ASME B31.8 Gas Pipeline Wall Thickness Calculator
Gas Transmission and Distribution Piping Systems
Allowable Stress Sa = F × E × T × Sy where F is the design factor (location class), E is the weld joint factor, T is the temperature derating factor, and Sy is the specified minimum yield strength of the pipe
Note: Design temperature for ASME B31.4 pipelines is typically up to 250°F. Mill tolerances are covered by the design factor (F).
1. Pipe wall thickness calculations are as per ASME B31.8 (Gas Transmission and Distribution Piping Systems).
2. Allowable stress S = F × E × T × Sy where F is the design factor (location class), E is the weld joint quality factor, T is the temperature derating factor, and Sy is the specified minimum yield strength.
3. Temperature Derating Factor (T) is determined from ASME B31.8-2012 Table 841.1.8-1 based on design temperature, or may be entered as a custom value.
4. Column (D/t < 100?) — pipelines with D/t ratio greater than 100 may require additional protective measures during construction. Yes means D/t < 100 (acceptable). No means D/t ≥ 100 (special care required).
5. t is the pressure design thickness: t = P·D / (2·S) where P is in bar, D is in mm, and S is in MPa.
6. tn is the nominal wall thickness: tn = t + A, where A is the sum of corrosion, erosion, and mechanical allowances.
7. The selected thickness must be greater than or equal to tn.
8. MAWP = 2·Th·S / D where Th = tselected - A (allowances) and S = F × E × T × Sy.
| NPS (DN) |
OD (mm) |
Type of Construction |
Weld Joint Factor (E) |
Pressure Design Thickness t (mm) |
D/t | D/t < 100? | Allowances A (mm) |
Nominal tn (mm) |
Recommended Standard Thickness (Schedule) |
Selected Thickness |
MAWP (bar) |
|---|
⚠ Disclaimer: This tool is intended for general reference and educational purposes. While we strive for accuracy, please verify critical calculations independently. Final pipeline design must be performed and certified by a qualified Professional Engineer (PE). piping-world.com accepts no liability for errors or actions taken based on the output of this calculator.