API (American Petroleum Institute)

TANKS SOLDIERS FOR

OIL STORAGE

Norma API 650

TWELFTH EDITION - March 2013
OBJECTIVE

Establish the general requirements necessary for the design of tanks for
oil storage according to API code 650.

SECTION 1–SCOPE

1.1 Scope

1.1.1 This Standard establishes the minimum requirements regarding materials, design,
manufacturing, assembly, and inspection for vertical welded tanks, cylindrical, above the
floor, closed and open roof storage, in various sizes and capacities
of internal pressure approximately equal to atmospheric pressure (which should not exceed the
weight of the roof sheets), but higher internal pressures are allowed when
They meet additional requirements. This standard is applicable only for tanks in the
that the entire fund is uniformly supported and for tanks in service
non-refrigerated with a maximum design temperature of 93°C (200°F) or less.

1.1.2 This Standard is designed to help the industry adequately secure and
economically reasonable for their use in the storage of oil and its derivatives
and other liquid products. The code does not specify specific tank sizes and for the
On the contrary, you can choose the size according to the need. Its intention is to help.
clients and manufacturers to buy, manufacture, and assemble the tanks; without intending to prohibit the

purchase or manufacture of tanks that meet other specifications.

Note: a star (*) at the beginning of a paragraph indicates that there is an express decision or a

action required by the buyer or client. The responsibility of the client is not
limited to those decisions or actions only. When such decisions or actions are
taken, it is necessary to specify in documents such as requirements, change orders,
data sheets and drawings.
This Standard has requirements in two alternatives of units systems, the
manufacturing must comply with any of them:
All requirements are provided in the International System (SI)
all the requirements given in this standard in American units (US)

The choice of either of the two systems (SI or customary in the USA) to apply must be
subject of a mutual agreement between the manufacturer and the customer and indicate it on a sheet of

data.
1.1.4 All tanks and their accessories must comply with the datasheet or the
attachments.
1.1.5 The assembly area must be fully equipped for assembly, inspection.
and ready
1.1.6 The appendices in this Standard provide a series of design options and
decisions required by the client, requirements of the Standard, recommendations and
additional information, a series of annexes are shown in table 1.
 Table 1. Statute of the annexes for the API 650 Standard
Annex Title Statute
A Basic design options for small tanks Customer option
AL Aluminum tanks for storage Requirements
B Recommendations for the design and construction of the recommendations
foundations for oil storage tanks
about the soil
C External floating roofs Requirements
D Technical inquiries Procedures
required
E Seismic design for storage tanks Customer option
EC Comment on Annex E Information
F Design of tanks for low internal pressures Requirements
G Structural requirements for aluminum dome roofs
supported
H Internal floating roofs Requirements
I Leak detection at the base of the tank and customer option protection
soil
J Storage tanks assembled on site Requirements
K Examples of application of the point design method Information
variable to determine the thickness of the sheets of
body
L Data sheets for API 650 storage tanks Information
required
M Requirements for tanks operating at temperatures Requirements
elevated
N Use of new materials that are not identified Requirements
O Recommendations for connections below the bottom Customer option
P Permissible external loads in body connections Customer option
tank
S Stainless Steel Storage Tanks Requirements
austenitic
SC Mixed storage tanks made of steel Requirements
stainless steel and carbon steel
T Summary of requirements for END Requirements
U Ultrasonic inspection instead of X-ray Customer option
V Design of storage tanks for pressures Customer option
external
W Commercial recommendations and documentation Recommendations
X Duplex stainless steel tanks Requirements
Y Monogram API Requirements
1.2 Limitations

The rules of the code do not apply beyond the following limits in the pipes
connected internally or externally to the ceiling, body, or bottom of the tank.
a) The face of the first flange in flanged connections, except when supplied.
caps or blind brackets.
b) The first sealing surface in accessories and instruments.
c) The first threaded joint in pipes in the pipe of a threaded connection for the
tank body.
d) The first circumferential joint in welded connections, unless they are welded to a
brida.

1.3 Responsibilities

The manufacturer is responsible for complying with all the requirements of the code.
inspection by the client's inspector does not relieve the manufacturer of the obligation to
provide the necessary quality control and inspection to ensure such compliance.
The manufacturer will also communicate the specific and relevant requirements to the
subcontractors or suppliers that work with him.

1.4 Documentation requirements

Refer to Annex W and the data sheet for the requirements that cover the various
documents that are prepared for the tank.

1.5 Formulas

Where the units are not defined in the formulas in this standard, use units.
consistent (for example, inch, inch23lbf/in2).
 SECTION 2 – REFERENCE REGULATIONS

The reference documents are essential for the application in this document.
For dated references, only the cited edition applies. For undated references, the latest one applies.
Document editing is applicable.

SECTION 3 – TERMS AND DEFINITIONS

For the purpose of this document, the terms and definitions cited in API 650 apply.

SECTION 4 – MATERIALS

4.1 Generalities

4.1.1 Miscellaneous information specified in 4.1.1.1 to 4.1.1.4

4.1.1.1 See the datasheet of the material specifications
4.1.1.2 We are allowed steels with mounting or layers
4.1.1.3 Any cast part that is subjected to pressure or a process is prohibited.
of welding
4.1.1.4 Due to hydrogen embrittlement precautions, they are not used.
components containing cadmium without the express consent of the customer.

The materials used in construction must comply with the specifications.

cited in the code, subject to the limitations and modifications indicated therein. It
they can use materials produced in accordance with unlisted specifications if
it is verified that it meets the requirements of an accepted specification and its
use is approved by the client.
4.1.3 Materials that are not fully listed or identified can be used.
as long as they pass all the tests established in appendix N.
4.1.4 When using certified construction materials for two specifications,
the chosen specification for the design calculations will also be used for all
the other provisions of this regulation.

