iii) above, the following details are to be complied with:
iv) Flat steel stanchion required by i), ii) or iii) above is to be aligned with member below
deck unless the deck plating thickness exceeds 20 mm (0.79 in.) and welded to deck with
double continuous fillet weld with minimum leg size of 7.0 mm (0.28 in.) or as specified
by the design standard.
v) The supporting member of the stanchion is to be of 100 × 12 mm (4.0 × 0.5 in.) flat bar
welded to deck by double continuous fillet

FIGURE 1
Guardrail Stanchion (2007)

bs

500 (Min.)

kbs

1.5.3
The opening below the lowest course is not to exceed 230 mm (9 in.). The distance between the
remaining courses is not to be more than 380 mm (15 in.).
1.5.4
For vessels with rounded gunwales, stanchions are to be placed on the flat of the deck.

3 Access and Crew Protection (1 July 1998)

3.1 General
Satisfactory means in the form of guard rails, lifelines, gangways or underdeck passages, etc., are to be
provided for the protection of the crew in getting to and from their quarters, the machinery space and all
other parts used in the necessary work of the vessel.

3.3 Access to Bow on Tankers

Tankers, including oil carriers, fuel oil carriers, gas carriers and chemical carriers, are to be provided with
means to enable the crew to gain safe access to the bow, even in severe weather conditions.

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TABLE 1
Acceptable Arrangement for Access (2014)
Assigned Acceptable arrangements according to type of freeboard
Summer assigned
Type of vessel Locations of access in Vessel Freeboard Type A Type B−100 Type B−60 Type B & B+
1.1: Access to Midship Quarters ≤ 3000 mm a a a a
1.1.1. Between poop and bridge, or (≤ 118 in.) b b b b
e e c(1) c(1)
1.1.2. Between poop and deckhouse e c(2)
containing living accommodation, or f(1) c(4)
navigation equipment, or both. > 3000 mm a a a d(1)
(> 118 in.) b b b d(2)
e e c(1) d(3)
c(2) e
e f(1)
f(1) f(2)
f(2) f(4)
1.2: Access to Ends ≤ 3000 mm a a a
All Vessels 1.2.1 Between poop and bow (if there is no (≤ 118 in.) b b b
other than bridge), or c(1) c(1) c(1)
Oil Tankers*, e c(2) c(2)
Chemical
1.2.2. Between bridge and bow, or f(1) e e
Tankers* and
f(1) f(1)
Gas Carriers*
1.2.3. Between a deckhouse containing living f(2) f(2)
accommodation or navigation > 3000 mm a a a
equipment, or both, and bow, or (> 118 in.) b b b
c(1) c(1) c(1)
d(1) c(2) c(2)
1.2.4 In the case of a flush deck vessel, e d(1) c(4)
between crew accommodation and the f(1) d(2) d(1)
forward and after ends of vessel. e d(2)
f(1) d(3)
f(2) e
f(1)
f(2)
f(4)
2.1: Access to Bow
2.1.1. Between poop and bow, or ≤ (Af + Hs)** e
f(1)
Oil Tankers*, 2.1.2. Between a deckhouse containing living f(5)
Chemical accommodation or navigation
Tankers* and equipment, or both, and bow, or
Gas Carriers*
2.1.3. In the case of a flush deck vessel, > (Af + Hs)** e
between crew accommodation and the f(1)
forward end of vessel. f(2)

* Oil Tanker, Chemical Tanker and Gas Carrier as defined in SOLAS: II-1/2.22, VII/8.2 and VII/11.2, respectively.
** Af: the minimum summer freeboard calculated as type A ship, regardless of the type freeboard actually assigned.
Hs: the standard height of superstructure, as defined in ICLL Regulation 33.

I. Construction Keys (a) through (f)

(a) A well-lighted and ventilated underdeck passageway with clear opening at least 0.8 m (2.6 ft) in width and 2.0 m (6.6 ft) in
height, providing access to the locations in question and located as close as practicable to the freeboard deck.
(b) A permanently constructed gangway fitted at or above the level of the superstructure deck on or as near as practicable to the
center line of the vessel, providing a continuous platform of a non-slip surface at least 0.6 m (2 ft) in width, with a foot-stop
and guard rails extending on each side throughout its length. Guard rails are to be as required in 3-2-14/3.1 and 3-2-14/1.5,
except that stanchions are to be fitted at intervals not more than 1.5 m (5 ft).
(c) A permanent walkway at least 0.6 m (2 ft) in width, fitted at freeboard deck level, consisting of two rows of guard rails with
stanchions spaced not more than 3 m (10 ft). The number of courses of rails and their spacing are to be as required in
3-2-14/1.5. On Type B ships, hatchway coamings not less than 0.6 m (2 ft) in height may be regarded as forming one side of
the walkway, provided that two rows of guard rails are fitted between the hatchways.

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TABLE 1 (continued)
Acceptable Arrangement for Access (2014)
(d) A 10 mm (0.4 in.) minimum diameter wire rope lifeline supported by stanchions about 10 m (33 ft) apart, or
A single hand rail or wire rope attached to hatch coamings, continued and adequately supported between hatchways.
(e) (2014) A permanently constructed gangway fitted at or above the level of the superstructure deck on or as near as practicable
to the center line of the vessel:
– located so as not to hinder easy access across the working areas of the deck;
– providing a continuous platform at least 1.0 m (3.3 ft) in width*;
– constructed of fire-resistant and non-slip material;
– fitted with guard rails extending on each side throughout its length. Guard rails are to be as required in 3-2-14/3.1 and
3-2-14/1.5.1 & 3-2-14/1.5.3, except that stanchions are to be fitted at intervals not more than 1.5 m (5 ft);
– provided with a foot stop on each side;
– having openings, with ladders where appropriate, to and from the deck. Openings are to be not more than 40 m (131 ft)
apart;
– having shelters of substantial construction set in way of the gangway at intervals not exceeding 45 m (148 ft) if the
length of the exposed deck to be traversed exceeds 70 m (230 ft). Every such shelter is to be capable of accommodating
at least one person and be so constructed as to afford weather protection on the forward, port and starboard sides.
(f) A permanent and efficiently constructed walkway fitted at freeboard deck level on or as near as practicable to the center line
of the vessel having the same specifications as those for a permanent gangway listed in (e)*, except for foot-stops. On Type
B ships certified for the carriage of liquids in bulk, the hatch coamings may be accepted as forming one side of the walkway,
provided a combined height of hatch coaming and hatch cover in the closed condition is not less than 1 m (3.3 ft) and two
rows of guard rails are fitted between the hatchways.
(*) For tankers less than [100 m (328 ft)] in length, the minimum width of the gangway platform or deck level walkway
fitted in accordance with arrangement (e) or (f), respectively, may be reduced to 0.6 m (2 ft).
II. Transverse Location Keys (1) through (5) - for Construction (c), (d) and (f) where specified in the Table
(1) At or near the center line of vessel; or fitted on hatchways at or near the center line of vessel.
(2) Fitted on each side of the vessel.
(3) Fitted on one side of the vessel, provision being made for fitting on either side.
(4) Fitted on one side only.
(5) Fitted on each side of the hatchways as near to the center line as practicable.
III. Notes:
1. In all cases where wire ropes are fitted, adequate devices are to be provided to enable maintaining their tautness.
2. A means of passage over obstructions, if any, such as pipes or other fittings of a permanent nature is to be
provided.
3. Generally, the width of the gangway or walkway should not exceed 1.5 m (5 ft).

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5 Freeing Ports

5.1 Basic Area

Where bulwarks on freeboard decks form wells, ample provision is to be made for rapidly freeing the
decks of water and for draining them. The minimum freeing-port area on each side of the vessel for each
well 20 m (66 ft) or less in length is to be obtained from the following equation:
A = 0.7 + 0.035l m2 A = 7.6 + 0.115l ft2
Where the bulwark length exceeds 20 m (66 ft):
A = 0.07l m2 A = 0.23l ft2
where
A = freeing-port area, in m2 (ft2)
l = bulwark length in m (ft), but need not exceed 0.7L
If a bulwark is more than 1.2 m (3.9 ft) in height, the freeing-port area is to be increased by 0.004 m2 per
meter (0.04 ft2 per foot) of length of well for each 0.1 m (1 ft) difference in height. If a bulwark is less than
0.9 m (3 ft) in height, the freeing port area may be decreased by the same ratio. In vessels with no sheer,
the calculated area is to be increased by 50%. Where sheer is less than standard, the percentage is to be
obtained by interpolation.

5.3 Trunks, Deckhouses, and Hatchway Coamings

Where a vessel is fitted with a trunk on the freeboard deck, and open rails are not fitted in way of the trunk
for at least one-half its length, or where continuous or substantially continuous hatchway side coamings are
fitted or long deckhouse exist between detached superstructures, the minimum area of freeing-port openings
is to be obtained from the following table.

Breadth of trunk, deckhouse or hatchway in relation to Area of freeing ports in relation to

breadth of vessel total area of bulwarks
40% or less 20%
75% or more 10%

The area of freeing ports at intermediate breadths is to be obtained by linear interpolation.

5.5 Superstructure Decks

Where bulwarks on superstructure decks form wells, the bulwarks are to comply with 3-2-14/5.1, except
that the minimum freeing-port area on each side of the vessel for each well is to be one-half of the area obtained
in 3-2-14/5.1 and 3-2-14/5.3.

5.7 Open Superstructures

In vessels having superstructures that are open at either end or both ends, adequate provisions for freeing
the spaces within such superstructures are to be provided. The arrangements will be subject to special approval.

5.9 Details of Freeing Ports

The lower edges of the freeing ports are to be as near the deck as practicable. Two-thirds of the required
freeing-port area is to be provided in the half of the well nearest the lowest point of the sheer curve.
Freeing-port openings are to be protected by rails or bars in such a manner that the maximum clear vertical
or horizontal space is 230 mm (9 in.). Where shutters are fitted, ample clearance is to be provided to prevent
them from jamming. Hinges are to have pins and bearings of corrosion-resistant material and, in general,
the hinges are to be located at the top of the shutter. If the shutters are equipped with securing appliances,
the appliances are to be of approved construction.

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Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 14 Bulwarks, Rails, Freeing Ports, Portlights, Windows, Ventilators, Tank Vents & Overflows 3-2-14

7 Portlights

7.1 Application (1 July 1998)

This subsection applies to passenger vessels and cargo vessels with the keel laid or in similar stage of
construction on or after 1 July 1998. As such, any reference to bulkhead/freeboard deck means bulkhead
deck in the case of passenger vessels and freeboard deck in the case of cargo vessels.

7.3 Location (1 July 1998)

The lower edges of the portlight sills are not to be below a line drawn parallel to the bulkhead/ freeboard
deck at side having as its lowest point either 2.5% of the breadth of the vessel or 500 mm (19.5 in.) above
the designed load waterline, whichever is the greater distance.
In addition, portlights are not to be fitted in spaces which are used exclusively for the carriage of cargo.

7.5 Construction (1 July 1998)

7.5.1 General
Portlights to spaces below the bulkhead/freeboard deck or to spaces within enclosed superstructures
and deckhouses protecting openings leading to below the bulkhead/freeboard deck are to be fitted
with efficient hinged, inside deadlights arranged so that they can be effectively closed and secured
watertight. The portlights, together with their glasses and deadlights, are to comply with a recognized
standard. They are to have strong frames (other than cast iron) and opening-type portlights are to have
noncorrosive hinge pins.
7.5.2 Non-opening Type
Where vessels are subject to damaged stability requirements of 3-3-1/3.3, portlights found to be
situated below a final damage equilibrium waterline are to be of non-opening type.
7.5.3 Locked Type
Portlights, where permitted in 3-2-14/7.5.2 to be of opening type, are to be of such construction as
will prevent unauthorized opening where:
i) The sills of which are below the bulkhead/freeboard deck, as permitted in 3-2-14/7.3, or
ii) Fitted in spaces used alternatively for the carriage of cargo or passengers.
7.5.4 Automatic Ventilating Type
Automatic ventilating portlights are not to be fitted in the shell plating below the bulkhead/ freeboard
deck without special approval.

9 Windows

9.1 Construction
Windows should generally not be fitted in deckhouses or the end bulkheads of superstructures in Position 1.
Windows to spaces within enclosed superstructure and deckhouses are to be fitted with strong, steel deadlight
covers.
Windows in other locations may be fitted without deadlight covers, depending upon the arrangement of the
vessel. Window frames are to be metal or other approval material and effectively secured to the adjacent
structure. Windows are to have a minimum of a 1/4-inch radius at all corners. The glazing is to be set into
the frames in a suitable, approved packing or compound. Special consideration is to be given to angled
house fronts.
The thickness of the window is not to be less than that obtained from 3-2-14/9.1.1, 3-2-14/9.1.2 or
3-2-14/9.1.3 below, whichever is greatest.

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9.1.1
 pk   pk 
t = s  mm t = s  in.
 1000σ   σ 
 a   a 

9.1.2
 pk1   pk1 
t = s 3  mm t = s 3  in.
 20E   0.02 E 
   

9.1.3 Minimum Tempered Monolithic Glass Thicknesses:

t = 9.5 mm (0.37 in.) for front windows
t = 6.5 mm (0.25 in.) for side and end windows
where
t = required window thickness, in mm (in.)
s = lesser dimension of window, in mm (in.)
h = pressure head, in m (ft), given in 3-2-9/3.3
p = 9.8h kN/m2 (0.44h psi)
k = factor given in 3-2-14/Table 2
k1 = factor given in 3-2-14/Table 2
σa = 0.30σf
σf = material flexural strength; see 3-2-14/Table 3
E = material flexural modulus; see 3-2-14/Table 3
TABLE 2
l/s k k1
>5 0.750 0.142
5 0.748 0.142
4 0.741 0.140
3 0.713 0.134
2 0.610 0.111
1.8 0.569 0.102
1.6 0.517 0.091
1.4 0.435 0.077
1.2 0.376 0.062
1 0.287 0.044

l = greater dimension of window panel, in mm (in.)

s = lesser dimension of window panel, in mm (in.)

TABLE 3
Glazing Flexural Strength Flexural Modulus
Tempered Monolithic 119 MPa (17,200 psi) 73,000 MPa (10,600,000 psi)
Laminated Glass 69 MPa (10,000 psi) 2,620 MPa (380,000 psi)
Polycarbonate* 93 MPa (13,500 psi) 2,345 MPa (340,000 psi)
Acrylic (poly methyl methacrylate)* 110 MPa (16,000 psi) 3,000 MPa (435,000 psi)

* Indicated values are for reference. Aging effects are to be considered for design.

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Part 3 Hull Construction and Equipment
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Section 14 Bulwarks, Rails, Freeing Ports, Portlights, Windows, Ventilators, Tank Vents & Overflows 3-2-14

9.3 Testing
All windows and portlights are to be hose-tested after installation.

11 Ventilators, Tank Vents, and Overflows (2004)

11.1 General (2004)

Ventilators are to comply with the requirements of 3-2-14/11.3. Tank vents and overflows are to comply
with the requirements in 3-2-14/11.5. In addition, for those located on the fore deck of vessels with length,
L, (as defined in 3-1-1/3.1) between 80 meters (263 feet) and 90 meters (295 feet), the requirements given
in 3-2-14/11.7 are to be complied with.

11.3 Ventilators (2004)

11.3.1 Coaming Construction (1 July 2016)
Ventilators on exposed freeboard decks, superstructure deck or deckhouses are to have coamings
of steel or equivalent material. Coaming plate thicknesses are to be obtained from the following
equation.
t = 0.01d + 5.5 mm
t = 0.01d + 0.22 in.
where
t = thickness of coaming in mm (in.)
d = diameter of ventilator in mm (in.), but not less than 200 mm (7.5 in.)
The maximum coaming plate thickness required is 10 mm (0.40 in.). The coamings are to be
effectively secured to the deck. Coamings which are more than 900 mm (35.5 in.) high and which
are not supported by adjacent structures are to have additional strength and attachment. Ventilators
passing through superstructures, other than enclosed superstructures, are to have substantially
constructed coamings of steel at the freeboard deck. Where a fire damper is located within a ventilation
coaming, an inspection port or opening at least 150 mm (6 in.) in diameter is to be provided in the
coaming to facilitate survey of the damper without disassembling the coaming or the ventilator.
The closure provided for the inspection port or opening is to maintain the watertight integrity of
the coaming and, if appropriate, the fire integrity of the coaming.
11.3.2 Coaming Height
Ventilators in Position 1 are to have coamings at least 900 mm (35.5 in.) high. Ventilators in
Position 2 are to have coamings at least 760 mm (30 in.) high. For definitions of Position 1 and
Position 2, see 3-2-12/5. Coaming heights may be reduced on vessels which have freeboard in
excess of the minimum geometric freeboard and/or a superstructure deck with the height of the
deck in excess of the standard height of a superstructure.
11.3.3 Means for Closing Ventilators
Except as provided below, ventilator openings are to be provided with efficient, permanently attached
closing appliances. In vessels measuring 24 m (79 ft) or more in length (as defined in the International
Convention on Load Lines, 1966), ventilators in Position 1, the coamings of which extend to more
than 4.5 m (14.8 ft) above the deck and in Position 2, the coamings of which extend to more than
2.3 m (7.5 ft) above the deck, need not be fitted with closing arrangements.
These coaming height requirements may be modified in vessels measuring less than 24 m (79 ft)
in length.

11.5 Tank Vents and Overflows (2004)

Tank vents and overflows are to be in accordance with the requirements of 4-4-3/9 and 4-4-3/11 of these
Rules and, where applicable, the requirements given below in 3-2-14/11.7.

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Section 14 Bulwarks, Rails, Freeing Ports, Portlights, Windows, Ventilators, Tank Vents & Overflows 3-2-14

11.7 Ventilators, Tank Vents and Overflows on the Fore Deck (2004)
11.7.1 Application
The requirements of this paragraph apply to all ventilators, tank vents and overflows located on
the exposed fore deck within the forward 0.25L on vessels with length, L, (as defined in 3-1-1/3.1)
between 80 meters (263 feet) and 90 meters (295 feet) and where the height of the exposed deck in
way of the item is less than 0.1L or 22 meters (72 ft) above the summer load waterline, whichever
is the lesser.
11.7.2 Applied Loading to the Air Pipes and Ventilators
11.7.2(a) Pressure (1 July 2014). The pressures, p, in kN/m2 (tf/m2, Ltf/ft2), acting on air pipes,
ventilator pipes and their closing devices, may be calculated from:
p = f ρ V2 Cd Cs Cp kN/m2 (tf/m2, Ltf/ft2)
where:
f = 0.5 (0.05, 0.0156)
ρ = density of sea water, 1.025 t/m3 (1.025 t/m3, 0.0286 Lt/ft3)
V = velocity of water over the fore deck
= 13.5 m/sec (44.3 ft/sec) for d ≤ 0.5d1

 d  d
= 13.5 21 −  m/sec (44.3 21 −  ft/sec) for 0.5d1 < d < d1
 d1   d1 
d = distance from summer load waterline to exposed deck
d1 = 0.1L or 22 m (72.2 ft), whichever is the lesser
Cd = shape coefficient
= 0.5 for pipes
= 1.3 for pipes or ventilator heads in general
= 0.8 for pipes or ventilator heads of cylindrical form with its axis in the
vertical direction
Cs = slamming coefficient, 3.2
Cp = protection coefficient:
= 0.7 for pipes and ventilator heads located immediately behind a
breakwater or forecastle
= 1.0 elsewhere including immediately behind a bulwark
11.7.2(b) Force. Forces acting in the horizontal direction on the pipe and its closing device may
be calculated from the above pressure using the largest projected area of each component.
11.7.3 Strength Requirements for Ventilators, Tank Vents and Overflows and their Closing Devices
11.7.3(a) Bending Moment and Stress. Bending moments and stresses in air pipes and ventilator
pipes are to be calculated at critical positions; at penetration pieces, at weld or flange connections,
at toes of supporting brackets. Bending stresses in the net section are not to exceed 0.8Y, where Y
is the specified minimum yield stress or 0.2% proof stress of the steel at room temperature.
Irrespective of corrosion protection, a corrosion addition to the net section of 2.0 mm (0.08 in.) is
then to be applied.

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Section 14 Bulwarks, Rails, Freeing Ports, Portlights, Windows, Ventilators, Tank Vents & Overflows 3-2-14

11.7.3(b) Tank Vents and Overflows

i) For standard tank vents and overflows of 760 mm (30 in.) height closed by heads of not
more than the tabulated projected area, pipe thicknesses and bracket heights are specified
in 3-2-14/Table 4. Where brackets are required, three or more radial brackets are to be fitted.
ii) Brackets are to be of gross thickness of 8 mm (0.32 in.) or more, of minimum length of
100 mm (4.0 in.) and height according to 3-2-14/Table 4, but need not extend over the
joint flange for the head. Bracket toes at the deck are to be suitably supported.
iii) For other configurations, loads according to 3-2-14/11.7.2 are to be applied and means of
support determined in order to comply with the requirements above. Brackets, where fitted,
are to be of suitable thickness and length according to their height.
iv) Final (gross) pipe thickness is not to be taken less than as indicated in 4-4-3/9.3.
v) The minimum internal diameter of the air pipe or overflow is not to be less than 65 mm.
11.7.3(c) Ventilators
i) For standard ventilators of 900 mm (35.4 in.) height closed by heads of not more than the
tabulated projected area, pipe thicknesses and bracket heights are specified in 3-2-14/Table 5.
Brackets, where required, are to be as specified in 3-2-14/11.7.3(b)ii).
ii) For ventilators of height greater than 900 mm (35.4 in.), brackets or alternative means of
support are to be provided. Coamings are not to be taken less than as indicated in 3-2-14/11.3
nor in 3-2-14/Table 4.
11.7.3(d) Components and Connections. All component parts and connections of the tank vents
and overflows or ventilators are to be capable of withstanding the loads defined in 3-2-14/11.7.2.
11.7.3(e) Rotary Heads. Rotating type mushroom ventilator heads are not to be used for application
in this location.

