GB1411921A - Pilot valve - Google Patents

Abstract

1411921 Fluid-pressure servomotor systems J E LONERGAN CO 5 Feb 1973 5527/73 Heading G3P A pilot valve for controlling a main pressure relief valve has a control port 11 for connection to the actuation chamber (14) of the main valvemember (16), a port 13 for connection to the pressure vessel (18) to be relieved and a vent port 12. An adjustable spring-loading 27 normally holds a valve-member 25 on its seat 24 to close off communication between the ports 11, 12 and a valve-member 35 away from its seat 34 to allow communication between the ports 11, 13. When the pressure in the vessel (18) and thus at port 13 and in chamber 22 rises to the blow-off value, valve member 25 is lifted off its seat 24 to vent chamber 22 and thus chamber (14) of the main valvemember which opens to relieve pressure. Valvemember 25 slides in a cylinder which has a restricted communication with the port 12 via passage 32 so that on initial opening of the valvemember the fluid-pressure passing to vent port 12 acts on the valve-member to accelerate further opening. Simultaneous with the opening of valve-member 25 valve-member 35 seats on its seat 34. When the blow-down pressure is reached in the vessel (18) and thus at port 13 valvemember 25 reseats and valve-member 35 moves off its seat 34. After initial movement of the valve-member 35 fluid-pressure at port 13 enters chamber 39 to accelerate the opening of the valvemember, fluid-pressure only passing to the control port 12 after further movement of the valvemember has allowed the lower lateral ports of axial passage 38 in the rod 37 inter-connecting the valve-members to communicate with chamber 39.