The Minister of Higher Education National School of

and Scientific Research

Engineers Sfax
  
Sfax University Electromechanical
   student
National Institute of Applied Science and
Technology

Host Company:

Engineering Procurement and Project

Management
Subject:
Development of sizing tool for storage tanks according to API 650 and
CODRES
Development of a comparative study between the two Codes"

Directed by : Zied ZOUARI

Company Supervisor: M. Eya ABDALLAH **** ENIS Supervisor: Mr. Ahmed FRIKHA

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 Acknowledgement

First and foremost I would like to thank God, the Almighty, for giving me strength and
courage to fulfill this work. I could never have done this without the faith I have in
you.

My deepest gratitude is also due to the board of supervisors for devoting me from their
precious time to evaluate my work, Ms Eya ABDALLAH and Mr. Ahmed FRIKHA.

The supervision and support that they gave truly help the progression and smoothness
of this work.

Great deals appreciated go of all the staff in EPPM for their help and valuable advices.

I would like to express my appreciation to all those who gave me the possibility to
complete this report.

Last but not least, I wish to express my love and gratitude to my treasured family and
my friends, for their support and limitless love through the duration of my studies.

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 Table of Contents
Table of Contents…………………………………………………………………………..…1
List of figures……………………………………………………………………………..…..2
List of tables………………………………………………………………………………..…3
ABSTRACT……………………………………………………………………………..……4
INTRODUCTION………………………………………………………………………….…5

Chapter 0: General presentation……………………………………………….……..8

I.0.1 EPPM presentation……………………………………………………………………....9
I.0.1.1.Historical overview…………………………………………………………………….9
I.0.1.2Profile……………………………………………………………………………….......9
I.0.1.3.Distribution of EPPM around the world…………………………………………........10
1.0.1.4. Organizational chart………………………………………………………………….11

Chapter I : storage tank.................................................................................... 12

I.1Definition………………………………………………………………………….……….13

I.2.Different types…………………………………………………………………………….13

I.2.Tank compounds…………………………………………………………………………14

I.3.Different tank design code………………………………………………………………..15

I.4.Tank construction/erection……………………….………………………………………16

I.5.1.Design considerations…………………………………………………………………..17

I.5.2Mechanical Failure………………………………………………………………………17

I.6.Tank inspection: METHODS OF EXAMINING JOINTS……………………………....18

I.6.1. Radiographic Method: ………………………………………………………………....19

I.6.2. Number and Location of Radiographs…………………………………………………22

I.6.3. Liquid Penetrant Examination…………………………………………………............24

I.6.4. Visual Examination: ………………………………………………………….…….....26

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I.6.5. Vacuum Testing……………………………………………………………………….26
I.7.Conclusion……………………………..............................................................................26

Chapter II :API STANDARD 650……...……………………………………….......27

II.1scope ……………………………………………………………………………………..28

II.2General considerations………………………………………………………………...…28

II.3.DESIGN: ……………………………………………………………………………......29
II.3.1.MATERIALS……………………………………………………………………….....29
II.3.2. Plates: …………………………………………………………………………………30
II.3.3 Joints…………………………………………………………………………….……..31
II.3.4. Typical Joints: ……………………………………………………………….………..31
II.3.5. Tank Capacity…………………………………………………………………….……34
II.3.6. Special Considerations………………………....………………………………..….....35
II.3.7. Bottom Plates…………………………………………………………………….……36
II.3.8. Annular Bottom Plates………………………………………………..……………….37
II.3.9. Shell Design………………………………………………………………..………….38
II.3.10. Allowable Stress.……………………………………………………..………………39
II.3.11Wind load……………………………………………………………………………...40
II.3.12.Anchorage of the tank……………………………………………………………...…41
II.3.13.Calculation of Thickness by the 1-Foot Method……………………………………..41
II.3.14.Calculation of Thickness by Elastic Analysis………………………………………..42

Chapter III: CODRES standard…..………………………………………….….…..43

II.1. Design data: ………………………………………………………………………….....44
II.2. Design and Calculations: …………………………………………………………….....45
a) Shell design……………………………………………………………………….…….....45
b. Bottom thickness:.………………………………………………………………...……….46
c. Roof calculation: ………………………………………………………………………….47
d. Joint shell and roof: ……………………………………………………………………….48

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e. Anchor Calculation……………………………………………………………….……….48

Chapter IV : Verification excel calculation …………………………...………….51

IV.1. API standard: …………………………………………………………………….........52
IV.2. CODRES standard……………………………………………………….…………….58

Chapter V: Comparasons and Conclusion…………………………….………….64

References………………………………………………………………………………...70

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 List of figures

Figure 1: Distribution of EPPM subsidiaries around the world……………………………...11

Figure 2: compound tank ………………….………………………………………………....16
Figure 3—Radiographic Requirements for Tank Shells………………..……………………21
Figure4.a : shells…………………………………………………………………………….32
Figure4.b : welding tank………………………………………………………...……………32
Figure 5—Typical Vertical Shell Joints……………………………………………………...34
Figure 6—Typical Horizontal Shell Joints………………………………………………..….34
Figure 7—Spacing of Three-Plate Welds at Annular Plates…………………………………35
Figure 8—Storage Tank……………………………………………………………………...36
Figure 9—Drip Ring (Suggested Detail) …………………………………………………….37
Figure 10 : tank…………………………………………………………………………….....43
Figure 11 :The shell-roof junction……………………………………………...…………….48
figure 12: anchor……………………………………………………………………….……..49

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 List of tables

Table1: Annular Bottom-Plate Thicknesses (tb) (SI) …………………………………..……39

Table2 : thickness………………………………………………………………………......…39
Table 3 : Minimum nominal thickness of the shell [ ] …………………………………….…46
Table 4:Minimum nominal thickness ef of the bottom plate (corrosion allowance excluded).47
Table 5 : Minimum dimensions of edge angles for tanks with fixed roofs…………………..48

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 ABSTRACT

The demand for petroleum products are on the increase and the need for reliable and safe
storage facilities is on increasing demand. This has called for indigenous design and
development of these facilities to augment the existing ones, and hence, to conserve foreign
exchange and enhance job creation. In this work attempt has been made to design storage tank
capable of holding a 10 million liter of DPK, PMS and AGO. Appropriate design codes and
standard are applied, an adequate design method is chosen, and material selection was done in
consonance with the requirements of the recent editions of API 650 and IS 803. Design
specifications and Sketches of the storage tank are presented. Fabrication and erection
procedures, examination, inspection and maintenance routine for the tank.

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 INTRODUCTION

Tanks are widely used for storing a range of substances in both liquid and gaseous state meant
to serve industrial or domestic purpose. These tanks may usually be installed below or above
the ground with a support or an appropriate foundation to hold its weight. There are numerous
types of tanks designed to meet different storage needs in the industry, these tanks can be
easily differentiated by their physical features like roof type, body or shell configuration, and
stance position if it is either horizontally or vertically positioned. Tanks are designed using
codes and standards with an appropriate design method. API 650 standards establishes
minimum requirements for material, design, fabrication, erection, and testing for vertical,
cylindrical, above-ground, closed-top, and open-top, welded storage tanks in various sizes,
and capacities for internal pressures approximating atmospheric .
The importance, and effect of oil and its related products, in politics, technology and
especially in the global market is compelling.

