Pneumatic Rotary Actuator - How They Work

November 25, 2021

       A pneumatic rotary actuator uses compressed air to generate its operating energy. Some are designed specifically to remotely control valves. The clean, dry air can be provided via a central compressed air station, or in case of a compressed gas system, from the process gas. The waste gas can then be released into the air or a downstream lower-pressure process piping. They are commonly used to automate and remotely control quarter turn or multi-turn valves, like ball or butterfly valves.



         A pneumatic rotary actuator consists of one or more air chambers with a piston or a bellows diaphragm. Depending on the design, the air pressure forces the piston or the diaphragm to move creating linear or rotary motion. If the created motion is linear, it then internally converts the linear motion to rotational motion. Pneumatic rotary actuators are durable, offer high force relative to their size and can be used in hazardous environments.

Generally, to drive a rotary valve, a rotary actuator is used. However, there are also designs that use pneumatic cylinders, which create linear motion, to generate torque by means of pivot arms or bearings. However, specifying pneumatic rotary actuators for these applications can simplify the design and increase service life. Pneumatic rotary actuators are self-contained, therefore, their parts are not exposed to contaminants and aggressive environments meaning they are less likely to require maintenance over their lifetime.