4.2 Sheets
4.2.1 Generalities
4.2.1.1 Except as provided in section 4.1, the plates shall comply with one of the
specifications cited in 4.2.2 to 4.2.6, subject to the modifications and limitations of
code.
4.2.1.2 Plates for the body, the roof, and the bottom can be ordered based on
thicknesses at the edge or based on weight per unit area (kg/m2pound per foot2]),
specified in 4.2.1.2.1, 4.2.1.2.2, and 4.2.1.2.3.
4.2.1.2.1 The ordered thickness cannot be less than the calculated one or than the thickness.

minimum allowed.
4.2.1.2.2 The ordered weight must be large enough to provide a thickness that
it must not be less than the calculated thickness or the minimum allowed.
4.2.1.2.3 In either case, the actual thickness cannot be more than 0.3 mm.
0.01 inch below the calculated thickness or the minimum allowed thickness.
All sheets must be manufactured by the 'open hearth' process.
electric oven or basic oxygen. Steels produced by the Thermo-control process.
Mechanical (TMCP) can be used if they meet the established requirements in
this paragraph.
4.2.1.4 The maximum thickness of the plate is 45mm (1.75 in) unless a thickness
the lower limit is established in this code in the specification of the board. Sheets used as
inserts or flanges can have a thickness greater than 45mm (1.75 in). The sheets more
thicker than 40mm must be normalized, tempered, annealed, and normalized, to make
a fine grain practice and impact testing.
4.2.1.5 Non-listed plate components (i.e., compression components of
contours without pressure must be limited by the maximum thickness designated by ASTM,
CSA, ISO, EN, or another recognized national standard.
 SECTION 5–DESIGN

5.1 Together
5.1.1 Definitions
The definitions are given from 5.1.1.1 to 5.1.1.8 and apply to the design of joints.
in tanks (See 9.1 for definitions that apply to welders and procedures
welding).
5.1.1.1 Butt welding: It is a welding with a groove between two elements, the grooves
they can be square, in V shape (simple or double) or in U shape (simple)
or double)
5.1.1.2 Double welded joint: a joint between two adjacent parts that are
approximately the same plane, which is welded on both sides.
5.1.1.3 Double lap weld joint: Joint between two overlapping members,
in which the overlapped edges of both members are welded with
fillet weld.
5.1.1.4 Fillet welding: A weld with an approximately triangular section that
a pair of approximately perpendicular surfaces, like a joint of
overlap, T-joint or corner joint.
5.1.1.5 Full fillet weld: A weld whose size is equal to the thickness.
of the thinnest member.
5.1.1.6 Simple soldier splice with backing: Welding between two splice parts
that extends approximately in the same plane that is being welded and
it needs suitable backing or support material.
5.1.1.7 Welded lap joint on one side only: Joint between two members
overlapping, in which the overlapping edge of one member is welded with
fillet welding.
5.1.1.8 Spot welding: Welding done to keep the parts aligned until
perform the final welding.
5.1.2 Size of the welds
5.1.2.1 The size of a groove weld should be based on the penetration of the
joint (bevel depth plus root penetration depth)

5.1.2.2 The size of a fillet weld of equal sides will be based on the length.
on the side of the largest isosceles right triangle that can be inscribed in the
cross section of the fillet weld. The size of a weld of
filet of unequal sides should be based on the length of the longer side
right triangle that can be inscribed in the cross section of the weld
fillet

5.1.3 Restrictions on the meetings

5.1.3.1 The restrictions on the type and size of the joints are given in 5.1.3.2 to
5.1.3.6
5.1.3.2 The assembly points (tack welds) should not be considered with any value.
for the welding resistance in the finished structure
5.1.3.3 The minimum size of the fillet welds shall be as follows: for
5mm (3/16 inch) thick plates will require the welding to be a fillet.
complete.
For sheets greater than 5mm (3/16 inch) thick, the thickness of the weld
it must be no less than one third of the thickness of the thinnest part in the
joint and must be at least 5mm (3/16 inch)
5.1.3.4 Simple welded overlapping joints are only allowed in the sheets of
background and ceiling.

5.1.3.5 Single overlapping welded joints must overlap at least 5 times the
nominal thickness of the thinnest part to be joined, however for joints
overlapped welded on both sides, a greater overlap is not necessary.
50mm (2 inches) and with overlapping joints welded on only one side, the overlap does not

needs to exceed 25mm (1inch).

5.1.3.6 The passes in welding are imitated like this for the materials mentioned in the
groups I, II, III and IIIA.
5.1.3.6.1 For the process of manual welding and groove welding with depths
greater than 6mm (1/4 inch), will be with multiple passes.

For semi-automatic processes except for gas-electro, for depths

Greater than 10mm for the groove will be done in multiple passes.

5.1.3.6.2 For groups IV, IVA, V or VI for welds in the body with any
At least two passes will be made in the process.

5.1.4 Welding symbols

In the manufacturing and construction drawings, symbols must be used.
welding of the AWS.
5.1.5 Typical meetings
5.1.5.1 The typical joints are shown in figures 5.1, 5.2, 5.3a, 5.3b, and 5.3c.
5.1.5.2 Vertical joints of the body
a) The welds must be butt welds with complete penetration and complete fusion
b) The vertical joints in adjacent rings should not be aligned and
they must have a minimum offset of 5 times the thickness of the ring sheet plus
thick that is found at the joint.
5.1.5.3 Horizontal joints of the body
a) The welds must be butt welds with complete penetration and full fusion,
with welding on both sides or procedures with complete penetration.
b) The horizontal butt joints must have a common vertical axis.
 Figure 5.1–Typical joints for vertical welds in the body

5.1.5.4 Overlapping joints of the background

5.1.5.4.1 The edges of the sheets must be reasonably straight and cut to
squad
5.1.5.4.2 The triple overlaps must be at least 300mm (12 inches) apart.
from any other, from the tank body, from the butt joints of the ring and from the
joints between the rings and the bottom.
5.1.5.4.3 The plates will be welded on only one side, with a continuous fillet weld.
All the joints of the fund. When annular plates are used, they must be
solders fully and they will have a separation radius of at least 600mm (24 inches)
between the lower part of the body and any welded overlap joint in the rest of the
tank.
Figure 5.2–Typical joints for horizontal welds in the body
Figure 5.3a–Typical joints for the roof and the bottom
Figure 5.3b–Method for preparing base plates for overlap joints below the
tank body.