All effort should be geared towards attaining self-sufficiency in meeting our petroleum
products demands through local refining. He further suggested that this could be achieved by
properly maintaining all the local refineries and building new ones both publicly and
privately. Hence the need for indigenous design and installation of bulk storage tanks in
refineries and depots to effectively store these petroleum products instead of dependence on
turnkey design by foreign experts.

Also, Practicing engineers face many issues and challenges when designing liquid storage
tanks. These challenges are generally either in the application of the current design codes
and standards, or in choosing an appropriate design method (Lisa, 2005). The design of
storage tanks are influenced by economic factors, regulatory requirements, the liquid to be
stored, internal pressures, external environmental forces, corrosion protection, and welding
needs.The design and safety of storage

Facilities have become a great concern, failures and other plight experienced by petroleum
industries can be associated to design factors or considerations not fully satisfied. Storage
tank failure can also be attributed to poor design. To properly address these issues and
challenges, it is recommended that appropriate design codes and standards are applied, an

6
adequate design method is chosen, appropriate material selection is done and stress analysis
performed to ascertain the strength and reliability of the tank against failure. This work
therefore strictly applied the twelfth edition of API 650 and IS 803 (Reaffirmed 2006)
CODRES standard in the design. It aims at revealing the procedures involved in correctly
applying the standard for welded tanks intended for oil storage and serve as a guide to
prospective investors.

And There are several types of storage tanks, e.g., above-ground, flat-bottomed, cylindrical
tanks for the storage of refrigerated liquefied gases, petroleum, etc., steel or concrete silos for
the storage of coke, coal, grains, etc., steel, aluminum, concrete or FRP tanks including
elevated tanks for the storage of water, spherical tanks (pressure vessels) for the storage of
high pressure liquefied gases, and under-ground tanks for the storage of water and oil. The
trend in recent years is for larger tanks, and as such the seismic design for these larger storage
tanks has become more important in terms of safety and the environmental impact on society
as a whole.

The failure mode of the storage tank subjected to a seismic force varies in each structural
type, with the structural characteristic coefficient (Ds) being derived from the relationship
between the failure mode and the seismic energy transferred to, and accumulated in the
structure. A cylindrical steel tank is the most common form of storage tank and its normal
failure mode is a buckling of the cylindrical shell, either in the so called Elephant Foot Bulge
(EFB), or as Diamond Pattern Buckling (DPB). The Ds value was originally calculated with
reference to experimental data obtained from cylindrical shell buckling, but was later re-
assessed and modified based on the restoring force characteristics of the structure after
buckling. Those phenomena at the Hanshin-Awaji Great Earthquake and the Niigataken
Chuetu-oki Earthquake were the live data to let us review the Ds value. For the EFB, which is
the typical buckling mode of a cylindrical shell storage tank for petroleum, liquefied
hydrocarbon gases, etc., it became possible to ascertain the buckling strength by experiments
on a cylindrical shell by applying an internal hydrodynamic pressure, an axial compressive
force, and a shear force simultaneously.

The seismic design calculations for other types of storage tanks have been similarly reviewed
and amended to take into account data obtained from recent experience and experiments.

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Design recommendation for sloshing phenomena in tanks has been added in this publication.
Design spectra for sloshing, spectra for long period range in other words, damping ratios for
the sloshing phenomena and pressures by the sloshing on the tank roof have been presented.

For above-ground vertical cylindrical storage tanks without any restraining element, such as
anchor bolts or straps, to prevent any overturning moment, only the bending resistance due to
the uplift of the rim of bottom plate exists. This recommendation shows how to evaluate the
energy absorption value given by plasticity of the uplifted bottom plate for unanchored tanks,
as well as the Ds value of an anchored cylindrical steel-wall tank.

As the number of smaller under-ground tanks used for the storage of water and fuel is
increasing in Japan, the Sub-committee has added them in the scope of the recommendation
and provided a framework for the seismic design of under-ground tanks. The recommendation
has accordingly included a new response displacement method and a new earth pressure
calculation method, taking into account the design methods adopted by the civil engineering
fraternity.[1]

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9
I.0.1. EPPM presentation
I.0.1.1.Historical overview
For more than 20 years, EPPM present structure has been active in Tunisia and abroad in
Engineering, Procurement, Construction, Management as well as turnkey projects.

Established in 1993 by a group of experimented managers and engineers, who brought their
know-how, skills and acquired experience, EPPM was been developed from a national to an
international company.

Currently, EPPM, throughout its qualified team, can manage and take charge of international
projects of around 100 Million USD.

I.0.1.2Profile

Business Name: E.P.P.M « Engineering Procurement & Project Management »

Share Capital: 5 000 000 $

Year of Establishment: 1993

Legal Form: Shares Capital

Sector: EPC Contractor in Oil & Gas, Water Treatment and Industrial Plants.

Head Office: Silver Street, Fatma Building -Lake Gardens – 1053 Tunis – Tunisia.

EPPM, is a privately owned company with headquarters in Tunis, it has also subsidiaries with
offices around the world.

EPPM provides a wide range of services including:

•Engineering Services,
•Procurement Services,
•Project Management,
•Construction Services,
•Commissioning & Start-up,
•Operating & Maintenance.

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I.0.1.3Distribution of EPPM around the world:

Since 1993, more than 150 projects have been carried out in Africa and the Middle East. With
more than two decades of experience and commitment around the world, it has set up 10
subsidiaries in different countries, such as; EPPM Algeria, EPPM Libya, EPPM Angola, EPPM
Republic of Congo, EPPM Kingdom of Saudi Arabia, EPPM United Arab Emirates (Dubai and
Abu Dhabi), EPPM Republic of Iraq, EPPM State of Qatar and EPPM Sultanate of Oman .

Figure 1: Distribution of EPPM subsidiaries around the world

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1.0.1.4. Organizational chart:
The EPPM has a well-defined organization to be able to manage its people as well as its
activities. As an illustration, here is the organization chart of the company below. Each
division is subdivided within itself into several departments, and each of them has a specific
job to ensure the smooth running of the work process.

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13
I.1.definition

Storage tanks are containers that hold liquids, compressed gases (gas tank; or in U.S.A
"pressure vessel", which is not typically labeled or regulated as a storage tank) or mediums
used for the short- or long-term storage of heat or cold.The term can be used for reservoirs
(artificial lakes and ponds), and for manufactured containers. The usage of the word tank for
reservoirs is uncommon in American English but is moderately common in British English. In
other countries, the term tends to refer only to artificial containers.

In the USA, storage tanks operate under no (or very little) pressure, distinguishing them from
pressure vessels. Storage tanks are often cylindrical in shape, perpendicular to the ground with
flat bottoms, and a fixed frangible or floating roof. There are usually many environmental
regulations applied to the design and operation of storage tanks, often depending on the nature
of the fluid contained within.

I.2.Different types:

* Types of storage tanks

-Domed external floating roof tanks.

-Horizontal tanks.

-Pressure tanks.

-Variable vapor space tanks.

-LNG (Liquefied Natural Gas) tanks.

Also there is

-Spheres – Used to storing products at pressures above 35 kPa.

-Spheroids – Spherical in shape except that it is somewhat flattened. They are used to storing
products above 35 kPa.

-Horizontal cylindrical tanks – Working pressure of these tanks can be from 100 to 7000 kPa
or even greater. They often have hemispherical heads.