TABLE 4
760 mm (30 in.) High Tank Vents and Overflows
Thickness and Bracket Standards (2004)
Nominal Pipe Size Minimum Fitted Maximum Projected Height (1)
A B Gross Thickness Area of Head of Brackets
mm in. mm in. cm2 in2 mm in.
65 21/2 6.0 --- --- --- 480 18.9
80 3 6.3 0.25 --- --- 460 18.1
100 4 7.0 0.28 --- --- 380 15.0
125 5 7.8 0.31 --- --- 300 11.8
150 6 8.5 0.33 --- --- 300 11.8
175 7 8.5 0.33 --- --- 300 11.8
(2) (2) (2)
200 8 8.5 0.33 1900 295 300 11.8 (2)
250 10 8.5 (2) 0.33 (2) 2500 388 300 (2) 11.8 (2)
(2) (2) (2)
300 12 8.5 0.33 3200 496 300 11.8 (2)
350 14 8.5 (2) 0.33 (2) 3800 589 300 (2) 11.8 (2)
(2) (2) (2)
400 16 8.5 0.33 4500 698 300 11.8 (2)
Notes:
1 Brackets [see 3-2-14/11.7.3(b)] need not extend over the joint flange for the head.
2 Brackets are required where the as fitted (gross) thickness is less than 10.5 mm (0.41 in.), or where the tabulated
projected head area is exceeded.
Note: For other air pipe heights, the relevant requirements of 3-2-14/11.7.3 are to be applied.

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TABLE 5
900 mm (35.4 in.) High Ventilator
Thickness and Bracket Standards (2004)
Nominal Pipe Size Minimum Fitted Maximum Projected Height (1)
A B Gross Thickness Area of Head of Brackets
mm in. mm in. cm2 in2 mm in.
80 3 6.3 0.25 - - 460 18.1
100 4 7.0 0.28 - - 380 15.0
150 6 8.5 0.33 - - 300 11.8
200 8 8.5 0.33 550 85 - -
250 10 8.5 0.33 880 136 - -
300 12 8.5 0.33 1200 186 - -
350 14 8.5 0.33 2000 310 - -
400 16 8.5 0.33 2700 419 - -
450 18 8.5 0.33 3300 511 - -
500 20 8.5 0.33 4000 620 - -
Note: For other ventilator heights, the relevant requirements of 3-2-14/11.7.3 are to be applied.

200 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Section 15: Ceiling, Sparring, and Protection of Steel

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 15 Ceiling, Sparring, and Protection of Steel

1 Ceiling
In cargo holds of vessels with single bottoms, close ceiling is to be fitted on the floors and up to the upper
turns of the bilges. The ceiling on the floors is to be laid in portable sections or other convenient
arrangements are to be made for removal for cleaning, painting or inspection. The ceiling may be omitted
where the bottom is filled with cement to the tops of the floors.
In cargo holds of vessels with double bottoms, close ceiling is to be fitted from the outboard edges of the
double bottoms up to the upper turns of the bilges. Under all cargo hatches, either ceiling is to be fitted or
the thickness of the inner bottom is to be increased by 2 mm (0.08 in.). Ceiling fitted at the bilges is to be
removable for cleaning, painting or inspection. Ceiling fitted on the inner bottom plating either is to be laid
on battens for drainage or is to be bedded in a suitable composition.
The thickness of wood ceiling is not to be less than 25 mm (1 in.) in vessels 9 m (30 ft) in length, not less
than 50 mm (2 in.) in vessels between 20 m (65 ft) and 61 m (200 ft) in length, not less than 57 mm (2.25 in.)
in vessels 61 to 76 m (200 to 250 ft) in length, nor less than 63 mm (2.5 in.) in vessels over 76 m (250 ft)
in length. Between 9 m (30 ft) and 20 m (65 ft) in length, the thicknesses may be determined by interpolation.

3 Sparring
In spaces intended to carry general cargo, sparring, where fitted, is to be arranged between the bilge ceiling
and the beam brackets. In vessels over 20 m (65 ft) in length, sparring is not to provide less protection to
the framing than would be obtained from wood battens 40 mm (1.625 in.) thick, 140 mm (5.5 in.) wide,
and spaced 380 mm (15 in.) center to center. In vessels 9 m (30 ft) in length, the thickness of wood battens
may be reduced to 20 mm (0.8 in.). Between 9 m (30 ft) and 20 m (65 ft) in length, the thicknesses may be
proportioned. Sparring is to be portable and fitted in cleats or in portable frames. If sparring is not fitted,
the notation NS will be entered in the Record, indicating no sparring.

5 Protection of Steel Work

5.1 All Spaces

Unless otherwise approved, all steel work is to be suitably coated with paint or equivalent.

5.3 Salt Water Ballast Space

Tanks or holds for salt water ballast are to have a corrosion-resistant hard type coating such as epoxy or
zinc on all structural surfaces. Where a long retention of salt water is expected due to the type of vessel or
unit, special consideration for the use of inhibitors or sacrificial anodes may be given.

5.5 Oil Spaces

Tanks intended for oil or the holds of combination carriers intended for the carriage of dry bulk cargoes
and oil cargoes need not be coated unless required by 3-2-15/5.7.

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Section 15 Ceiling, Sparring and Protection of Steel 3-2-15

5.7 Cargo Holds on Bulk Carriers (including Combination Carriers) (1998)

All internal and external surfaces of hatch coamings and hatch covers, and all internal surfaces of cargo
holds, excluding the flat tank top areas and the hopper tank sloping plating up to approximately 300 mm
(12 in.) below the side shell frame end brackets, are to have an epoxy or equivalent coating applied in
accordance with the manufacturer’s recommendations. The internal surface of the cargo hold includes
those surfaces of stiffening members of the top wing tank bottom, where fitted on the hold side, and deck
plating and associated beams, girders, etc. facing holds such as those between the main hatchways. See
3-2-15/Figure 1.
In the selection of coatings, due consideration is to be given by the Owner to the intended cargoes and
conditions expected in service.

FIGURE 1
Extent of Coatings (1998)

Coating
Coating

Minimum
300 mm
(12 in)

a) TRANSVERSE b) HOLD, HATCH COAMINGS

BULKHEAD AND HATCH COVER

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PART Section 16: Weld Design

3
CHAPTER 2 Hull Structures and Arrangements

SECTION 16 Weld Design

1 Fillet Welds

1.1 General
1.1.1 Plans and Specifications
The actual sizes of fillet welds are to be indicated on detail drawings or on a separate welding
schedule and submitted for approval in each individual case.
1.1.2 Workmanship
Completed welds are to be to the satisfaction of the attending Surveyor. The gaps between the
faying surfaces of members being joined should be kept to a minimum. Where the opening
between members being joined exceeds 2.0 mm (1/16 in.) and is not greater than 5 mm (3/16 in.), the
weld leg size is to be increased by the amount of the opening in excess of 2.0 mm (1/16 in.). Where
the opening between members is greater than 5 mm (3/16 in.), corrective procedures are to be
specially approved by the Surveyor.
1.1.3 Special Precautions
Special precaution such as the use of preheat or low-hydrogen electrodes or low-hydrogen welding
processes may be required where small fillets are used to attach heavy plates or sections. When
heavy sections are attached to relatively light plating, the weld size may be required to be modified.
1.1.4 (1 July 2015)
For all welds in ballast tanks in all types of vessels and/or double side skin spaces of bulk carriers
required to be in compliance with the IMO PSPC and/or IMO PSPC-COT Regulations, continuous
welding is to be adopted.

1.3 Tee Connections

1.3.1 Size of Fillet Welds
Frames, beams, bulkheads stiffeners, floors and intercostals, etc. are to have at least the disposition
and sizes of intermittent or continuous fillet welds, as required by 3-2-16/Table 1. Where it is desirable
to substitute continuous welding for intermittent welding, as given in 3-2-16/Table 1, a reduction
from the required size of fillet may be allowed if equivalent strength is provided.
1.3.2 Intermittent Welding at Intersection
Where beams, stiffeners, frames, etc., are intermittently welded and pass through slotted girders,
shelves or stringers, there is to be a pair of matched intermittent welds on each side of each such
intersection and the beams, stiffeners and frames are to be efficiently attached to the girders,
shelves and stringers.
1.3.3 Welding of Longitudinal to Plating
Welding of longitudinals to plating is to have double continuous welds at the ends and in way of
transverses equal in length to the depth of the longitudinal. For deck longitudinals only, a matched
pair of welds is required at the transverses.

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Section 16 Weld Design 3-2-16

1.3.4 Stiffeners and Webs to Hatch Covers

Unbracketed stiffeners and webs of hatch covers are to be welded continuously to the plating and
to the face plate for a length at ends equal to the end depth of the member.

1.5 Tee Type End Connections

Tee type end connections, where fillet welds are used, are to have continuous welds on each side. In
general, the sizes of the welds, w, are not to be less than 3/4 times the thickness of the member being
attached, but in special cases where heavy members are attached to relatively light plating, the sizes may
be modified. In certain cases, only the webs of girders, beams and stiffeners need be attached. In such
cases, it is recommended that the unattached face plates or flanges be cut back.

1.7 Tee Joints at Boundary Connections

Tee joints at boundary connections of bulkheads, decks, inner bottoms, etc. are to have continuous welding
on both sides where the thinner of the plates is 12.5 mm (1/2 in.) thick or greater. In general, the size of the
welds, w, is to be such that the two together are not less than the thickness of the thinner plate plus 1.5 mm
(1/16 in.). Where the thickness of the thinner plate is less than 12.5 mm (1/2 in.), the attachment may be
made by a continuous weld on one side 1.5 mm (1/16 in.) less than the thickness of the thinner plate with
intermittent welding on the opposite side of the size required by 3-2-16/Table 1 for stiffeners to deep tank
bulkheads, except in way of tanks where equivalent continuous welds are to be used.

1.9 Ends of Unbracketed Stiffeners

Unbracketed stiffeners of shell, watertight and oiltight bulkheads and house fronts are to have double
continuous welds for one-tenth of their length at each end.
Unbracketed stiffeners of nontight structural bulkheads, deckhouse sides and after ends are to have a pair
of matched intermittent welds at each end.

1.11 Reduced Weld Size

Reduction in fillet weld sizes, except for slab longitudinals of thickness greater than 25 mm (1.0 in.), may
be specially approved by the Surveyor, in accordance with either 3-2-16/1.11.1 or 3-2-16/1.11.2, provided
the requirements of 3-2-16/1.3 are satisfied.
1.11.1 Controlled Gaps
Where quality control facilitates working to a gap between members being attached of 1 mm (0.04 in.)
or less, a reduction in fillet weld leg size w of 0.5 mm (0.02 in.) may be permitted.
1.11.2 Deep Penetration Welds
Where automatic double continuous fillet welding is used and quality control facilitates working
to a gap between members being attached of 1 mm (0.04 in.) or less, a reduction in fillet weld leg
size of 1.5 mm (1/16 in.) may be permitted, provided that the penetration at the root is at least 1.5 mm
(1/16 in.) into the members being attached.

1.13 Lapped Joints

Lapped joints are generally to have overlaps of not less width than twice the thinner plate thickness plus
25 mm (1 in.).
1.13.1 Overlapped End Connections
Overlapped end connections of longitudinal strength members within the midship 0.4L are to have
continuous fillet welds on both edges, each equal in size w to the thickness of the thinner of the
two plates joined. All other overlapped end connections are to have continuous welds on each edge
of sizes w such that the sum of the two is not less than 1.5 times the thickness of the thinner plate.
1.13.2 Overlapped Seams (2018)
Overlapped seams are to have welds on both edges of the sizes required by 3-2-16/1.7 for
tee-connections at boundaries.

204 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 16 Weld Design 3-2-16

Overlapped seams are not to be fitted in way of bottom shell, side shell, bilge, freeboard deck, or
tanks carrying flammable liquids. Where used elsewhere, overlapped seams are not to be in
connections subject to compressive stresses and are not to be in connections with in-plane shear
exceeding 10.35 kN/cm2 (1.055 tf/cm2, 6.7 Ltf/in2).

1.15 Plug Welds or Slot Welds

Plug welds or slot welds may be specially approved for particular applications. Where used in the body of
doublers and similar locations, such welds may be spaced about 305 mm (12 in.) between centers in both
directions.

3 Full or Partial Penetration Corner or Tee Joints

A full or partial penetration weld may be required for highly stressed (75% or more of the yield) critical
(e.g., oil/water boundary) joints.
The designer is to give consideration to minimizing the possibility of lamellar tearing in such joints. Ultrasonic
inspection of the plate in way of the connection may be required prior to and after fabrication to assure the
absence of possible laminations and lamellar tearing.

5 Alternatives
The foregoing are considered minimum requirements for electric-arc welding in hull construction, but
alternate methods, arrangements and details will be considered for approval. Fillet weld sizes may be
determined from structural analyses based on sound engineering principles, provided they meet the overall
strength standards of the Rules.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 205
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 16 Weld Design 3-2-16

TABLE 1
Weld Sizes and Spacing – Millimeters
For weld requirements for thicknesses intermediate to those shown in the table, use the nearest thickness shown in the table.
Where beams, stiffeners, frames, etc., are intermittently welded and pass through slotted girders, shelves or stringers, there is
to be a pair of matched intermittent welds on each side of each such intersection and the beams, stiffeners and frames are to
be efficiently attached to the girders, shelves and stringers.
For slab longitudinals, the attachment is to be made by double continuous fillet welds of a size w which is 0.3 times the
thickness of the thinner plate, but need not be greater than 8.0 mm.
Where automatic double continuous fillet welding is provided, a reduction in fillet size of 1.5 mm will be permitted,
provided that the specified size of fillet in 3-2-16/Table 1 is 6.5 mm or greater, the gap between the members does not
exceed 1.0 mm and the penetration at the root is at least 1.5 mm into the member being attached. This reduction does not
apply for slab longitudinals.
For double continuous welding as an alternative to intermittent welding, see 3-2-16/1.3.1.

w
t

S l

Staggered S Chained S

Weld size for lesser thickness of members joined, mm

5 6.5 8 9.5 11 12.5 14.5 16
Nominal leg size of fillet w 3 5 6.5 6.5 8 8 8 8
Nominal throat size of fillet t 2 3.5 4.5 4.5 5.5 5.5 5.5 5.5
Length of fillet weld 40 65 75 75 75 75 75 75

Structural Items Spacing of Welds S, mm

Single-Bottom Floors
To center keelson Note: Connections elsewhere to take In accordance with 3-2-16/1.7
same weld as floors in double bottom
Double-Bottom Floors
To shell in aft peaks of vessels having high power and — — 150 125 150 150 150 125
fine form
To shell flat of bottom forward (fore-end strengthening) — — 250 225 250 250 225 200
and in peaks
To shell elsewhere *300 *300 300 275 300 275 250 250
Solid floors to center vertical keel plate in engine room, In accordance with 3-2-16/1.7
under boiler bearers, wide-spaced floors with
longitudinal frames
Solid floors to center vertical keel plate elsewhere, and *250 *250 250 225 250 225 200 175
open-floor brackets to center vertical keel
Solid floors and open-floor brackets to margin plate In accordance with 3-2-16/1.7
To inner bottom in engine room In accordance with 3-2-16/1.7
To inner bottom at forward end (fore-end strengthening) *275 *275 275 250 275 250 225 200
To inner bottom elsewhere *300 *300 300 275 300 275 250 250
Wide spaced with longitudinal framing to shell and In accordance with 3-2-16/1.7
inner bottom
Solid floor stiffeners at watertight or oiltight boundaries 300 300 300 275 300 275 250 250
Watertight and oiltight periphery connections of floors In accordance with 3-2-16/1.7
throughout double bottom

206 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 16 Weld Design 3-2-16

TABLE 1 (continued)
Weld Sizes and Spacing – Millimeters
Weld size for lesser thickness of members joined, mm
5 6.5 8 9.5 11 12.5 14.5 16
Nominal leg size of fillet w 3 5 6.5 6.5 8 8 8 8
Nominal throat size of fillet t 2 3.5 4.5 4.5 5.5 5.5 5.5 5.5
Length of fillet weld 40 65 75 75 75 75 75 75

Structural Items Spacing of Welds S, mm

Center Girder
Nontight to inner-bottom or center strake in way of In accordance with 3-2-16/1.7
engine and to shell or bar keel
Nontight to inner-bottom or center strake clear of engine 150 150 150 125 150 125 125 125
Watertight or oiltight to inner bottom, rider plate, shell In accordance with 3-2-16/1.7
or bar keel
Intercostals
Intercostals and continuous longitudinal girders to shell — 150 150 125 150 125 125 ‡Dbl.
on flat bottom forward (fore-end strengthening) and to Cont.
inner bottom in way of engines
Intercostals and continuous longitudinal girders to shell *275 *275 275 250 275 250 225 225
and inner bottom elsewhere and to floors
Watertight and oiltight periphery connections of In accordance with 3-2-16/1.7
longitudinal girders in double bottom
Frames
To shell in aft peaks of vessels having high power and — — 150 125 150 150 150 125
fine form
To shell for 0.125L forward and in peaks — — 250 225 250 250 225 225
To shell elsewhere—See Note 1 *300 *300 300 275 300 275 250 250
Unbracketed to inner bottom Dbl. Dbl. Dbl. Dbl. Dbl. Dbl. †Dbl. †Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Frame brackets to frames, decks and inner bottom Dbl. Dbl. ‡Dbl. Dbl. ‡Dbl. Dbl. Dbl. †Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Longitudinals to shell and inner bottom *300 *300 300 275 300 275 250 250
Longitudinals to shell on flat of bottom forward Dbl. Dbl. Dbl. Dbl. ‡Dbl. ‡Dbl. Dbl. Dbl.
(fore-end strengthening) Cont. Cont. Cont. Cont. Cont Cont. Cont. Cont.
Girders and Webs
To shell and to bulkheads or decks in tanks — 200 225 200 225 200 175 150
To bulkheads or decks elsewhere — — 250 225 250 225 200 175
Webs to face plate where area of face plate is 64.5 sq. *250 *250 300 275 300 275 250 250
cm. or less
Webs to face plate area of face plate exceeds 64.5 sq. cm — — 250 225 250 225 200 175
Bulkheads
Peripheries of swash bulkheads — 200 225 200 225 200 175 150
Peripheries of nontight structural bulkheads — 225 250 225 250 225 200 175
Peripheries of deep tank or watertight bulkheads In accordance with 3-2-16/1.7
Stiffeners to deep tank bulkheads – See Note 1 — *300 300 275 300 275 250 250
Stiffeners to ordinary watertight bulkheads and — *300 300 275 300 275 250 250
deckhouse fronts – See Note 1
Stiffeners to nontight structural bulkheads; stiffeners on *300 *300 *‡300 300 ‡300 300 300 250
deckhouse sides and after ends – See Note 2
Stiffener brackets to beams, decks, etc. Dbl. Dbl. ‡Dbl. Dbl. ‡Dbl Dbl. Dbl. †Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Decks
Peripheries of platform decks and nontight flats
Upper Weld Cont. Cont. ‡Cont. Cont. ‡Cont. Cont. Cont. †Cont.
Lower Weld 300 300 ‡300 300 ‡300 300 300 250

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 207
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 16 Weld Design 3-2-16

TABLE 1 (continued)
Weld Sizes and Spacing – Millimeters
Weld size for lesser thickness of members joined, mm
5 6.5 8 9.5 11 12.5 14.5 16
Nominal leg size of fillet w 3 5 6.5 6.5 8 8 8 8
Nominal throat size of fillet t 2 3.5 4.5 4.5 5.5 5.5 5.5 5.5
Length of fillet weld 40 65 75 75 75 75 75 75

Structural Items Spacing of Welds S, mm

Decks (continued)
Peripheries of strength decks, exposed decks, and all In accordance with 3-2-16/1.7
watertight or oiltight decks, tunnels and flats
Beams (transverse or longitudinal) to decks *300 *300 300 275 300 275 250 250
Beams knees to beams and frames Dbl. Dbl. ‡Dbl. Dbl. ‡Dbl. Dbl. Dbl. †Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Hatch coamings to exposed decks — — — In accordance with 3-2-16/1.7
Transverses or deep beams to decks in tanks — 200 225 200 225 200 175 150
Transverse or deep beams to deck elsewhere — — 250 225 250 225 200 175
Foundations
To top plates, shell or inner bottom for main engines Dbl. Dbl. Dbl. Dbl. Dbl. Dbl. †Dbl. †Dbl.
and major auxiliaries Cont. Cont. Cont. Cont. Cont. Cont. Cont. Cont.
To top plates, shell or inner bottom for boilers and other In accordance with 3-2-16/1.7
auxiliaries
Additional Welding for Vessels Classed “Oil Carrier” (See Note 4)
Girders and Webs
Centerline girder to shell — Dbl. Dbl. Dbl. Dbl. †Dbl. †Dbl. †Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Centerline girder to deck — Dbl. Dbl. Dbl. Dbl. Dbl. †Dbl. Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Bulkhead webs to plating — Dbl. Dbl. Dbl. Dbl. Dbl. Dbl. Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont.
To face plates — 150 150 150 150 125 125 ‡Dbl.
Cont.
Transverses
Bottom transverses to shell — Dbl. Dbl. Dbl. Dbl. †Dbl. †Dbl. †Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Side, deck and bulkhead transverses to plating — Dbl. Dbl. Dbl. Dbl. Dbl. Dbl. Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont.
To face plates — 150 150 150 150 125 125 ‡Dbl.
Cont.
See general notes at beginning of table
Notes
1 Unbracketed stiffeners of shell, watertight and oiltight bulkheads and house fronts are to have double continuous
welds for one-tenth of their length at each end.
2 Unbracketed stiffeners of nontight structural bulkheads, deckhouse sides and after ends are to have a pair of
matched intermittent welds at each end.
3 Where the symbol, “—” (dash), is shown in place of the spacing of intermittent fillet welds, it is to indicate that the
corresponding thickness is not anticipated for that particular structural member.
4 The welding of longitudinals may be as required under frames or decks above. In addition, they are to have double
continuous welds at the ends and in way of transverses equal in length to the depth of the longitudinal. For deck
longitudinals, only a matched pair of welds is required at the transverses. For slab longitudinals, the attachment is
to be made by double continuous fillet welds of a size w which is 0.3 times the thickness of the thinner plate, but
need not be greater than 8.0 mm.
‡ Nominal size of fillet w may be reduced 1.5 mm.
† Nominal size of fillet w is increased 1.5 mm.
* Fillet welds are to be staggered.

208 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 16 Weld Design 3-2-16

TABLE 1
Weld Sizes and Spacing – Inches
For weld requirements for thicknesses intermediate to those shown in the table, use the nearest thickness shown in the table.
Where beams, stiffeners, frames, etc., are intermittently welded and pass through slotted girders, shelves or stringers, there is
to be a pair of matched intermittent welds on each side of each such intersection, and the beams, stiffeners and frames are to
be efficiently attached to the girders, shelves and stringers.
For slab longitudinals, the attachment is to be made by double continuous fillet welds of a size w which is 0.3 times the
thickness of the thinner plate, but need not be greater than 5/16 in.
Where automatic double continuous fillet welding is provided, a reduction in fillet size of 1/16 in. will be permitted, provided
that the specified size of fillet in 3-2-16/Table 1 is 1/4 in. or greater, the gap between the members does not exceed 0.04 in.
and the penetration at the root is at least 1/16 in. into the member being attached. This reduction does not apply for slab
longitudinals.
For double continuous welding as an alternative to intermittent welding, see 3-2-16/1.3.1.