Figure 5.3c–Detail for the weld with double fillet for annular bottom plates with
nominal thickness greater than 13mm (1/2 inch)
 Figure 5.3d–Welding of three plates welded to annular plates

5.1.5.5 Ramps at the bottom

When used, they must have a square or V-shaped bezel. The details are the same as those
used for vertical joints. A backing plate of at least 3mm can be used.
(1/8 inch) thick and if it has a square bevel, the light at the root must be at least 6mm
(1/4 inch). The joints connecting three sheets must be at least a distance of
300mm (12 in) between them and the tank body.
5.1.5.6 Bottom ring seals

They must have flush radial joints and must have complete penetration and complete fusion. If
a backing plate is used, it must be made of a weldable material and compatible with the
material of the ring.

5.1.5.7 Fillet welds of the body-bottom joint

a) For bottom plates and bottom rings with nominal thicknesses of up to 13mm
(1/2 inch) or less, the union between the lower edge of the body and the bottom sheet must be
a continuous weld bead on each side of the body sheet. The size of each
Welding should not be greater than 13mm (1/2 inch) and should not be less than the thickness
nominal of the thinnest plate or than the thickness values shown:

Nominal thickness of the sheet Minimum size of the weld bead

b) For bottom ring plates with nominal thicknesses greater than 13mm (1/2
weld), the welding must be sized so that the fillets on both sides or the
welds of bevels and fillets should be of a size equal to the thickness of the ring, but must not
exceed the nominal thickness of the body sheets.

c) A fillet weld will be made between the body and the bottom of the tank and around.
from the reinforcement pads.

d) The bottom or the annular plates must be sufficient to provide a minimum of 13.
mm (1/2 in) from the tip of the fillet weld.
5.1.5.8 Wind shear connections

Full penetration welds must be used for the joining of the sections.
of the ring.
b) Continuous welding must be used for all horizontal joints on the side
superior and for all vertical joints and if the client requires it, a will be made
seal welding on the underside of the ring.

5.1.5.9 Roof joints and upper body corner

a) The roof joints must be welded on the upper side at a minimum, with fillets.
Continuous at all joints of the sheets. Butt welds are also allowed.
b) The roof panels must be joined at the upper angle of the tank with a fillet.
I continue on the upper side only.
c) The upper angle sections for self-supporting roofs must be joined
with butt welds with complete fusion and penetration
d) At the manufacturer's option, for self-supporting roofs of the cone, dome type or
umbrella, the edges of the roof panels can be fringed
horizontally to fit flat against the upper angle for improvement
the welding conditions.
e) The bodies of the tanks must have upper angles with a minimum size.
which shall not be less than the following sizes, except as specified
for open tanks, for self-supporting roofs, and for tanks with the detail of
eyelash joint roof-body.

Tank diameter Minimum angle size Minimum angle size

(D) superiora superiora
(mm) (inch)
 f) For tanks with a diameter less than or equal to 9m (30ft) and a cone roof
supported, the upper edge, the body of the tank can be bridled instead of
a full installation at an angle.

5.2 Design considerations

5.2.1 Loads
The charges are given as follows
a) Dead load (DL)
b) Design external pressure (PeIt must not be less than 0.25KPa (1 inch of
water), except that this should not be considered
c) Design internal pressure (PIIt should not exceed 18 KPa (2.5 lbf/in)2)
d) Hydrostatic test (Htload due to filling the tank to the level of
design of the liquid.
e) Loads on the internal floating ceiling:
1) Load due to the internal floating roof (Df)
2) Uniform live load on the internal floating ceiling (Lf)1(0.6 KPa [12.5 lbf/ft2]
if automatic drainage is not provided, (0.24 KPa [5 lbf/ft2if it is planned to
automatic drainage
3) Point load of the internal floating roof (Lf2of at least two men who
they walk anywhere on the roof, an applied load of 2.2KN [500 lbf]
about 0.1m21 ft2]
4) Design external pressure of the internal floating roof (Pfe) of (0.24 KPa [5
lbf/ft2as a minimum.
f) Minimum live load on the roof (Lr1.0 KPa [20 lbf/ft]2about the area
projected horizontal of the ceiling. The minimum live load can be determined at
in accordance with ASCE 7, but it cannot be less than 0.72 kPa (15 psf)
g) Snow (S): the snow load must be determined in accordance with ASCE 7
1) Constant snow design load (SbIt must be 0.84 times the load of
ground snow
2) Variable snow load (Sufor conical roofs with a
Inclination of 10° or less must be equal to the balanced snow load.
 the design load for unbalanced snow for other roofs must be 1.5 times the
balanced snow load design
h) Stored liquid (F):
i) Test pressure (Pt)
j) Wind (W): the design wind speed (V) must be any:
- 3-second gust design speed determined by ASCE 7-05
multiplied by √
- Burst design speed of 3 seconds determined by ASCE 7-10 for
a specific category of risks determined by the client.
1) Design wind pressure (PWSy PWR) used for wind speeds (V): the
design wind pressure on the body (PWSIt should be 0.86KPa (V/190)2
lbf/ft2] [V/120]2) projected onto vertical areas of cylindrical surfaces. The
design lift pressure of the roof (PWRIt should be 1.44KPa (V/190)2,
([30 lbf/ft2] [V/120]2)

k) External loads:
The client must establish the magnitude and direction of the external loads and the
restrictions, if there are any for which the body or the
connections.

