Fluid pressure operated shut-off valve

摘要

984,799. Fluid-pressure servomotor systems. R. S. WILLIS. May 9, 1962 [Nov.14, 1961], No. 17785/62. Heading G3P. A shut off valve V, Fig. 1, controlling the flow from an inlet 4 to an outlet 7, such as flow from an oil well, is actuated to close in the event that the pressure in the pipe 7 falls below a predetermined minimum or rises above a predetermined maximum. The value V, Fig. 4, comprises a closure member MV connected to a main piston 27,the chamber above the piston being supplied with fluid under the control of a pilot valve member 34, or connected to exhaust by a pilot valve member 341, the valve members being connected to pistons 61, 611 respectively. The valve member 34 cooperates with a seat 43 and controls flow from a port 46, passages 45, 50, ports 52 and groove 52a past the valve to recess 56, ports 54, axial bore 53, ports 55 to passage 59 leading into the chamber. The valve 34 is loaded by a spring 38 towards the open position. The valve 341 is of similar construction, but is assembled in a reverse manner to control flow from the chamber through passage 59a to an exhaust port 511. The valve 341 is loaded by a spring 381 towards its seat 431. The closure member MV is also connected to a spring loaded actuator 76. A fluid pressure supply, normally fed to a port 1081,acts on piston 76 in a valve opening direction and on pistons 61,611 to hold the valves 34,341 in the position shown. When the fluid supply fed to port 1081 is exhausted, valve 341 is closed by spring 381 to close the exhsust from the chamber while the valve 34 is opened by spring 38 to feed pressure fluid to the chamber to act on piston 27 to close the valve MV. The fluid fed to the chamber is preferably that flowing through the valve and if this pressure is small, the spring loading 78 of the piston 76 will act to close the valve. The supply and exhaust of fluid through port 1081 is controlled by a controller CD, Fig. 1, which comprises a high pressure actuator 83 and a low pressure actuator 82, each actuator having a spring loaded piston 85 subjected to pressure in the line 7 through pipes 831,821. When the pressure falls, the piston of actuator 82 rises to move a rod 91 and when the pressure rises the rod 91 is raised by the piston of actuator 83. The rod 91 is connected to a relief valve carrier 95 provided with a passageway 96 which is normally closed by a spring loaded poppet valve 97. The poppet valve 97 also has a valve head 98 to control flow of a fluid supply through pipe 101. The valve carrier 95 is connected to a diaphragm 94 and carries a rod 103 contacting a diaphragm 104. With the valve 97, 98 in the position shown, fluid pressure is supplied from pipe 101 through pipe 108 to 1081 to hold valve MV open. When pressure in line 7 moves outside a predetermined range, one of the actuators 82,83 moves rod 91 upward so that valve 98 closes the supply pipe 101 and the valve poppet 97 then opens passage 96 to exhaust fluid from pipe 108 and the valve MV closes as above. A manually operated valve 108b may be provided to control the supply and exhaust through pipe 108. Specifications 914,111 and 947,897 are referred to.