Pipe MAOP Calculator

What is MAOP in pipeline engineering?

MAOP (Maximum Allowable Operating Pressure) is the maximum pressure at which a pipeline is legally and safely permitted to operate. It is determined by federal regulations (49 CFR Part 192) and engineering standards (ASME B31.8) based on the pipe's strength, location, and condition.

How does this calculator determine MAOP?

It uses the ASME B31.8 design formula: P = (2St/D) × F × E × T. It automatically handles variables like Design Factor (F) based on location class and Temperature Derating (T) for high-temp service. It also accounts for corrosion allowance and manufacturing tolerance (12.5%).

Why is the calculated wall thickness different from the nominal thickness?

This calculator applies a 12.5% manufacturing under-tolerance per ASME B31.8 §817.1. This means if you select a 0.375" wall, the calculation assumes the pipe could be as thin as 0.328" due to manufacturing variations, ensuring a conservative and compliant safety margin.

What are the Design Factors for different Location Classes?

• Class 1 (Rural): 0.72 (72% SMYS)
• Class 2 (Fringe): 0.60 (60% SMYS)
• Class 3 (Suburban): 0.50 (50% SMYS)
• Class 4 (Urban): 0.40 (40% SMYS)

Does this calculator handle Hydrostatic Test Pressure?

Yes. The results section includes the minimum required hydrostatic test pressure per 49 CFR §192.505 (e.g., 1.25× MAOP for Class 2, 1.4× or 1.5× for other classes) to validate the pipeline before service.