S l

Staggered S Chained S

Leg size for lesser thickness of members joined, in.

0.19 0.25 0.32 0.38 0.44 0.50 0.57 0.63
Nominal leg size of fillet w 1/8 3/16 1/4 1/4 5/16 5/16 5/16 5/16

Length of fillet weld 11/2 2 /2

1 3 3 3 3 3 3

Structural Items Spacing of Welds S, in.

Single-Bottom Floors
To center keelson Note: Connections elsewhere to take In accordance with 3-2-16/1.7
same weld as floors in double bottom
Double-Bottom Floors
To shell in aft peaks of vessels having high power and — — 6 5 6 6 6 5
fine form
To shell flat of bottom forward (fore-end strengthening) — — 10 9 10 10 9 8
and in peaks
To shell elsewhere *12 *12 12 11 12 11 10 10
Solid floors to center vertical keel plate in engine room, In accordance with 3-2-16/1.7
under boiler bearers, wide-spread floors with
longitudinal frames
Solid floors to center vertical keel plate elsewhere, and *10 *10 10 9 10 9 8 7
open-floor brackets to center vertical keel
Solid floors and open-floor brackets to margin plate In accordance with 3-2-16/1.7
To inner bottom in engine room In accordance with 3-2-16/1.7
To inner bottom at forward end (fore-end strengthening) *11 *11 11 10 11 10 9 8
To inner bottom elsewhere *12 *12 12 11 12 11 10 10
Wide spaced with longitudinal framing to shell and In accordance with 3-2-16/1.7
inner bottom
Solid floor stiffeners at watertight or oiltight boundaries — 12 12 11 12 11 10 10
Watertight and oiltight periphery connections of floors In accordance with 3-2-16/1.7
throughout double bottom

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 209
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 16 Weld Design 3-2-16

TABLE 1 (continued)
Weld Sizes and Spacing – Inches
Leg size for lesser thickness of members joined, in.
0.19 0.25 0.32 0.38 0.44 0.50 0.57 0.63
Nominal leg size of fillet w 1/8 3/16 1/4 1/4 5/16 5/16 5/16 5/16

Length of fillet weld 11/2 2 /2

1 3 3 3 3 3 3

Structural Items Spacing of Welds S, in.

Center Girder
Nontight to inner-bottom or center strake in way of In accordance with 3-2-16/1.7
engine and to shell or bar keel
Nontight to inner-bottom or center strake clear of engine 6 6 6 5 6 5 5 5
Watertight or oiltight to inner bottom, rider plate, shell In accordance with 3-2-16/1.7
or bar keel
Intercostals
Intercostals and continuous longitudinal girders to shell — 6 6 5 6 5 5 ‡Dbl.
on flat bottom forward (fore-end strengthening) and to Cont.
inner bottom in way of engines
Intercostals and continuous longitudinal girders to shell *11 *11 11 10 11 10 9 9
and inner bottom elsewhere and to floors
Watertight and oiltight periphery connections of In accordance with 3-2-16/1.7
longitudinal girders in double bottom
Frames
To shell in aft peaks of vessels having high power and — — 6 5 6 6 6 5
fine form
To shell for 0.125L forward and in peaks — — 10 9 10 10 9 9
To shell elsewhere—See Note 1 *12 *12 12 11 12 11 10 10
Unbracketed to inner bottom Dbl. Dbl. Dbl. Dbl. Dbl. Dbl. †Dbl. †Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Frame brackets to frames, decks and inner bottom Dbl. Dbl. ‡Dbl. Dbl. ‡Dbl. Dbl. Dbl. †Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Longitudinals to shell and inner bottom *12 *12 12 11 12 11 10 10
Longitudinals to shell on flat of bottom forward (fore- Dbl. Dbl. Dbl. Dbl. ‡Dbl. ‡Dbl. Dbl. Dbl.
end strengthening) Cont. Cont. Cont. Cont. Cont Cont. Cont. Cont.
Girders and Webs
To shell and to bulkheads or decks in tanks — 8 9 8 9 8 7 6
To bulkheads or decks elsewhere — — 10 9 10 9 8 7
Webs to face plate where area of face plate is 10 sq. in. *10 *10 12 11 12 11 10 10
or less
Webs to face plate area of face plate exceeds 10 sq. in. — — 10 9 10 9 8 7
Bulkheads
Peripheries of swash bulkheads — 8 9 8 9 8 7 6
Peripheries of nontight structural bulkheads — 9 10 9 10 9 8 7
Peripheries of deep tank or watertight bulkheads In accordance with 3-2-16/1.7
Stiffeners to deep tank bulkheads – See Note 1 — *12 12 11 12 11 10 10
Stiffeners to ordinary watertight bulkheads and — *12 12 11 12 11 10 10
deckhouse fronts – See Note 1
Stiffeners to nontight structural bulkheads; stiffeners on *12 *12 *‡12 12 ‡12 12 12 10
deckhouse sides and after ends – See Note 2
Stiffener brackets to beams, decks, etc. Dbl. Dbl. ‡Dbl. Dbl. ‡Dbl Dbl. Dbl. †Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Decks
Peripheries of platform decks and nontight flats
Upper Weld Cont. Cont. ‡Cont Cont. ‡Cont Cont. Cont. †Cont
Lower Weld 12 12 ‡12 12 ‡12 12 12 10

210 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 2 Hull Structures and Arrangements
Section 16 Weld Design 3-2-16

TABLE 1 (continued)
Weld Sizes and Spacing – Inches
Leg size for lesser thickness of members joined, in.
0.19 0.25 0.32 0.38 0.44 0.50 0.57 0.63
Nominal leg size of fillet w 1/8 3/16 1/4 1/4 5/16 5/16 5/16 5/16

Length of fillet weld 11/2 2 /2

1 3 3 3 3 3 3

Structural Items Spacing of Welds S, in.

Decks (continued)
Peripheries of strength decks, exposed decks, and all In accordance with 3-2-16/1.7
watertight or oiltight decks, tunnels and flats
Beams (transverse or longitudinal) to decks *12 *12 12 11 12 11 10 10
Beams knees to beams and frames Dbl. Dbl. ‡Dbl. Dbl. ‡Dbl. Dbl. Dbl. †Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Hatch coamings to exposed decks — — — In accordance with 3-2-16/1.7
Transverses or deep beams to decks in tanks — 8 9 8 9 8 7 6
Transverses or deep beams to decks elsewhere — — 10 9 10 9 8 7
Foundations
To top plates, shell or inner bottom for main engines Dbl. Dbl. Dbl. Dbl. Dbl. Dbl. †Dbl. †Dbl.
and major auxiliaries Cont. Cont. Cont. Cont. Cont. Cont. Cont. Cont.
To top plates, shell or inner bottom for boilers and other In accordance with 3-2-16/1.7
auxiliaries
Additional Welding for Vessels Classed “Oil Carrier” (See Note 4)
Girders and Webs
Centerline girder to shell — Dbl. Dbl. Dbl. Dbl. †Dbl. †Dbl. †Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Centerline girder to deck — Dbl. Dbl. Dbl. Dbl. Dbl. †Dbl. Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Bulkhead webs to plating — Dbl. Dbl. Dbl. Dbl. Dbl. Dbl. Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont.
To face plates — 6 6 6 6 5 5 ‡Dbl.
Cont.
Transverses
Bottom transverses to shell — Dbl. Dbl. Dbl. Dbl. †Dbl. †Dbl. †Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont.
Side, deck and bulkhead transverses to plating — Dbl. Dbl. Dbl. Dbl. Dbl. Dbl. Dbl.
Cont. Cont. Cont. Cont. Cont. Cont. Cont.
To face plates — 6 6 6 6 6 6 ‡Dbl.
Cont.
See general notes at beginning of table
Notes
1 Unbracketed stiffeners of shell, watertight and oiltight bulkheads and house fronts are to have double continuous
welds for one-tenth of their length at each end.
2 Unbracketed stiffeners of nontight structural bulkheads, deckhouse sides and after ends are to have a pair of
matched intermittent welds at each end.
3 Where the symbol, “—” (dash), is shown in place of the spacing of intermittent fillet welds, it is to indicate that the
corresponding thickness is not anticipated for that particular structural member.
4 The welding of longitudinals may be as required under frames or decks above. In addition, they are to have double
continuous welds at the ends and in way of transverses equal in length to the depth of the longitudinal. For deck
longitudinals only, a matched pair of welds is required at the transverses. For slab longitudinals, the attachment is
to be made by double continuous fillet welds of a size w which is 0.3 times the thickness of the thinner plate, but
need not be greater than 1/16 in.
‡ Nominal size of fillet w may be reduced 1/16 in.
† Nominal size of fillet w is increased 1/16 in.
* Fillet welds are to be staggered.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 211
PART Chapter 3: Subdivision and Stability

3
CHAPTER 3 Subdivision and Stability

CONTENTS
SECTION 1 General Requirements ....................................................................... 214
1 General ...........................................................................................214
3 Criteria.............................................................................................214
3.1 Intact Stability .............................................................................. 214
3.3 Subdivision and Damage Stability ............................................... 214
5 Review Procedures .........................................................................215
5.1 Administration Review ................................................................. 215
5.3 ABS Review ................................................................................. 215
7 Damage Control Information ...........................................................215
7.1 General ........................................................................................ 215
7.3 Damage Control Plan .................................................................. 215
7.5 Damage Control Booklet .............................................................. 216
9 Onboard Computers for Stability Calculations ................................216

APPENDIX 1 Intact Stability of Tankers During Liquid Transfer Operations ...... 217
1 General ...........................................................................................217
1.1 Note ............................................................................................. 217
1.3 Operations to be Addressed ........................................................ 217

APPENDIX 2 Computer Software for Onboard Stability Calculations.................. 220

1 General ...........................................................................................220
1.1 Scope .......................................................................................... 220
1.3 Design ......................................................................................... 220
3 Calculation Systems .......................................................................220
5 Types of Stability Software .............................................................220
7 Functional Requirements ................................................................221
7.1 Calculation Program .................................................................... 221
7.3 Direct Damage Stability Calculations ........................................... 221
7.5 Warning ....................................................................................... 221
7.7 Data Printout ................................................................................ 221
7.9 Date and Time ............................................................................. 221
7.11 Information of Program ................................................................ 222
7.13 Units ............................................................................................ 222
7.15 Computer Model .......................................................................... 222
7.17 Further Requirements for Type 4 Stability Software .................... 222

212 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
 9 Acceptable Tolerances ................................................................... 224
9.1 Calculation Program of the Approved Stability Information ......... 225
9.3 Independent Program for Assessment of Stability....................... 225
11 Approval Procedure ........................................................................ 226
11.1 Conditions of Approval of the Onboard Software for Stability
Calculations ................................................................................. 226
11.3 General Approval (optional)......................................................... 226
11.5 Specific Approval ......................................................................... 227
13 Operation Manual ........................................................................... 228
15 Installation Testing .......................................................................... 228
17 Periodical Testing ........................................................................... 228
19 Other Requirements........................................................................ 229

TABLE 1 Acceptable Tolerances ......................................................... 225

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 213
PART Section 1: General Requirements

3
CHAPTER 3 Subdivision and Stability

SECTION 1 General Requirements

1 General
Vessels of the following categories are to have subdivision and stability in accordance with the criteria as
shown.

3 Criteria

3.1 Intact Stability

All vessels which have a length of 24 m (79 ft) or over, as defined in the International Convention on Load
Lines, are to have intact stability guidance as required by Regulation 10 of the International Convention on
Load Lines. The following criteria may be used for classification purposes:
• Cargo vessels of 24 m (79 ft) in length and over with or without deck cargo: IMO Code on Intact
Stability
In case the above criteria are not applicable to a particular vessel, the intact stability will be reviewed by
ABS in accordance with other recognized criteria appropriate to the vessel’s type, size and intended service.
Tankers for which the request for class for new construction is received on or after 1 July 1997 are to meet
the requirements in Appendix 3-3-A1, “Intact Stability of Tankers During Liquid Transfer Operations.”

3.3 Subdivision and Damage Stability

Vessels of applicable size, type and service are to have subdivision and damage stability as required by the
International Convention for the Safety of Life at Sea, 1974, as amended as follows:
• Passenger vessel Regulation II-1/4 through 8-1 (Section 5C-7-3 of the ABS Rules for
Building and Classing Steel Vessels)
• Gas Carrier IGC Code (Section 5C-8-2 of the ABS Rules for Building and Classing
Steel Vessels)
• Chemical carrier IBC Code (Section 5C-9-2 of the ABS Rules for Building and Classing
Steel Vessels)
• Offshore support vessel Section 3-3-1 of the ABS Rules for Building and Classing Offshore
Support Vessels
• (1 July 1998) Cargo vessel Regulation II-1/4 through 7-3
of 80 m (262 ft)or more in
subdivision length

214 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 3 Subdivision and Stability
Section 1 General Requirements 3-3-1

5 Review Procedures

5.1 Administration Review

When the vessel is issued an International Load Line Certificate, Passenger Ship Safety Certificate, Cargo
Ship Safety Construction Certificate, International Certificate of Fitness for the Carriage of Liquefied
Gases in Bulk or International Certificate of Fitness for Carriage of Dangerous Chemicals in Bulk by the
flag Administration or its agent other than ABS, such Certificate will be accepted as evidence that the
vessel has subdivision and stability in accordance with the criteria in the respective Convention.
Where the Administration undertakes the review of subdivision and stability and ABS is issuing the above
Certificate, the acceptance of subdivision and stability by the Administration will be required before the
certificate is issued.

5.3 ABS Review (1 July 2016)

In all other cases, the information and calculations for subdivision and stability are to be submitted to ABS
for review. Where the intact stability criteria are not applicable to a particular vessel, the review will be in
accordance with other recognized criteria acceptable to ABS.
For all vessels to be assigned the Towing Service notation or those designed for towing, the sea trial
conditions including the anticipated drafts of the vessel, levels in each tank, weights and locations of any
additional equipment onboard during the trials, and the maximum number of persons onboard the vessel
during the sea trials are to be submitted to ABS for review, prior to the sea trials.

7 Damage Control Information (2015)

7.1 General
A plan showing clearly for each deck and hold and boundaries of the watertight compartments, the openings
therein with the means of closure and position of any controls thereof, and the arrangements for the correction
of any list due to flooding, is to be permanently exhibited or readily available on the navigation bridge for
the guidance of the officer in charge of the vessel. Furthermore, the damage control plan is to be permanently
exhibited or readily available on the bridge, in the cargo control room, machinery control room, and engineering
office.
In addition, booklets containing the aforementioned information are to be made available to the officers of
the vessel.
The damage control plan and damage control booklet are to be clear and easy to understand. Information
which is not directly relevant to damage control is not to be included.
General precautions to be included are consisting of a listing of equipment, conditions, and operational
procedures considered being necessary to maintain watertight integrity under normal ship operations.
Specific precautions to be included are consisting of a listing of elements (i.e., closures, security of cargo,
sounding of alarms, etc.) considered to be vital to the survival of the ship and crew.
For ships to which the damage stability requirements of SOLAS 1974 as amended apply, damage stability
information is to be provided in a simple and easily understandable way of assessing the ship’s survivability
in the anticipated damage cases involving a compartment or group of compartments.

7.3 Damage Control Plan

The damage control plan is to be of a scale adequate to show clearly the required content of the plan.
The plan is to include inboard profile, plan views of each deck and transverse sections to the extent necessary
to show the following:
i) The watertight boundaries of the ship;
ii) The locations and arrangement of cross-flooding systems, blow-out plugs and any mechanical means to
correct list due to flooding, together with the locations of all valves and remote controls, if any;

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Section 1 General Requirements 3-3-1

iii) The locations of all internal watertight closing appliances including, on ro-ro ships, internal ramps
or doors acting as extension of the collision bulkhead and their controls and the locations of their
local and remote controls, position indicators and alarms . The locations of those watertight closing
appliances which are not allowed to be opened during the navigation and of those watertight
closing appliances which are allowed to be opened during navigation, according to the regulation
II-1/22.4 of SOLAS 1974 as amended , are to be clearly indicated;
iv) The locations of all doors in the shell of the ship, including position indicators, leakage detection
and surveillance devices;
v) The locations of all external watertight closing appliances in cargo ships, position indicators and
alarms;
vi) The locations of all weather-tight closing appliances in local subdivision boundaries above the
bulkhead deck and on the lowest exposed weather decks, together with locations of controls and
position indicators, if applicable; and
vii) The locations of all bilge and ballast pumps, their control positions and associated valves.

7.5 Damage Control Booklet

The information listed in the damage control plan is to be repeated in the damage control booklet.
The damage control booklet is to include general instructions for controlling the effects of damage, such as:
i) Immediately closing all watertight and weather-tight closing appliances;
ii) Establishing the locations and safety of persons on board, sounding tanks and compartments to
ascertain the extent of damage and repeated soundings to determine rates of flooding; and
iii) Cautionary advice regarding the cause of any list and of liquid transfer operations to lessen list or
trim, and the resulting effects of creating additional free surfaces and of initiating pumping
operations to control the ingress of water.
The booklet is to contain additional details to the information shown on the damage control plan, such as
the locations of flooding detection systems, sounding devices, tank vents and overflows which do not
extend above the weather deck, pump capacities, piping diagrams, instructions for operating cross-flooding
systems, means of accessing and escaping from watertight compartments below the bulkhead deck for use
by damage control parties, and alerting ship management and other organizations to stand by and co-
ordinate assistance, if required.
If applicable to the ship, locations of non-watertight openings with non-automatic closing devices through
which progressive flooding might occur are to be indicated as well as guidance on the possibility of non-
structural bulkheads and doors or other obstructions retarding the flow of entering seawater to cause at
least temporary conditions of unsymmetrical flooding.
Where the results of the subdivision and damage stability analyses are included, additional guidance is to
be provided for the crew to be aware that the analysis results are only for assisting them in estimating the
ship’s relative survivability.
The guidance is to indicate the criteria on which the analyses were based and clearly indicate that the initial
conditions of the ship’s loading extents and locations of damage, permeability, assumed for the analyses
may have no correlation with the actual damaged condition of the ship.

9 Onboard Computers for Stability Calculations (1 July 2007)

The use of onboard computers for stability calculations is not a requirement of class. However, if stability
software is installed onboard vessels contracted on or after 1 July 2005, it should cover all stability
requirements applicable to the vessel and is to be approved by ABS for compliance with the requirements
of Appendix 3-3-A2, “Onboard Computers for Stability Calculations”.

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PART Appendix 1: Intact Stability of Tankers During Liquid Transfer Operations

3
CHAPTER 3 Subdivision and Stability

APPENDIX 1 Intact Stability of Tankers During Liquid Transfer

Operations

1 General

1.1 Note
The following requirements for tankers (i.e., vessels designed to carry liquid in bulk) were developed from
the IMO draft MSC Circular containing recommendations for existing oil tankers and the anticipated
amendments to MARPOL for new tankers. The phenomenon of lolling is considered to be a safety issue
for double hull tankers, as well as for other tankers having exceptionally wide cargo tanks (i.e. having cargo
tank breadths greater than 60% of the vessel’s maximum beam), which should be solved for vulnerable
existing tankers and for new tankers now rather than be deferred until the proposed amendments to
MARPOL enter into force. The solution should not be limited only to tankers subject to MARPOL.

1.3 Operations to be Addressed

Liquid transfer operations include cargo loading and unloading, lightering, ballasting and deballasting,
ballast water exchange and tank cleaning operations.

3
Every tanker is to comply with the intact stability criteria specified in subparagraphs 3-3-A1/3.1 and
3-3-A1/3.3 for any operating draft reflecting actual, partial or full load conditions, including the intermediate
stages of liquid transfer operations.

3.1
In port, the initial metacentric height, GM0, is not to be less than 0.15 m. Positive intact stability is to
extend from the initial equilibrium position at which GM0 is calculated over a range of at least 20 degrees
to port and to starboard.

3.3
At sea, the intact stability criteria contained in paragraphs 2.2.1 to 2.2.4 of Part A, Chapter 2 of the IMO
Code on Intact Stability, are applicable, or the criteria contained in the national requirements of the flag
Administration are applicable if the national stability requirements provide at least an equivalent degree of
safety.

5
For all loading conditions in port and at sea, including intermediate stages of liquid transfer operations, the
initial metacentric height and the righting lever curve are to be corrected for the effect of free surfaces of
liquids in tanks.

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7
The intact stability criteria specified in 3-3-A1/3 is preferably to be met by design of the vessel, i.e., the
design should allow for maximum free surface effects in all cargo, ballast and consumables tanks during
liquid transfer operations.

9
If the intact stability criteria specified in 3-3-A1/3 are not met through design of the vessel alone, the
Master is to be provided with clear instructions covering the operational restrictions and methods necessary
to ensure compliance with these criteria during liquid transfer operations. These instructions should be
simple and concise, and:

9.1
In a language understood by the officer-in-charge of transfer operations;

9.3
Require no more than minimal mathematical calculations by the officer-in-charge;

9.5
Indicate the maximum number of cargo and ballast tanks which may be slack under any possible condition
of liquid transfer;

9.7
Provide pre-planned sequences of cargo/ballast transfer operations which indicate the cargo and ballast
tanks which may be slack to satisfy the stability criteria under any specific condition of liquid transfer,
including possible range of cargo densities. The slack tanks may vary during stages of the transfer operations
and be any combination which satisfies the stability criteria;

9.9
Provide instructions for pre-planning other sequences of cargo/ballast transfer operations, including use of
stability performance criteria in graphical or tabular form which enable comparisons of required and attained
stability. These instructions for pre-planning other sequences, in relation to individual vessels, should take
account of:
i) The degree of criticality with respect to the number of tanks which can simultaneously have maximum
free surface effects at any stage of liquid transfer operations;
ii) The means provided to the officer-in-charge to monitor and assess the effects on stability and hull
strength throughout the transfer operations;
iii) The need to give sufficient warning of an impending critical condition by reference to suitable
margins (and the rate and direction of change) of the appropriate stability and hull strength parameters.
If appropriate, the instructions should include safe procedures for suspending transfer operations
until a suitable plan of remedial action has been evaluated;
iv) The use of on-line shipboard computer systems during all liquid transfer operations, processing
cargo and ballast tank ullage data and cargo densities to continuously monitor the vessel’s stability
and hull strength and, when necessary, to provide effective warning of an impending critical situation,
possibly automatic shut-down, and evaluation of possible remedial actions. The use of such systems
is encouraged;

9.11
Provide for corrective actions to be taken by the officer-in-charge in case of unexpected technical difficulties
with the recommended pre-planned transfer operations and in case of emergency situations. A general
reference to the vessel’s shipboard oil pollution emergency plan may be included; and

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9.13
The instructions required above be prominently displayed:
i) In the approved trim and stability booklets;
ii) At the cargo/ballast transfer control station;
iii) In any computer software by which intact stability is monitored or calculations performed;
iv) In any computer software by which hull strength is monitored or calculations performed.

