API 5L X70 Pipe Calculator
ASME B31.8 — design pressure, minimum wall thickness and MAOP. SMYS is locked to the grade value.
API 5L X70 is a TMCP grade with a minimum yield of 485 MPa (70 ksi), produced to API 5L PSL2 as X70M in large-diameter LSAW form. It is specified for large-diameter gas transmission where reduced wall thickness versus X65 delivers project cost savings.
When to use this calculator: Size wall thickness for large-diameter X70 transmission pipelines and confirm the wall reduction benefit versus X65 at the project design pressure.
Example (API 5L X70)
| OD (mm) | Wall (mm) | Result |
|---|---|---|
| 609.6 | 14.3 | 16.3 MPa | 163 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 Technical Guide
API 5L X70 — Grades, Specifications & Selection Guide →Related Resources