5.2.2 Combination of loads

The loads should be combined as follows:

a) Fluid and internal pressure: DL + F + Pi

b) Hydrostatic test: DL + Ht + Pt
c) Wind and internal pressure: DL+W+Fp Pi
Wind and external pressure: DL + W + 0.4Pe
e) Gravitational loads:
1) DL+ (LroSuoSb) + 0.4Pe
2) DL + Pe + 0.4(LroSuoSb)
f) Earthquake: DL+F+E+ 0.1Sb+Fp Pi
 g) Gravity loads for fixed roofs with suspended floating roofs:
1)DL+Df+ (LroS) +Pe+ 0.4(PfeoLf1oLf2)
2) DL + Df + (PfeoLf1oLf2) + 0.4[(LroS) + Pe]

The pressure combination factor (FP) is defined as the operating radius of the
design pressure, with a minimum value of 0.4

5.2.3 Design factors

The client must establish the design temperature of the metal (based on the temperature
environment), the maximum design temperature and the maximum design specific gravity,
corrosion tolerance and seismic factors.
5.2.4 Tank capacity
The client must specify the maximum capacity or the required volume.
5.3 Special considerations
5.3.1 Foundations
The selection of the tank location, the design and construction of the civil work must
to have careful consideration, to ensure adequate support for the tank.
5.3.2 Corrosion tolerance
It is the customer's responsibility to determine the required over thickness for the tolerance to the
corrosion.
5.3.3 Terms of Service
It is the client's responsibility to determine if the service conditions
they include the presence of hydrogen or another condition that may cause cracks
induced by hydrogen.

5.3.4 Thickness
When 6mm of material thickness is specified, it can be used in units.
Americans, in a similar way when a thickness of 5mm of the material is
specified, 4.8mm thick can be used in the international system.
5.4 Background plates
5.4.1 All background sheets must have a minimum nominal thickness of 6mm.
49.8 Kg/m2) without including any atmospheric corrosion tolerance. All the
rectangular sheets and the edge of the bottom on which the body rests and
that have a rectangular end must have a minimum width of 1800mm.
5.4.2 Background sheets of sufficient size must be ordered so that when they are
I was left with a projection of at least 50mm outward from the edge.
exterior of the body-to-bottom joint welding.
5.4.3 If specified in the data sheet, a drip ring will be installed to prevent
water entry between the bottom and the foundations, in this case the ring the material
It must be carbon steel with a minimum thickness of 3mm.

Figure 5.5–Drip ring (suggested detail)

5.5 Bottom annular plate
5.5.1 When the lower ring of the body has been designed using the efforts
acceptable materials from groups IV, IVA, V, or VI, a must use a
ring made of platinum at the bottom joined with butt welding. When the lower ring
the body is made of materials from groups IV, IVA, V or VI and the maximum
 effort per product for the first body ring is less than or equal to 160
MPa or the maximum hydrostatic test stress for the first ring is
less than or equal to 171 MPa the bottom with overlapping welds can be used
instead of a ring plate at the bottom welded with a butt weld.

5.5.2 The annular plates at the bottom should have a radial width that provides to the
less than 600mm between the inside of the body and any overlapped joint.
it requires a larger radial width of the bottom ring when calculated from the
next way:

In the SI

Where:
It is the thickness of the annular plate in mm;

It is the maximum liquid design level in m;

It is the design specific gravity of the stored liquid.

In units in the USC

Where:
It is the thickness of the annular plate in inches;

It is the maximum liquid design level in feet;

It is the design specific gravity of the stored liquid.

5.5.3 The thickness of the annular bottom plates shall not be less than the greater
thickness determined using tables 5.1a and 5.1b, which are applicable for the value
effective from H x G ≤ 23m. Beyond this height, an analysis must be carried out.
elastic to determine the thickness of the plate.

Tab 5.1a–thickness of the bottom annular plate (

 Table 5.1b - thickness of the annular plate at the bottom ( (USC)

5.6 Body design

5.6.1 Generalities
5.6.1.1 The required thickness of the body sheets must be greater than the thickness
of design, including any corrosion tolerance or body thickness
for the hydrostatic test, but it should not be less than the thicknesses
established below:

Nominal diameter of the tank Nominal sheet thickness

NOTE 1 Unless otherwise specified by the buyer, the nominal diameter of the tank shall be
the diameter of the midpoint of the sheets of the lower ring of the body
NOTE 2 The specified thicknesses are based on mounting requirements
NOTE 3 When specified by the client, sheet with a nominal minimum thickness of 6mm can
replace ¼ inch sheet
NOTE 4 For diameters less than 15m but greater than 3.2m, the nominal thickness of the plates of
the body must not be less than 6mm.

5.6.1.2 Unless otherwise agreed with the client, the body panels must
to have a nominal width of 1800mm. The sheets that are going to be welded edge to edge

They should be cut approximately square.

5.6.1.3 The calculated effort for each ring of the body must not be greater than the
admissible effort allowed for the material used to manufacture the ring and none
The body ring can be thinner than the ring located immediately
on top of him.
5.6.1.4 Isolated radial loads, such as those generated by heavy loads in
platforms and elevated walkways between tanks must be distributed through
sections of structural elements, reinforcement plates in sheet metal or others
appropriate elements.

5.6.2 Admissible efforts

5.6.2.1 The maximum admissible design efforts of product Sdthey are shown
in tables 5.2a and 5.2b. the thicknesses of corroded plates will be used in the
calculation. The basic design effort Sdit will be either 2/3 of the elastic limit or 2/5
of the tensile strength, the lower one.
5.6.2.2 The maximum permissible effort in the hydrostatic test, Stit must be like this
Show in tables 5.2a and 5.2b. The nominal thickness of the plate must be used.
In the calculations. The basis of the hydrostatic test will be three-quarters of the limit.

elastic or 3/7 of the tensile strength, whichever is lower.

