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Pipe Thickness Calculator

Pipe wall thickness calculator

Straight pipe under internal pressure, ASME B31.3 ¶304.1.2

t = PD2 ( SEW + PY )
tm = t + c tnom = tm / (1 − mill tol.)
Pipe
Outside diameter D is filled in from ASME B36.10M / B36.19M.
Design conditions
Used to work out Y. Read S at this temperature.
Material and weld joint
From B31.3 Table A-1 for your material at the design temperature. Interpolate between temperatures.
Typical values from Table A-1B. Confirm for your material specification.
1.00 below the creep range. Above about 510 °C (950 °F) check ¶302.3.5(e).
Y = –
Allowances and tolerance
12.5 % is usual for seamless pipe. Use your spec’s value.
Many project specs set a minimum wall such as STD for handling and rigidity.
How this pipe thickness calculation works

ASME B31.3 ¶304.1.2 gives the pressure design thickness of straight pipe under internal pressure as t = PD / [2(SEW + PY)], valid when t is less than D/6. P is the internal design pressure, D the outside diameter, S the allowable stress at design temperature, E the quality factor, W the weld joint strength reduction factor and Y a temperature-dependent coefficient.

The minimum required thickness is tm = t + c, where c covers corrosion, erosion and thread or groove depth. Because pipe is delivered with a mill tolerance (commonly 12.5 % for seamless pipe), the nominal wall to order is tm / (1 − mill tolerance). The calculator then picks the next available wall from the ASME B36.10M and B36.19M schedules for the chosen NPS.

For learning and preliminary sizing. Calculation follows the method in Piping thickness calculation with an example. Standard wall thicknesses are nominal values from ASME B36.10M and B36.19M. Always check S, E, W and Y against the current edition of ASME B31.3 and have the final design reviewed by a qualified engineer. See the disclaimer.