14
-Fixed Roofs – Roofs that are permanently attached to the tank shell. Welded tanks of 80 m3
capacity and larger may be provided with a frangible roof in which case the design pressure
shall not exceed the equivalent pressure of the dead weight of the roof.

-Floating Roof – Tank roof floats over the contents. They are designed to move vertically in
the tank to maintain a constant void between the surface of liquid and the roof. It is fabricated
in a way so as to provide a constant seal between the periphery of the roof and the shell.
Internal floating roof tanks with external fixed roofs are used in areas of extreme snowfall.

-Bolted – designed as segmental elements that are assembled on site to provide any
configuration required. They offer an advantage of easy transportation and are erected by
hand.

+Typically the type of storage tank is selected based upon capacity and vapor pressure of the
product being stored. The working pressure required depends upon the vapor pressure, the
temperature variations of the liquid surface

I.2.Tank compounds:

Pressure vessels are subject to a variety of loads and other conditions that cause stress and can
result in failure and there are a number of design features associated with pressure vessels that
need to be carefully considered.

Discontinuities such as vessel ends, changes of cross-section and changes of thickness;

Joints (bolted and welded);

Bimetallic joints;

Holes and openings;

Flanges;

Nozzles and connections;

Bolt seating and tightening;

Supports and lugs.

Emission characteristics of volatile organic compounds (VOC) emitted from the tank farm of
petroleum refinery were evaluated in this study in order to analyze for the potential impacts
on health and odor nuisance problems. Estimation procedures were carried out by using the

15
U.S.EPA TANK 4.0.9d emission model in conjunction with direct measurements of gas phase
of each stored liquid within aboveground storage tanks. Results revealed that about 61.12% of
total VOC emitted from the tank farm by volume were alkanes, in which pentane were richest
(27.4%), followed by cyclopentane (19.22%), propene (19.02%), and isobutene (14.22%).
Mostly of pentane (about 80%) were emitted from the floating roof tanks contained crude oil
corresponded to the largest annual throughput of crude oil as compared with other petroleum
distillates. Emission data were further analyzed for their ambient concentration using the
AERMOD dispersion model in order to determine the extent and magnitude of odor and
health impacts caused by pentane. Results indicated that there was no health impact from
inhalation of pentane. However, predicted data were higher than the odor threshold values of
pentane which indicated the possibility of odor nuisance problem in the vicinity areas of the
refinery. In order to solve this problem, modification of the type of crude oil storage tanks
from external floating roof to domed external floating roof could be significant success in
reduction of both emissions and ambient concentrations of VOC from petroleum refinery tank
farm.

Figure 2: tank compounds

I.3.Different tank design code:

Two principal codes and standards are employed in the design and manufacture of pressure
vessels - the American ASME VIII system and BS 5500 in the UK. Importantly both of these
demand adherence to satisfaction in the design and manufacturing process of an independent

16
inspection authority. This authority is responsible for adherence during both the design and
construction phases in accordance with the standard code. The codes and standards cover
design, materials of construction, fabrication (manufacture and workmanship), inspection and
testing, and form the basis of agreement between the manufacturer and customer and the
appointed independent inspection authority. These codes relate to vessels fabricated in carbon
and alloy steels and aluminium.

Computer programmes to aid the design of vessels to BS 5500 and the ASME VIII codes are
commercially available.

I.4.Tank construction/erection:

One of our most appreciated innovations on the world market is the Bygging-Uddemann
steel tank construction set-up. The steel tank construction set-up is a very cost-efficient way
of constructing large-volume cisterns and has been developed from our knowledge of
controlled heavy lifting technique with hydraulic jacks.

The Bygging-Uddemann method was introduced at the end of the 1950s to rationalize the
erection of steel cisterns for various storage purposes. The method is used for cisterns of
various design of all sizes. The construction and welding work is carried out entirely on the
ground. This gives a high degree of safety and precision in the workmanship and facilitates
the inspections required.

All work takes place under adequate protection and safety for the workmen. Most of the
welding work is carried out inside the cistern, independently of the weather conditions. The
method reduces construction time.

Bygging Uddemann has been leading steel tank manufacturers in the industry for years,
contact us for construction of steel tank

With the know-how to meet specific requirements and specifications, and using a variety of
metals such as stainless, carbon steel and aluminum, for example Ideas IT have successfully
fabricated and installed tanks for food and beverage and chemical industry clients to suit a
range of uses including syrup, juice, milk and water tanks, as well as chemical, oil, fuel and
CIP tanks. We have further experience with pressure vessels, cookers, jacketed and insulated
tanks.

17
In addition to tank fabrication and supply, we can assist with the accompanying process
pipework, pumps, valves and structural platforms.

I.5.1.Design considerations:
Factors that should be taken into account in the design process for pressure vessels include:

Internal and external static and dynamic pressures;

Ambient and operational temperatures;

Weight of vessel and contents;

Wind loading;

Residual stress, localised stress, thermal stress etc.;

Stress concentrations;

Reaction forces and moments from attachments, piping etc;

Fatigue;

Corrosion/erosion;

Creep;

Buckling.

Failure modes

Pressure vessels are subject to a variety of loads and other conditions that cause stress and in
certain cases may cause serious failure. Any design should take into account the most likely
failure modes and causes of deterioration. Deterioration is possible on all vessel surfaces in
contact with any range of organic or inorganic compounds, with contaminants, or fresh water,
with steam or with the atmosphere. The form of deterioration may be electrochemical,
chemical, mechanical or combinations of all.

I.5.2Mechanical Failure

The most common causes of mechanical failure in process plant are:

Faulty materials;

Faulty fabrication and assembly;

18
Excessive stress;

External loading including reaction forces;

Overpressure;

Overheating;

Mechanical and thermal fatigue;

Mechanical shock;

Brittle failure;

Creep;

Corrosion failure.

Corrosion Failure

The most common corrosion mechanisms are:

General corrosion;

Crevice corrosion;

Corrosion pitting;

External corrosion including corrosion beneath lagging;

Stress corrosion cracking;

Corrosion fatigue.

I.6.Tank inspection: METHODS OF EXAMINING JOINTS:

IV.1. Radiographic Method:

Radiographic examination is required for shell butt-welds, annular-plate butt-welds and flush-
type connections with butt-welds. Radiographic examination is not required for the following:
roof-plate welds, bottom-plate welds, welds joining the top angle to either the roof or shell,
welds joining the shell plate to the bottom plate, welds in nozzle and manway necks made
from plate, or appurtenance welds to the tank. [2]

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IV.2.Number and Location of Radiographs

a)For butt-welded joints in which the thinner shell plate is less than or equal to 10 mm (3/8
in.) thick, one spot radiograph shall be taken in the first 3 m (10 ft) of completed vertical joint
of each type and thickness welded by each welder or welding operator. The spot radiographs
taken in the vertical joints of the lowest course may be used to meet the requirements of Note
3 in Figure 8.1 for individual joints. Thereafter, without regard to the number of welders or
welding operators, one additional spot radiograph shall be taken in each additional 30 m (100
ft) (approximately) and any remaining major fraction of vertical joint of the same type and
thickness. At least 25 % of the selected spots shall be at junctions of vertical and horizontal
joints, with a minimum of two such intersections per tank. In addition to the foregoing
requirements, one random spot radiograph shall be taken in each vertical joint in the lowest
course.

