Flame Arresters for explosion protection

Detonation occurs in open or closed duct systems with long ducts, such as ventilation ducts or vapor collection systems. When the gas/air mixture catches fire in the tube the combustion mixture increases in volume causing the unburned mixture in front of it to be pre-compressed and the flame front to accelerate as the combustion rate increases. The early stage of this process is called deflagellation when the flame velocity is subsonic and the pressure wave is far behind the flame front; Usually for the explosion triggered under environmental conditions, the flame speed is less than 100m/s and the pressure is less than 0.1MPa.g, but if it is converted into detonation,fire arrestor the flame speed and pressure can reach 200~300m/s and 1MPa.g, respectively. As the combustion process accelerates further, the flame front and the pressure wave meet in the "demilitarization to detonation" (DDT) region to form a high-pressure shock wave near the front of the flame front. Another characteristic of the DDT region is overpressure detonation or unstable detonation, where the violent shock compression can bring instantaneous pressures above 15 Mpa. g and flame velocities above 3,000 m/s. These shock waves dissipate quickly and the detonation wave becomes stable while the pressure is about 2-3 Mpa.g and the flame velocity is usually 1600-2000m/s.

The working principle of explosion-retarded flame arrester

Flame box type detonation arrester uses a small flame box and zuijia flame box length to provide a large heat transfer area. The heat from the combustion gas dissipates through the boundary layer inside the flame retarder and eventually cools below its spontaneous combustion temperature. The required flame box size depends on the actual gas/vapor and can be defined using the "Maximum Test Safety Gap (MESG)", a basic property of all easily ran gases/vapors. The required length of the flame arrester is determined by test to be essentially a function of flame velocity - the length of the flame arrester is usually larger than that of the deflagration arrester due to the high flame velocity of the deflagration arrester. Generally, the length of the flame box of the unstable detonation arrester is larger than that of the stable detonation arrester, but more importantly, it requires a stronger component support frame to withstand the greater force brought by the unstable event. Detonation can also be attenuated to deflagration before reaching the element by using integral countercurrent shock absorbers.