GB494374A - Safety device for preventing the return of oxygen and backfiring into a gas piping - Google Patents

Abstract

494,374. Fluid actuated valves; gas mains. TORNOW, M. Nov. 2, 1937, No. 29958. [Classes 54 and 135] A safety cut-off device for preventing the return of oxygen and backfiring into a gas piping system c, particularly one supplying acetylene gas to an oxyacetylene burner on the outlet-pipe d comprises a pair of valves a, m, arranged in series and actuated by independent diaphragms e, f respectively. Return of oxygen from the burner causes an increase in pressure in the outlet-pipe d, which acts, through a nozzle-ended pipe k, above the diaphragm e, so as to close the valve a in the same direction as that of the flow of acetylene gas, cutting off the latter. The weight of the valve a assists the closing movement. Backfiring creates a violent pressure increase in the outlet pipe d which acts under the diaphragm f to raise the valve m, again cutting off the acetylene supply, the closing movement taking place in a direction opposite to that of the flow of acetylene gas, and being against the weight of the valve m. The latter is not connected with its diaphragm and is frictionally guided in the casing. Between the outlet of the valve m and the chamber below the diaphragm f is a pipe o through which the acetylene gas passes on its way to the diaphragm-chamber and thence to the outlet-pipe d. The purpose of the pipe o is to ensure that the backfire will have had sufficient time to close the valve before pressure reaches the upper side of the diaphragm via the pipe o. The diaphragm f may be of lead and e may be of rubber, strengthened by plates r. Specification 490,929 is referred to.