b)For butt-welded joints in which the thinner shell plate is greater than 10 mm (3/8 in.) but
less than or equal to 25 mm (1 in.) in thickness, spot radiographs shall be taken according to
Item a. In addition, all junctions of vertical and horizontal joints in plates in this thickness
range shall be radiographed; each film shall clearly show not less than 75 mm (3 in.) of
vertical weld and 50 mm (2 in.) of weld length on each side of the vertical intersection. In the
lowest course, two spot radiographs shall be taken in each vertical joint: one of the
radiographs shall be as close to the bottom as is practicable, and the other shall be taken at
random.

c) Vertical joints in which the shell plates are greater than 25 mm (1 in.) thick shall be fully
radiographed. All junctions of vertical and horizontal joints in this thickness range shall be
radiographed; each film shall clearly show not less than 75 mm (3 in.) of vertical weld and 50
mm (2 in.) of weld length on each side of the vertical intersection.

d)The butt-weld around the periphery of an insert plate that extends less than the adjacent
shell course height and that contains shell openings (i.e. nozzle, manway, flush-type cleanout,
flush type shell-connection) and their reinforcing elements shall be completely radiographed.

20
Figure 3—Radiographic Requirements for Tank Shells [3]

21
The finished surface of the weld reinforcement at the location of the radiograph shall either be
flush with the plate or have a reasonably uniform crown not to exceed the following values:

*Determination of Limits of Defective Welding

When a section of weld is shown by a radiograph to be unacceptable under the provisions or

the limits of the deficient welding are not defined by the radiograph, two spots adjacent to the
section shall be examined by radiography; however, if the original radiograph shows at least
75 mm (3 in.) of acceptable weld between the defect and any one edge of the film, an
additional radiograph need not be taken of the weld on that side of the defect. If the weld at
either of the adjacent sections, additional spots shall be examined until the limits of
unacceptable welding are determined, or the erector may replace all of the welding performed
by the welder or welding operator on that joint. If the welding is replaced, the inspector shall
have the option of requiring that one radiograph be taken at any selected location on any other
joint on which the same welder or welding operator has welded. If any of these additional
spots, the limits of unacceptable welding shall be determined as specified for the initial
section.

So The Manufacturer shall prepare a radiograph map showing the final location of all
radiographs taken along with the film identification marks.

After the structure is completed, the films shall be the property of the Purchaser unless
otherwise agreed upon by the Purchaser and the Manufacturer

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IV.3. Liquid Penetrant Examination

The Manufacturer shall determine and certify that each liquid penetrant examiner meets the
following requirements.

a) Has vision (with correction, if necessary) to enable him to read a Jaeger Type 2 standard
chart at a distance of not less than 300 mm (12 in.) and is capable of distinguishing and
differentiating contrast between the colors used. Examiners shall be checked annually to
ensure that they meet these requirements.

b) Is competent in the technique of the liquid penetrant examination method for which he is
certified, including making the examination and interpreting and evaluating the results;
however, where the examination method consists of more than one operation, the examiner
may be certified as being qualified for one or more of the operations.

IV.4. Visual Examination:

The Manufacturer shall determine and certify that each visual examiner meets the following
requirements.

a) Has vision (with correction, if necessary) to be able to read a Jaeger Type 2 standard chart
at a distance of not less than 300 mm (12 in.) and is capable of passing a color contrast test.
Examiners shall be checked annually to ensure that they meet this requirement;

b) Is competent in the technique of the visual examination, including performing the

examination and interpreting and evaluating the results; however, where the examination
method consists of more than one operation, the examiner performing only a portion of the
test need only be qualified for the portion that the examiner performs.

-A weld shall be acceptable by visual examination if the inspection shows the following.

a) There are no crater cracks, other surface cracks or arc strikes in or adjacent to the welded
joints.

23
b) Maximum permissible undercut is 0.4 mm (1/64 in.) in depth for vertical butt joints,
vertically oriented permanent attachments, attachment welds for nozzles, manholes, flush-
type openings, and the inside shell-to-bottom welds. For horizontal butt joints, horizontally
oriented permanent attachments, and annular-ring butt joints, the maximum permissible
undercut is 0.8 mm (1/32 in.) in depth.

c) The frequency of surface porosity in the weld does not exceed one cluster (one or more
pores) in any 100 mm (4 in.) of length, and the diameter of each cluster does not exceed 2.5
mm (3/32 in.).

d) The reinforcement of the welds on all butt joints on each side of the plate shall not exceed
the following thicknesses:

-A weld that fails to meet the criteria shall be reworked before hydrostatic testing as follows:

a) Any defects shall be removed by mechanical means or thermal gouging processes. Arc
strikes discovered in or adjacent to welded joints shall be repaired by grinding and rewelding
as required. Arc strikes repaired by welding shall be ground flush with the plate.

b) Rewelding is required if the resulting thickness is less than the minimum required for
design or hydrostatic test conditions. All defects in areas thicker than the minimum shall be
feathered to at least a 4:1 taper.

c) The repair weld shall be visually examined for defects. [4]

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IV.5. Vacuum Testing

Vacuum testing is performed using a testing box approximately 150 mm (6 in.) wide by 750
mm (30 in.) long with a clear window in the top, which provides proper visibility to view the
area under examination. During testing, illumination shall be adequate for proper evaluation
and interpretation of the test. The open bottom shall be sealed against the tank surface by a
suitable gasket. Connections, valves, lighting and gauges, as required, shall be provided. A
soap film solution or commercial leak detection solution, applicable to the conditions, shall be
used.

-Vacuum testing shall be performed in accordance with a written procedure prepared by the
Manufacturer of the tank. The procedure shall require:

a) performing a visual examination of the bottom and welds prior to performing the vacuum-
box test;

b) Verifying the condition of the vacuum box and its gasket seals;

c) Verifying that there is no quick bubble or spitting response to large leaks; and

d) Applying the film solution to a dry area, such that the area is thoroughly wetted and a
minimum generation of application bubbles occurs.

*A partial vacuum of 21 kPa to 35 kPa gauge shall be used for the test. If specified by the
Purchaser, a second partial vacuum test of 56 kPa to 70 kPa shall be performed for the
detection of very small leaks.

-The Manufacturer shall determine that each vacuum-box operator meets the following
requirements:

25
a) has vision (with correction, if necessary) to be able to read a Jaeger Type 2 standard chart
at a distance of not less than 300 mm (12 in.). Operators shall be checked annually to ensure
that they meet this requirement; and

b) is competent in the technique of the vacuum-box testing, including performing the

examination and interpreting and evaluating the results; however, where the examination
method consists of more than one operation, the operator performing only a portion of the test
need only be qualified for that portion the operator performs.

The vacuum-box test shall have at least 50 mm (2 in.) overlap of previously viewed surface
on each application.

The metal surface temperature limits shall be between 4 °C (40 °F) and 52 °C (125 °F), unless
the film solution is proven to work at temperatures outside these limits, either by testing or
Manufacturer’s recommendations.

A minimum light intensity of 1000 Lux (100 fc) at the point of examination is required during
the application of the examination and evaluation for leaks.

The vacuum shall be maintained for the greater of either at least 5 seconds or the time
required to view the area under test.

