Abstract: A valve actuation system is provided for a valve of the type wherein at least two separate movements are utilized to achieve either opening or closing thereof. The actuation system includes a pair of hydraulic or pneumatic actuator units for automatically performing these two separate operations. An electrically energizable control valve is associated with each of these actuators for controlling the flow of a pressurized control medium therethrough to achieve actuation in the proper sequence for attaining the desired valve movement. A control circuit preferably comprises a plurality of switches responsive to the positions of these two valve actuators as well as the position, (viz., "valve open" or "valve close") of an operator accessible main control lever or switch. These switches deliver electrical power to energize the fluid flow control valves so as to automatically perform the correct sequence of actuator operations to open or close the valve, as desired.

Abstract: A hydraulic valve actuator includes at least one piston mounted for reciprocating movement in a cylinder for bidirectionally rotating a valve shaft mounted in the housing. A resilient spring member is held in compression between one side of the piston and an end wall of the cylinder for yieldably urging the piston to rotate the shaft in one direction, in the absence of a sufficient opposing hydraulic pressure. A hydraulic pump driven by an electric motor selectively drives the piston against the force of the spring member for rotating the valve shaft in the opposite direction. An electric solenoid operated valve is connected with the cylinder at either side of the piston, to provide a selectively openable path for hydraulic fluid, by-passing the pump to relieve the pressure applied thereby.