Annex 2C: Thickness and MAWP Alpha · 2026-10-04

API 579-1 (2021) Annex 2C — Minimum required thickness, MAWP and membrane stress for shells, heads, pipes and tanks

API 579 Annex 2C — Thickness and MAWP

Finds the minimum required thickness t_{min}, the maximum allowable working pressure MAWP and the nominal membrane stress of a component, per API 579-1/ASME FFS-1 (2021) Annex 2C. The uniform metal loss LOSS and the future corrosion allowance FCA are taken off the wall first. It is the base for Part 4 and Part 5 thinning assessments.

• Vessel parts (ASME VIII-1 equations): cylinder, sphere or hemispherical head, elliptical head, torispherical head, cone.
• Piping (ASME B31.3 equations): straight pipe and pipe bend.
• Tank (API 650 one-foot method): shell course, result is the maximum fill height MFH.

The check is t \ge t_{min} (Option 1, 2C.2.2(a)). Annex 2C does not replace the original construction code. You choose the allowable stress S and the joint efficiency E.

Engineering data

• Material Query
• Pipe Dimensions

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