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PART Appendix 2: Computer Software for Onboard Stability Calculations

3
CHAPTER 3 Subdivision and Stability

APPENDIX 2 Computer Software for Onboard Stability

Calculations (2018)

1 General

1.1 Scope
The scope of stability calculation software is to be in accordance with the stability information as approved
by the flag Administration or ABS on behalf of the flag Administration. The software is at least to include
all information and perform all calculations or checks as necessary to ensure compliance with the applicable
stability requirements.
Approved stability software is not a substitute for the approved stability information, and is used as a
supplement to the approved stability information to facilitate stability calculations.

1.3 Design
The input/output information is to be easily comparable with approved stability information so as to avoid
confusion and possible misinterpretation by the operator relative to the approved stability information.
An operation manual is to be provided for the onboard computer stability software.
The language in which the stability information is displayed and printed out as well as the operation manual
is written is to be the same as used in the vessel’s approved stability information. The primary language is
to be English.
The onboard computer for stability calculations is to be vessel specific equipment and the results of the
calculations are to be only applicable to the vessel for which it has been approved.
In case of modifications implying changes in the main data or internal arrangement of the vessel, the
specific approval of any original stability calculation software is no longer valid. The software is to be
modified accordingly and reapproved.

3 Calculation Systems
This Appendix covers either system, a passive system that requires manual data entry or an active system,
which replaces the manual with the automatic entry with sensors reading and entering the contents of tanks,
etc., provided the active system is in the off-line operation mode. However, an integrated system, which
controls or initiates actions based on the sensor-supplied inputs is not within the scope of this Appendix.

5 Types of Stability Software (2018)

Four types of calculations performed by stability software are acceptable depending upon a vessel’s
stability requirements:
• Type 1 Software calculating intact stability only (for vessels not required to meet a damage stability
criterion)
• Type 2 Software calculating intact stability and checking damage stability on basis of a limit curve
(for vessels applicable to SOLAS Part B-1 damage stability calculations, etc.) or checking
all the stability requirements (intact and damage stability) on the basis of a limit curve

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• Type 3 Software calculating intact stability and damage stability by direct application of
preprogrammed damage cases based on the relevant Conventions or Codes for each loading
condition (for some tankers etc.)
• Type 4 Software calculating damage stability associated with an actual loading condition and
actual flooding case, using direct application of user defined damage, for the purpose of
providing operational information for safe return to port (SRtP).
Damage stability of both Type 3 and Type 4 stability software is to be based on a hull form model, that is,
directly calculated from a full three-dimensional geometric model.

7 Functional Requirements

7.1 Calculation Program (2018)

The calculation program is to present relevant parameters of each loading condition in order to assist the
Master in their judgment on whether the vessel is loaded within the approval limits. The following parameters
are to be presented for a given loading condition:
• Deadweight data
• Lightship data
• Trim
• Draft at the draft marks and perpendiculars
• Summary of loading condition displacement, VCG, LCG and, if applicable, TCG
• Downflooding angle and corresponding downflooding opening (not applicable for Type 2 software
which uses limit curve for checking all the stability requirements. However, if intact stability criteria are
given in addition to the limit curve, downflooding angle and the corresponding downflooding opening
is to be indicated).
• Compliance with stability criteria: Listing of all calculated stability criteria, the limit values, the obtained
values and the conclusions (criteria fulfilled or not fulfilled) (not applicable for Type 2 software which
uses limit curve for checking all the stability requirements. However, if intact stability criteria are given
in addition to the limit curve, the limit values, the obtained values and the conclusion is to be indicated).

7.3 Direct Damage Stability Calculations

If direct damage stability calculations are performed, the relevant damage cases according to the applicable
rules are to be pre-defined for automatic check of a given loading condition.

7.5 Warning (2018)

A clear warning is to be given on screen and in hard copy printout if any of the loading limitations are not
complied with.
As applicable, loading limitations are to include, but may not be limited to:
• Trim, draft, liquid densities, tank filling levels, initial heel
• Use of limit KG/GM curves in conjunction with above for Type 2
• Restrictions to the stowage height for timber where timber load lines are assigned

7.7 Data Printout

The data are to be presented on screen and in hard copy printout in a clear unambiguous manner.

7.9 Date and Time

The date and time of a saved calculation are to be part of the screen display and hard copy printout.

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7.11 Information of Program

Each hard copy printout is to include identification of the calculation program with version number.

7.13 Units
Units of measurement are to be clearly identified and used consistently within a loading calculation.

7.15 Computer Model (2018)

For Type 3 and Type 4 software, the system is to be pre-loaded with a detailed computer model of the
complete hull, including appendages, all compartments, tanks and the relevant parts of the superstructure
considered in the damage stability calculation, wind profile, down-flooding and up-flooding openings,
cross-flooding arrangements, internal compartment connections and escape routes, as applicable and
according to the type of stability software.
For Type 1 and Type 2 software, in case a full three dimensional model is used for stability calculations,
the requirements of the computer model are to be as per the paragraph above to the extent as applicable
and according to the type of stability software.

7.17 Further Requirements for Type 4 Stability Software (2018)

7.17.1
The normal (Type 1, 2 and 3) and SRtP (Type 4) software need not be “totally separated”. Where
the normal and SRtP software are not totally separated:
• The function of switching between normal software and Type 4 software is to be provided.
• The actual intact loading condition is to be the same for both functions (normal operation and
SRtP); and
• The SRtP module needs only to be activated in case of an incident.
Approval of Type 4 (SRtP) software is for stability only.
7.17.2
In passenger vessels which are subject to SRtP and have an onboard stability computer and shore-
based support, such software need not be identical.
7.17.3
Each internal space is to be assigned its permeability as shown below, unless a more accurate
permeability has been reflected in the approved stability information.

Permeability
Spaces
Default Full Partially Filled Empty
Container Spaces 0.95 0.70 0.80 0.95
Dry Cargo spaces 0.95 0.70 0.80 0.95
Ro-Ro spaces 0.95 0.90 0.90 0.95
Cargo liquids 0.95 0.70 0.80 0.95
Intended for consumable liquids 0.95 0.95 0.95 0.95
Stores 0.95 0.60 0.60 0.95
Occupied by machinery 0.85
Void spaces 0.95
Occupied by accommodation 0.95

7.17.4
The system is to be capable of accounting for applied moments such as wind, lifeboat launching,
cargo shifts and passenger relocation.

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7.17.5
The system is to account for the effect of wind by using the method in SOLAS regulation II-1/7-
2.4.1.2 as the default, but allow for manual input of the wind speed/pressure if the on-scene pressure
is significantly different (P = 120 N/m2 equates to Beaufort 6; approximately 13.8 m/s or 27 knots).
7.17.6
The system is to be capable of assessing the impact of open main watertight doors on stability
(e.g., for each damage case provided for verification, additional damage stability calculation is to
be done and presented, taking into account any watertight door located within the damaged
compartment(s)).
7.17.7
The system is to utilize the latest approved lightship weight and center of gravity information.
7.17.8
The output of the software is to be such that it provides the master with sufficient clear unambiguous
information to enable quick and accurate assessment of the stability of the vessel for any actual
damage, the impact of flooding on the means of escape and the controls of devices necessary for
managing and/or controlling the stability of the vessel.
When the actual loading condition is input in the SRtP software, the following output (intact
stability) is to be available:
• Deadweight data
• Lightship data
• Trim
• Heel
• Draft at the draft marks and perpendiculars
• Summary of loading condition displacement, VCG, LCG and, if applicable, TCG
• Downflooding angle and corresponding downflooding opening
• Free surfaces
• GM value
• GZ values relevant to an adequate range of heeling (not less than 60°) available indicatively at
the following intervals: 0 5 10 15 20 25 30 40 50 60 deg
• Compliance with relevant intact stability criteria (i.e., 2008 IS Code): listing of all calculated
intact stability criteria, the limiting values, the obtained values and the evaluation (criteria
fulfilled or not fulfilled)
• GM/KG limiting curve according to SOLAS, Ch II-1, Regulation 5-1
When the actual loading condition is associated to the actual damage case(s) due to the casualty,
the following output (damage stability) is to be available:
• Trim
• Heel
• Draft at the draft marks and perpendiculars
• Progressive flooding angle and corresponding progressive flooding openings
• GM value
• GZ values relevant to an adequate range of heeling (not less than 60°) available indicatively at
the following intervals: 0 5 10 15 20 25 30 40 50 60 deg

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• Compliance with stability criteria: listing of all calculated stability criteria, the limit values,
the obtained values and the conclusions (criteria fulfilled or not fulfilled)
• The survivability criteria for Type 4 software (SRtP) are left to the discretion of the Administration
• Relevant flooding points (unprotected or weathertight) with the distance from the damage
waterline to each point
• List of all flooded compartments with the permeability considered
• Amount of water in each flooded compartment
• Escape route immersion angles
• A profile view, deck views and cross-sections of the vessel indicating the flooded water-plane
and the damaged compartments
7.17.9
For ro-ro passenger vessels, there are to be algorithms in the software for estimating the effect of
water accumulation on deck (WOD) (e.g., 1. In addition to the predefined significant wave height,
taken from the approved stability document, there is to be possibility for the crew to input manually
the significant wave height of the vessel navigation area in the system, 2. In addition to the predefined
significant wave height, taken from the approved stability document, calculations with two additional
significant wave heights are to be submitted for checking the correctness of the algorithms in the
software for estimating the effect of WOD). *
* This paragraph applies to Ro-Ro Passenger vessels subject to the Stockholm Agreement (IMO Circular Letter
No. 1891)

9 Acceptable Tolerances
Depending on the type and scope of programs, the acceptable tolerances are to be determined differently,
according to 3-3-A2/9.1 or 3-3-A2/9.3. In general, deviation from these tolerances is not to be accepted
unless a satisfactory explanation for the difference is submitted for review and the same is satisfactorily
confirmed by ABS that there would be no adverse effect on the safety of the vessel.
Examples of pre-programmed input data include the following:
• Hydrostatic data: Displacement, LCB, LCF, VCB, KMt and MCT vs. draft
• Stability data: KN or MS values at appropriate heel/trim angles vs. displacement, stability limits.
• Compartment data: Volume, LCG, VCG, TCG and FSM/Grain heeling moments vs. level of the
compartment’s contents.
Examples of output data include the following:
• Hydrostatic data: Displacement, LCB, LCF, VCB, KMt and MCT versus draft, as well as actual
drafts, trim.
• Stability data: FSC (free surface correction), GZ-values, KG, GM, KG/GM limits, allowable
grain heeling moments, derived stability criteria (e.g., areas under the GZ curve),
weather criteria.
• Compartment data: Calculated Volume, LCG, VCG, TCG and FSM/Grain heeling moments vs. level
of the compartment’s contents
The computational accuracy of the calculation program results is to be within the acceptable tolerances
specified in 3-3-A2/9.1 or 3-3-A2/9.3, of the results using an independent program or the approved stability
information with identical input.

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9.1 Calculation Program of the Approved Stability Information

Programs which use only pre-programmed data from the approved stability information as the basis for
stability calculations are to have zero tolerances for the printouts of input data.
Output data tolerances are to be close to zero. However, small differences associated with calculation rounding
or abridged input data are acceptable. Additionally differences associated with the use of hydrostatic and
stability data for trims that differ from those in the approved stability information are acceptable subject to
review by ABS.

9.3 Independent Program for Assessment of Stability

Programs which use hull form models as their basis for stability calculations are to have tolerances for the
printouts of basic calculated data established against either data from the approved stability information or
data obtained using the approval authority’s model. Acceptable tolerances shall be in accordance with
3-3-A2/Table 1.

TABLE 1
Acceptable Tolerances (2018)
Hull Form Dependent Acceptable Tolerance (1)
Displacement ±2%
Longitudinal center of buoyancy, from AP ±1% or 50 cm, whichever is greater
Vertical center of buoyancy ±1% or 5 cm, whichever is greater
Transverse center of buoyancy ±0.5% of B or 5 cm, whichever is greater
Longitudinal center of flotation, from AP ±1% or 50 cm, whichever is greater
Moment to trim 1 cm ±2%
Transverse metacentric height ±1% or 5 cm, whichever is greater
Longitudinal metacentric height ±1% or 50 cm, whichever is greater
Cross curves of stability ±5 cm

Compartment Dependent Acceptable Tolerance (1)

Volume or deadweight ±2%
Longitudinal center of gravity, from AP ±1% or 50 cm, whichever is greater
Vertical center of gravity ±1% or 5 cm, whichever is greater
Transverse center of gravity ±0.5% of B or 5 cm, whichever is greater
Free surface moment ±2%
Shifting moment ±5%
Level of contents ±2%

Trim and Stability Acceptable Tolerance (1)

Drafts (forward, aft, mean) ±1% or 5 cm, whichever is greater
GMt (both solid and corrected for free surfaces) ±1% or 5 cm, whichever is greater
GZ values ±1% or 5 cm, whichever is greater
Downflooding angle ±2°
Equilibrium angles ±1°
Distance from WL to unprotected and weathertight ±5% or 5 cm, whichever is greater
openings, or other relevant point, if applicable
Areas under righting arm curve ±5% or 0.0012 mrad

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TABLE 1 (continued)
Acceptable Tolerances (2018)
Notes:
1 Deviation in % = [(base value – applicant’s value)/base value] × 100.
where the “base value” may be from the approved stability information or the society’s
computer model.
2 When applying a tolerance in 3-3-A2/Table 1 that contains two values, the allowable
tolerance is the greater of the two values.
3 Where differences in calculation methodology exist between the programs used in
the comparison, this may be a basis for accepting deviations greater than that specified
in 3-3-A2/Table 1 provided a software examination is carried out in sufficient detail
to clearly document that such differences are technically justifiable.
4 Deviation from these tolerances are not to be accepted unless ABS considers that
there is a satisfactory explanation for the difference and that it is clearly evident
from ABS’s stability calculations that the deviation does not impact compliance
with the required stability criteria for the vessel under consideration.

11 Approval Procedure

11.1 Conditions of Approval of the Onboard Software for Stability Calculations (2018)
The onboard software used for stability calculations is subject to approval, which is to include:
• Verification of type approval, if any,
• Verification that the data used is consistent with the current condition of the vessel (see 3-3-A2/11.5),
• Verification and approval of the test conditions, and
• Verification that the software is appropriate for the type of vessel and stability calculations required.
• Verification that the software is installed so that failure of the primary computer or server does not prevent
the stability calculation from being carried out (this is to be demonstrated onboard as noted below)
• Verification of functional requirements under 3-3-A2/7.
The satisfactory operation of the software for stability calculations is to be verified by testing upon installation
on the primary computer or server and at least one back-up computer or redundant server onboard (see
3-3-A2/15). A copy of the approved test conditions and the operation manual for the computer/software are
to be available onboard.

11.3 General Approval (optional)

Upon receipt of application for general approval of the calculation program, ABS may provide the applicant
with test data consisting of two or more design data sets, each of which is to include a vessel’s hull form
data, compartmentation data, lightship characteristics and deadweight data, in sufficient detail to accurately
define the vessel and its loading condition.
Acceptable hull form and compartmentation data may be in the form of surface coordinates for modeling
the hull form and compartment boundaries (e.g., a table of offsets) or in the form of pre-calculated tabular
data (e.g., hydrostatic tables, capacity tables) depending upon the form of data used by the software being
submitted for approval. Alternatively, the general approval may be given based on at least two test vessels
agreed upon between the applicant and ABS.
In general, the software is to be tested for two types of vessels for which approval is requested, with at
least one design data set for each of the two types. Where approval is requested for only one type of vessel,
a minimum of two data sets for different hull forms of that type of vessel are required to be tested.

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For calculation software which is based on the input of hull form data, design data sets are to be provided
for three types of vessels for which the software is to be approved, or a minimum of three data sets for
different hull forms if approval is requested for only one type of vessel. Representative vessel types which
require different design data sets due to their hull forms, typical arrangements, and nature of cargo include:
tanker, bulk carrier, container carrier, and other dry cargo and passenger vessels.
The test data sets are to be used by the applicant to run the calculation program for the test vessels. The
results obtained, together with the hydrostatic data and cross-curve data developed by the program, if
appropriate are to be submitted to ABS for the assessment of the program’s computational accuracy. ABS
is to perform parallel calculations using the same data sets and a comparison of these results will be made
against the applicant’s submitted program’s results.

11.5 Specific Approval (2018)

ABS is to verify the accuracy of the computational results and actual vessel data used by the calculation
program for the particular vessel on which the program will be installed.
Upon receipt of application for data verification, ABS and the applicant are to agree on a minimum of four
loading conditions, taken from the vessel’s approved stability information, which are to be used as the test
conditions.
For vessels carrying liquids in bulk, at least one of the conditions is to include partially filled tanks. For
vessels carrying grain in bulk, one of the grain loading conditions is to include a partially filled grain
compartment. Within the test conditions each compartment is to be loaded at least once. The test conditions
normally are to cover the range of load drafts from the deepest envisaged loaded condition to the light
ballast condition and are to include at least one departure and one arrival condition.
For Type 4 stability software for SRtP, ABS is to examine at least three damage cases, each of them
associated with at least three loading conditions taken from the vessel’s approved stability information.
Output of the software is to be compared with results of corresponding load/damage case in the approved
damage stability booklet or an alternative independent software source.
ABS is to verify that the following data, submitted by the applicant, is consistent with arrangements and
most recently approved lightship characteristics of the vessel according to current plans and documentation
on file with ABS, subject to possible further verification onboard:
• Identification of the calculation program including version number.
• Main dimensions, hydrostatic particulars and, if applicable, the vessel profile.
• The position of the forward and after perpendiculars, and if appropriate, the calculation method to
derive the forward and after drafts at the actual position of the vessel’s draft marks.
• Vessel lightweight and center of gravity derived from the most recently approved inclining experiment
or light weight check.
• Lines plan, offset tables or other suitable presentation of hull form data if necessary for ABS to model
the vessel.
• Compartment definitions, including frame spacing, and centers of volume, together with capacity
tables (sounding/ullage tables), free surface corrections, if appropriate
• Cargo and Consumables distribution for each loading condition.
Verification by ABS does not absolve the applicant and shipowner of responsibility for ensuring that the
information programmed into the onboard computer software is consistent with the current condition of the
vessel.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 227
Part 3 Hull Construction and Equipment
Chapter 3 Subdivision and Stability
Appendix 2 Computer Software for Onboard Stability Calculations 3-3-A2

13 Operation Manual
A simple and straightforward operation manual is to be provided, containing descriptions and instructions,
as appropriate, for at least the following:
• Installation
• Function keys
• Menu displays
• Input and output data
• Required minimum hardware to operate the software
• Use of the test loading conditions
• Computer-guided dialogue steps
• List of warnings

15 Installation Testing (2018)

To ensure correct working of the computer after the final or updated software has been installed, it is the
responsibility of the vessel’s master to have test calculations carried out according to the following pattern
in the presence of the Surveyor:
• From the approved test conditions at least one load case (other than lightship) is to be calculated.
Note: Actual loading condition results are not suitable for checking the correct working of the computer.

• Normally, the test conditions are permanently stored in the computer.

Steps to be performed:
• Retrieve the test load case and start a calculation run; compare the stability results with those in the
documentation.
• Change several items of deadweight (tank weights and the cargo weight) sufficiently to change the
draft or displacement by at least 10%. The results are to be reviewed to ensure that they differ in a
logical way from those of the approved test condition.
• Revise the above modified load condition to restore the initial test condition and compare the results.
Confirm that the relevant input and output data of the approved test condition have been replicated.
• Alternatively, one or more test conditions shall be selected and the test calculation performed by
entering all deadweight data for each selected test condition into the program as if it were a proposed
loading. The results shall be verified as identical to the results in the approved copy of the test conditions.

17 Periodical Testing
It is the responsibility of the vessel’s master to check the accuracy of the onboard computer for stability
calculations at each Annual Survey by applying at least one approved test condition.
If the Surveyor is not present for the computer check, a copy of the test condition results obtained by the
computer check is to be retained onboard as documentation of satisfactory testing for the Surveyor’s
verification.
At each Special Periodical Survey, this checking for all approved test loading conditions is to be done in
presence of the surveyor.
The testing procedure is to be carried out in accordance with 3-3-A2/15.

228 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 3 Subdivision and Stability
Appendix 2 Computer Software for Onboard Stability Calculations 3-3-A2

19 Other Requirements
The following features are to be provided to the software:
• Protection against unintentional or unauthorized modification of programs and data is to be provided.
• The program is to monitor operations and activate an alarm when the program is incorrectly or
abnormally used.
• The program and any data stored in the system are to be protected from corruption by loss of power.
• Error messages with regard to limitations such as filling a compartment beyond capacity, or exceeding
the assigned load line, etc. are to be included.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 229
PART Chapter 4: Fire Safety Measures

3
CHAPTER 4 Fire Safety Measures

CONTENTS
SECTION 1 Structural Fire Protection .................................................................. 231 
1  General ...........................................................................................231 
1.1   SOLAS Application ...................................................................... 231 
1.3   Regulation ................................................................................... 231 
1.5   Definitions .................................................................................... 231 
1.7   Materials Containing Asbestos .................................................... 231 
3  Passenger Vessels .........................................................................231 
5  Cargo Vessels .................................................................................231 
5.1   All Vessels ................................................................................... 231 
5.3   Tankers........................................................................................ 231 
5.5   Vessels Carrying Chemicals or Liquefied Gases in Bulk ............. 232 
7  Review Procedures .........................................................................232 
7.1   Administration Review ................................................................. 232 
7.3   ABS Review ................................................................................. 232 
9  Fiber Reinforced Plastic (FRP) Gratings ........................................232 

APPENDIX 1 Fiber Reinforced Plastic (FRP) Gratings .......................................... 233 

1  General ...........................................................................................233 
3  FRP Grating Material Systems .......................................................233 
5  Fire Test Requirements ..................................................................233 
5.1  Structural Fire Integrity ................................................................ 233 
5.3  Flame Spread .............................................................................. 234 
5.5  Smoke Generation ....................................................................... 234 
7  Structural Fire Integrity Test Procedures ........................................234 
9  Structural Fire Integrity Matrix .........................................................234 
11  Other Authorized Uses....................................................................235

TABLE 1 Structural Fire Integrity Matrix ...............................................234 

230 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Section 1: Structural Fire Protection

3
CHAPTER 4 Fire Safety Measures

SECTION 1 Structural Fire Protection

1 General

1.1 SOLAS Application

For classification purposes, the fire and safety measures contained in the International Convention for the
Safety of Life at Sea, 1974 (1974 SOLAS), as amended, are applicable to vessels of type, size and service
coming under that Convention.
This section does not relax the requirements in other sections of the Rules.
Gross tonnage is to be taken as defined in 3-1-1/17.

