Flare Tip Mach Number & Husa Purge Calculator
Compute emergency relief exit velocity, Mach number, and continuous purge gas consumption ($Q_{purge}$) via the Husa equation to prevent internal flashback.
Flare Tip Geometry & Gas Properties
Tip Velocity & Continuous Purge Rate
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Flare Tip Hydraulics & Husa Purge Physics
During peak emergency plant overpressure, relief gases exit through the flare tip at high velocities. API Standard 537 recommends sizing flare tip diameters to maintain exit velocities below $\text{Mach } 0.20$ during normal maximum relief and below $\text{Mach } 0.50$ during short-duration emergency blowdown to prevent excessive backpressure on upstream relief valves.
Internal Flashback & Continuous Purge
When the flare is idle, cold atmospheric air naturally migrates down the open flare stack due to wind draft and density differences between ambient air and warm hydrocarbon vapors. If an ignition source is present at the tip, oxygen ingress creates a flammable mixture inside the stack, causing an internal explosion (flashback). The Husa correlation calculates the minimum continuous purge rate required to keep internal oxygen below $6\%$.