Abstract: A hydraulic system for precise positioning of a control device, such as a valve actuator. A double-acting, hydraulic cylinder, which operates the control device, is held in any set position by a hydraulic lock ensured by one-way check valves which prevent interflow between the chambers on opposite sides of the piston. Occurrence of a signal indicating a need to change position activates one of two three-way directional control valves allowing exhaust flow from the appropriate cylinder volume. Connected in parallel in the exhaust line is a plurality of on-off valves, each having a flow capacity that is some multiple of that of the next smaller valve, e.g. twice as large. This provides a wide range of distinct and precise flow capacities to provide close and instantaneous control over rate of movement of the positioning device.

Abstract: The disclosure is of a selective-mode valve operator comprising a handwheel adapted to be mounted on a valve body with an output sleeve keyed onto the input shaft or stem of the valve. A motor may be mounted directly onto the handwheel, and locking means selectively lock the handwheel to the output sleeve or to a stationary member. When the handwheel is locked to the output sleeve, shift means prevent motor operation, and when it is locked against rotation the shift means enable motor operation. The shift means pass through a neutral condition whereby one mode is inactivated before the other mode is activated.

Abstract: An emergency hydraulic ram valve actuator having redundant power sources and controls. At least two pressure fluid sources, such as hydraulic accumulators, are connected through separate controls to the cylinder head. Check valves in the cylinder head and base prevent outward flow to insure containment of the fluid even when dismantled for service. Both sets of controls are contained in manifolds connected between the pressure sources and pressure and exhaust lines to and from the cylinder. Flow from each accumulator is normally prevented by a pilot check valve, but selectively operated valves initiate flow which, in turn, biases the pilot check valves to full flow. As full flow commences a portion thereof is diverted to open the exhaust pilot check valves which allow cylinder evacuation. In the event one power and/or control system is disabled, the other will function independently. The pressure and exhaust lines are contained within protective shields throughout their lengths.