Flame, Deflagration & Detonation Arresters

Flame front interruption for tanks, vents, and piping.

What It Is & How It Works

Flame, deflagration, and detonation arresters are passive safety devices that stop a flame front from propagating through tank openings, vent outlets, or interconnected piping into a flammable vapor space. They address the risk of an external ignition source, such as lightning, static discharge, or nearby equipment, reaching stored product through any opening that connects the tank interior to atmosphere or to another vessel.

Each arrester contains a metallic element, typically crimped ribbon or parallel plate, that divides the gas passage into channels narrower than the quenching distance of the target gas group. A flame entering the element loses heat to the metal faster than combustion can sustain it, extinguishing the flame front while allowing normal vapor flow. Element type, gap size, and housing strength determine whether the device arrests a deflagration, a stable detonation, or an unstable detonation.

Arresters mount at tank nozzles, vent-pipe terminations, or inline within piping. Selection depends on installation position, gas group classification, the flame-propagation scenario the device must arrest, and the length-to-diameter (L/D) ratio of connected piping that governs whether a deflagration can transition to detonation.

Deflagration vs. Detonation: Why It Matters

A deflagration is a flame front traveling below the speed of sound at moderate pressure. A detonation travels at supersonic speed with a high-pressure shock wave. Standard flame arresters stop deflagrations; detonation arresters are built to withstand the shock energy of a supersonic flame front without failing. Specifying the wrong type for the scenario provides no protection.

When to Specify Flame, Deflagration & Detonation Arresters

Flame, deflagration, and detonation arresters are specified wherever a flammable vapor space connects to a potential ignition source through an opening, vent, or piping run:

Fixed-Roof Petroleum and Chemical Storage Tanks: Atmospheric tanks storing flammable liquids where NFPA 30, API 2000, and EPA 40 CFR 60/63 require flame protection at every vent opening connecting the vapor space to atmosphere.
Vent Pipe Terminations and Manifolded Systems: End-of-line installations at vent outlets, or manifolded systems where multiple tanks share a common header and one ignition event could propagate across vessels.
Inline Piping to Vapor Recovery: Vapor return lines, vapor recovery unit inlet piping, and tank-to-tank equalization lines where flame propagation through interconnected piping must be interrupted.
Biogas and Digester Gas Piping: Collection headers and piping between digesters and CHP engines, flares, or upgrading equipment, where methane creates continuous flame-propagation risk.
ATEX or IECEx Classified Areas: Classified hazardous areas where explosion-protection regulations require certified flame-interruption devices at defined points in the vapor-handling system.

Shand & Jurs Model 94306 Vertical End-of-Line Flame Arrester

Why It Excels

Tank Openings Requiring Certified Flame Interruption

End-of-line and tank-mounted arresters provide tested, certified flame interruption at every opening where the vapor space meets atmosphere, satisfying NFPA 30 and API 2000 flame-protection requirements at storage tanks.

Manifolded Vent Systems Connecting Multiple Tanks

Inline arresters in a shared vent header keep a flame event at one tank from propagating through the manifold to other connected vessels, isolating the ignition to a single source.

Piping Where Deflagration-to-Detonation Transition Is Possible

Detonation-rated models arrest a supersonic flame front and its shock wave, protecting long pipe runs where the length-to-diameter ratio creates conditions for a deflagration to accelerate into detonation.

Facilities Needing Both Deflagration and Detonation Protection

A range spanning plate-element flame arresters through inline deflagration and detonation models lets one source address every flame-hazard severity level across a facility.

Flame Arrester Type — Selection Guide

Attribute	End-of-Line / Tank-Mounted	Inline Deflagration	Inline Detonation
Installation position	At a vent outlet or tank nozzle open to atmosphere	Within piping between vessels or to vapor recovery	Within piping where long runs create detonation risk
Flame scenario arrested	External ignition propagating inward through the vent	Deflagration, a subsonic flame front, within piping	Detonation, a supersonic flame front with shock wave
Typical length-to-diameter (L/D) ratio	Not applicable (open to atmosphere)	Short to moderate pipe runs	Long runs exceeding the deflagration-transition threshold
Pressure Resistance	Low: atmospheric vent service	Moderate: deflagration pressures	High: detonation shock-wave energy
Regulatory Driver	NFPA 30, API 2000, EPA 40 CFR 60/63	NFPA 69, EN 12874, site hazard analysis	EN 12874, ATEX/IECEx, site detonation risk assessment
Representative Models	94306, 94309	94406, 94407	9431X (94311–94314)
Recommendation	Specify for every atmospheric vent opening on tanks storing flammable liquids	Specify for interconnected piping where deflagration risk exists and the L/D ratio is below the detonation-transition threshold	Specify for long pipe runs where deflagration-to-detonation transition is possible given gas group and pipe geometry

What to Consider Alongside Flame, Deflagration & Detonation Arresters

Consider an alternative when:

You need pressure and vacuum relief for thermal breathing and pumping, not flame interruption. See Pressure & Vacuum Conservation Vents.
You need large-volume vapor discharge during fire exposure, not flame-propagation prevention.
You need flame arresters configured for digester cover openings in biogas service rather than petroleum or chemical storage. See Biogas Cover Equipment.
You need inline deflagration or detonation arresters specifically for biogas piping between the digester and utilization equipment. See Biogas Stream Equipment.

How Flame, Deflagration, and Detonation Arresters Fit Into a Larger System

Pair end-of-line flame arresters with conservation vents to deliver both emissions-controlled tank breathing and flame interruption at the same vent opening. See Pressure & Vacuum Conservation Vents.

Combine tank-mounted flame arresters with L&J Technologies level alarm probes, emergency vents, and Varec FuelsManager® feeding Clairvoyance to build a layered system covering flame, overfill, and overpressure from sensor to software. See Level Alarms and FuelsManager®.