Table 5.2a–Allowed materials for sheets and permissible stresses (SI)
Table 5.2b - Allowed materials for sheets and permissible stresses (SI)
continuation
Table 5.2–Allowed materials for sheets and permissible stresses (USC)
 Table 5.2b–Allowed materials for sheets and permissible stresses (USC)
continuation

Annex A allows an alternative calculation method with a fixed allowable effort of 145.
Mpa and a joint efficiency of 0.85 0 0.70. this design can only be used for
tanks with body thicknesses of 13mm or less.
5.6.3 Calculation of thickness by the 1-foot method
5.6.3.1 This method allows calculating the required thickness at design points.
located 0.3m above the bottom edge of each ring of the body. This
Method n should be used to calculate tanks with diameters greater than 61m.
5.6.3.2 The minimum thickness required for each ring of the body shall be the greatest
value among those calculated by the formulas:

In the SI of units:

Where:
It is the design thickness of the body in mm
It is the thickness of the body for the hydrostatic test in mm
It is the nominal diameter of the tank in m
It is the liquid design level in m
It is the specific gravity of the liquid to be stored, it will be specified by
the client
It is the permissible corrosion in mm, specified by the client
It is the allowable stress for the design condition in MPa
It is the allowable stress for the hydrostatic test condition in MPa.

In USC units:
Where:

It is the design thickness of the body in inches.

It is the thickness of the body for the hydrostatic test in inches

It is the nominal diameter of the tank in feet
It is the liquid design level in feet
It is the specific gravity of the liquid to be stored, which will be specified by the customer.
It is the permissible corrosion in mm, specified by the client.
It is the allowable stress for the design condition in lbf/inch.2
It is the permissible stress for the hydrostatic test condition in lbf/inch2

5.6.4 Calculation of thickness by the variable point design method

5.6.4.1 The design by the variable point method provides body thicknesses.
for several points result in calculated stresses close to the stresses in
the real body. This method can only be used if the client has not
specified the design by the method of 1 foot when the following results
true

In the SI of units;

Where:

It is equal to (500Dt)0.5in mm

It is the diameter of the tank, in m

It is the corroded thickness of the bottom, in mm

It is the maximum liquid design level, in m

In the USC of units:
 Where:

It is equal to (6Dt)0.5, in inch

It is the diameter of the tank, in feet.

It is the corroded thickness of the bottom, in inches

It is the maximum liquid design level, in feet.

5.6.4.2 The minimum sheet thickness for any of the design conditions and
The condition of the hydrostatic test must be determined as follows: They will be made

Independent calculations for each design condition and the hydrostatic test.
The thickness of the required deposit will be greater than the design thickness plus one

tolerance for corrosion due to hydrostatic testing.

5.6.4.3 To calculate the thicknesses of the bottom layer, the following must first be calculated
values of y for the hydrostatic test.
5.6.4.4 The thickness of the bottom plates y for the design and testing
Hydrostatics must be calculated using the following formulas:

In the SI unit system:

( √ )( )

In the USC of units:

( √ )( )

NOTE: for the design code, does not need to be greater than
In the SI of units:
 ( √ )( )

In the USC of units:

( √ )( )

NOTE: The condition in the hydrostatic test, does not need to be greater than

5.6.4.5 For the calculation of thicknesses in the second layer, both for the condition of
Design for the hydrostatic test will calculate the value of the following
relationship

Where:

It is the height of the bottom layer, in mm (inches)

It is the nominal radius of the tank, in mm (inches)

It is the calculated corroded thickness for the bottom layer, in mm (inches);

used to calculate (design). The calculation of the thickness for the bottom plates
in the hydrostatic test will be used to calculate (hydrostatic test).

If the value of the radius is less than or equal to 1.375:

If the value of the radius is greater than or equal to 2.625:

If the value of the radius is greater than 1.375 but less than 2.625:

[ ]

Where:
 It is the minimum design thickness of the second body layer in mm (inch)
It is the corroded thickness of the second layer of the body, in mm (inches). In the

calculation of the second thickness of the body for the case of design and testing
hydrostatics, applicable values must be used from y .

5.6.4.6 For thicknesses at the top for the design and testing condition
Hydrostatics, a preliminary value for the corrosion thickness must be calculated.
5.6.3.2 and the distance x from the variable design point to the bottom layer must be
calculated using the indicated formulas and selecting the lowest value:

In the SI of units

Where:

It is the corrosion thickness in the upper layer at the circular joint, in

mm
Equal to [ ]
Equal to
It is the corroded thickness for the bottom of the layer at the joint
circular, in mm
It is the liquid level design, in m

In the USC of units:

 Where:

It is the corrosion thickness in the upper layer at the circular joint, in inches.
Equal to [ ]
Equal to
It is the corroded thickness for the bottom of the layer in the circular joint, in
bug
It is the liquid design level, in feet

5.6.4.7 The minimum thickness for the upper body layer must be calculated both

for the design condition , as for the test condition

hydrostatics using the minimum value of x obtained in 5.6.4.6.

In the SI of units:

( )

( )

In the USC of units:

( )

( )

5.6.5 Calculation of thickness by elastic analysis

For tanks where L/H is greater than 1000/6 (2 inch USC units), the
the thickness selection should be based on an elastic analysis that shows the
 calculated circumferential stresses that must be lower than the stress
permissible given in tables
5.7 Openings in the body
The following requirements aim to restrict the use of accessories that are
They will be fixed to the body by welding as indicated in figure 5.6.
5.7.1 Generalities

5.7.1.1 When an intermediate size is between those indicated in tables 5.3a to 5.13b
specified by the client, the construction of details and reinforcements will be
according to these tables. The size of the connection opening should not be greater
that the maximum size indicated in the corresponding table.

