Fire Safety Science Digital Archive

The effect of relief vents protected with flame arresters on the maximum experimental safe gaps of 4.2 per cent propane-air and 6.5 per cent ethylene-air flammable mixtures was investigated using an explosion vessel of volume 8 l. Flanges of the following nominal breadths were used: 25 mm (1 in), 12.5 mm (t in), 6 mm (t in), 3.2 mm (t in) and 1.6 mm (1/16 in). Under the most critical conditions for the gas mixtures the MESG was marginally affected when reliefs were present. The maximum explosion pressure was increased by obstacles within the explosion vessel but the MESG remained unchanged.