Detonation arrest testing provides objective, standards-based proof that a storage tank flame arrester can stop supersonic flame fronts and their accompanying shock waves without allowing flame transmission to the protected side of the device. This technical article explains the applicable international standards, sample requirements, core test items, laboratory test methods, and typical applications of detonation arrest testing for storage tank flame arresters.
Technical Overview
Flame arresters are passive mechanical explosion protection devices installed on storage tank vents, breather valve inlets, and connected vapor piping. The device contains a flame-quenching element—typically crimped metal ribbon, woven wire gauze, parallel plates, or sintered metal—whose narrow channels extract heat from a propagating flame faster than the combustion reactions can release it, extinguishing the flame before it reaches the tank vapor space or downstream equipment.
When a flammable vapor–air mixture ignites inside a vent line or header, combustion can propagate in two distinct regimes. A deflagration travels at subsonic velocity with a moderate pressure rise, while a detonation is a supersonic combustion wave coupled to a leading shock front, propagating at roughly 1,600–2,200 m/s in hydrocarbon–air mixtures and generating pressures around 20 bar or higher. Between these regimes, during the deflagration-to-detonation transition (DDT), unstable or overdriven detonations occur with local pressure spikes that can far exceed those of stable detonations and place the most severe mechanical demand on an arrester.
A detonation-rated flame arrester must extinguish all of these regimes without any flame transmission, retain structural integrity, and continue functioning afterwards. Detonation arrest testing—performed by accredited third-party laboratories against ISO 16852 (EN ISO 16852), UL 525, ASTM F1273, and the Chinese national standard GB/T 13347 for petroleum gas pipeline flame arresters—subjects full-scale arrester samples to controlled detonations in instrumented pipeline rigs and verifies performance under repeatable worst-case conditions.
Certification results define the certified gas group (IIA, IIB, or IIC), the maximum operating pressure, the operating temperature range, and the allowable installation orientation and pipe configuration. These limits for use must be respected during system design, as performance outside the tested envelope cannot be assumed.
Testing Samples
In-Line Detonation Flame Arresters
These units are installed in pipework, for example between a tank vapor outlet and a vapor recovery header, where flame acceleration and detonation are credible. Samples are full-scale production units complete with housing, quenching element, and end connections, typically ranging from DN25 to DN600 (1 to 24 in). Elements are usually crimped corrugated ribbon in stainless steel (304, 316L, or 321), with samples submitted together with manufacturing drawings and the declared gas group and MESG classification.
End-of-Line Flame Arresters
Mounted directly at the tank vent outlet, these devices are primarily exposed to atmospheric deflagrations and are tested mainly for deflagration flame transmission and endurance burning. However, when an end-of-line device is connected through piping, manifolds, or a combined breather valve assembly in which flame acceleration can occur, detonation arrest testing becomes applicable.
Flame Arrester Elements and Cartridges
Replacement elements and cartridges are tested in housings identical to the certified configuration, because element gap width, crimp height, ribbon thickness, element length, and housing geometry all directly influence quenching performance. Any dimensional or material deviation from the tested design invalidates the certification.
Breather Valve and Arrester Assemblies
Combined pressure/vacuum vent valves with integrated flame arresting elements are tested as complete assemblies. The pallet and seat arrangement must not create flame paths or leakage routes that bypass the quenching element under detonation loading.
Testing Items
A complete detonation arrest qualification program typically includes the following test items:
- Stable detonation flame transmission test—repeated arrest of fully developed detonations in both flow directions
- Unstable (overdriven) detonation flame transmission test—arrest of detonations in the DDT transition regime with maximum pressure loading
- Deflagration flame transmission test—arrest of subsonic flames at short run-up lengths, at near-atmospheric and elevated initial pressures
- Short-time endurance burning test—resistance to a flame stabilized on the element surface
- Long-time endurance burning test—extended flame stabilization for higher-risk services, as defined in ISO 16852
- Flow resistance (pressure drop) test—verification of differential pressure at rated flow
- Housing strength and leak tests—hydrostatic or pneumatic proof pressure verification
- Thermal and mechanical integrity after detonation—no cracking, deformation, or displacement of the element
- Corrosion resistance—salt spray exposure and, where required, qualification for sour gas service
Testing Methods
Test Apparatus
Testing is conducted in a closed pipeline rig consisting of a run-up pipe of the same nominal diameter as the sample, a gas mixing and metering system, a high-energy ignition source at a defined distance from the arrester, and an array of piezoelectric pressure transducers plus photodiodes or ionization probes spaced along the pipe. High-speed data acquisition, typically at 100 kHz or higher, resolves detonation velocity and peak pressure at the arrester face. The protected side of the rig terminates in an observation chamber where any flame transmission is detected both visually and by sensors.
