Gas reverse flow blocking device - has round membrane on axially guided holder bearing against radiused seat edge

摘要

The safety device prevents reverse gas flow and acts as a flame trap for combustible gas particularly for welding and flame-cutting tips. It comprises a housing with flexible membrane spring-loaded against a seat and a baffle plate weakening any backfiring flame. When reverse gas flow occurs and the pressure difference between the valve inlet and outlet sides becomes less than the opening pressure to which the spring (18) is set a round membrane (16) fixed to holder (10) guided axially in a perforated disc (12) first bears only against the polished and radiused edge of the cone valve seat (9). As the result of the pressure on the small annular surface this prevents reverse leakage of the gas without causing any appreciable pressure drop in the normal flow direction. Any flame from a backfire is weakened by the baffle causing the pressure wave to move the membrane holder towards the seat. The high detonation pressure combined with the matched cone angles of seat and holder and set prestress of the membrane cause the latter to bear rapidly sufficiently long and over a large area against the seat before flames or hot gas can reach it.