Flame Arrestor Types and Working Principle
A flame arrestor is a passive safety device that allows gas to pass through but prevents flame propagation from one side to the other. It works by absorbing heat from the flame front as it passes through narrow channels in a metal element, quenching the flame before it can reach the protected side. Flame arrestors are critical safety components on storage tanks, vent lines, and piping systems handling flammable gases in oil and gas facilities.
When Flame Arrestors Are Used
Flame arrestors are installed wherever a flammable gas mixture could ignite and propagate back into a tank or process vessel:
- Storage tank vents: Protect atmospheric tanks from external ignition sources
- Vapor recovery lines: Prevent flame travel between connected equipment
- Flare header piping: Stop flashback from the flare tip reaching upstream vessels
- Fuel gas systems: Protect gas supply piping from burner flashback
- Marine loading arms: Prevent ignition from ship-to-shore vapor return lines
The device is selected based on the gas group (determined by the Maximum Experimental Safe Gap, or MESG) and the expected flame speed (deflagration or detonation).
Specifications and Standards
| Parameter | Details |
|---|---|
| Deflagration arrestor | Stops subsonic flame front (flame speed below speed of sound) |
| Detonation arrestor | Stops supersonic flame front with associated pressure wave |
| Endurance burn | Withstands sustained flame on one side without transmitting ignition |
| MESG (IEC 60079-20-1) | Group IIA: >0.90 mm; Group IIB: 0.50-0.90 mm; Group IIC: <0.50 mm |
| Element type | Crimped metal ribbon, perforated plate, or sintered metal |
| Body materials | Carbon steel, stainless steel, aluminum |
| Sizes | 1 in to 48 in |
| Standards | ISO 16852, API 2028, EN 12874, USCG 33 CFR 154 |
| Pressure drop | 0.5 to 5 mbar (clean); increases with fouling |
| End connections | Flanged (ASME B16.5), threaded, or tank-mount (end-of-line) |
Deflagration vs Detonation Arrestors
A deflagration arrestor is designed for relatively short pipe runs (typically less than 20-50 pipe diameters from the ignition source) where the flame has not had enough distance to accelerate to detonation speed. An in-line detonation arrestor must handle the much higher pressures and temperatures of a detonation wave and is required for long pipe runs where flame acceleration and deflagration-to-detonation transition (DDT) can occur.
Flame arrestors must be inspected regularly, as fouling, corrosion, or debris buildup increases pressure drop and can block venting capacity. Blocked vent paths on atmospheric tanks can cause vacuum collapse or overpressure. Maintenance records should be part of the facility inspection program.
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