Table 5.3a–Thickness of the cover plate for the well in the body and flange bolts (SI)

5.7.1.2 The external loads will be minimized or the connections in the body must
to be relocated outside the rotation area. Annex P provides a method for the
evaluation of the openings according to tables 5.6a and 5.6b.
Figure 5.6–Minimum requirements for welding in the body openings
Table 5.3b–Thickness of the cover plate for well in the body and flange bolts (USC)
Table 5.4a - Neck mouth thickness dimensions (SI)
 Table 5.4b–Dimensions of the neck mouth thickness (USC)

5.7.1.3 The openings in the body can be reinforced with the use of inserts of
sheets as shown in figure 5.7b.
5.7.1.4 The shape and dimensions of the reinforcing opening are illustrated in the figures.
5.7a, 5.7b, and 5.8.
 Table 5.5a–Dimensions of the bolt circle diameter Dband diameter of the plate of
cover Dc (YES)

Table 5.5b–Dimensions of the diameter of the bolt circle Dband diameter of the plate of
cover Dc(USC)

5.7.2 Reinforcements and welds

5.7.2.1 Connections larger than two inches (NPS) flanged or threaded must be
reinforced
All connections that require reinforcement must be made with welding.
complete penetration in the body sheet.
5.7.2.2 The only manholes that can use welds that do not have penetration
complete are those that do not require reinforcement and use an insertion plate
as shown in figure 5.7b and figure 5.8.
Figure 5.7a–Manhole in the body
Figure 5.7b - Detail of manhole in the body and nozzles
Figure 5.8–Nozzles for the body
5.7.2.3 The reinforcements and welding must be configured to meet the requirements.
of effort. The permissible efforts for the elements are:
a) For reinforcements and exterior plates with the body and fillet weld in between
blade and the nozzle neck: Sdx 0.6.
b) For the tension across groove welds: Sdx 0.875 x 0.70.
c) For cutting at the neck of the nozzle: Sdx 0.8 x 0.875.

5.7.2.4 The reinforcement plates of the connections must have a threaded hole of 6mm.
1/4 inch diameter for leak detection.
5.7.3 Spacing of the welds through the connections
The minimum spacing of the body welds around the
connections are indicated in figure 5.6
By agreement with the client, circular connections and reinforcements can be placed.
at the edge welds of the vertical or horizontal joints of the body,
as long as the spacing requirements of figure 5.6 are met and
that a radiographic examination of the joint be done at 100% over a length of
5 times the diameter of the hole on each side of its horizontal centerline.

5.7.4 Thermal stress relief

5.7.4.1 All flush connections and flush cleaning doors shall
be thermally relieved after being manufactured and before being assembled in the
body, the thermal relief should be done between a temperature ranging from
600°C and 650°C for one hour for every 25mm of thickness of the material.
5.7.4.2 12 inch (NPS) connections or larger in body materials I, II, III or IIIA
with thicknesses greater than 25mm must be prefabricated in the body and the
the assembly must be thermally relieved before being installed in the body.
Thermal relief is similar to 5.7.4.1

5.7.4.3 When it is not possible to apply thermal relief at the minimum temperature of
600°C, it is allowed, subject to customer approval, to carry out the treatment.
 thermal at lower temperatures for longer periods of time, such as
as it is shown.

5.7.5 Body manhole

The dimensions and size of the body manhole must be in accordance
with what is shown in figures 5.7a and 5.7b and with what is established in tables 5.3a
up to 5.4b. Instead of manholes as the case indicates, alternative options can be used.

connections with flanges and blind caps.

5.7.6 Body connections and flanges
The dimensions and sizes of the body connections and flanges shall be
According to what is shown in figure 5.10, the connections can be made.
angles different from 90°.
5.7.6.1 The minimum nominal thickness of the nozzles' neck must be used as such
in such a way that it is equal to the required thickness identified by the term tn in the
table 5.6a and 5.6b.
5.7.7 Cleaning door
The dimensions and size of the connections and flanges of the cleaning door
You must agree with figures 5.12 and 5.13, backed by the
tables 5.9a to 5.11b.
When an intermediate size between those included in these tables is specified,
the construction and reinforcement details must be in accordance with those of
next largest size of those listed in the table.
 The reinforced connection must be fully pre-assembled on a sheet of
body and thermal relief of stresses must be done.

Figure 5.10–Flanged nozzles on the body

5.7.7.1 The area of the required cross-sectional reinforcement must be calculated as

It continues, both for the design condition and for the hydrostatic test.

Where:
It is the area of the cross-section of the reinforcement above the part
superior of the opening in mm2(inch2)
Area coefficient of figure 5.11
It is the vertical height of the hole in mm (inches)
It is the calculated thickness of the lower ring of the body, in mm (in), with
coefficient of the joint E=1, including corrosion tolerance.
5.7.7.2 The thickness of the amine in the cleaning door must be at least
similar to that of the adjacent body sheet in the lower ring.
The cleaning door reinforcement on the body plane must be
supplied within a height L above the bottom of the hole. L not
It must exceed 1.5 hours, except for small connections, L.h not
must be less than 150mm. When this exception results in an L that is
greater than 1.5h, only the portion of the reinforcement that is within the height
1.5h will be considered as effective.

Figure 5.11 – Area coefficient to determine the minimum reinforcement in

cleaning door type seal.

5.7.7.3 The minimum thickness of the reinforcement sheet at the bottom of the tank must be
250mm plus the combined thickness of the body and the reinforcement.

