| 摘要 |
A valve actuator and a pilot assembly responsive to control fluid pressure for moving an operative means of a valve. The actuator has a housing defining a cylindrical bore therethrough and a shaft is carried in the housing which is engagable with the operative means. A piston is carried by one of the shaft and the housing and is sealingly slidable along the other of the shaft and the housing and is longitudinally movable within the cylindrical bore. A plurality of piston chambers are companionly associated with the piston and is responsive to control of source fluid pressure within a pilot assembly to manipulate the piston.
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