Flame arresters are safety devices fitted to openings of enclosures or to pipe work, and are intended to allow flow but prevent flame transmission. A flame arrester functions by absorbing the heat from a flame front thus dropping the burning gas/air mixture below its auto-ignition temperature; consequently, the flame cannot survive. The heat is absorbed through channels (passages) designed into an element. These channels are chosen and measured as the MESG (
maximum experimental safe gap) of the gas for a particular installation. These passages can be regular, like crimped metal ribbon or wire
mesh or a
sheet metal plate with
punched holes, or irregular, such as those in
random packing. In a
coal mine containing highly explosive
coal dust or
methane, the wire mesh of a
Davy lamp must be very tightly spaced. For flame arresters used as a safety device, the mesh must be protected from damage due to being dropped or struck by another object, and the mesh must be capable of rigidly retaining its shape during the propagation of a flame front. Any shifting of the individual wires that make up the mesh can create an opening large enough to allow the flame to penetrate and spread beyond the barrier. On a fuel storage vent, flame arresters also serve a secondary purpose of allowing air pressure to equalize inside the tank when fuel is added or removed, while also preventing
insects from flying or crawling into the vent piping and fouling the fuel in the tanks and pipes. == Usage and applications ==