The presence of a through-thickness leak indicated by continuous formation or growth of a

bubble(s) or foam, produced by air passing through the thickness, is unacceptable. The
presence of a large opening leak, indicated by a quick bursting bubble or spitting response at
the initial setting of the vacuum box is unacceptable. Leaks shall be repaired and retested.

A record or report of the test including a statement addressing temperature and light intensity
shall be completed and furnished to the Purchaser upon request.

- As an alternate to vacuum-box testing, a suitable tracer gas and compatible detector can be
used to test the integrity of welded bottom joints for their entire length. Where tracer gas
testing is employed as an alternate to vacuum-box testing, it shall meet the following
requirements:

26
a) Tracer gas testing shall be performed in accordance with a written procedure which has
been reviewed and approved by the Purchaser and which shall address as a minimum: the type
of equipment used, surface cleanliness, type of tracer gas, test pressure, soil permeability, soil
moisture content, satisfactory verification of the extent of tracer gas permeation, and the
method or technique to be used including scanning rate and probe standoff distance.

b) The technique shall be capable of detecting leakage of 1  10–4 Pa m3/ or smaller.

c) The test system parameters (detector, gas, and system pressure, i.e., level of pressure under
bottom) shall be calibrated by placing the appropriate calibrated capillary leak, which will
leak at a rate consistent above, in a temporary or permanent fitting in the tank bottom away
from the tracer gas pressurizing point. Alternatively, by agreement between the Purchaser and
the Manufacturer, the calibrated leak may be placed in a separate fitting pressurized in
accordance with the system parameters.

d) While testing for leaks in the welded bottom joints, system parameters shall be unchanged
from those used during calibration. [5]

I.7.Conclusion:

So how we can do the Development of sizing tool for storage tanks according to API 650 and
CODRES and Development a comparative study between the two Codes

27
28
II.1.Scope
The API 650 is the American standard for welded flat-bottomed vertical storage tanks. This
standard dictates tank design, manufacture, welding, inspection and installation requirements.
The API 650 is widely used for tanks designed to withstand low internal pressures, for the
storage of typical products such as crude oil, petrol, chemicals and water. Gpi has extensive
experience when it comes to API 650 tanks, varying from tanks built in the factory up to +/-
500m3, to tanks built on-location up to +/-15,000 m3.

II.2General considerations

There are several general topics that are common to the detailed mechanical design of many
types of equipment and these are discussed in greater detail below:

Temperature and Pressure;

Materials of Construction;

Corrosion/Erosion.

A number of potential hazards can be introduced if these are not given adequate
consideration. Loss of containment may occur due to leaks, equipment failure, fire or
explosion and result in a major accident.

*Temperature and pressure

Temperature and pressure are two basic design parameters. Any equipment that is to be
installed should be designed to withstand the foreseeable temperature and pressure over the
whole life of the plant. The combination of temperature and pressure should be considered
since this affects the mechanical integrity of any equipment that is installed.

-Temperature: In determining design temperatures a number of factors should be considered

including:

the temperature of the fluids to be handled;

Joule-Thomson effect (The Joule-Thomson effect is the change in temperature that

accompanies expansion of a gas without production of work or transfer of heat. At ordinary
temperatures and pressures, all real gases except hydrogen and helium cool upon expansion

29
and this phenomenon is often utilized in liquefying gases); ambient temperatures; solar
radiation; and heating and cooling medium temperatures.

Consideration needs to be given to the temperature of the fluids that are to be handled and any
excursions in temperature that could occur as a result of the failure of temperature control
systems. Account should be taken of foreseeable reactions that may occur that are likely to
increase or reduce the heat input to the system.

-Pressure: A vessel should be designed to withstand the maximum pressure to which it is

likely to be subjected in operation.

II.3DESIGN:
II.3.1 MATERIALS:
Materials used in the construction of tanks shall conform to the specifications listed in this
section, subject to the modifications and limitations indicated in this standard. Another
important consideration in mechanical design is the selection of the material of construction.

In some cases the available materials of construction may constrain the design temperatures
and pressures that can be achieved and limit the design of the equipment.

The most important characteristics that should be considered when selecting a material of
construction are summarised below:

Mechanical Properties;

Tensile strength;

Stiffness;

Toughness;

Hardness;

Fatigue resistance;

Creep resistance;

The effect of low and high temperatures on the mechanical properties;

Corrosion resistance;

Ease of fabrication;

30
Special properties - electrical resistance, magnetic properties, thermal conductivity;

Availability in standard sizes;

Cost.

The selection of a suitable material of construction is often carried out by disciplines such as
process engineers. The advice of specialist materials engineers should be sought in the event
of difficult applications being identified.

The Safety report should contain evidence that the materials of construction that have been
selected are compatible with the process fluids to be handled and the design conditions that
have been chosen.

*Include the pertinent information in the documents provided to the Purchaser, including a
certification statement that the substituted material fully all respects, and provide all other
records covered by the work processes applied to the material such as impact testing, weld
procedures, nondestructive examinations, and heat treatments.[10]

II.3.2. Plates:

Plate for shells, roofs, and bottoms may be ordered on an edge-thickness basis or on a weight
(kg/m2 [lb/ft2]) basis.

The edge thickness ordered shall not be less than the computed design thickness or the
minimum permitted thickness.

The weight ordered shall be great enough to provide an edge thickness not less than the
computed design thickness or the minimum permitted thickness.

Whether an edge-thickness or a weight basis is used, an underrun not more than 0.3 mm (0.01
in.) from the computed design thickness or the minimum permitted thickness is acceptable.

All plates shall be manufactured by the open-hearth, electric-furnace, or basic oxygen

process. Steels produced by the thermo-mechanical control process (TMCP) may be used,
provided that the combination of chemical composition and integrated controls of the steel
manufacturing is mutually acceptable to the Purchaser and the Manufacturer, and provided
that the specified mechanical properties in the required plate thicknesses are achieved.
Copper-bearing steel shall be used if specified by the Purchaser.

31
Shell plates are limited to a maximum thickness of 45 mm (1.75 in.) unless a lesser thickness
is stated in this standard or in the plate specification. Plates used as inserts or flanges may be
thicker than 45 mm (1.75 in.). Plates, and thicker than 40 mm (1.5 in.), shall be normalized or
quench tempered, killed, made to fine-grain practice, and impact tested. [11]

Figure4.a : shell [13] figure4.b : welding tank [12]

II.3.3 Joints
A weld placed in a groove between two abutting members. Grooves may be square, V-shaped
(single or double), or U-shaped (single or double), or they may be either single or double
beveled.
A joint between two abutting parts lying in approximately the same plane that is welded from
both sides.
A joint between two overlapping members in which the overlapped edges of both members
are welded with fillet welds.
A fillet weld whose size is equal to the thickness of the thinner joined member.
The size of a groove weld shall be based on the joint penetration (that is, the depth of
chamfering plus the root penetration when specified).
The size of an equal-leg fillet weld shall be based on the leg length of the largest isosceles
right triangle that can be inscribed within the cross-section of the fillet weld. The size of an
unequal-leg fillet weld shall be based on the leg lengths of the largest right triangle that can be
inscribed within the cross-section of the fillet weld.

II.3.4. Typical Joints:

*Vertical shell joints shall be butt joints with complete penetration and complete fusion
attained by double welding or other means that will obtain the same quality of deposited

32
weld metal on the inside and outside weld surfaces. The suit ability of the plate preparation
and welding procedure shall.