The nominal thickness of the bottom reinforcement is determined by the equation:

In the SI system of units:

√
 Where:
It is the thickness of the reinforcement sheet of the bottom, in mm
It is the vertical height of the free hole, in mm
It is the horizontal width of the free opening, in mm.
It is the liquid level design, in m
It is the specific gravity, not less than 1.

In USC units:

Where:
It is the thickness of the reinforcing sheet of the bottom, in inches
It is the vertical height of the free hole, in inches
It is the horizontal width of the free opening, in inches
It is the liquid design level, in feet
It is the specific gravity, no less than 1

5.7.8 Flush-Type Connections in the body

The tanks can have other flush connections, whose dimensions and sizes
they must comply with figure 5.14. the conditions must be met and
limitations regarding loads, efforts, and maximum dimensions. The
The dimensions of the connections will be according to tables 5.12a and 5.12b.
5.7.8.1 The maximum value of b cannot exceed 900mm, the maximum height h cannot
may exceed 300mm and the thickness tain the transition sheet with the background in
the assembly was at least 13mm.

5.7.8.2 The reinforced connection must be fully pre-assembled in an amine of the

heat treatment must be done at a temperature of 600°C to 650°C and
for a period of one hour for every 25mm of thickness.
 Table 5.12a - Dimensions of Flush-Type Connections with the Body (SI)

Table 5.12b–Dimensions of Flush-Type Connections with the Body (USC)

5.8 Body accessories and the tank

5.8.1 Body-mounted accessories
The accessories attached to the body must be made, inspected and
removed in accordance with the requirements of section 5 of API 650. There are
special considerations for accessories when attached to bodies of
materials from groups IV, IVA, V, and VI.
5.8.2 Connections in the background

Connections are allowed in the background by mutual agreement between the client and the

manufacturer to define the applicable resistance and construction details.

5.8.3 Flat plates
Connections smaller than NPS 2 can be placed without reinforcement on flat covers.
without the need to increase their thickness. Reinforced voids in flat plates are
 limited in size to half the diameter of the manhole hole without
exceed 12 NPS.
5.8.4 Manhole input connections in the ceiling
The Manhole connections on the roof must be in accordance with the figure.
5.16 and tables 5.13a and 5.13b.

Table 5.13a – Dimensions of manholes on the roof (SI)

Table 5.13b–Dimensions of manholes on the roof (USC)

Figure 5.16–Roof Manholes
5.8.5 Connections on the ceiling
The threaded and flanged connections on the ceiling will be according to the figure.
5.16 and 5.17.
5.8.6 Rectangular gaps in the ceiling
The rectangular openings in the ceiling, in supported ceilings, must be
according to figures 5.17 and 5.18.

Figure 5.17–Rectangular ceiling openings with flange covers

 Figure 5.18–Rectangular ceiling openings with hinge cover

5.8.7 Water drainage sumps

5.8.8 Support for the scaffolding cable
5.8.9 Threaded connections
5.8.10 Platforms, bridges, and stairs

5.9 Beams against upper and intermediate wind

5.9.1 Generalities
Open-top reservoirs must have a stiffening ring or
a beam to measure wind to maintain the roundness of the body when the tank
it is subjected to wind loads.
 These stiffening rings should preferably be located at the
upper extreme or near it, preferably from the outside of the tank.
5.9.2 Types of stiffening rings
The stiffening rings can be made of sections or profiles.
structural, made from sheet formed by bending or sections
fabricated by welding or a combination of both processes.

Figure 5.24 - Typical sections of stiffening rings for the tank body
5.9.3 Upper wind resistance beam
The minimum required section modulus of the upper stiffening ring
it must be determined by the following equation:

In the SI units:

( )

It is the required section modulus, in cm3

It is the nominal diameter of the tank, in meters
It is the body height of the tank, in meters, including any length.
additional that has been added as a free end for roof guide
floaters above the maximum fill height.
It is the design wind speed (3-second gust), in km/h

In the USC system of units:

( )

It is the required section modulus, in inches.3

It is the nominal diameter of the tank, in feet.

It is the body height of the tank, in meters, including any

additional length that has been added as a free end for guide of
floating roofs above the maximum filling height.
It is the design wind speed (3-second gust), in mph

5.9.4 Intermediate wind braces

5.9.4.1 The maximum height of the body without stiffeners must be calculated as
continue:
 In the international system:

()( √ )

Where:
vertical distance in meters between the beam and the intermediate wind
upper angle or the upper beam against wind of n end tank
open.
Nominal thickness as indicated, (of the upper ring of the body), to
unless otherwise specified, in mm
It is the nominal diameter of the tank, in meters.
It is the design wind speed (3-second gust), in Km/h

In the USC system of units:

()( √ )

Where:
Vertical distance in feet between the beam and the intermediate wind
upper angle or the upper beam against wind of n tank at the end
open.
Nominal thickness as indicated, (of the upper ring of the body), to
unless otherwise specified, in inches
It is the nominal diameter of the tank, in feet
It is the design wind speed (3-second gust) in mph

NOTE: this formula applies to tanks with closed or open lids, the
which meet the following factors:
a) The pressure of the speed is:
p = 0.00256Kz Kzt Kd V2I G= 1.48 kPa (31 lbf/ft)2)

where:
 Equal to the coefficient of exposure for pressure by
speed=1.04 for exposure C at a height of 40 feet
it is one for all structures, except those on the hills
the isolated cliffs
KdFactor direccional=0.95 para tanques redondos
It is the design wind speed (3-second gust), 190
Km/h at 10m above the ground
Importance factor = 1 for category II structures
Equal to the burst factor = 0.85 for exposure C

5.9.4.2 After the maximum height of the body without stiffeners, H1it has been
determined, the transformed height of the body must be transformed
how it continues:

a. With the following equation, change the current width of each ring of the body
for a transformed ring of each ring of the body that has a thickness
equal to that of the upper body ring:

