ASME B31.3

Key requirements (10)

• Process piping — refining, chemical, pharmaceutical, semiconductor.
• Categories: Normal Fluid Service (default), Category D (low pressure < 150 psig & temp 38–186 °C), Category M (lethal), High Pressure, Severe Cyclic, High Purity.
• Allowable stress: lower of UTS/3, Yield/1.5, etc., from Table A-1.
• Wall thickness: t = P·D / (2·(S·E·W + P·Y)) where Y = 0.4 for ductile under 482 °C.
• Joint efficiency E: 1.0 (seamless), 0.85–0.95 (welded depending on RT).
• Hydrotest: 1.5 × design pressure × (S_test/S_design) — ≥ 10 minutes hold.
• Pneumatic test (when hydro impractical): 1.1 × design pressure with safety analysis.
• Examination: 5% RT for Normal service; 100% RT for Category M and Severe Cyclic.
• Flexibility analysis required when temperature differential > 28 °C and complex routing.
• Stress range allowable SA = f·(1.25·Sc + 0.25·Sh) with f = cyclic reduction factor.