ASME B31.1 Power Piping Wall Thickness Calculator — Sample Report

ProjectSample Project — Demonstration Only	Job No.SAMPLE-001	Client—
CalculationASME B31.1 Power Piping Wall Thickness Calculator	Calc byPiping Toolset (calc-core)	Checked byUNCHECKED — sample
Date2026-09-03	Rev0	BasisASME B31.1 ¶104.1.2 (also B31.5/B31.9 form)

1 · Design inputs

NPS 8 (8.625 in OD) main steam-class line at 1,000 psi. SE = 15,000 psi, y = 0.4, allowance A = 0.065 in, 12.5% mill tolerance.

Design pressure P	1,000	psi
Outside diameter Do	8.625	in
Allowable SE	15,000	psi
Coefficient y	0.4	—
Allowance A	0.065	in
Mill tolerance	12.5	%

2 · Method

Pressure design of straight pipe under internal pressure, B31.1 ¶104.1.2 (Eq. 7 form):

t = P·D_o / ( 2 (S·E + P·y) )

t_m = t + A

t_order = t_m / (1 − mill tolerance)

The calculator applies the equation exactly as written. It first forms the denominator 2·(S·E + P·y): S·E is the maximum allowable stress including longitudinal joint efficiency, taken from the B31.1 Appendix A tables for the material at design temperature, and y is the temperature coefficient of Table 104.1.2-1, which credits stress redistribution through the wall as temperature rises. Dividing P·D_o by that denominator gives the pressure design thickness t. The additional thickness allowance A — corrosion, erosion, threading or grooving, structural — is added to give the minimum required wall t_m, and dividing by (1 − mill tolerance) grosses t_m up to the nominal thickness to order, so pipe delivered at the bottom of the mill's under-tolerance still meets t_m. Units are consistent-unit: psi with inches, or MPa with millimetres. If t reaches D_o/6 the calculator flags the result as outside the thin-wall validity of the equation.

3 · Calculation

Denominator: 2·(SE + P·y) = 2·(15,000 + 1,000·0.4) = 2·15,400 = 30,800 psi.
Pressure design thickness: t = 1,000·8.625 / 30,800 = 0.28003 in.
Minimum wall: t_m = 0.28003 + 0.065 = 0.34503 in.
Ordering thickness: 0.34503 / 0.875 = 0.39432 in → Sch 60 (0.406 in) covers it; Sch 40 (0.322 in) does not.

4 · Results COMPUTED

t — pressure design thickness	0.28003	in
tm — minimum required	0.34503	in
Ordering thickness	0.39432	in

5 · Verification statement

The result values above are locked as fixture b311-wall-thickness.json, case “NPS 8 @ 1000 psi, S=15000, E=1, y=0.4, A=0.065, 12.5% mill tol”, tolerance 0.00001, in the calc-core continuous verification gate (see https://pipingtoolset.com/trust/validation.html). Allowable-stress and factor data are user-supplied inputs; citations: ASME B31.1, Power Piping — ¶104.1.2, pressure design of straight pipe (Eq. 7 form). · ASME B31.1 — Appendix A allowable stress tables; Table 104.1.2-1 coefficient y — values user-supplied, not embedded. · ASME B31.5 / B31.9 — same equation form used by the Building & HVAC line with those sections' allowables.

SAMPLE REPORT — auto-generated from a verification fixture to show the report format. Not a project calculation. ⚠ Engineering-aid tool. Public code equations; allowable-stress and factor data are user-supplied. Results MUST be independently verified and reviewed by a qualified/licensed engineer before any design, fabrication, or operation decision.