### Pressure Piping Minimum Wall Equations and Calculator:

ASME I and ASME-ANSI B31 – Pressure Piping - Minimum Wall Thickness: Equations and Calculator:

ASME Section I and ANSI B31, the minimum thickness of piping under pressure is:

or

For For t ≥ D/6 or for P/SE > 0.385, calculation of pressure design thickness for straight pipe requires special consideration of factors such as theory of failure, effects of fatigue, and thermal stress.

t (min)= Minimum wall thickness required (in);
P = Design pressure (psig);
D = Outside diameter of pipe (in);
S = Allowable stress in pipe material (psi);
E = Joint factor - E = 1.0 for seamless pipe, E = 0.85 for ERW pipe;
C = Corrosion allowance, typically 0.05 in.;
W = Weld joint strength reduction factor per para. 302.3.5(e)
y or Y = Wall thickness coefficient in ASME B31.3 Table 304.1.1 for ferritic steels, see table below.

 Wall Thickness Coefficient for Y Materials C° (F° ) ≤ 482 (900 & Lower) 510 (950) 538 (1,000) 566 (1,050) 593 (1,100) ≥ 621 (1,150 & up) Ferritic Steels 0.4 0.5 0.7 0.7 0.7 0.7 Austenitic steels 0.4 0.4 0.4 0.4 0.5 0.7 Other ductile metals 0.4 0.4 0.4 0.4 0.4 0.4 Cast Iron 0.0 - - - - -

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