Minimum Thickness Measurement of Tank

API 650: never less than 5 mm

3.6.1.1

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:

3.6.1.2

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.

3.6.1.3

The design shell thickness shall be computed on

the basis that the tank is filled to a level H (see 3.6.3.2) with a

liquid that has a specific gravity specified by the purchaser.

3.6.1.4

The hydrostatic test shell thickness shall be computed

on the basis that the tank is filled to a level H (see

3.6.3.2) with water.

3.6.1.5

The calculated stress for each shell course shall not

be greater than the stress permitted for the particular material

used for the course. No shell course shall be thinner than the

course above it.

3.6.1.6

The tank shell shall be checked for stability against

buckling from the design wind velocity, as specified by the

purchaser, in accordance with 3.9.7. If required for stability,

intermediate girders, increased shell-plate thicknesses, or both

shall be used. If the design wind velocity is not specified, the

Nominal Tank Diameter

(See Note 1)

Nominal Plate Thickness

(See Note 2)

(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

Notes:

1. Unless otherwise specified by the purchaser, the nominal tank

diameter shall be the centerline diameter of the bottom shell-course

plates.

2. Nominal plate thickness refers to the tank shell as constructed.

The thicknesses specified are based on erection requirements.

3. When specified by the purchaser, plate with a minimum nominal

thickness of 6 millimeters may be substituted for 1/4-inch plate.

Regards, Whitephone

What material is it made from?

Dear friend...

you have not mentioned the type of tank(rectangular or cylindrical, atmospheric operated or under certain pressure.).

i dont know how to update the calculation sheets in this site...

Kindly reply ur persinal id i will forward the calculations

i am just sending u the formula for your immediate work...

CALCULATION OF SHELL PLATE THICKNESS (Tank operated under atmospheric pressure ):

As per Clause No. 6.3.3.1 and 6.3.3.3, Page 22 & 23 of IS-803; Thickness of various shell courses can be worked out as follows:

t = 50 G D( H - 0.3 ) + C (1) S E

Where

t = Minimum Thickness of Shell Plate in mm

G = Sp. Gr. Of liquid to be stored

D = Nominal Diameter of Tank in m

H = Height from the bottom of course under consideration to max overflow liquid level in m.

S = Sd = Maximum Allowable Working Stress in Kg/cm²

E = Joint efficiency

C = Corrosion Allowance in mm

4.0 Thickness calculation for cylindrical shell as per clause No. 3.3.2.2 of IS:2825-1969 ( Tank operated under certain pressure)

Minimum thickness of the shell shall be determined by the given Formula :

t = p D_i (A) 200 fJ - p

Where, t = thickness of shell plates exclusive of corrosion allowance in mm

p = Design Pressure in kg/cm² = 1

D_i = Inside diameter of shell in mm = 2500

f = Allowable stress value in kg/mm² = 14

J = Joint efficiency factor = 0.85

Thickness Calculation :( Tank operated under certain pressure as per 31.3 code)

As per ASME B31.3-1999, minimum thickness of wall,

tm = P Do + A

2 [ S E + P y ]

Internal Design Pressure, P = 10.0 kg/cm²

Maximum Allowable Stress, S = 1406 kg/cm²

Weld Joint Efficiency, E = 0.95

Coefficient for Ductile Material, y = 0.4

Minimum Thickness of Pipe Wall, tm = in cm

Allowance for Corrosion etc., A = 0.2 cm

Outside Diameter of Pipe, Do = 6.03 cm

Hi Rakesh,

First I would like to thank you for mentioning IS codes. I don't know about these codes.

I want to design Atmospheric tanks of Stainless steel. But I do not want to use API.

As 5 mm minimum wall thickness is condition as per API.

I want to design tank of diameter range from 2.5 m to 5.0 m.

And TL To TL height is in the range of 6 m to 12 m.

Tanks with conical bottom & conical top. rested on pipe leg supports.

By which standard I shall design tanks.

Thanks in Advance.

The best is to design with IS 2825 - Code for Unfired presure vessels.