Pipe Wall Thickness Calculator
ASME B31.3 Process Piping — required wall thickness with mill tolerance, corrosion allowance, and schedule lookup
Results
Required Thickness t
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Min Ordered (+ 12.5% mill tol.)
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Design Thickness (+ corrosion)
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Pipe OD Used
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Recommended Schedule: —
Formula Reference (ASME B31.3)
t_required = P × D / (2 × (S × E + P × Y))
t_min = t_required / (1 − 0.125) [12.5% mill tolerance]
t_design = t_min + corrosion_allowance
where:
P = design pressure (psi)
D = pipe outside diameter (in)
S = allowable stress at temperature (psi)
E = joint quality factor
Y = temperature correction factor
t_min = t_required / (1 − 0.125) [12.5% mill tolerance]
t_design = t_min + corrosion_allowance
where:
P = design pressure (psi)
D = pipe outside diameter (in)
S = allowable stress at temperature (psi)
E = joint quality factor
Y = temperature correction factor
Worked Example
NPS 4 pipe (OD = 4.500″), P = 600 psi, A106-B (S = 17,100 psi), Seamless (E = 1.0), Y = 0.4, CA = 0.05″.
| Step | Calculation | Result |
|---|---|---|
| t_required | 600 × 4.500 / (2 × (17100×1.0 + 600×0.4)) | 0.0778″ |
| t_min | 0.0778 / (1 − 0.125) | 0.0889″ |
| t_design | 0.0889 + 0.05 | 0.1389″ |
| Recommended Schedule | Sch 40 wall = 0.237″ ≥ 0.139″ | Schedule 40 |