GB789993A - A valve and method of operating the valve - Google Patents

Abstract

789,993. Fluid-pressure servomotor-control systems. SULZER FRERES SOC. ANON. April 5, 1955 [April 6, 1954], No. 9997/55. Class 135. A method of operating by means of a servomotor a lift valve which closes in the direction of fluid flow and in which the valve spindle joins the closure member on the side remote from the valve seat, the valve being held open by the pressure of the flowing fluid acting on the spindle and being held closed at least partly by the pressure of the fluid acting on the differential area of the valve opening and the valve spindle, in which the servomotor force on the spindle is progressively reduced automatically as the closure member approaches its seating. Pressure from the control pipe 22 moves the piston valve 21 downward and the space below the piston 15 is connected to pressure at 26 via a throttle 27 and the space above is exhausted via a throttle 28 and pipe 29 so that valve 6 is lifted from its seat 4 and the valve stem 5 through a lever 18 and spring 20 re-centres the piston valve 21. On exhausting pressure fluid via pipe 22 the piston valve 21 is raised for pressure fluid via pipe 34, piston valves 33, 21, and pipe 30 to enter the space above the piston 15 and pressure below the piston to exhaust at 31 so that the valve 6 approaches its seat. As the valve approaches its seat the lever 18 not only re-centres the piston valve 21 but also lifts the valve 33 to reduce the flow of pressure fluid via pipes 34, 30, and eventually open an exhaust 35 so that the closing force on valve 6 is reduced as it approaches its seat. The valve 27 may also be closed as the valve 6 approaches its seat.