Vertical joints in adjacent shell courses shall not be aligned, but shall be offset from each
other a minimum distance of 5t, where t is the plate thickness of the thicker course at the point
of offset.

*Horizontal shell joints shall have complete penetration and complete fusion; however, as an
alternative, top angles may be attached to the shell by a double-welded lap joint. The
suitability of the plate preparation and welding procedure shall.

Unless otherwise specified, abutting shell plates at horizontal joints shall have a common
vertical centerline. [14]

Single-V butt joint Single-U butt joint

Double-V butt joint

Square-groove butt joint Double-U butt joint

33
 Figure 4—Typical Vertical Shell Joints [7]

Optional outside
angle

Angle-to-shell butt joint Alternative angle-to-shell joint Square-groove butt

complete penetration joint

Single-bevel butt joint Double-bevel butt joint

Figure 5—Typical Horizontal Shell Joints [15]

When annular plates are used, they shall be butt-welded and shall have a radial width that
provides at least 600 mm (24 in.) between the inside of the shell and any lap-welded joint in
the remainder of the bottom. Bottom plates need to be welded on the top side only, with a
continuous full-fillet weld on all seams. Unless annular bottom plates are used, the bottom
plates under the bottom shell ring shall have the outer ends of the joints fitted and lap-welded
to form a smooth bearing surface for the shell plates, Lap-welded bottom plates shall be seal-
welded to each other on the exposed outer periphery of their lapped edges

34
 Figure 6—Spacing of Three-Plate Welds at Annular Plates

II.3.5. Tank Capacity:

The Purchaser shall specify the maximum capacity and the overfill protection level (or
volume) .

Maximum capacity is the volume of product in a tank when the tank is filled to its design
liquid level

35
The net working capacity is the volume of available product under normal operating
conditions. The net working capacity is equal to the maximum capacity less the minimum
operating volume remaining in the tank, less the overfill protection level (or volume) .

II.3.6. Special Considerations:

*Foundation: The selection of the tank site and the design and construction of the foundation
shall be given careful consideration, to ensure adequate tank support. The adequacy of the
foundation is the responsibility of the Purchaser. Foundation loading data shall be provided by
the Manufacturer on the Data Sheet,

Sliding friction resistance shall be verified for tanks subject to lateral wind loads or seismic
loads

*Corrosion Allowances: The Purchaser, after giving consideration to the total effect of the
liquid stored, the vapor above the liquid, and the atmospheric environment, shall specify in
the Data Sheet, any corrosion allowances to be provided for all components, including each
shell course, for the bottom, for the roof, for nozzles and manholes, and for structural
members.

Figure 7—Storage Tank

36
II.3.7. Bottom Plates

All bottom plates shall have a corroded thickness of not less than 6 mm (0.236 in.) [49.8
kg/m2] Unless otherwise agreed to by the Purchaser, all rectangular and sketch plates (bottom
plates on which the shell rests that have one end rectangular) shall have a nominal width of
not less than 1800 mm (72 in.).

Bottom plates of sufficient size shall be ordered so that, when trimmed, at least a 50 mm (2
in.) width will project outside the shell or meet requirements

1) Material shall be carbon steel, 3 mm (1/8 in.) minimum thickness.

2) All radial joints between sections of the drip rings, as well as between the drip ring and the
annular plate or bottom, shall be continuously seal-welded.

3) The drip ring shall extend at least 75 mm (3 in.) beyond the outer periphery of the
foundation ring wall and then turn down (up to 90°) at its outer diameter.

4) The top and bottom of the drip ring, and the top of the tank bottom edge projection beyond
the shell, and a portion of the tank shell shall be coated if specified by the Purchaser . [9]

Figure 8—Drip Ring (Suggested Detail)

37
II.3.8. Annular Bottom Plates

When the bottom shell course is designed using the allowable stress for materials butt-welded
annular bottom plates shall be used. When the bottom shell course is of a material in Group
IV, IVA, V, or VI and the maximum product stress for the first shell course is less than or
equal to 160 MPa (23,200 lbf/in.2) or the maximum hydrostatic test stress for the first shell
course is less than or equal to 171 MPa (24,900 lbf/in.2), lap-welded bottom plates may be
used in lieu of butt-welded annular bottom plates.

Annular bottom plates shall have a radial width that provides at least 600 mm (24 in.) between
the inside of the shell and any lap-welded joint in the remainder of the bottom. Annular
bottom plate projection outside the shell shall meet the requirements of 5.4.2. A greater radial
width of annular plate is required when calculated as follows:

In SI units:

215 tb /(G H)^0.5

Where;

tb : is the thickness of the annular plate (see 5.5.3), in mm;

H : is the maximum design liquid level (see 5.6.3.2), in m;

G : is the design specific gravity of the liquid to be stored.

The thickness of the annular bottom plates shall not be less than the greater thickness
determined using Table 1.1 for product design (plus any specified corrosion allowance) or for
hydrostatic test design. Table 1.1 and are applicable for effective product height of H * G <23
m (75 ft). Beyond this height an elastic analysis must be made to determine the annular plate
thickness.

The ring of annular plates shall have a circular outside circumference, but may have a regular
polygonal shape inside the tank shell, with the number of sides equal to the number of annular
plates. These pieces shall be welded

In lieu of annular plates, the entire bottom may be butt-welded provided that the requirements
for annular plate thickness, welding, materials, and inspection are met for the annular distance

38
 Plate Thicknessa of First Stressb in First Shell Course (MPa)
Shell Course
(mm)  190  210  220  250

t  19 6 6 7 9

19 < t  25 6 7 10 11

25 < t  32 6 9 12 14

32 < t  40 8 11 14 17

40 < t  45 9 13 16 19

a Plate thickness refers to the corroded shell plate thickness for product design and nominal thickness for hydrostatic t est
design.
b The stress to be used is the maximum stress in the first shell course (greater of product or hydrostatic test stress). The
stress may be determined using the required thickness divided by the thickness from “a” then multiplied by the applicable
allowable stress:
Product Stress = (td – CA/ corroded t ) (Sd)
Hydrostatic Test Stress = (tt / nominal t ) (St)
NOTE The thicknesses specified in the table, as well as the width specified in 5.5.2, are based on the foundation providing
uniform support under the full width of the annular plate. Unless the foundation is properly compacted, particularly at the
inside of a concrete ringwall, settlement will produce additional stresses in the annular plate.

Table1.—Annular Bottom-Plate Thicknesses (tb) (SI) [16]

II.3.9. Shell Design

The required shell thickness shall be the greater of the design shell thickness, including any corrosion
allowance, or the hydrostatic test shell thickness, but the shell thickness shall not be less than the
following:
Nominal Tank Diameter Nominal Plate thickness

(m) (ft) (mm) (in.)

< 15 < 50 5 3/16

15 to < 36 50 to < 120 6 1/4

36 to 60 120 to 200 8 5/16

> 60 > 200 10 3/8

NOTE 1 Unless otherwise specified by the Purchaser, the nominal tank diameter shall be the
centerline diameter of the bottom shell-course plates.
NOTE 2 The thicknesses specified are based on erection requirements.
● NOTE 3 When specified by the Purchaser, plate with a nominal thickness of 6 mm may be substituted for 1 /4-
in. plate.
NOTE 4 For diameters less than 15 m (50 ft) but greater than 3.2 m (10.5 ft), the nominal thickness
of the lowest shell course shall not be less than 6 mm (1/4 in.).