1.3 Regulation
Regulation means the regulation contained in 1974 SOLAS, as amended. An abbreviated notation is used,
e.g., Regulation II-2/5.2 means Regulation 5.2 of Chapter II-2.

1.5 Definitions
See Regulation II-2/3.

1.7 Materials Containing Asbestos (1 July 2011)

Installation of materials which contain asbestos is prohibited.

3 Passenger Vessels
For passenger vessels, the requirements of Section 5C-7-4 of the ABS Rules for Building and Classing Steel
Vessels are applicable.

5 Cargo Vessels

5.1 All Vessels

For all cargo vessels as defined in Regulation II-2/3.7, the relevant requirements in Part B: Regulation 4, 5, 6;
Part C: Regulations 7, 8, 9, 10, 11; Part D: Regulation 13; and Part G: Regulations 19 and 20, Chapter II-2
of 1974 SOLAS, as amended, are applicable.

5.3 Tankers
For tankers as defined in Regulation 3.48, Chapter II-2 of 1974 SOLAS, as amended, the following
requirements are additional to 3-4-1/5.1.
5.3.1 Low Flash Point Cargoes
For tankers intended for the carriage of cargoes having flash point of 60°C (140°F) or less, the
relevant requirements in Part A: Regulation 1; Part B: Regulation 4; Part C: Regulations 9, 10, 11;
and Part E: Regulations 16, Chapter II-2 of 1974 SOLAS, as amended, are applicable. Furthermore,
the requirements of Chapters 2, 14 and 15 of the Fire Safety Systems Code are also applicable.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 231
Part 3 Hull Construction and Equipment
Chapter 4 Fire Safety Measures
Section 1 Structural Fire Protection 3-4-1

5.3.2 High Flash Point Cargoes

For tankers intended for the carriage of cargoes having flash point above 60°C (140°F), the
requirements in 3-4-1/5.1 are applicable, except that in lieu of the fixed fire extinguishing system
required by Regulation II-2/10.7.1.3, they are to be fitted with a fixed deck foam system which is
to comply with Chapter 14 of the Fire Safety Systems Code.

5.5 Vessels Carrying Chemicals or Liquefied Gases in Bulk

Vessels intending to carry chemicals or liquefied gases in bulk are to comply with the applicable requirements
of Part 5C, Chapters 8 and 9 of the Steel Vessel Rules, as applicable, and the governing Administrative
Regulations.

7 Review Procedures

7.1 Administration Review

When the vessel is issued a Passenger Ship Safety Certificate, Cargo Ship Safety Equipment Certificate or
Cargo Ship Safety Construction Certificate by the flag Administration or its agent other than ABS, such
Certificate will be accepted as evidence that the vessel is in accordance with the applicable criteria in 1974
SOLAS, as amended.
Where the Administration undertakes any part of the review and ABS is issuing the above Certificate, the
acceptance by the Administration will be required before the certificate is issued.
Compliance with the Rule requirements, in addition to those in 1974 SOLAS, as amended, is to be verified
by ABS.

7.3 ABS Review

In all other cases, the required information and plans are to be submitted to ABS for review.

9 Fiber Reinforced Plastic (FRP) Gratings (2015)

Where approved by the Administration, the use of Fiber Reinforced Plastic (FRP) gratings is to be in
accordance with Appendix 3-4-A1.

232 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Appendix 1: Fiber Reinforced Plastic (FRP) Gratings

3
CHAPTER 4 Fire Safety Measures

APPENDIX 1 Fiber Reinforced Plastic (FRP) Gratings (2015)

1 General

1.1 (2018)
FRP gratings may be used in other machinery spaces, cargo areas, and on-deck areas. FRP gratings are not
accepted in accommodation, service, control spaces, and areas where smoke and toxicity is a concern. The
floor plating and gratings in Category A machinery spaces is to be made of steel. Refer to 3-4-A1/Table 1.
FRP gratings are to meet the performance requirements of and are to be tested in accordance with ASTM
F3059-15, Standard Specification for Fiber-Reinforced Polymer (FRP) Gratings Used in Marine Construction
and Shipbuilding.

1.3
Changes in either the type, amount, and/or architecture, of either the reinforcement materials, resin matrix,
coatings, or manufacturing processes require separate testing in accordance with the procedures below.
Manufacturers are required to provide evidence, such as enrollment in a follow-up program, that the FRP
gratings being installed are the same as those which were tested and approved.

3 FRP Grating Material Systems

3.1
Where required, all fire integrity, flame spread, smoke, and toxicity testing are to be conducted on each
material system.

5 Fire Test Requirements (2018)

5.1 Structural Fire Integrity

The structural fire integrity requirements are intended for self-supporting personnel platforms or walkways,
and are not intended for grating overlaid on steel decking or used in other applications such as pipe guards,
sea chest screenings, safety guards, etc.
The structural fire integrity matrix in 3-4-A1/Table 1 establishes the structural fire integrity characteristics
that FRP gratings are to have based on location and service. Where a specific application satisfies more
than one block in the matrix, the highest level of fire integrity is required. The test procedures required to
qualify FRP gratings to one of four levels are described in 3-4-A1/7. The location and service of the FRP
gratings are to be determined on the basis of the following considerations for each of the four performance
levels:
5.1.1 Level 1 (L1)
FRP gratings meeting the L1 performance criteria are intended to be satisfactory for use in escape
routes or access for firefighting, emergency operation or rescue, after having been exposed to a
significant hydrocarbon or cellulosic fire incident. In addition, they are also acceptable for the
services and functions described for levels L2 and L3.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 233
Part 3 Hull Construction and Equipment
Chapter 4 Fire Safety Measures
Appendix 1 Fiber Reinforced Plastic (FRP) Gratings 3-4-A1

5.1.2 Level 2 (L2)

FRP gratings meeting the L2 performance criteria are intended to be satisfactory for use in open
deck areas where groups of people are likely to assemble, such as temporary safe refuge or lifeboat
embarkation areas. In addition, they are also acceptable for the services and functions described
for level L3.
5.1.3 Level 3 (L3)
FRP gratings meeting the L3 performance criteria are intended to be satisfactory for use in egress
routes and any areas that may require access for firefighting, rescue or emergency operations
during exposure to or shortly after exposure to a transitory hydrocarbon or cellulosic fire.
5.1.4 Level 0 (L0)
L0 FRP gratings are to be tested in accordance with ASTM E84 with a flame spread index not to
exceed 20 and a smoke developed index not to exceed 450. L0 FRP gratings have no fire integrity.
L0 FRP gratings may be used for personnel walkways, catwalks, ladders, platforms, or access
areas in cargo holds and tanks.

5.3 Flame Spread

All FRP gratings are to have low flame spread characteristics as determined by the following test procedure:
5.3.1
Tested to ASTM E84 with a flame spread rating not to exceed 20.

5.5 Smoke Generation

All FRP gratings are to have low smoke characteristics as determined by the following test procedure:
5.5.1
Tested to ASTM E84 with a smoke developed index limit not to exceed 450.

7 Structural Fire Integrity Test Procedures (2018)

Structural fire integrity tests are to be in accordance with ASTM F3059-15 according to the structural fire
integrity performance levels (L1, L2, L3, L0).

9 Structural Fire Integrity Matrix

TABLE 1
Structural Fire Integrity Matrix (2018)
Location Service Fire Integrity
Machinery Spaces of Category A(1) Steel Grating -
Walkways or areas which may be used for escape, or access for
L1(2)
firefighting, emergency operation or rescue
Other Machinery Spaces
Personnel walkways, catwalks, ladders, platforms or access areas other
L3
than those described above
Cargo Pump Rooms All personnel walkways, catwalks, ladders, platforms or access areas L1
Walkways or areas which may be used for escape, or access for
L1
firefighting, emergency operation or rescue
Cargo Holds
Personnel walkways, catwalks, ladders, platforms or access areas other
L0
than those described above
Cargo Tanks All personnel walkways, catwalks, ladders, platforms or access areas L0(3, 6)
Fuel Oil Tanks All personnel walkways, catwalks, ladders, platforms or access areas L0(3)
Ballast Water Tanks All personnel walkways, catwalks, ladders, platforms or access areas L0(4)
Cofferdams, void spaces, double
All personnel walkways, catwalks, ladders, platforms or access areas L0(4)
bottoms, pipe tunnels, etc.

234 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 4 Fire Safety Measures
Appendix 1 Fiber Reinforced Plastic (FRP) Gratings 3-4-A1

TABLE 1 (continued)
Structural Fire Integrity Matrix (2018)
Location Service Fire Integrity
Accommodation, service, and
All personnel walkways, catwalks, ladders, platforms or access areas Not permitted
control spaces
Lifeboat embarkation or temporary
safe refuge stations in open deck All personnel walkways, catwalks, ladders, platforms or access areas L2
areas
Operational areas and access routes for deck foam firefighting systems
L2
on tank vessels
Walkways or areas which may be used for escape, or access for
firefighting systems and AFFF hose reels, emergency operation, or
L2
rescue on MODUs and production platforms including safe access to
Open Decks or semi-enclosed areas tanker bows
Walkways or areas which may be used for escape, or access for
firefighting, emergency operation or rescue other than those described L3(5)
above
Personnel walkways, catwalks, ladders, platforms or access areas other
L3
than those described above
Notes:
1 Machinery spaces of category A is as defined in 4-1-1/13.1.
2 If the machinery space does not contain any internal combustion machinery, other oil-burning, oil-heating, or oil-
pumping units, fuel oil filling stations, or other potential hydrocarbon fire sources, and has not more than 2.5 kg/m2
(0.51 lb/ft2) of combustible storage, gratings of L3 integrity may be used in lieu of L1.
3 If these spaces are normally entered when underway, gratings of L1 integrity are to be required.
4 If these spaces are normally entered when underway, gratings of L3 integrity shall be required.
5 (2018) Vessels fitted with deck foam or dry powder firefighting systems require gratings of L2 integrity for the
firefighting system operational areas and access routes.
6 With regard to the use of FRP/GRP grating inside LNG/LPG tanks, although the gratings are not to be used at
cryogenic temperatures, the manufacturer has to demonstrate the suitability for the intended purpose showing that
low temperature does not affect the material characteristics when used.

11 Other Authorized Uses (2018)

The ABS Surveyor may authorize the use of FRP gratings without Main Office approval in applications
where structural fire integrity of the FRP gratings is not a concern, provided they meet the applicable flame
spread and smoke generation requirements set forth in 3-4-A1/5.3 and 3-4-A1/5.5. Applications where the
uses of FRP gratings have been authorized in the past, without any structural fire integrity requirement,
include the following:
i) Sea chest coverings;
ii) Small sundeck awnings and supports;
iii) Lifeboat bilge flooring;
iv) Electrical control flooring;
v) Pipe guards on deck, in cargo holds, and in engine rooms;
vi) Removable guards over hawse holes, anchor hawse pipes, and scuppers;
vii) Personnel barriers, such as protection for electrical panels; and
viii) Ship staging and work platforms (Occupational Safety and Health Administration (OSHA)
requirements may also apply).

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 235
PART Chapter 5: Equipment

3
CHAPTER 5 Equipment

CONTENTS
SECTION 1 Anchoring, Mooring and Towing Equipment ................................... 237
1 General ...........................................................................................237
3 Calculation of EN ............................................................................237
3.1 Basic Equation ............................................................................. 237
3.3 Vessels of Unrestricted Service Having EN of 205 and
Above .......................................................................................... 238
3.5 Vessels Having EN Less Than 205 or Vessels Intended for
Towing Service ............................................................................ 238
5 Equipment with the Symbol Á ........................................................239
7 Equipment without the Symbol Á ...................................................239
7.1 General ........................................................................................ 239
7.3 Vessels intended for Limited Service ........................................... 239
7.5 Vessels Intended for Towing Service........................................... 239
9 Materials and Tests .........................................................................239
11 Anchor Types ..................................................................................239
13 Windlass or Winch Support Structure .............................................239
13.1 General ........................................................................................ 239
13.3 Support Structure......................................................................... 240
13.5 Trial.............................................................................................. 242
15 Hawse Pipes ...................................................................................243
17 Hawsers and Towlines ....................................................................243
19 Bollard, Fairlead and Chocks ..........................................................244
19.1 General ........................................................................................ 244
19.3 Deck Fittings ................................................................................ 244
19.5 Safe Working Load (SWL) ........................................................... 244
19.7 Towing and Mooring Arrangements Plan ..................................... 244

TABLE 1 Equipment for Self-propelled Ocean-going Vessels .............245

TABLE 2 Towline and Hawsers for Self-propelled Ocean-going
Vessels ..................................................................................249

FIGURE 1 Effective Heights of Deckhouses ..........................................238

FIGURE 2 Direction of Forces and Weight.............................................242
FIGURE 3 Sign Convention ....................................................................243

236 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Section 1: Anchoring, Mooring and Towing Equipment

3
CHAPTER 5 Equipment

SECTION 1 Anchoring, Mooring and Towing Equipment

1 General (2012)
All self-propelled vessels are to have anchors and chains. The anchors and their cables are to be connected
and positioned ready for use. Means are to be provided for stopping each cable as it is paid out and the
windlass is to be capable of heaving in either cable. Suitable arrangements are to be provided for securing
the anchors and stowing the cables. Cables which are intended to form part of the equipment are not to be
used as check chains when the vessel is launched. The inboard ends of the cables of the bower anchors are
to be secured by efficient means.
Equipment Number calculations for unconventional vessels with unique topside arrangements or operational
profiles may be specially considered. Such consideration may include accounting for additional wind areas
of widely separated deckhouses or superstructures in the equipment number calculations or equipment sizing
based on direct calculations. However, in no case may direct calculations be used to reduce the equipment
size to be less than that required by 3-5-1/3.

3 Calculation of EN

3.1 Basic Equation (2012)

The basic Equipment Number (EN) is to be obtained from the following equation for use in determining
required equipment.
EN = k∆2/3 + mBh + nA
where
k = 1.0 (1.0, 1.012)
m = 2 (2, 0.186)
n = 0.1 (0.1, 0.00929)
∆ = molded displacement, in metric tons (long tons), to the summer load waterline
B = molded breadth, as defined in 3-1-1/5, in m (ft)
h = a + h1 + h2 + h3 + …, as shown in 3-5-1/Figure 1. In the calculation of h, sheer,
camber and trim may be neglected.
a = freeboard, in m (ft), from the summer load waterline amidships.
h1, h2, h3… = height, in m (ft), on the center line of each tier of houses having a breadth greater
than B/4

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 237
Part 3 Hull Construction and Equipment
Chapter 5 Equipment
Section 1 Anchoring, Mooring and Towing Equipment 3-5-1

A = profile area, in m2 (ft2), of the hull, superstructure and houses above the summer load
waterline which are within the Rule length. Superstructures or deck houses having a
breadth at any point no greater than 0.25B may be excluded. Screens and bulwarks more
than 1.5 m (4.9 ft) in height are to be regarded as parts of houses when calculating h and
A. The height of the hatch coamings and that of any deck cargo, such as containers, may
be disregarded when determining h and A. With regard to determining A, when a bulwark
is more than 1.5 m (4.9 ft) high, the area shown below as A2 should be included in A.

1.5 m (4.9 ft)

A2

F.P.

3.3 Vessels of Unrestricted Service Having EN of 205 and Above

For vessels of unrestricted service having an EN of 205 or above in accordance with 3-5-1/3.1, the calculated
EN is to be used in association with 3-5-1/Table 1. For vessels intended for towing service, see 3-5-1/3.5.

3.5 Vessels Having EN Less Than 205 or Vessels Intended for Towing Service
For vessels of unrestricted service having EN less than 205 calculated in accordance with 3-5-1/3.1 or for
vessels intended for towing service, the EN for use with 3-5-1/Table 1 may be calculated in accordance
with the following equation.
Equipment Number = k2/3 + m (Ba + bh) + nA
Where k, m, n, , B, a and A are as defined in 3-5-1/3.1 above and;
b = breadth, in m (ft), of the widest superstructure or deckhouse on each tier.
h = height, in m (ft), of each tier of deckhouse or superstructure having a width of B/4 or
greater. In the calculation of h, sheer, camber and trim may be neglected.
See 3-5-1/Figure 1.

FIGURE 1
Effective Heights of Deckhouses

h2

h1

b/8
b2/2 a
b1/2

238 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 5 Equipment
Section 1 Anchoring, Mooring and Towing Equipment 3-5-1

5 Equipment with the Symbol Á

The equipment weight and size for all vessels with the symbol Á is to be in accordance with 3-5-1/Table 1
in association with EN calculated by 3-5-1/3.

7 Equipment without the Symbol Á

7.1 General
Where the symbol Á is not desired for vessels with EN calculated as permitted by 3-5-1/3.5, the equipment
is to be in accordance with 3-5-1/Table 1, in association with the EN so calculated, but the following
modifications may be accepted. See also 3-5-1/9.

7.3 Vessels intended for Limited Service

Vessels intended for limited service (see 1-1-3/7 of the ABS Rules for Conditions of Classification (Part 1))
and having their own moorage, e.g., ferries, launch, etc. with an equipment number less than 150, obtained
from 3-5-1/3.5, are to have one anchor of the tabular weight and one-half the tabulated length of anchor
chain in 3-5-1/Table 1. Alternatively, two anchors of one-half the tabular weight with the total length of
anchor chain listed in 3-5-1/Table 1 may be fitted, provided both anchors are positioned and ready for use
and the windlass is capable of heaving in either anchor.

7.5 Vessels Intended for Towing Service (2001)

Vessels intended for towing service are to have at least one anchor of one-half the tabular weight listed in
3-5-1/Table 1.
The towing winch can be used for releasing and heaving in the anchor, provided that the anchor is positioned
ready for use and is capable of being quickly connected to the winch’s wire rope.

9 Materials and Tests

Material and testing for anchors and chains on vessels receiving the Á symbol are to be in accordance with
the requirements of Chapter 2 of the ABS Rules for Materials and Welding (Part 2) for the respective sizes
of anchors and chains. See Sections 2-2-1 and 2-2-2 of the above referenced Part 2. Materials and tests for
wire rope are to be in accordance with a national or other recognized standard.
Where the symbol Á is not desired in accordance with 3-5-1/7.1, the testing is to be carried out in accordance
with the approved specification, and the manufacturer’s test certificate to that effect is to be submitted to
the Surveyor.

11 Anchor Types
Anchors are, in general, to be of the stockless type. The weight of the head of a stockless anchor, including
pins and fittings, is not to be less than three-fifths of the total weight of the anchor. Where specifically
requested by the Owners, ABS is prepared to give consideration to the use of special types of anchors, and
where these are of proven superior holding ability, consideration may also be given to some reduction in
the weight, up to a maximum of 25%, from the weight specified in 3-5-1/Table 1. In such cases, an
appropriate notation will be made in the Record.

13 Windlass or Winch Support Structure

13.1 General (2014)

The windlass is to be of good and substantial make, suitable for the size of intended anchor cable. The
winch is to be well bolted down to a substantial bed, and deck beams below the windlass are to be of extra
strength and additionally supported. Where wire ropes are used in lieu of chain cables, winches capable of
controlling the wire rope at all times are to be fitted.

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 239
Part 3 Hull Construction and Equipment
Chapter 5 Equipment
Section 1 Anchoring, Mooring and Towing Equipment 3-5-1

Construction and installation of all windlasses and winches used for anchoring are to be carried out in
accordance with the following requirements, to the satisfaction of the Surveyor. In general, the design is to
conform to an applicable standard or code of practice. As a minimum, standards or practices are to indicate
strength, performance and testing criteria.
The manufacturer or builder is to submit, in accordance with 4-1-1/7, the following, as applicable:
13.1.1 Plans
i) Arrangement and details of the windlass or winch, drums, brakes, shaft, gears, coupling bolts,
wildcat, sheaves, pulleys and foundation.
ii) Electric one line diagram
iii) Piping system diagrams
iv) Control arrangements
Plans or data are to show complete details including power ratings, working pressures, welding details,
material specifications, pipe and electric cable specifications, etc.
13.1.2 Calculations
Detailed stress calculations for the applicable system components listed in 3-5-1/13.1.1 above.
The calculations are to be based on the breaking strength of the chain or wire rope, are to indicate
maximum torque or load to which the unit will be subjected and also show compliance with either
applicable sections of the Rules, such as Section 4-3-1 and Appendix 4-3-1A1 of the Steel Vessel
Rules, for the gears and shafts, or to other recognized standard or code of practice.

13.3 Support Structure (2004)

The windlass is to be bolted down to a substantial foundation which is to meet the following load cases and
associated criteria.
13.3.1 Operating Loads
13.3.1(a) Load on Windlass Support Structure (2006). The following load is to be applied in the
direction of the chain.
With cable stopper not attached to windlass: 45% of B.S.
With cable stopper attached to windlass: 80% of B.S.
Without cable stopper: 80% of B.S.
B.S. = minimum breaking strength of the chain, as indicated in 2-2-2/Tables 2 and 3
of the ABS Rules for Materials and Welding (Part 2).
13.3.1(b) Load on Cable Stopper and Support Structure (2006). A load of 80% of B.S. is to be
applied in the direction of the chain.
13.3.1(c) Allowable Stress (2006). The stresses in the structures supporting the windlass and cable
stopper are not to exceed the yield point.
13.3.2 Sea Loads (2014)
For vessels with length, L (as defined in 3-1-1/3.1), between 80 meters (263 feet) and 90 meters
(295 feet), where the height of the exposed deck in way of the item is less than 0.1L or 22 m above
the summer load waterline, whichever is the lesser, the windlass supporting structures located on
the exposed fore deck within the forward 0.25L are to meet the following requirements. Where the
mooring winch is integral with the windlass, it is to be considered as a part of the windlass for the
purpose of said paragraph.

