Pneumatic Valve Actuators

Pneumatic valve actuators adjust valve position by converting air pressure into linear or rotary motion. Linear motion devices open and close gate, globe, diaphragm, pinch and angle-style valves with a sliding stem that controls the position of the closure element. Rotary motion devices move ball, plug and butterfly valves a quarter-turn (90°) or more from open to close.  There are several actuation methods for pneumatic valve actuators. Diaphragm actuators are used mainly with linear motion valves, but are suitable for rotary motion valves when used with some type of linear-to-rotary motion linkage. Piston cylinder actuators are suitable for both linear and rotary motion valves. Typically, rack- and-pinion actuators are used to transfer the linear motion of a piston cylinder actuator to rotary motion. Rack-and-pinion designs are also suitable for adjusting manually-operated valves. Scotch yoke devices are used to transfer linear motion to rotary motion. By contrast, vane actuators are suitable only for rotary motion valves. Link and lever actuators attach a splined or slotted lever to the valve shaft in order to transfer the linear motion of diaphragm or piston cylinder actuators to rotary motion.

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