Calculators
Flare Header Sizing
Sizes a flare main header from relief load, gas properties, and Mach number limit. Computes sonic velocity, required flow area, Darcy pressure drop, and back-pressure at the flare tip for a user-specified pipe ID. Based on API 521.
Reference: API Standard 521 — Pressure-Relieving and Depressuring Systems, Sections on flare header sizing and back-pressure limits. Typical main header Mach limit: 0.5 (some operators use 0.6); lateral Mach limit: 0.7. Equivalent length adds ~5·D per elbow as a screening approximation. For final design, use a dedicated flare network simulator (Flarenet, Aspen Flare System Analyzer).
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