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Section 1 Anchoring, Mooring and Towing Equipment 3-5-1

13.3.2(a) Pressures. The following pressures and associated areas are to be applied (see
3-5-1/Figure 2):
- 200 kN/m2 (20.4 tf/m2, 4178 lbf/ft2) normal to the shaft axis and away from the forward
perpendicular, over the projected area in this direction,
- 150 kN/m2 (15.3 tf/m2, 3133 lbf/ft2) parallel to the shaft axis and acting both inboard and
outboard separately, over the multiple of f times the projected area in this direction,
where f is defined as:
f = 1 + B/H, but need not be taken as greater than 2.5
B = width of windlass measured parallel to the shaft axis
H = overall height of windlass.
13.3.2(b) Forces. Forces in the bolts, chocks and stoppers securing the windlass to the deck are
to be calculated. The windlass is supported by N groups of bolts, each containing one or more
bolts, see 3-5-1/Figure 2.
i) Axial Forces. The aggregate axial force, Ri, in respective group of bolts (or bolt), i,
positive in tension, may be calculated from the following equations:
Rxi = Px hxi Ai/Ix
Ryi = Py hyi Ai/Iy
and
Ri = Rxi + Ryi – Rsi
where
Px = force, kN (tf, lbf), acting normal to the shaft axis
Py = force, kN (tf, lbf), acting parallel to the shaft axis, either inboard or
outboard, whichever gives the greater force in bolt group i
h = shaft height above the windlass mounting, cm (in.)
xi , y i = x and y coordinates of bolt group i from the centroid of all N bolt
groups, positive in the direction opposite to that of the applied force,
cm (in.)
Ai = cross sectional area of all bolts in group i, cm2 (in2)

Ix = Ai xi2 for N bolt groups

Iy = Ai yi2 for N bolt groups

Rsi = static reaction at bolt group i, due to weight of windlass.
ii) Shear forces. Aggregated shear forces, Fxi, Fyi, applied to the respective bolt group, i, of
bolts, and the resultant combined force, Fi, may be calculated from:
Fxi = (Px – αgM)/N

Fyi = (Py – αgM)/N

and

Fi = ( Fxi2 + Fyi2 )0.5

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where
α = coefficient of friction (0.5)
M = mass of windlass, in tonnes (Ltons)
g = gravity: 9.81 m/sec2 (32.2 ft/sec2)
N = number of groups of bolt.
The axial tensile/compressive and lateral forces from the above equations are also to be
considered in the design of the supporting structure.
13.3.2(c) Stresses in Bolts. Tensile axial stresses in the individual bolts in each group of bolt i
are to be calculated. The horizontal forces, Fxi and Fyi, are normally to be reacted by shear chocks.
Where “fitted” bolts are designed to support these shear forces in one or both directions, the von Mises
equivalent stresses in the individual “fitted” bolts are to be calculated and compared to the stress
under proof load. Where pourable resins are incorporated in the holding down arrangements, due
account is to be taken in the calculations.
13.3.2(d) Allowable Stress
i) Bolts. The safety factor against bolt proof strength is to be not less than 2.0.
ii) Supporting Structures. The stresses in the above deck framing and the hull structure
supporting the windlass are not to exceed the following values:
Bending Stress 85% of the yield strength of the material
Shearing Stress 60% of the yield strength of the material

13.5 Trial
See 3-7-2/1.

FIGURE 2
Direction of Forces and Weight (2004)

Py Px

h
W

Fore

Centerline of Vessel Py

Centerline of B
Windlass

Note: Px
Py to be examined from both inboard and outboard
directions separately - see 3-5-1/13.3.2(a). The
sign convention for yi is reversed when Py is from
the opposite direction as shown.

242 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
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Chapter 5 Equipment
Section 1 Anchoring, Mooring and Towing Equipment 3-5-1

FIGURE 3
Sign Convention (2004)

Px Coordinates xi and yi are shown as either

positive (+ve) or negative (-ve).
Centerline of
Windlass
Py
x3 (-ve)
y3 (+ve)
x4 (-ve)
x2 (+ve) x1 (+ve)
Centroid of Bolt Groups
y4 (+ve)

y2 (+ve)

y1 (+ve)

15 Hawse Pipes
Hawse pipes are to be of ample size and strength. They are to have full rounded flanges and the least
possible lead, in order to minimize the nip on the cables. They are to be securely attached to thick doubling
or insert plates by continuous welds, the size of which are to be in accordance with Section 3-2-16 for the
plating thickness and type of joint selected. When in position, they are to be thoroughly tested for
watertightness by means of a hose in which the water pressure is not to be less than 2.06 bar (2.1 kgf/cm2,
30 psi). Hawse pipes for stockless anchors are to provide ample clearances. The anchors are to be shipped
and unshipped so that the Surveyor may be satisfied that there is no risk of the anchor jamming in the
hawse pipe. Care is to be taken to ensure a fair lead for the chain from the windlass to the hawse pipes and
to the chain pipes.

17 Hawsers and Towlines

Hawsers and towlines are not required as a condition of classification. The hawsers and towlines listed in
3-5-1/Table 2 are intended as a guide. Where the tabular breaking strength exceeds 490 kN (50,000 kgf,
110,200 lbf), the breaking strength and the number of individual hawsers given in the Table may be
modified, provided their product is not less than that of the breaking strength and the number of hawsers
given in the Table. For vessels having an A/EN ratio greater than 0.9 for metric units (9.7 for US units), the
number of hawsers given in 3-5-1/Table 2 is to be increased by the number given below.

A/EN Ratio
SI Units, Metric Units U.S. Units Increase number of hawsers by
above 0.9 up to 1.1 above 9.7 up to 11.8 1
above 1.1 up to 1.2 above 11.8 up to 12.9 2
above 1.2 above 12.9 3

where
A = defined in 3-5-1/3
EN = determined by the equation in 3-5-1/3

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19 Bollard, Fairlead and Chocks (2007)

19.1 General (2016)

For vessels which are required to comply with SOLAS, the arrangements and details of deck fittings used
for mooring operations and/or towing operations at bow, sides and stern are to comply with the requirements
of this section. The requirements for the supporting structures of these deck fittings are specified in 3-2-6/1.6.

19.3 Deck Fittings (1 July 2015)

The size of deck fittings is to be in accordance with recognized standards (e.g., ISO 13795 Ships and marine
technology – Ship’s mooring and towing fittings – Welded steel bollards for sea-going vessels). The design
load used to assess deck fittings and their attachments to the hull are to be in accordance with the requirements
as specified in 3-2-6/1.6.

19.5 Safe Working Load (SWL)

The requirements on SWL apply for a single post basis (no more than one turn of one cable).
19.5.1 Mooring Operations
The SWL is not to exceed 80% of the design load per 3-2-6/1.6.2(a).
19.5.2 Towing Operations
The SWL used for normal towing operations (e.g., harbor/maneuvering) is not to exceed 80% of
the design load per 3-2-6/1.6.2(b)i) and the SWL used for other towing operations (e.g., escort) is
not to exceed the design load per 3-2-6/1.6.2(b)ii). For deck fittings used for both normal and other
towing operations, the design load of 3-2-6/1.6.2(b) is to be used.
19.5.3 Marking and Plan
19.5.3(a) Marking. The SWL of each deck fitting is to be marked (by weld bead or equivalent)
on the deck fittings used for towing/mooring.
19.5.3(b) Plan. The towing and mooring arrangements plan mentioned in 3-5-1/19.7 is to define
the method of use of mooring lines and/or towing lines.

19.7 Towing and Mooring Arrangements Plan

The SWL for the intended use for each deck fitting is to be noted in the towing and mooring arrangements
plan available on board for the guidance of the Master.
Information provided on the plan is to include in respect of each deck fitting:
• Location on the ship;
• Fitting type;
• SWL;
• Purpose (mooring/harbor towing/escort towing); and
• Manner of applying towing or mooring line load including limiting fleet angles.
Note: Where the arrangements and details of deck fittings and their supporting structures are designed based on the
mooring arrangements as permitted in Note 2 of 3-2-6/1.6.2(a)i), the arrangement of mooring lines showing
number of lines together with the breaking strength of each mooring line are to be clearly indicated on the plan.
This information is to be incorporated into the pilot card in order to provide the pilot proper information on
harbor/escorting operations.

244 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 5 Equipment
Section 1 Anchoring, Mooring and Towing Equipment 3-5-1

TABLE 1
Equipment for Self-propelled Ocean-going Vessels
SI, MKS Units
The weight per anchor of bower anchors given in 3-5-1/Table 1 is for anchors of equal weight. The weight of individual anchors
may vary 7% plus or minus from the tabular weight, provided that the combined weight of all anchors is not less than that required
for anchors of equal weight. The total length of chain required to be carried onboard, as given in 3-5-1/Table 1, is to be reasonably
divided between the two bower anchors. Where three anchors are given in 3-5-1/Table 1, the third anchor is intended as a spare
bower anchor and is listed for guidance only. It is not required as a condition of classification.
Stockless Bower Anchors Chain Cable Stud Link Bower Chain**
Diameter
Normal- High- Extra High-
Mass per Strength Steel Strength Steel Strength Steel
Equipment Equipment Anchor, Length, (Grade 1), (Grade 2), (Grade 3),
Numeral Number* Number kg m mm mm mm
UA1 30 2 75 192.5 12.5 — —
UA2 40 2 100 192.5 12.5 — —
UA3 50 2 120 192.5 12.5 — —
UA4 60 2 140 192.5 12.5 — —
UA5 70 2 160 220 14 12.5 —

UA6 80 2 180 220 14 12.5 —

UA7 90 2 210 220 16 14 —
UA8 100 2 240 220 16 14 —
UA9 110 2 270 247.5 17.5 16 —
UA10 120 2 300 247.5 17.5 16 —

UA11 130 2 340 275 19 16 —

UA12 140 2 390 275 20.5 17.5 —
U6 150 2 480 275 22 19 —
U7 175 2 570 302.5 24 20.5 —
U8 205 3 660 302.5 26 22 20.5
U9 240 3 780 330 28 24 22
U10 280 3 900 357.5 30 26 24

U11 320 3 1020 357.5 32 28 24

U12 360 3 1140 385 34 30 26
U13 400 3 1290 385 36 32 28
U14 450 3 1440 412.5 38 34 30
U15 500 3 1590 412.5 40 34 30

U16 550 3 1740 440 42 36 32

U17 600 3 1920 440 44 38 34
U18 660 3 2100 440 46 40 36
U19 720 3 2280 467.5 48 42 36
U20 780 3 2460 467.5 50 44 38

U21 840 3 2640 467.5 52 46 40

U22 910 3 2850 495 54 48 42
U23 980 3 3060 495 56 50 44
U24 1060 3 3300 495 58 50 46
U25 1140 3 3540 522.5 60 52 46

U26 1220 3 3780 522.5 62 54 48

U27 1300 3 4050 522.5 64 56 50
U28 1390 3 4320 550 66 58 50
U29 1480 3 4590 550 68 60 52
U30 1570 3 4890 550 70 62 54

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Section 1 Anchoring, Mooring and Towing Equipment 3-5-1

TABLE 1 (continued)
SI, MKS Units
Stockless Bower Anchors Chain Cable Stud Link Bower Chain**
Diameter
Normal- High- Extra High-
Mass per Strength Steel Strength Steel Strength Steel
Equipment Equipment Anchor, Length, (Grade 1), (Grade 2), (Grade 3),
Numeral Number* Number kg m mm mm mm
U31 1670 3 5250 577.5 73 64 56
U32 1790 3 5610 577.5 76 66 58
U33 1930 3 6000 577.5 78 68 60
U34 2080 3 6450 605 81 70 62
U35 2230 3 6900 605 84 73 64

U36 2380 3 7350 605 87 76 66

U37 2530 3 7800 632.5 90 78 68
U38 2700 3 8300 632.5 92 81 70
U39 2870 3 8700 632.5 95 84 73
U40 3040 3 9300 660 97 84 76

U41 3210 3 9900 660 100 87 78

U42 3400 3 10500 600 102 90 78
U43 3600 3 11100 687.5 105 92 81
U44 3800 3 11700 687.5 107 95 84
U45 4000 3 12300 687.5 111 97 87

U46 4200 3 12900 715 114 100 87

U47 4400 3 13500 715 117 102 90
U48 4600 3 14100 715 120 105 92
U49 4800 3 14700 742.5 122 107 95
U50 5000 3 15400 742.5 124 111 97

U51 5200 3 16100 742.5 127 111 97

U52 5500 3 16900 742.5 130 114 100
U53 5800 3 17800 742.5 132 117 102
U54 6100 3 18800 742.5 — 120 107
U55 6500 3 20000 770 — 124 111

U56 6900 3 21500 770 — 127 114

U57 7400 3 23000 770 — 132 117
U58 7900 3 24500 770 — 137 122
U59 8400 3 26000 770 — 142 127
U60 8900 3 27500 770 — 147 132
U61 9400 3 29000 770 — 152 132

U62 10000 3 31000 770 — — 137

U63 10700 3 33000 770 — — 142
U64 11500 3 35500 770 — — 147
U65 12400 3 38500 770 — — 152
U66 13400 3 42000 770 — — 157
U67 14600 3 46000 770 — — 162
* For intermediate values of equipment number, use equipment complement in sizes and weights given for the lower equipment
number in the table.
** Wire ropes may be used in lieu of chain cables for both anchors on vessels less than 30 m (98.4 ft) in length. For vessels between
30 m (8.4 ft) and 40 m (131.2 ft) in length, wire rope may be used in lieu of chain cable for one anchor, provided normal chain
cable is provided for the second anchor.
The wire is to have a breaking strength not less than the grade 1 chain of required size and a length of at least 1.5 times the chain
it is replacing.
Between the wire rope and anchor, chain cable of the required size having a length of 12.5 m (41.0 ft), or the distance between
anchor in stored position and winch, whichever is less, is to be fitted.

246 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 5 Equipment
Section 1 Anchoring, Mooring and Towing Equipment 3-5-1

TABLE 1
Equipment for Self-propelled Ocean-going Vessels
US Units
The weight per anchor of bower anchors given in 3-5-1/Table 1 is for anchors of equal weight. The weight of individual anchors
may vary 7% plus or minus from the tabular weight, provided that the combined weight of all anchors is not less than that required
for anchors of equal weight. The total length of chain required to be carried onboard, as given in 3-5-1/Table 1, is to be reasonably
divided between the two bower anchors. Where three anchors are given in 3-5-1/Table 1, the third anchor is intended as a spare
bower anchor and is listed for guidance only. It is not required as a condition of classification.
Stockless Bower Anchors Chain Cable Stud Link Bower Chain**
Diameter
Normal- High- Extra High-
Mass per Strength Steel Strength Steel Strength Steel
Equipment Equipment Anchor, Length, (Grade 1), (Grade 2), (Grade 3),
Numeral Number* Number pounds fathoms inches inches inches
UA1 30 2 165 105 1/2 — —
UA2 40 2 220 105 1/2 — —
UA3 50 2 265 105 1/2 — —
UA4 60 2 310 105 1/2 — —
UA5 70 2 350 120 9/16 1/2 —

UA6 80 2 400 120 9/16 1/2 —

UA7 90 2 460 120 5/8 9/16 —
UA8 100 2 530 120 5/8 9/16 —
UA9 110 2 595 135 11/16 5/8 —
UA10 120 2 670 135 11/16 5/8 —

UA11 130 2 750 150 3/4 11/16 —

UA12 140 2 860 150 13/16 11/16 —
U6 150 2 1060 150 7/8 3/4 —
U7 175 2 1255 165 15/16 13/16 —
U8 205 3 1455 165 1 7/8 13/16

U9 240 3 1720 180 1 1/8 15/16 7/8

U10 280 3 1985 195 1 3/16 1 15/16

U11 320 3 2250 195 1 1/4 1 1/8 15/16

U12 360 3 2510 210 1 5/16 1 3/16 1

U13 400 3 2840 210 1 7/16 1 1/4 1 1/8
U14 450 3 3170 225 1 1/2 1 5/16 1 3/16
U15 500 3 3500 225 1 9/16 1 5/16 1 3/16

U16 550 3 3830 240 1 5/8 1 7/16 1 1/4

U17 600 3 4230 240 1 3/4 1 1/2 1 5/16
U18 660 3 4630 240 1 13/16 1 9/16 1 7/16
U19 720 3 5020 255 1 7/8 1 5/8 1 7/16
U20 780 3 5420 255 2 1 3/4 1 1/2

U21 840 3 5820 255 2 1/16 1 13/16 1 9/16

U22 910 3 6280 270 2 1/8 1 7/8 1 5/8
U23 980 3 6740 270 2 3/16 1 15/16 1 3/4
U24 1060 3 7270 270 2 5/16 2 1 13/16
U25 1140 3 7800 285 2 3/8 2 1/16 1 13/16

U26 1220 3 8330 285 2 7/16 2 1/8 1 7/8

U27 1300 3 8930 285 2 1/2 2 3/16 2
U28 1390 3 9520 300 2 5/8 2 5/16 2
U29 1480 3 10120 300 2 11/16 2 3/8 2 1/16
U30 1570 3 10800 300 2 3/4 2 7/16 2 1/8

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 247
Part 3 Hull Construction and Equipment
Chapter 5 Equipment
Section 1 Anchoring, Mooring and Towing Equipment 3-5-1

TABLE 1 (continued)
Equipment for Self-propelled Ocean-going Vessels
US Units
Stockless Bower Anchors Chain Cable Stud Link Bower Chain**
Diameter
Normal- High- Extra High-
Mass per Strength Steel Strength Steel Strength Steel
Equipment Equipment Anchor, Length, (Grade 1), (Grade 2), (Grade 3),
Numeral Number* Number pounds fathoms inches inches inches
U31 1670 3 11600 315 2 7/8 2 1/2 2 3/16
U32 1790 3 12400 315 3 2 5/8 2 5/16
U33 1930 3 13200 315 3 1/16 2 11/16 2 3/8
U34 2080 3 14200 330 3 /16
3 2 /4
3 2 7/16
U35 2230 3 15200 330 3 5/16 2 7/8 2 1/2

U36 2380 3 16200 330 3 7/16 3 2 5/8

U37 2530 3 17200 345 3 9/16 3 1/16 2 11/16
U38 2700 3 18300 345 3 5/8 3 3/16 2 3/4
U39 2870 3 19200 345 3 3/4 3 5/16 2 7/8
U40 3040 3 20500 360 3 7/8 3 5/16 3

U41 3210 3 21800 360 3 15/16 3 7/16 3 1/16

U42 3400 3 23100 360 4 3 9/16 3 1/16
U43 3600 3 24500 375 4 1/8 3 5/8 3 3/16
U44 3800 3 25800 375 4 1/4 3 3/4 3 5/16
U45 4000 3 27100 375 4 3/8 3 7/8 3 7/16

U46 4200 3 28400 390 4 1/2 3 15/16 3 7/16

U47 4400 3 29800 390 4 5/8 4 3 9/16
U48 4600 3 31100 390 4 3/4 4 1/8 3 5/8
U49 4800 3 32400 405 4 3/4 4 1/4 3 3/4
U50 5000 3 33900 405 4 7/8 4 3/8 3 7/8

U51 5200 3 35500 405 5 4 3/8 3 7/8

U52 5500 3 37200 405 5 1/8 4 1/2 3 15/16
U53 5800 3 39200 405 5 1/8 4 5/8 4
U54 6100 3 41400 405 — 4 3/4 4 1/4
U55 6500 3 44000 420 — 4 7/8 4 3/8

U56 6900 3 47400 420 — 5 4 1/2

U57 7400 3 50700 420 — 5 1/8 4 5/8
U58 7900 3 54000 420 — 5 3/8 4 3/4
U59 8400 3 57300 420 — 5 5/8 5
U60 8900 3 60600 420 — 5 3/4 5 1/8
U61 9400 3 63900 420 — 6 5 1/8

U62 10000 3 68000 420 — — 5 3/8

U63 10700 3 72500 420 — — 5 5/8
U64 11500 3 78000 420 — — 5 3/4
U65 12400 3 85000 420 — — 6
U66 13400 3 92500 420 — — 6 1/8
U67 14600 3 101500 420 — — 6 3/8
* For intermediate values of equipment number, use equipment complement in sizes and weights given for the lower equipment
number in the table.
** Wire ropes may be used in lieu of chain cables for both anchors on vessels less than 30 m (98.4 ft) in length. For vessels between
30 m (8.4 ft) and 40 m (131.2 ft) in length, wire rope may be used in lieu of chain cable for one anchor, provided normal chain
cable is provided for the second anchor.
The wire is to have a breaking strength not less than the grade 1 chain of required size and a length of at least 1.5 times the chain
it is replacing.
Between the wire rope and anchor, chain cable of the required size having a length of 12.5 m (41.0 ft), or the distance between
anchor in stored position and winch, whichever is less, is to be fitted.

