Valve actuator

摘要

An actuator for fluid control valves with a reversible power module having a stationary inner member and a coaxially aligned movable outer member coupled to the valve flow control element and slidably movable on the inner member. A chamber is formed between respective ends of the members. Pneumatic pressure applied to the chamber drives the movable member to actuate the valve in a first direction. A spring returns the movable member in the second direction. A second chamber is defined within the inner member and pneumatic pressure applied to the second chamber drives the movable member with or without the spring.