Valves and valve actuation – Fluid actuated or retarded – Piston type expansible chamber reciprocating valve actuator
Patent
1989-12-11
1990-06-19
Walton, George L.
Valves and valve actuation
Fluid actuated or retarded
Piston type expansible chamber reciprocating valve actuator
92 62, 92 65, 251327, 251328, F16K 31122
Patent
active
049346520
ABSTRACT:
An actuator for opening and closing the gate of a surface safety valve includes a primary piston and an auxiliary piston. The primary drive piston is directly connected to the valve stem, while the auxiliary piston is slideably connected thereto. Extension movement of the auxiliary piston is stopped by a divider plate after initial breakaway forces are overcome. The thrusting force developed by the auxiliary piston during a valve opening operation is transmitted to the valve stem and the primary piston by a shuttle sleeve. The shuttle sleeve is radially spaced about the valve stem, thereby defining a bridge annulus which maintains fluid communication between the primary pressure chamber and the auxiliary pressure chamber at all times. The thrusting force produced by the auxiliary piston is combined with the thrusting force produced by the primary piston to break the static gate seal and overcome the gate drag during a first stage of operation. After breakaway has been accomplished, the auxiliary piston is mechanically decoupled from the valve stem, whereby the valve stem is driven only by the primary piston at a substantially reduced thrusting force level during a second stage of operation, thereby avoiding gate damage which might otherwise occur if the valve stem velocity was not restrained.
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Griggs Dennis T.
Otis Engineering Corporation
Walton George L.
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