Table2: thickness

39
Unless otherwise agreed to by the Purchaser, the shell plates shall have a minimum nominal
width of 1800 mm (72 in.). Plates that are to be butt-welded shall be properly squared.

The calculated stress for each shell course shall not be greater than the stress permitted for the
particular material used for the course. When the allowable stress for an upper shell course is
lower than the allowable stress of the next lower shell course, then either a or b shall be
satisfied.

a) The lower shell course thickness shall be no less than the thickness required of the upper
shell course for product and hydrostatic test.

b) The thickness of all shell courses shall be that determined from an elastic analysis using
final plate thicknesses.

The inside of an upper shell course shall not project beyond the inside surface of the shell
course below

The tank shell shall be checked for stability against buckling from the design wind speed, if
required for stability, intermediate girders, increased shell-plate thicknesses, or both shall be
used.

Isolated radial loads on the tank shell, such as those caused by heavy loads on platforms and
elevated walkways between tanks, shall be distributed by rolled structural sections, plate ribs,
or built-up members.

II.3.10. Allowable Stress:

The maximum allowable product design stress, Sd, shall be as shown in Table 3. The
corroded plate thicknesses shall be used in the calculation. The design stress basis, Sd, shall
be either two-thirds the yield strength or two-fifths the tensile strength, whichever is less.

The maximum allowable hydrostatic test stress, St, shall be as shown in Table 3 the nominal
plate thicknesses shall be used in the calculation. The hydrostatic test basis shall be either
three-fourths the yield strength or three-sevenths the tensile strength, whichever is less.

40
II.3.11.Wind load:

Nature of wind in Atmosphere In general, wind speed in the atmospheric boundary layer
increases with height from zero at ground level to a maximum at a height called the gradient
height. There is usually a slight change in direction (Ekman effect) but this is ignored in the
Code. The variation with height depends primarily on the terrain conditions. However, the
wind speed at any height never remains constant and it has been found convenient to resolve
its instantaneous magnitude into an average or mean value and a fluctuating component
around this average value. The average value depends on the averaging time employed in
analyzing the meteorological data and this averaging time can be taken to be from a few
seconds to several minutes. The magnitude of fluctuating component of the wind speed,
which represents the gustiness of wind, depends on the averaging time. Smaller the averaging
interval, greater is the magnitude of the wind speed.

As is explained in Code, wind speed can be taken to comprise of a static (mean) component
and a fluctuating component, with the magnitude of the latter varying with time interval over
which the gust is averaged. Thus with reduction in the averaging time, the fluctuating wind
speed would increase. The fluctuating velocity is normally expressed in terms of turbulence
intensity which is the ratio of the standard deviation to the mean wind speed and is expressed
in percentage.

– Basic Wind Speed (Vb) Figure 1 gives basic wind speed map of India, as applicable at 10 m
height above mean ground level for different zones of the country. Basic wind speed is based
on peak gust speed averaged over a short time interval of about 3 seconds and corresponds to
10m height above the mean ground level in an open terrain (Category 2). Basic wind speeds
presented in Fig. 1 have been worked out for a 50-year return period. The basic wind speed
for some important cities/towns

Design wind pressure (PWS and PWR) using design wind speed (V): The design wind
pressure on shell (PWS) shall be 0.86 kPa (V/190)2, ([18 lbf/ft2][V/120]2) on vertical
projected areas of cylindrical surfaces. The design wind uplift pressure on roof (PWR) shall
be 1.44 kPa (V/190)2, ([30 lbf/ft2][V/120]2) (see item 2) on horizontal projected areas of
conical or doubly curved surfaces.

41
II.3.12.Anchorage of the tank

+The anchorage should be principally attached to the cylindrical shell and not to the base ring
plate alone.

+ The design should accommodate movements of the tank due to thermal changes and
hydrostatic pressure to minimize stresses induced in the shell by these effects.

+ Where the tank is supported on a rigid anchorage, and is subject to horizontal loads (e.g.
wind, impact) the anchorage forces should be calculated according to shell theory.

II.3.13. Calculation of Thickness by the 1-Foot Method

The 1-foot method calculates the thicknesses required at design points 0.3 m (1 ft) above the
bottom of each shell course. Annex A permits only this design method. This method shall not
be used for tanks larger than 61 m (200 ft) in diameter.

The required minimum thickness of shell plates shall be the greater of the values computed by
the following formulas:

In SI units:

where

td:is the design shell thickness, in mm;

tt:is the hydrostatic test shell thickness, in mm;

D:is the nominal tank diameter, in m;

H:is the design liquid level, in m;

= height from the bottom of the course under consideration to the top of the shell including
the top angle, if any; to the bottom of any overflow that limits the tank filling height; or to any

42
other level specified by the Purchaser, restricted by an internal floating roof, or controlled to
allow for seismic wave action;

G:is the design specific gravity of the liquid to be stored, as specified by the Purchaser;

CA: is the corrosion allowance, in mm, as specified by the Purchaser;

Sd: is the allowable stress for the design condition, in MPa;

St:is the allowable stress for the hydrostatic test condition, in MPa.

II.3.14. Calculation of Thickness by Elastic Analysis;

For tanks where L/H is greater than 1000/6 (2 in USC units), the selection of shell thicknesses
shall be based on an elastic analysis that shows the calculated circumferential shell stresses to
be below the allowable stresses given in Table 3. The boundary conditions for the analysis
shall assume a fully plastic moment caused by yielding of the plate beneath the shell and zero
radial growth.

Figure9: tank

43
44
III.1. Design data:
▪ Product density: d;
▪ Corrosion allowance: c1 = mm;
▪ Rolling allowance: c = mm;
▪ Study pressure: P = mbar;
▪ Study depression: Pv = mbar;
▪ Calculation temperature: T =° C;
▪ Welding coefficient: z =;
▪ Wind: Vw = m / s;
▪ Diameter of the tank: D = mm;
▪ Height of the tank: H = mm;
▪ Filling height: Hr = mm;
▪ Volume of the liquid: V = m3;
▪ Air density: 𝜌𝑎𝑖𝑟 = 𝑘𝑔𝑚 − 3;
▪ Density of water: 𝜌𝑒𝑎𝑢 = 𝑘𝑔𝑚 − 3;
▪ Steel density: 𝜌𝑎𝑐𝑖𝑒𝑟 = 𝑘𝑔𝑚 − 3;
▪ Gravity acceleration: g = m / s²;
▪ Angle of inclination of the cone for the roof: 𝜃 =° 𝐶;
▪ Sheet dimensions: L x G;
▪ Produce stored;
▪ Material;
▪ Young modulus: E = GPa;
▪ Young's modulus at maximum temperature: Et: GPa;
▪ Standard: NF EN 10.025;
▪Height of shell hs
*Allowable constraints:
▪ Re0.2 = 235 MPa;
▪ Rm = 410 MPa;
▪ f = (2/3) * Re0.2;

45
III.2. Design and Calculations:

a) Shell design
The minimum nominal thicknesses of the shell according to the diameter of the tank.
This table is taken by the standard codres

