Flame arresters protect systems subject to explosion Explosion Abrupt oxidation or decomposition reaction producing an increase in temperature, pressure, or in both simultaneously. hazards. They sit at the opening of an enclosure or on the connecting pipe of a system of enclosures. Their job is simple, which is to allow flow but prevent the transmission of flame.

Potentially explosive gas / air mixtures can form around tanks and processing equipment Equipment Machines, appliances, fixed or mobile devices, control parts and accessories, and warning and prevention systems, whether separate or combined, intended for the generation, transfer, storage, measurement, control, and conversion of energy, and for the processing of materials, which have their own potential source of ignition and may cause an explosion. . They could ignite. Protective devices are required for safe handling in dangerous atmospheres across industrial applications.

In modern process plants, vapours need to be disposed of in an environmentally friendly manner. They are incinerated according to air pollution control regulations, and explosive mixtures are sent to an ignition source Ignition source Any source with enough energy to initiate combustion. during operation. These are particular hazards that must be countered with special measures.

Early flame protection used gravel pots on fuel tanks. The gravel stopped explosions Explosion Abrupt oxidation or decomposition reaction producing an increase in temperature, pressure, or in both simultaneously. from entering storage tanks or connected lines. However, it had two serious drawbacks: non-reproducible flame-arresting capability and high pressure Pressure (gauge pressure) Pressure for which the value is equal to the algebraic difference between the absolute pressure and the atmospheric pressure. losses.

In 1929, a new development replaced loose gravel with wound corrugated metal strips. Combined with a patented shock absorber Shock absorber A shock absorber is a device that reduces the kinetic energy of a detonation. , this design stopped detonative combustion processes in the pipe with the lowest possible pressure loss. This became the PROTEGO® Detonation Detonation Explosion propagating at supersonic velocity and characterized by a shock wave. Flame Arrester Flame arrester Device fitted to the opening of an enclosure, or to the connecting pipe work of a system of enclosures, and whose intended function is to allow flow but prevent the transmission of a flame. , developed by Robert Leinemann. He went on to found Braunschweiger Flammenfilter GmbH in 1954.

The gap width and gap length of the flame arrester element determine its extinguishing ability:

• The narrower and longer the gap, the greater the extinguishing effectiveness
• The wider and shorter the gap, the lower the pressure loss

PROTEGO® designs balance these two conditions. Special design features such as the patented Shock Wave Guide Tube Effect (SWGTE) and the shock absorber enable superior flow with minimum pressure loss.
 

Deflagration Deflagration Explosion propagating at subsonic velocity. is an explosion Explosion Abrupt oxidation or decomposition reaction producing an increase in temperature, pressure, or in both simultaneously. that propagates at subsonic velocity. Three types exist:

• Atmospheric deflagration: occurs in open air without a noticeable increase in pressure
• Pre-volume deflagration: occurs in a confined space, such as within a vessel Vessel Container or structural envelope in which materials are processed, treated or stored. , initiated by an internal ignition source
• In-line deflagration: an accelerated explosion Explosion Abrupt oxidation or decomposition reaction producing an increase in temperature, pressure, or in both simultaneously. within a pipe, moving along its axis below the speed of sound

Stabilised burning is the even, steady burning of a flame stabilised at or close to the flame arrester element. Short-time burning lasts for a specific period. Endurance burning Endurance burning Stabilized burning for an unlimited time. continues for an unlimited period.

The position of the deflagration-to-detonation transition (DDT) zone depends on several factors. These include operating pressure Operating pressure Operating pressure is the pressure existing at normal operating conditions within the system being protected. , operating temperature Operating temperature Temperature reached when the equipment is operating under design conditions. , pipe diameter, pipe configuration, test gas, and explosion Explosion Abrupt oxidation or decomposition reaction producing an increase in temperature, pressure, or in both simultaneously. group. It must be predetermined by experiments in each case.

Flame Arresters are categorised by combustion process and installation type:
 

• Static dry flame arresters are based on the FLAMEFILTER® principle of flame quenching in narrow gaps, using wound corrugated metal strips.

• Static liquid seal Seal A seal prevents or limits unwanted transfer of product from one container to another. Seal is used as superordinate term for all types of sealing elements. flame arresters use liquid barriers to stop incoming deflagrations or detonations from entering protected components. Two types exist. The liquid product flame arrester uses the product itself to form the seal. The hydraulic flame arrester Hydraulic flame arrester Flame arrester designed to break the flow of an explosive mixture into discrete bubbles in a water column, thus preventing flame transmission. breaks the flow of an explosive mixture into small bubbles flowing through water.

   

The location of installation determines the protective task:

Explosion Groups and MESG

Different gases have different flame propagation capacities. They are categorised into explosion Explosion Abrupt oxidation or decomposition reaction producing an increase in temperature, pressure, or in both simultaneously. groups according to their hazard level. The standard for this is the MESG, or Maximum Experimental Safe Gap. It is a characteristic number measured in the laboratory for the flame propagation ability of the product. Explosion Explosion Abrupt oxidation or decomposition reaction producing an increase in temperature, pressure, or in both simultaneously. groups use reference substances including methane, propane, ethene, and hydrogen.

Flame arresters tested under standard conditions are approved for use at temperatures up to 60°C (140°F) and a pressure of 1.1 bar (15.9 psi). Higher operating temperatures or pressures require special examination.