GB267978A - Safety valve - Google Patents

Abstract

267,978. Soc. Anon. des Forges et Chantiers de la MediterranÚe. March 20, 1926, [Convention date]. Safety valves. - A safety valve of the kind controlled by an auxiliary valve has the auxiliary valve provided with a piston subject to the pressure in a chamber having a restricted outlet to atmosphere and with a second piston subject to the inlet pressure and adapted to interrupt the supply of fluid pressure to the main actuating chamber. The main valve 4 which is adjustably loaded by a spring 10 co-operates with a seat 5<a> and is coupled to a piston 6 working in a chamber 7. The seat 13 for the auxiliary valve is held in position by the housing 17 for loading spring 22 and has ports 19 leading to the chamber 7 and ports 18 leading to a chamber 15 connected by a passage 16 with the inlet. In the event of excessive pressure arising the auxiliary valve is lifted against the action of the spring to cause the piston 20 to close the ports 18 and to open the valve 14 to connect the chamber 7 to atmosphere and so allow the inlet pressure beneath the piston to open the main valve. The valve 14 is fitted with a piston 26 of larger nrea open to atmosphere on its upper face and is arranged in a chamber 27 having a restricted communication with atmosphere through a port 25 to ensure a full lift of the auxiliary valve and consequential closing of the ports 18. The piston 20 is of larger area than the valve so that the valve is maintained in its raised position until the pressure has fallen below that at which the valve lifted.