Table 4: Minimum nominal thickness of the shell

*Thickness ec and thikness of every shell of tank eci:

So if ec < ec (selected by the table 4)

Take ec of table 4
So eci = d/20𝑓 (98 ∗ 𝑑 ∗ (ℎi − 0.3) + 500) + 𝐶1 + 𝐶 and put to test with table 4
With hi=hi-1-hs

46
b. Bottom thickness:

The table below gives us the minimum nominal thickness of the bottom plate. Taken by the standard
CODRES

Table 5 - Minimum nominal thickness ef of the bottom plate (corrosion allowance excluded)

*Annular bottom:
-Thickness ea :

-width La:

-length lf:

c. Roof calculation:
Radius of curvature:
R1=R/sin O

47
d. Joint shell and roof:
The shell-roof junction: it is made with the angles as shown in the figure opposite:

Figure 10 :The shell-roof junction

And the Angle dimensions taken by the table 5 :

Table 6 -Minimum dimensions of edge angles for tanks with fixed roofs. [17]

48
e. anchors Calculation :
Seeing if we need to anchor tank.
The tank may not be anchored if both of the following
conditions are true:

[I] , 𝟔𝑴wind+ 𝑴𝒑𝒓𝒆𝒔𝒔𝒊𝒐𝒏 < 𝑴weight /𝟏,𝟓

[II] wind+ 𝟎. 𝟒 ∗ 𝑴𝒑𝒓𝒆𝒔𝒔𝒊𝒐𝒏< (𝑴weight+𝑴liquid)/𝟐

Moment due to wind pressure

𝑃wind =(½) 𝜌𝑎𝑖𝑟𝑉wind ; 𝑠 = (𝜋 /2) 𝐷*H

Moment due to the weight of residual product:

1
𝑀𝑝𝑟𝑜𝑑𝑢𝑖𝑡 = 𝐷𝜌water𝑉𝑔
2

Moment due to internal pressure figure 11: anchor

Moment due to the weight of the empty structure:

49
 1
𝑀weight = 𝐷𝜌steel𝑉𝑣𝑜𝑙𝑢𝑚𝑒𝑔
2

So if both conditions ([I]and [II]) are true, then it is no longer necessary to anchor our tank.

50
51
V.1. API standard:
Verification of requested work:

52
53
54
**So we refer to the project sheet of water storage in South Africa

55
56
57
V.2. CODRES standard:
Verification of requested work:

58
59
**So we refer to the project sheet of Sizing of a fire-fighting water storage tank: case of the
BOCOM GROUP's domestic gas production unit (French langue):

60
61
62
63
64
If we Consider this data for calculation:

•Crude storage tank

•Capacity:11322 m3

•working capacity: 7949 m3

•crude density: 870 kg/m3

•design temperature:90°C

•liquid level 15 m

•internal design pressure 147.15 Kpa

•external design pressure: 0.25 kPa

•Material S275JR

•Floating roof

•Diamer: 15m

•St (MPa) test allow. Stress: 176

•Sd (Mpa) design allow. Stress: 164

•shell courses height: 2m

•corrosion allowance: 3 mm

•wind velocity 162 km/h

•Internal design pressure Pi (kPa): 18

•External design pressure Pe (kPa): 0.25

•minim yield strength of bottom plate under the shell: 275

65
*For CODRES sheet

66
See excel sheet

For API 650 sheet

67
See excel sheet

68
So :

*All through the design API 650, CODRES and other relevant standards were successfully
used to design the proposed storage tank. MS Excel spreadsheet was used to perform design
calculations. Appropriate design method and material selection were done; design factors and
considerations were observed in the process of design to ensure a safe and reliable storage
system. A fair assessment of the cost of the tank.

*The following basic parameters for the tank were determined: the nominal diameter, height,
and number of shell course and height of shell course Also the liquid height was determined
using the capacity design equation. The bottom of the tank consisting of the bottom and
annular plates was designed. The bottom and annular plate thickness were determined .The
bottom plate dimension and the annular plate dimension. The difference in thickness is due to
the fact that the shell of the tank rest directly on the annular plate, therefore it is under
continuous load from the shell and roof weight. The shell varying thicknesses in turn were
determined using the one-foot method. The design stress and hydrostatic test shell thickness
was determined for each course respectively. The shell thicknesses were adopted after
iterative adjustment to withstand hydrostatic load, and it was girded the height H from the
bottom by an intermediate wind girder, and at the top by a top wind girder to ensure stability
of tank against external loads like wind.

Fittings and appurtenance for the tank were determined. Sizing for Vents, Manholes, Valves
and other appurtenance were done as recommended by standard. The overall weight of the
tank was determined. The tank was determined to the required number of anchorage due to
the fact that the height to diameter ratio was small. Hence it is more economical in design
resulting from same plate choice to reduce weld joints, and cost saved for anchorage design

*Both of two standards (CODRES and API 650) were successfully used with great security
and controls but the API 650 code is more severe and strict than CODRES code in some
dimensions of tanks.

*But Also CODRES code is more economics than API 650.

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References:

[1].A.H. Isa, S. Hamisu, H. S. Lamin, M. Z. Ya’u and J. S. Olayande (2013),The Perspective

of Nigeria’sprojected demand for Petroleum Products, JPGE Vol. 4(7), 184-187.
[2]. Courses CND Mr mezghani
[3]. API 650 standard
[4]. Courses CND Mr mezghani
[5]. API 650 standard
[6].Okpala A. N. and Jombo P. P. (2012). Design of Diesel Storage Tank in Consonance with
Requirements of American Petroleum Institute (API) Standard 650. Industrial Engineering
Letters. ISSN 2225-0581 (Online). Vol 2, No.4, 2012.
[7].Enarevba D. R. (2015). Design of a Petroleum Product Storage Tank of 10 Million Liters
Capacity. Bachelor’s Dissertation, Department of Mechanical Engineering, College of
Technology. Federal University of Petroleum Resources, Effurun, Delta State, Nigeria.
(Unpublished).
[8].https://www.google.com/search?q=+of++tanks+plates+&tbm=isch&ved=2ahUKEwiiisK2
upnsAhXM_4UKHZlPAnQQ2-
[9].https://www.google.com/search?authuser=1&ei=XTFmX_-
QAvSdjLsP3Lmc8As&q=+construction+code+for+cylindrical%2C+vertical%2C+flat+botto
m+storage+tanks&oq=+construction+code+for+cylindrical%2C+vertical%2C+flat+bottom+s
torage+tanks&gs_lcp=CgZwc3ktYWIQDFCJtAFY_swBYPHbAWgBcAF4AIABfogBfpIBA
zAuMZgBAKABAaABAqoBB2d3cy13aXqwAQDAAQE&sclient=psy-
ab&ved=0ahUKEwi_s-e10fXrAhX0DmMBHdwcB74Q4dUDCA0
[10]. Courses Mr Mohamed KHLIF
[11]. Courses Mr Moez FRIKHA
[12]. Courses Mr Mohamed KHLIF
[13]. Indian Standard IS 803(Reaffirm 2006), Code of Practice for Design Fabrication and
Erectionof VerticalMild Steel Cylindrical Welded Oil Storage Tanks, Bureau of Indian
Standards, Manak Bhavan, New Delhi 110002.
[14] [15] [16]. API 650 standard
[17]. CODRES standard

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