248 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 5 Equipment
Section 1 Anchoring, Mooring and Towing Equipment 3-5-1

TABLE 2
Towline and Hawsers for Self-propelled Ocean-going Vessels
SI & MKS Units
Towline Wire or Rope Hawsers
Breaking Strength, Length Breaking Strength,
Equipment Equipment of Each,
Numeral Number* Length, m KN kgf Number m kN kgf
U6 150 180 98.0 10000 3 120 54.0 5500
U7 175 180 112.0 11400 3 120 59.0 6000
U8 205 180 129.0 13200 4 120 64.0 6500
U9 240 180 150.0 15300 4 120 69.0 7000
U10 280 180 174.0 17700 4 140 74.0 7500

U11 320 180 207.0 21100 4 140 78.0 8000

U12 360 180 224.0 22800 4 140 88.0 9000
U13 400 180 250.0 25500 4 140 98.0 10000
U14 450 180 277.0 28200 4 140 108.0 11000
U15 500 190 306.0 31200 4 160 123.0 12500

U16 550 190 338.0 34500 4 160 132.0 13500

U17 600 190 370.0 37800 4 160 147.0 15000
U18 660 190 406.0 41400 4 160 157.0 16000
U19 720 190 441.0 45000 4 170 172.0 17500
U20 780 190 479.0 48900 4 170 186.0 19000

U21 840 190 518.0 52800 4 170 201.0 20500

U22 910 190 559.0 57000 4 170 216.0 22000
U23 980 200 603.0 61500 4 180 230.0 23500
U24 1060 200 647.0 66000 4 180 250.0 25500
U25 1140 200 691.0 70500 4 180 270.0 27500

U26 1220 200 738.0 75300 4 180 284.0 29000

U27 1300 200 786.0 80100 4 180 309.0 31500
U28 1390 200 836.0 85200 4 180 324.0 33000
U29 1480 220 888.0 90600 5 190 324.0 33000
U30 1570 220 941.0 96000 5 190 333.0 34000

U31 1670 220 1024.0 104400 5 190 353.0 36000

U32 1790 220 1109.0 113100 5 190 378.0 38500
U33 1930 220 1168.0 119100 5 190 402.0 41000
U34 2080 240 1259.0 128400 5 200 422.0 43000
U35 2230 240 1356.0 138300 5 200 451.0 46000

U36 2380 240 1453.0 148200 5 200 480.0 49000

U37 2530 260 1471.0 150000 6 200 480.0 49000
U38 2700 260 1471.0 150000 6 200 490.0 50000
U39 2870 260 1471.0 150000 6 200 500.0 51000
U40 3040 280 1471.0 150000 6 200 520.0 53000

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Section 1 Anchoring, Mooring and Towing Equipment 3-5-1

TABLE 2 (continued)
Towline and Hawsers for Self-propelled Ocean-going Vessels
SI & MKS Units
Towline Wire or Rope Hawsers
Breaking Strength, Length Breaking Strength,
Equipment Equipment of Each,
Numeral Number* Length, m KN kgf Number m kN kgf
U41 3210 280 1471.0 150000 6 200 554.0 56500
U42 3400 280 1471.0 150000 6 200 588.0 60000
U43 3600 300 1471.0 150000 6 200 618.0 63000
U44 3800 300 1471.0 150000 6 200 647.0 66000
U45 4000 300 1471.0 150000 7 200 647.0 66000

U46 4200 300 1471.0 150000 7 200 657.0 67000

U47 4400 300 1471.0 150000 7 200 667.0 68000
U48 4600 300 1471.0 150000 7 200 677.0 69000
U49 4800 300 1471.0 150000 7 200 686.0 70000
U50 5000 300 1471.0 150000 8 200 686.0 70000

U51 5200 300 1471.0 150000 8 200 696.0 71000

U52 5500 300 1471.0 150000 8 200 706.0 72000
U53 5800 300 1471.0 150000 9 200 706.0 72000
U54 6100 300 1471.0 150000 9 200 716.0 73000
U55 6500 300 1471.0 150000 9 200 726.0 74000

U56 6900 300 1471.0 150000 10 200 726.0 74000

U57 7400 300 1471.0 150000 11 200 726.0 74000
U58 7900 — — — 11 200 736.0 75000
U59 8400 — — — 12 200 736.0 75000
U60 8900 — — — 13 200 736.0 75000
U61 9400 — — — 14 200 736.0 75000

U62 10000 — — — 15 200 736.0 75000

U63 10700 — — — 16 200 736.0 75000
U64 11500 — — — 17 200 736.0 75000
U65 12400 — — — 18 200 736.0 75000
U66 13400 — — — 19 200 736.0 75000
U67 14600 — — — 21 200 736.0 75000

* For intermediate values of equipment number, use equipment complement in sizes and weights given for the lower equipment
number in the table.

250 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 5 Equipment
Section 1 Anchoring, Mooring and Towing Equipment 3-5-1

TABLE 2
Towline and Hawsers for Self-propelled Ocean-going Vessels
US Units
Towline Wire or Rope Hawsers
Breaking Length of Breaking
Equipment Equipment Length, Strength, Each Strength,
Numeral Number* Fathoms Pounds Number Fathoms Pounds
U6 150 98 22000 3 66 12100
U7 175 98 25100 3 66 13200
U8 205 98 29100 4 66 14300
U9 240 98 33700 4 66 15400
U10 280 98 39000 4 77 16500

U11 320 98 46500 4 77 17600

U12 360 98 50300 4 77 19800
U13 400 98 56200 4 77 22000
U14 450 98 62200 4 77 24200
U15 500 104 68800 4 88 27600

U16 550 104 76000 4 88 29800

U17 600 104 83300 4 88 33100
U18 660 104 91200 4 88 35300
U19 720 104 99200 4 93 38600
U20 780 104 107800 4 93 41900

U21 840 104 116400 4 93 45200

U22 910 104 125600 4 93 48500
U23 980 109 135500 4 98 51800
U24 1060 109 145500 4 98 56200
U25 1140 109 155400 4 98 60600

U26 1220 109 166000 4 98 63900

U27 1300 109 176500 4 98 69400
U28 1390 109 187800 4 98 72800
U29 1480 120 199700 5 104 72800
U30 1570 120 211500 5 104 75000

U31 1670 120 230000 5 104 79400

U32 1790 120 249500 5 104 84900
U33 1930 120 262500 5 104 90400
U34 2080 131 283000 5 109 94800
U35 2230 131 305000 5 109 101400

U36 2380 131 326500 5 109 108000

U37 2530 142 330500 6 109 108000
U38 2700 142 330500 6 109 110200
U39 2870 142 330500 6 109 112400
U40 3040 153 330500 6 109 116800

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Part 3 Hull Construction and Equipment
Chapter 5 Equipment
Section 1 Anchoring, Mooring and Towing Equipment 3-5-1

TABLE 2 (continued)
Towline and Hawsers for Self-propelled Ocean-going Vessels
US Units
Towline Wire or Rope Hawsers
Breaking Length of Breaking
Equipment Equipment Length, Strength, Each Strength,
Numeral Number* Fathoms Pounds Number Fathoms Pounds
U41 3210 153 330500 6 109 124600
U42 3400 153 330500 6 109 132300
U43 3600 164 330500 6 109 138900
U44 3800 164 330500 6 109 145500
U45 4000 164 330500 7 109 145500

U46 4200 164 330500 7 109 147700

U47 4400 164 330500 7 109 149900
U48 4600 164 330500 7 109 152100
U49 4800 164 330500 7 109 154300
U50 5000 164 330500 8 109 154300

U51 5200 164 330500 8 109 156500

U52 5500 164 330500 8 109 158700
U53 5800 164 330500 9 109 158700
U54 6100 164 330500 9 109 160900
U55 6500 164 330500 9 109 163100

U56 6900 164 330500 10 109 163100

U57 7400 164 330500 11 109 163100
U58 7900 — — 11 109 165300
U59 8400 — — 12 109 165300
U60 8900 — — 13 109 165300
U61 9400 — — 14 109 165300

U62 10000 — — 15 109 165300

U63 10700 — — 16 109 165300
U64 11500 — — 17 109 165300
U65 12400 — — 18 109 165300
U66 13400 — — 19 109 165300
U67 14600 — — 21 109 165300

* For intermediate values of equipment number, use equipment complement in sizes and weights given for the lower equipment
number in the table.

252 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Chapter 6: Navigation

3
CHAPTER 6 Navigation

CONTENTS
SECTION 1 Visibility .............................................................................................. 254
1 Navigation Bridge Visibility.............................................................. 254
1.1 Field of Vision .............................................................................. 254
1.3 Windows and Their Arrangements .............................................. 257
1.5 Unconventional Design ............................................................... 258
1.7 Articulated Tug-Barge Units ........................................................ 258

FIGURE 1..................................................................................................... 254

FIGURE 2..................................................................................................... 255
FIGURE 3..................................................................................................... 256
FIGURE 4..................................................................................................... 256
FIGURE 5..................................................................................................... 256
FIGURE 6..................................................................................................... 257

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PART Section 1: Visibility

3
CHAPTER 6 Navigation

SECTION 1 Visibility (1 July 1998)

1 Navigation Bridge Visibility

(2011) Vessels of not less than 55 m (180 ft) in length overall having the keel laid or in similar stage of
construction on or after 1 July 1998 are to meet the following requirements with regard to the visibility
from the navigation bridge, unless they are navigating solely the Great Lakes of North America and their
connecting and tributary waters as far east as the lower exit of the St. Lambert Lock at Montreal in the
Province of Quebec, Canada. Special consideration will be given to vessels that operate only on domestic
or on short, limited, international voyages.

1.1 Field of Vision

1.1.1 Conning Position
1.1.1(a) (1 July 2006) The view of the sea surface from the conning position is not to be obscured
by more than 2LOA (Length Overall) or 500 m (1640 ft), whichever is less, forward of the bow to
10° on either side for all conditions of draft, trim and deck cargo under which the particular vessel
is expected to operate. See 3-6-1/Figure 1.

FIGURE 1 (1 July 2006)

Conning position
Sea surface

2 Ship's lengths or 500 m

whichever is less

1. A conning position is a place on the bridge with a commanding view and which is used by
navigators when commanding, maneuvering and controlling a vessel.
2. Attention is drawn to flag Administrations requiring lengths of less than 2LOA.

1.1.1(b) No blind sector caused by cargo, cargo gear or other obstructions outside of the wheelhouse
forward of the beam which obstructs the view of the sea surface as seen from the conning position
is to exceed 10°. The total arc of blind sectors is not to exceed 20°. The clear sectors between blind
sectors are to be at least 5°. However, in the view described in 3-6-1/1.1.1(a), each individual blind
sector is not to exceed 5°.
1.1.1(c) The horizontal field of vision from the conning position is to extend over an arc of not
less than 225°, that is, from right ahead to not less than 22.5° abaft the beam on either side of the
vessel. See 3-6-1/Figure 3.

254 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 6 Navigation
Section 1 Visibility 3-6-1

1.1.2 Bridge Wing

1.1.2(a) From each bridge wing, the horizontal field of vision is to extend over an arc of at least
225°, that is, from at least 45° on the opposite bow to right ahead and then from right ahead to
right astern through 180° on the same side of the vessel. See 3-6-1/Figure 4.
1.1.2(b) (1 July 2011) The vessel’s side is to be visible from the bridge wing.
i) The requirements of 3-6-1/1.1.2(b) are accomplished when:
• A view from the bridge wing plus a distance corresponding to a reasonable and safe
distance of a seafarer leaning over the side of the bridge wing, which needs not to be
more than 400 mm (16 in.), to the location vertically right under the maximum beam
of the ship at the lowest seagoing draft is not obscured; or
• The sea surface at the lowest seagoing draft and with a transverse distance of 500 mm
(19.5 in.) and more from the maximum beam throughout the ship’s length is visible
from the side of the bridge wing.
See 3-6-1/Figure 2.
ii) For particular ship types, such as tug/tow boat, offshore supply vessel (OSV), rescue ship,
work ship (e.g., floating crane ships), etc., that are designed such that, in normal operations,
they come along side, or operate in close proximity to, other vessels or offshore structures
at sea, 3-6-1/1.1.2(b) is met provided the bridge wings extend at least to a location from
which the sea surface, at the lowest seagoing draft and at a transverse distance of 1500 mm
(59 in.) from the maximum beam throughout the ship’s length, is visible. If this ship type
is changed to a type other than those addressed in this paragraph, then the interpretation in
this paragraph would no longer apply.

FIGURE 2 (1 July 2011)

Max.
400 mm

Max.
Minimum Minimum
500 mm
draft draft

Max. 400 mm Max. 500 mm

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 255
Part 3 Hull Construction and Equipment
Chapter 6 Navigation
Section 1 Visibility 3-6-1

1.1.3 Main Steering Position

From the main steering position, the horizontal field of vision is to extend over an arc from right
ahead to at least 60° on each side of the vessel. See 3-6-1/Figure 5.

FIGURE 3 FIGURE 4 FIGURE 5 (2017)

Conning
position

Main
steering
position

1.1.4 Remote Camera System (1 July 2014)

For vessels of 55 m (180 ft) in length, and above, the use of a remote camera system may be
accepted for ships of unconventional design, other than those mentioned in 3-6-1/1.1.2(b)ii) above,
as means for achieving the view of the ship’s side from the bridge wing, provided:
i) The installed remote camera system is to be redundant from the circuit breaker to the
camera and screen, including communication cables, i.e. the system is to provide on each
side of the ship redundancy of:
• The power cables and circuit breakers from the main switchboard to the camera and
the screen;
• The camera;
• The screen;
• The transmission lines from the camera to the display screen; and
• The components associated with these lines and cables;
ii) The remote camera system is powered from the ship’s main source of electrical power
and is not required to be powered by the emergency source of electrical power;
iii) The remote camera system is capable of continuous operation under environmental
conditions as per 4-7-2/Table 1 and 4-7-4/Table 1;
vi) The view provided by the remote camera system is analogous to that from the bridge
wing so the ship’s side is to be visible, and is also displayed at locations where the
maneuvering of the ship may take place;
v) The upper edge of the ship’s side abeam is directly visible from locations where the
maneuvering of the ship may take place.

256 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 6 Navigation
Section 1 Visibility 3-6-1

1.3 Windows and Their Arrangements

Windows and their arrangements are to meet the following requirements:
1.3.1 Framing
Framing between navigation bridge windows is to be kept to a minimum to meet the structural
strength and stiffness requirements, and is not to be installed immediately in front of any workstations;
1.3.2 Inclination Angle
The bridge front windows are to be inclined from a vertical plane top out, at an angle of not less
than 10° and not more than 25°, see 3-6-1/Figure 6;

FIGURE 6

10º

750 mm (29.5 in.) 10º-25º

2000 mm (79 in.)

Window
1800 mm (71 in.)

Bulkhead

Deck surface

1.3.3 Glass
Polarized and tinted windows are not to be fitted, and
1.3.4 Clear View
At all times, regardless of the weather conditions, at least two of the navigation bridge front windows
are to provide a clear view, and in addition, depending on the bridge configuration, an additional
number of windows are to provide a clear view. To this end, the following, or equivalent, is to be
provided:
1.3.4(a) Sun Screens. Sunscreens with minimum color distortion. These sunscreens are to be readily
removable and not permanently installed.
1.3.4(b) Wipers and Fresh Water Wash Systems. Heavy-duty wipers, preferably provided with
an interval function, and fresh water wash systems. These wipers are to be capable of operating
independently of each other.
1.3.4(c) De-icing and De-misting Systems. De-icing and de-misting systems to be provided.
1.3.4(d) Fixed Catwalk. A fixed catwalk with guardrails, fitted forward of the bridge windows,
to enable manual cleaning of windows in the event of failure of the above systems.

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Part 3 Hull Construction and Equipment
Chapter 6 Navigation
Section 1 Visibility 3-6-1

1.3.5 Lower Edge

The height of the lower edge of the navigation bridge front windows above the bridge deck is to
be kept as low as possible. In no case is the lower edge to present an obstruction to the forward
view as described in this Section.
1.3.6 Upper Edge
The upper edge of the navigation bridge front windows is to allow a forward view of the horizon
for a person with a height of eye of 1800 mm (5 ft-11 in.) above the bridge deck at the conning
position when the vessel is pitching in heavy seas. ABS, if satisfied that an 1800 mm (5 ft-11 in.)
height of eye is unreasonable and impractical, may allow reduction of the height of eye, but not to
less than 1600 mm (5 ft-3 in.). See 3-6-1/Figure 6.

1.5 Unconventional Design

For vessels of unconventional design which cannot comply with the above requirements, arrangements are
to be provided to the satisfaction of ABS to achieve a level of visibility that is as near as practical to those
prescribed in this Section.

1.7 Articulated Tug-Barge Units (2017)

Tugboats designed to push barges as part of an Articulated Tug-Barge unit (ATB), are required to meet the
requirements of 3-6-1/1.1.1. The Length Overall is to be based on the length from the Barge’s stem to the
stern of the Tug when operating as a combined unit. The visibility is to be determined based on the largest
barge that the tugboat is designed to operate with as an articulated unit.

258 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Chapter 7: Testing, Trials and Surveys During Construction - Hull

3
CHAPTER 7 Testing, Trials and Surveys During Construction –
Hull

CONTENTS
SECTION 1 Tank, Bulkhead and Rudder Tightness Testing .............................. 260
1 General ........................................................................................... 260
3 Testing Requirements for Ships Built in Compliance with
SOLAS 1974 as Amended .............................................................. 260
3.1 Application ................................................................................... 260
3.3 Test Types and Definitions .......................................................... 261
3.5 Test Procedures .......................................................................... 262
5 Testing Requirements for Ships Not Built in Compliance with
SOLAS 1974 as Amended .............................................................. 268

TABLE 1 Testing Requirements for Tanks and Boundaries ................ 265

TABLE 2 Additional Testing Requirements for Vessels or Tanks of
Special Service ..................................................................... 267
TABLE 3 Application of Leak Testing, Coating and Provision of Safe
Access for Type of Welded Joints......................................... 267

SECTION 2 Trials.................................................................................................... 269

1 Anchor Windlass Trials ................................................................... 269
3 Bilge System Trials ......................................................................... 269
5 Steering Trials ................................................................................. 269

SECTION 3 Surveys ............................................................................................... 270

1 Construction Welding and Fabrication ............................................ 270
3 Hull Castings and Forgings ............................................................. 270
5 Piping .............................................................................................. 270

ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018 259
PART Section 1: Tank, Bulkhead and Rudder Tightness Testing

3
CHAPTER 7 Testing, Trials and Surveys During Construction –
Hull

SECTION 1 Tank, Bulkhead and Rudder Tightness Testing

(2018)

1 General
Testing to confirm the watertightness of tanks and watertight boundaries and the structural adequacy of tanks
which form the watertight subdivisions(1) of ships is to be completed. Verification of the weathertightness
of structures and shipboard outfitting is to be carried out. The tightness of all tanks and tight boundaries of
new ships and those tanks and boundaries whose structural integrity is affected by major conversions or major
repairs(2) is to be confirmed prior to the delivery of the ship or prior to the completion of the modification
or repair as relevant.
Testing procedures of watertight compartments for ships built in compliance with SOLAS 1974 as amended
are to be carried out in accordance with 3-7-1/3, unless:
i) The shipyard provides documentary evidence of the Owner’s agreement to a request to the flag
Administration for an exemption from the application of Chapter II-1, Regulation 11 of SOLAS 1974
as amended, or for an equivalency agreeing that the content of 3-7-1/5 is equivalent to Chapter II-1,
Regulation 11 of SOLAS 1974 as amended; and
ii) The above-mentioned exemption/equivalency has been granted by the responsible flag Administration.
Testing procedures of watertight compartments are to be carried out in accordance with 3-7-1/5 for ships
not built in compliance with SOLAS 1974 as amended and those ships built in compliance with SOLAS
1974 as amended for which:
i) The shipyard provides documentary evidence of the Owner’s agreement to a request to the flag
Administration for an exemption from the application of Chapter II-1, Regulation 11 of SOLAS 1974
as amended, or for an equivalency agreeing that the content of 3-7-1/5 is equivalent to Chapter II-1,
Regulation 11 of SOLAS 1974 as amended; and
ii) The above-mentioned exemption/equivalency has been granted by the responsible flag Administration.
Notes:
1 Watertight subdivision means the transverse and longitudinal subdivisions of the ship required to satisfy
the subdivision requirements of SOLAS Chapter II-1.
2 Major repair means a repair affecting structural integrity.

3 Testing Requirements for Ships Built in Compliance with SOLAS

1974 as Amended

3.1 Application
All gravity tanks which are subjected to vapor pressure not greater than 0.7 bar (0.7 kgf/cm2, 10 psi) and
other boundaries required to be watertight or weathertight are to be tested in accordance with this Subsection
and proven to be tight or structurally adequate as follows:

260 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 7 Testing, Trials and Surveys During Construction – Hull
Section 1 Tank, Bulkhead and Rudder Tightness Testing 3-7-1

3.1.1
Gravity Tanks for their structural adequacy and tightness,
3.1.2
Watertight Boundaries Other Than Tank Boundaries for their watertightness, and
3.1.3
Weathertight Boundaries for their weathertightness.
For the testing of cargo containment systems of liquefied gas carriers, the requirements in 5C-8-4/20 of the
Steel Vessel Rules will apply.
Testing of structures not listed in 3-7-1/Table 1 and 3-7-1/Table 2 is to be specially considered.

3.3 Test Types and Definitions

3.3.1
The following two types of tests are specified in this requirement.
3.3.1(a) Structural Test. A test to verify the structural adequacy of tank construction. This may be a
hydrostatic test or, where the situation warrants, a hydropneumatic test.
3.3.1(b) Leak Test. A test to verify the tightness of a boundary. Unless a specific test is indicated,
this may be a hydrostatic/hydropneumatic test or an air test. A hose test may be considered an
acceptable form of leak test for certain boundaries, as indicated by Note 3 of 3-7-1/Table 1.
3.3.2
The definition of each test type is as follows:
Hydrostatic Test: A test wherein a space is filled with a liquid to a specified head.
(Leak and Structural)
Hydropneumatic Test: A test combining a hydrostatic test and an air test, wherein a space
(Leak and Structural) is partially filled with a liquid and pressurized with air.
Hose Test: A test to verify the tightness of a joint by a jet of water with the
(Leak) joint visible from the opposite side.
Air Test: A test to verify tightness by means of air pressure differential and
(Leak) leak indicating solution. It includes tank air test and joint air tests,
such as compressed air fillet weld tests and vacuum box tests.
Compressed Air Fillet An air test of fillet welded tee joints wherein leak indicating
Weld Test: solution is applied on fillet welds.
(Leak)
Vacuum Box Test: A box over a joint with leak indicating solution applied on the
(Leak) welds. A vacuum is created inside the box to detect any leaks.
Ultrasonic Test: A test to verify the tightness of the sealing of closing devices such
(Leak) as hatch covers by means of ultrasonic detection techniques.
Penetration Test: A test to verify that no visual dye penetrant indications of potential
(Leak) continuous leakages exist in the boundaries of a compartment by
means of low surface tension liquids (i.e., dye penetrant test).