Test Gases and Conditions
Test media represent the MESG group for which certification is sought: hydrogen for Group IIC, ethylene for Group IIB, and propane or methane for Group IIA. Near-stoichiometric mixtures are prepared by partial pressure or flow metering and verified by gas analysis. Tests are conducted at ambient temperature and, for extended pressure ratings, at elevated initial pressures in accordance with ISO 16852.
Stable Detonation Test Procedure
The ignition position is set at a sufficient run-up length so the flame accelerates to a stable detonation before reaching the arrester. Measured flame velocities and peak pressures confirm that Chapman–Jouguet conditions have been achieved. The arrester must arrest a defined consecutive series of stable detonations in both flow directions; a single flame pass constitutes failure of the test series.
Unstable Detonation Test Procedure
The ignition distance is progressively shortened to place the arrester within the deflagration-to-detonation transition zone, where the detonation is overdriven and local pressures are highest. Testing sweeps multiple run-up lengths to capture the worst-case loading condition for the element and housing, and the arrester must again prevent flame transmission at every condition tested.
Endurance Burning Test Procedure
A flame is stabilized directly on the element surface using an optimized mixture and pilot ignition, with a controlled air supply on the protected side. The flame must burn for the specified short-time or long-time duration without flashback through the element, burn-through, or loss of mechanical integrity, while element temperature is continuously monitored.
Flow Resistance and Auxiliary Tests
Air is drawn through the arrester at rated volumetric flow while the differential pressure across the unit is recorded and compared against the manufacturer's declared flow curve. Housing proof pressure testing, seat leakage checks where applicable, and material verification complete the qualification file.
Across all detonation and endurance tests, acceptance is based on zero flame transmission to the protected side, retention of structural integrity of the element and housing, and demonstrated continued arresting capability after the test series.
Applications
Detonation-tested flame arresters are essential wherever stored flammable liquids generate ignitable vapor and where vent geometry permits flame acceleration:
- Crude oil, gasoline, jet fuel, and diesel storage tank vents and breather valve inlets
- Chemical storage tanks containing solvents, alcohols, ketones, ethers, and aromatics
- Vapor recovery units and shared vent collection headers where DDT is credible
- Truck, rail, and marine loading terminals
- Biogas digesters, landfill gas collection systems, and anaerobic wastewater treatment covers
- Fuel ethanol plants and edible oil tank farms
Correct selection requires matching the certified gas group, temperature class, maximum operating pressure, and installation configuration to the process hazard identified in the safety analysis. Detonation-rated arresters are mandatory whenever the device is not mounted directly at the vent outlet and connected piping lengths allow flame acceleration beyond deflagration limits.
FAQ
What is the difference between a deflagration and a detonation flame arrester?
A deflagration arrester is certified to stop subsonic flame fronts, typically for direct end-of-line installation. A detonation arrester is certified to stop supersonic detonations, including unstable overdriven detonations in the DDT regime, and may be installed in-line where flame acceleration is possible.
Which standards govern detonation arrest testing of storage tank flame arresters?
ISO 16852 is the principal international performance standard covering flame arresters, including detonation, endurance burning, and limits for use. UL 525 and ASTM F1273 apply in North America, while GB/T 13347 covers flame arresters for petroleum gas pipelines in China.
What is MESG and why does it matter?
MESG (Maximum Experimental Safe Gap) is the largest gap through which a flame of a given gas will not propagate. It determines the gas group classification: Group IIA (e.g., propane), IIB (e.g., ethylene), and IIC (e.g., hydrogen). The arrester element gap must be smaller than the MESG of the target vapor for reliable flame arrestment.
Can one tested arrester cover all stored fluids?
No. An arrester is certified for a specific gas group, pressure, and temperature range. Group IIC certification also covers IIA and IIB gases, but the reverse is not true, and operating conditions must always remain within the certified limits for use.
How often should flame arresters be inspected or retested?
In-service units should be periodically inspected on site for element plugging, corrosion, and mechanical damage according to the plant maintenance program. Laboratory detonation testing is required for new designs, design modifications, or recertification, rather than as routine in-service verification.
