API 5L Grade B Pipe Calculator
ASME B31.8 — design pressure, minimum wall thickness and MAOP. SMYS is locked to the grade value.
API 5L Grade B is the base-strength line pipe grade with a minimum yield of 245 MPa (35 ksi), produced in seamless, ERW, or LSAW form. It is the standard grade for gas gathering, water distribution, and low-pressure transmission pipelines.
When to use this calculator: Verify wall thickness and design pressure for gathering and distribution pipelines using ASME B31.8 Class 1–4 design factors.
Example (API 5L Grade B)
| OD (mm) | Wall (mm) | Result |
|---|---|---|
| 219.1 | 8.18 | 13.2 MPa | 132 bar design pressure (F=0.72) |
Results are reference values — verify against API TR 5C3 (OCTG) or ASME B31.8 (line pipe) before use in final design.
Design Pressure
P = (2 × t × SMYS × F × E × T) / OD | ASME B31.8 §841.11
E = 1.0 (seamless / full-NDE ERW / LSAW), T = 1.0 (≤120 °C). Adjust per B31.8 Tables 841.115A/B for temperature derating or reduced joint efficiency.
Minimum Wall Thickness
t = (P × OD) / (2 × SMYS × F × E × T) | Rearranged ASME B31.8
Maximum Allowable Operating Pressure (MAOP)
MAOP = (2 × t_actual × SMYS × F × E × T) / OD
Related Resources