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Part 3 Hull Construction and Equipment
Chapter 7 Testing, Trials and Surveys During Construction – Hull
Section 1 Tank, Bulkhead and Rudder Tightness Testing 3-7-1

3.5 Test Procedures

3.5.1 General
Tests are to be carried out in the presence of a Surveyor at a stage sufficiently close to the
completion of work with all hatches, doors, windows, etc., installed and all penetrations including
pipe connections fitted, and before any ceiling and cement work is applied over the joints. Specific
test requirements are given in 3-7-1/3.5.4 and 3-7-1/Table 1. For the timing of application of
coating and the provision of safe access to joints, see 3-7-1/3.5.5, 3-7-1/3.5.6, and 3-7-1/Table 3.
3.5.2 Structural Test Procedures
3.5.2(a) Type and Time of Test. Where a structural test is specified in 3-7-1/Table 1 or 3-7-1/Table 2,
a hydrostatic test in accordance with 3-7-1/3.5.4(a) will be acceptable. Where practical limitations
(strength of building berth, light density of liquid, etc.) prevent the performance of a hydrostatic
test, a hydropneumatic test in accordance with 3-7-1/3.5.4(b) may be approved instead.
A hydrostatic test or hydropneumatic test for the confirmation of structural adequacy may be carried
out while the vessel is afloat, provided the results of a leak test are confirmed to be satisfactory
before the vessel is afloat.
3.5.2(b) Testing Schedule for New Construction or Major Structural Conversion.
i) Tanks which are intended to hold liquids, and which form part of the watertight subdivision
of the ship*, shall be tested for tightness and structural strength as indicated in 3-7-1/Table 1
and 3-7-1/Table 2.
ii) The tank boundaries are to be tested at least from one side. The tanks for structural test
are to be selected so that all representative structural members are tested for the expected
tension and compression.
iii) The watertight boundaries of spaces other than tanks for structural testing may be exempted,
provided that the watertightness of boundaries of exempted spaces is verified by leak tests
and inspections. Structural testing may not be exempted and the requirements for structural
testing of tanks in 3-7-1/3.5.2(b)i) to 3-7-1/3.5.2(b)ii) shall apply, for ballast holds, chain
lockers and a representative cargo hold if intended for in-port ballasting.
iv) Tanks which do not form part of the watertight subdivision of the ship*, may be exempted
from structural testing provided that the watertightness of boundaries of exempted spaces
is verified by leak tests and inspections.
* Note: Watertight subdivision means the main transverse and longitudinal subdivisions of the ship required to
satisfy the subdivision requirements of SOLAS Chapter II-1.

3.5.3 Leak Test Procedures

For the leak tests specified in 3-7-1/Table 1, tank air tests, compressed air fillet weld tests, vacuum
box tests in accordance with 3-7-1/3.5.4(d) through 3-7-1/3.5.4(f), or their combination, will be
acceptable. Hydrostatic or hydropneumatic tests may also be accepted as leak tests provided that
3-7-1/3.5.5, 3-7-1/3.5.6, and 3-7-1/3.5.7 are complied with. Hose tests will also be acceptable for
such locations as specified in 3-7-1/Table 1, note 3, in accordance with 3-7-1/3.5.4(c).
The application of the leak test for each type of welded joint is specified in 3-7-1/Table 3.
Air tests of joints may be carried out in the block stage provided that all work on the block that may
affect the tightness of a joint is completed before the test. See also 3-7-1/3.5.5(a) for the application
of final coatings and 3-7-1/3.5.6 for the safe access to joints and the summary in 3-7-1/Table 3.
3.5.4 Test Methods
3.5.4(a) Hydrostatic Test. Unless another liquid is approved, hydrostatic tests are to consist of
filling the space with fresh water or sea water, whichever is appropriate for testing, to the level
specified in 3-7-1/Table 1 or 3-7-1/Table 2. See also 3-7-1/3.5.7.
In cases where a tank is designed for cargo densities greater than sea water and testing is with fresh
water or sea water, the testing pressure height is to simulate the actual loading for those greater
cargo densities as far as practicable.

262 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 7 Testing, Trials and Surveys During Construction – Hull
Section 1 Tank, Bulkhead and Rudder Tightness Testing 3-7-1

All external surfaces of the tested space are to be examined for structural distortion, bulging and
buckling, other related damage and leaks.
3.5.4(b) Hydropneumatic Test. Hydropneumatic tests, where approved, are to be such that the
test condition, in conjunction with the approved liquid level and supplemental air pressure, will
simulate the actual loading as far as practicable. The requirements and recommendations for tank
air tests in 3-7-1/3.5.4(d) will also apply to hydropneumatic tests. See also 3-7-1/3.5.7.
All external surfaces of the tested space are to be examined for structural distortion, bulging and
buckling, other related damage and leaks.
3.5.4(c) Hose Test. Hose tests are to be carried out with the pressure in the hose nozzle maintained
at least at 2 bar (2 kgf/cm2, 30 psi) during the test. The nozzle is to have a minimum inside diameter
of 12 mm (0.5 in.) and be at a perpendicular distance from the joint not exceeding 1.5 m (5 ft).
The water jet is to impinge directly upon the weld.
Where a hose test is not practical because of possible damage to machinery, electrical equipment
insulation or outfitting items, it may be replaced by a careful visual examination of welded
connections, supported where necessary by means such as a dye penetration test or ultrasonic leak
test or the equivalent.
3.5.4(d) Tank Air Test. All boundary welds, erection joints, and penetrations, including pipe
connections, are to be examined in accordance with approved procedure and under a stabilized
pressure differential above atmospheric pressure not less than 0.15 bar (0.15 kgf/cm2, 2.2 psi) with
a leak indicating solution such as soapy water/detergent or a proprietary brand applied.
A U-tube with a height sufficient to hold a head of water corresponding to the required test
pressure is to be arranged. The cross sectional area of the U-tube is not to be less than that of the
pipe supplying air to the tank. Arrangements involving the use of two calibrated pressure gauges
to verify the required test pressure may be accepted taking into account the provisions in F5.1 and
F7.4 of IACS Recommendation 140, “Recommendation for Safe Precautions during Survey and
Testing of Pressurized Systems”.
Other effective methods of air testing, including compressed air fillet weld testing or vacuum
testing, may be considered in accordance with 3-7-1/3.5.4(i).
A double inspection is to be made of tested welds. The first is to be immediately upon applying
the leak indication solution; the second is to be after approximately four or five minutes, without
further application of leak indication solution, in order to detect those smaller leaks which may
take time to appear.
3.5.4(e) Compressed Air Fillet Weld Test. In this air test, compressed air is injected from one end
of a fillet welded joint and the pressure verified at the other end of the joint by a pressure gauge.
Pressure gauges are to be arranged so that an air pressure of at least 0.15 bar (0.15 kgf/cm2, 2.2 psi)
can be verified at each end of all passages within the portion being tested.
For limited portions of the partial penetration or fillet welded joints forming tank boundaries, such
as corners and section of the weld adjacent to the testing apparatus, the attending Surveyor may
accept the use of Magnetic Particle Inspection or Dye Penetration examination as an alternative to
fillet air testing.
Where a leaking test of partial penetration welding is required and the root face is sufficiently
large, such as 6-8 mm (0.24-0.32 inch), the compressed air test is to be applied in the same manner
as for a fillet weld.
3.5.4(f) Vacuum Box Test. A box (vacuum testing box) with air connections, gauges and an
inspection window is placed over the joint with a leak indicating solution applied to the weld cap
vicinity. The air within the box is removed by an ejector to create a vacuum of 0.20 bar (0.20 kgf/cm2,
2.9 psi) – 0.26 bar (0.27 kgf/cm2, 3.8 psi) inside the box.
3.5.4(g) Ultrasonic Test. An ultrasonic echo transmitter is to be arranged inside of a compartment
and a receiver is to be arranged on the outside. The watertight/weathertight boundaries of the
compartment are scanned with the receiver in order to detect an ultrasonic leak indication. A location
where sound is detectable by the receiver indicates a leakage in the sealing of the compartment.

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Part 3 Hull Construction and Equipment
Chapter 7 Testing, Trials and Surveys During Construction – Hull
Section 1 Tank, Bulkhead and Rudder Tightness Testing 3-7-1

3.5.4(h) Penetration Test. A test of butt welds or other weld joints using the application of a low
surface tension liquid at one side of a compartment boundary or structural arrangement. If no liquid
is detected on the opposite sides of the boundaries after the expiration of a defined period of time,
this indicates tightness of the boundaries. In certain cases, a developer solution may be painted or
sprayed on the other side of the weld to aid leak detection.
3.5.4(i) Other Test. Other methods of testing, except as provided in 3-7-1/5, may be considered
upon submission of full particulars prior to the commencement of testing.
3.5.5 Application of Coating
3.5.5(a) Final Coating. For butt joints welded by an automatic process, the final coating may be
applied any time before the completion of a leak test of spaces bounded by the joints, provided
that the welds have been carefully inspected visually to the satisfaction of the Surveyor.
Surveyors reserve the right to require a leak test prior to the application of final coating over
automatic erection butt welds.
For all other joints, the final coating is to be applied after the completion of the leak test of the
joint. See also 3-7-1/Table 3.
3.5.5(b) Temporary Coating. Any temporary coating which may conceal defects or leaks is to be
applied at the time as specified for the final coating [see 3-7-1/3.5.5(a)]. This requirement does not
apply to shop primer.
3.5.6 Safe Access to Joints
For leak tests, safe access to all joints under examination is to be provided. See also 3-7-1/Table 3.
3.5.7 Hydrostatic or Hydropneumatic Tightness Testing
In cases where the hydrostatic or hydropneumatic tests are applied instead of a specific leak test,
examined boundaries must be dew-free, otherwise small leaks are not visible.

264 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 7 Testing, Trials and Surveys During Construction – Hull
Section 1 Tank, Bulkhead and Rudder Tightness Testing 3-7-1

TABLE 1
Testing Requirements for Tanks and Boundaries (2018)
Tank or Boundary to be Tested Test Type Test Head or Pressure Remarks
The greater of
- top of the overflow,
Leak &
1 Double bottom tanks(4) - to 2.4 m (8 ft) above top of
Structural (1)
tank (2), or
- to bulkhead deck
Including pump room
double bottom and
See 3-7-1/3.5.4(d) through
2 Double bottom voids(5) Leak bunker tank protection
3-7-1/3.5.4(f), as applicable
double hull required by
MARPOL Annex I
The greater of
- top of the overflow,
Leak &
3 Double side tanks - to 2.4 m (8 ft) above top of
Structural (1)
tank (2), or
- to bulkhead deck
See 3-7-1/3.5.4(d) through
4 Double side voids Leak
3-7-1/3.5.4(f), as applicable
The greater of
Deep tanks other than those listed elsewhere Leak & - top of the overflow, or
5
in this table Structural (1) - to 2.4 m (8 ft) above top of
tank (2)
The greater of water head
- to top of the overflow,
Leak & - to 2.4 m (8 ft) above top of
6 Cargo oil tanks
Structural (1) tank (2), or
- to top of tank (2) plus setting
of any pressure relief valve
Leak & See item 16 for hatch
7 Ballast hold of bulk carriers Top of cargo hatch coaming
Structural (1) covers.
The greater of
After peak to be tested
Leak & - top of the overflow, or
8 Peak tanks after installation of stern
Structural (1) - to 2.4 m (8 ft) above top of tube
tank (2)
See 3-7-1/3.5.4(c) through
.1 Fore peak spaces with equipment Leak
3-7-1/3.5.4(f), as applicable
See 3-7-1/3.5.4(d) through
.2 Fore peak voids Leak
3-7-1/3.5.4(f), as applicable
9 See 3-7-1/3.5.4(c) through
.3 Aft peak spaces with equipment Leak
3-7-1/3.5.4(f), as applicable
After peak to be tested
See 3-7-1/3.5.4(d) through
.4 Aft peak voids Leak after installation of stern
3-7-1/3.5.4(f), as applicable
tube
See 3-7-1/3.5.4(d) through
10 Cofferdams Leak
3-7-1/3.5.4(f), as applicable
See 3-7-1/3.5.4(c) through
.1 Watertight bulkheads Leak (8)
3-7-1/3.5.4(f), as applicable (7)
11 See 3-7-1/3.5.4(c) through
.2 Superstructure end bulkheads Leak
3-7-1/3.5.4(f), as applicable
.3 Cable penetrations in watertight bulkheads Hose See 3-7-1/3.5.4(c)
See 3-2-9/9.11 of the
Watertight doors below freeboard or See 3-7-1/3.5.4(c) through Steel Vessel Rules for
12 Leak (6, 7)
bulkhead deck 3-7-1/3.5.4(f), as applicable additional test at the
manufacturer.

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Part 3 Hull Construction and Equipment
Chapter 7 Testing, Trials and Surveys During Construction – Hull
Section 1 Tank, Bulkhead and Rudder Tightness Testing 3-7-1

TABLE 1 (continued)
Testing Requirements for Tanks and Boundaries (2018)
Tank or Boundary to be Tested Test Type Test Head or Pressure Remarks
See 3-7-1/3.5.4(d) through
13 Double plate rudder blades Leak
3-7-1/3.5.4(f), as applicable
See 3-7-1/3.5.4(c) through
14 Shaft tunnels clear of deep tanks Leak (3)
3-7-1/3.5.4(f), as applicable
See 3-7-1/3.5.4(c) through
15 Shell doors Leak (3)
3-7-1/3.5.4(f), as applicable
Hatch covers closed by
Weathertight hatch covers and closing See 3-7-1/3.5.4(c) through
16 Leak (3, 7) tarpaulins and battens
appliances 3-7-1/3.5.4(f), as applicable
excluded
See 3-7-1/3.5.4(c) through In addition to structural
17 Dual purpose tanks/dry cargo hatch covers Leak (3, 7)
3-7-1/3.5.4(f), as applicable test in item 6 or 7
Leak &
18 Chain lockers Top of chain pipe
Structural (1)
L.O. sump tanks and other similar See 3-7-1/3.5.4(c) through
19 Leak (9)
tanks/spaces under main engine 3-7-1/3.5.4(f), as applicable
The greater of
- ballast pump maximum
Leak &
20 Ballast ducts pressure, or
Structural (1)
- setting of any pressure relief
valve
The greater of
- top of the overflow, or
- to 2.4 m (8 ft) above top of
Leak & tank (2), or
21 Fuel Oil Tanks
Structural (1) - to top of tank (2) plus setting
of any pressure relief valve,
or
- to bulkhead deck
Notes:
1 (2018) Refer to 3-7-1/3.5.2(b).
2 Top of tank is the deck forming the top of the tank, excluding any hatchways.
3 (2018) Hose Test may also be considered as a medium of the test. See 3-7-1/3.3.2.
4 Including tanks arranged in accordance with the provisions of SOLAS regulation II-1/9.4
5 (2016) Including duct keels and dry compartments arranged in accordance with the provisions of SOLAS regulation
II-1/11.2 and II-1/9.4 respectively, and/or oil fuel tank protection and pump room bottom protection arranged in
accordance with the provisions of MARPOL Annex I, Chapter 3, Part A regulation 12A and Chapter 4, Part A,
regulation 22, respectively.
6 Where water tightness of a watertight door has not confirmed by prototype test, testing by filling watertight spaces
with water is to be carried out. See SOLAS regulation II-1/16.2 and MSC/Circ.1176.
7 (2018) As an alternative to the hose testing, other testing methods listed in 3-7-1/3.5.4(g) through 3-7-1/3.5.4(i) may
be applicable subject to adequacy of such testing methods being verified. See SOLAS regulation II-1/11.1. For watertight
bulkheads (item 11.1) alternatives to the hose testing may only be used where a hose test is not practicable.
8 (2018) A “Leak and structural test”, see 3-7-1/3.5.2(b), is to be carried out for a representative cargo hold if
intended for in-port ballasting. The filling level requirement for testing cargo holds intended for in-port ballasting
is to be the maximum loading that will occur in-port as indicated in the loading manual.
9 (2018) Where L.O. sump tanks and other similar spaces under main engines intended to hold liquid form part of
the watertight subdivision of the ship, they are to be tested as per the requirements of Item 5, Deep tanks other than
those listed elsewhere in this table.

266 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
Part 3 Hull Construction and Equipment
Chapter 7 Testing, Trials and Surveys During Construction – Hull
Section 1 Tank, Bulkhead and Rudder Tightness Testing 3-7-1

TABLE 2
Additional Testing Requirements for Vessels
or Tanks of Special Service (2018)
Type of Vessels Type of
Structures to be Tested Hydrostatic Testing Head Remarks
or Tanks Testing
1 Liquefied Gas Ballast or Fuel Oil Tanks Leak & The greater of See 5C-8-4/20 of
Carriers adjacent to or between Structural - the top of overflow, or the Steel Vessel
Cargo Tank Hold Spaces - to 2.4 m (8 ft) above top of Rules for testing
tank (2) requirements
applicable to
integral cargo tanks,
independent cargo
tanks and hull
structure supporting
membrane or
semi-membrane
cargo tanks.
2 Edible Liquid Independent Tanks Leak & The greater of
Tanks Structural - the top of overflow, or
- to 0.9 m (3 ft) above top of
tank (2)
3 Chemical Integral or Independent Tanks Leak & The greater of Where a cargo tank
Carriers Structural - to 2.4 m (8 ft) above top of is designed for the
tank (2), or carriage of cargoes
- to top of tank (2) plus setting with specific
of any pressure relief valve gravities larger than
1.0, an appropriate
additional head is
to be considered.
Notes:
1 (2018) See 3-7-1/3.5.2(b).
2 (1 July 2013) Top of tank is the deck forming the top of the tank, excluding any hatchways.

TABLE 3
Application of Leak Testing, Coating and Provision of Safe Access
for Type of Welded Joints (2016)
Coating (1) Safe Access (2)
After
Type of Welded Joints Leak Testing Before Leak Testing
Leak Testing Structural Test
Leak Testing & Before
Structural Test
Automatic Not required Allowed(3) N/A Not required Not required
Butt Manual or
Required Not allowed Allowed Required Not required
Semi-automatic(4)
Boundary
Fillet including Required Not allowed Allowed Required Not required
penetrations
Notes:
1 Coating refers to internal (tank/hold coating), where applied, and external (shell/deck) painting. It does not refer to
shop primer.
2 Temporary means of access for verification of the leak testing.
3 The condition applies provided that the welds have been carefully inspected visually to the satisfaction of the Surveyor.
4 (2016) Flux Core Arc Welding (FCAW) semiautomatic butt welds need not be tested provided that careful visual
inspections show continuous uniform weld profile shape, free from repairs, and the results of the Rule and Surveyor
required NDE testing show no significant defects.

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Part 3 Hull Construction and Equipment
Chapter 7 Testing, Trials and Surveys During Construction – Hull
Section 1 Tank, Bulkhead and Rudder Tightness Testing 3-7-1

5 Testing Requirements for Ships Not Built in Compliance with SOLAS

1974 as Amended

5.1
Testing procedures are to be carried out in accordance with the requirements of 3-7-1/3 in association with
the following alternative procedures for 3-7-1/3.5.2(b) “Testing Schedule for New Construction or Major
Structural Conversion” and alternative test requirements for 3-7-1/Table 1.

5.3
The tank boundaries are to be tested from at least one side. The tanks for structural test are to be selected
so that all representative structural members are tested for the expected tension and compression.

5.5
Structural tests are to be carried out for at least one tank of a group of tanks having structural similarity
(i.e., same design conditions, alike structural configurations with only minor localized differences
determined to be acceptable by the attending Surveyor) on each vessel provided all other tanks are tested for
leaks by an air test. The acceptance of leak testing using an air test instead of a structural test does not
apply to cargo space boundaries adjacent to other compartments in tankers and combination carriers or to
the boundaries of tanks for segregated cargoes or pollutant cargoes in other types of ships.

5.7
Additional tanks may require structural testing if found necessary after the structural testing of the first
tank.

5.9
Where the structural adequacy of the tanks of a vessel were verified by the structural testing required in
3-7-1/Table 1, subsequent vessels in the series (i.e., sister ships built from the same plans at the same
shipyard) may be exempted from structural testing of tanks, provided that:
i) Watertightness of boundaries of all tanks is verified by leak tests and thorough inspections are
carried out.
ii) Structural testing is carried out for at least one tank of each type among all tanks of each sister
vessel.
iii) Additional tanks may require structural testing if found necessary after the structural testing of the
first tank or if deemed necessary by the attending Surveyor.
For cargo space boundaries adjacent to other compartments in tankers and combination carriers or boundaries
of tanks for segregated cargoes or pollutant cargoes in other types of ships, the provisions of 3-7-1/5.3
shall apply in lieu of 3-7-1/5.5.

5.11
Sister ships built (i.e., keel laid) two years or more after the delivery of the last ship of the series, may be
tested in accordance with 3-7-1/5.5 at the discretion of the Surveyor, provided that:
i) General workmanship has been maintained (i.e., there has been no discontinuity of shipbuilding or
significant changes in the construction methodology or technology at the yard, and shipyard personnel
are appropriately qualified and demonstrate an adequate level of workmanship as determined by
the Surveyor).
ii) An NDT plan is implemented and evaluated by the Surveyor for the tanks not subject to structural
tests. Shipbuilding quality standards for the hull structure during new construction are to be reviewed
and agreed during the kick-off meeting. Structural fabrication is to be carried out in accordance
with IACS Recommendation 47, “Shipbuilding and Repair Quality Standard”, or a recognized
fabrication standard to the satisfaction of the attending Surveyor prior to the commencement of
fabrication/construction. The work is to be carried out in accordance with the Rules and under
survey of the Surveyor.

268 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018
PART Section 2: Trials

3
CHAPTER 7 Testing, Trials and Surveys During Construction –
Hull

SECTION 2 Trials

1 Anchor Windlass Trials (1 July 2012)

Each windlass is to be tested under working conditions after installation onboard to demonstrate satisfactory
operation. Each unit is to be independently tested for braking, clutch functioning, lowering and hoisting of
chain cable and anchor, proper riding of the chain over the chain lifter, proper transit of the chain through
the hawsepipe and the chain pipe, and effecting proper stowage of the chain and the anchor. It is to be
confirmed that anchors properly seat in the stored position and that chain stoppers function as designed if
fitted. Also, it is to be demonstrated that the windlass is capable of lifting each anchor with 82.5 m (45 fathoms)
length of chain submerged and hanging free. The braking capacity is to be tested by intermittently paying
out and holding the chain cable by means of the application of the brake. Where the available water depth
is insufficient, the proposed test method will be specially considered.

3 Bilge System Trials

All elements of the bilge system are to be tested to demonstrate satisfactory pumping operation, including
emergency suctions and all controls. Upon completion of the trials, the bilge strainers are to be opened,
cleaned and closed up in good order.

5 Steering Trials
Refer to 4-3-3/15.3 for the technical details of the steering trials.

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PART Section 3: Surveys

3
CHAPTER 7 Testing, Trials and Surveys During Construction –
Hull

SECTION 3 Surveys

1 Construction Welding and Fabrication

For surveys of hull construction welding and fabrication, refer to Chapter 4 of the ABS Rules for Materials
and Welding (Part 2) and the ABS Guide for Nondestructive Inspection of Hull Welds.

3 Hull Castings and Forgings

For surveys in connection with the manufacture and testing of hull castings and forgings, refer to Chapter 1
of the ABS Rules for Materials and Welding (Part 2).

5 Piping
For surveys in connection with the manufacture and testing of piping, refer to Part 4, Chapter 4.

270 ABS RULES FOR BUILDING AND CLASSING STEEL VESSELS UNDER 90 METERS (295 FEET) IN LENGTH . 2018