( √ )

Where:
Transformed width of each ring of the body, in mm
Current width of each body ring, in mm
Thickness as indicated, (of the upper ring of the body),
unless other things are indexed, in mm
Thickness as ordered from the ring of the body for which the
transformed width is being calculated, in mm

b. Sum the transformed widths of the rings. The sum of the widths
transformed will give the height of the transformed body.
5.9.4.3 If the height of the transformed body is greater than the maximum height of
body, H1an intermediate wind brace is required.
5.9.4.3.1 For equal stability above and below the beam against
intermediate wind, the beam should be located in the middle of the
height of the transformed body.
5.9.4.3.2 Other locations can be used for the beam, as long as
when that the height of the body without stiffeners in the body
transformed does not exceed H1.
5.9.4.4 If half of the height of the transformed body exceeds the maximum height
H1A second intermediate beam should be used to reduce the height.
of the body without stiffeners at a height less than the maximum.
5.9.4.5 The intermediate beams should be joined to the body within a
distance of 150mm from the horizontal joint of the body. When the
preliminary location of the beam is within 150mm of the joint
horizontal, the beam must be located 150mm below the joint;
however, the maximum height of the body without stiffeners should not be
exceeded.
5.9.4.6 The minimum section modulus required for an intermediate beam against
wind shall be determined by the following equation:

In the SI of units:

( )

Where:
It is the minimum required section modulus, in cm.3
It is the nominal diameter of the tank, in meters.
Vertical distance in meters between the beam and the intermediate wind
the upper angle or the upper beam against the wind of a tank of
open end.
It is the design wind speed (3-second gust), in km/h
 In the USC system of units:

( )

Where:
It is the minimum required section module, in plg.3
It is the nominal diameter of the tank, in feet
Vertical distance in feet between the beam and the intermediate wind counter.
upper angle or the upper beam against the wind of an end tank
open.
It is the design wind speed (3-second gust), in mph

5.9.4.7 The section modulus of the intermediate wind beam will be based on the
properties of the attached members and may include a portion of the
tank body at a distance above and below the joint
with the body given in mm (inches).

In the SI:

Where:
It is the nominal diameter of the tank, in meters.
It is the thickness of the body indicated, unless otherwise specified.
opposite, in millimeters.

In USC units:

Where:
It is the nominal diameter of the tank, in feet.
 It is the thickness of the body indicated, unless specified otherwise.
opposite, in inches

5.10 Roofs
5.10.1 Definitions
The code gives design requirements for the following types of roofs
a. conical roof supported by beams and brackets in the body and with or without
columns.
b. Self-supporting conical roof supported only on the perimeter of the body
c. self-supporting spherical section roof (donor) (supported only on the
body periphery
d. Self-supporting umbrella-type roof (supported only on the perimeter of the
body) similar to the previous one but made up of regular polygons in the
horizontal section.
5.10.2 Generalities
5.10.2.1 All roofs and supporting structures must be designed for the
combination of loads (a), (b), (c), (e), (f), and (g).
5.10.2.2 the ceiling panels must have a nominal thickness of 5mm plus the
corrosion tolerance, for self-supporting conical roofs can be
the use of greater thicknesses is necessary.
5.10.2.3 The sheets of the supported conical roofs should not be welded to the
support structure elements, unless approved by the
client.
5.10.2.4 All structural elements of the roof must have a thickness
nominal of 4.3mm.
5.10.2.5 The sheets of the conical roofs must be welded to the angle.
superior with a continuous welding seam on the upper side
only.
 5.10.2.6 A ceiling is considered fracturable if the ceiling-body joint,
it can fail before the failure at the body-bottom joint occurs, in the
event of excessive internal pressure when the customer specifies a
A tank with a frangible roof can have the following:
a. Tanks with a diameter of 15m or larger
1) All members in the roof-body union region,
including rings for insulation should be considered
taxpayers in the transversal area (A), which can be calculated
in the following way;

NOTE: the terms of this equation are defined in the annex

F.
b. Independently anchored tanks with diameters greater than 9m
but less than 15m.
c. Alternatives for self-anchored tanks of less than 15m
diameter
d. For anchored tanks of any diameter where the tank the
counterweight anchoring must be designed for three times the
calculated failure pressure.
5.10.3 Allowable efforts
5.10.3.1 Generalities
The admissible efforts of all the components of the roof must be
determined under the requirements of ANSI/AISC 360 using the
allowable stress design method (ASD).
5.10.3.2 For columns the value of L/rcshould not exceed 180. For others
compression elements, L7r must not exceed 200. For the others
components except for the straps must be designed based on the
tension effort, the value L/r should not exceed 300.
Where:
L is the unbraced length in mm (inches)
 rcit is the minimum turning radius of the column, in mm (inch)
r is the predominant turning radius, in mm (inches).
5.10.4 Supported conical roofs
The slope on the roof must be 1:16 or greater. The centers of the beams
they must be spaced on the outer ring in such a way as to satisfy:

Where:
b is the maximum permitted ceiling separation measured circumferentially
It is the minimum allowed deflection effort for the ceiling sheets.
It is the corroded thickness of the ceiling

It is the uniform pressure determined by the combination of given loads.

5.10.5 Self-supporting conical roofs
The nominal thickness of the roof sheets must not be less than 4.8mm.
5.10.5.1 Self-supporting conical roofs must meet the following:

In the SI:
The nominal thickness shall not be less than the greater of:

√ , √ , and 5mm of corrosion thickness not

they must exceed 13mm.

Where:

It is the nominal diameter of the tank, in m

It is the highest level of load combinations with balanced snow load, in KPa
It is the highest degree of load combinations, with the unbalanced snow load, in
KPa
It is the angle of the elements of the cone with the horizontal, in degrees
It is the tolerance to corrosion