Rack-and-pinion pneumatic actuators, also called limited rotation cylinders, are rotary actuators used for turning, opening, closing, mixing, oscillating, positioning, steering and many more mechanical functions involving restricted rotation. These actuators are also often used for automation of quarter-turn valves, like ball or butterfly valves. Pneumatic rack-and-pinion
actuators convert the energy of compressed air by means of a pneumatic cylinder to an oscillating rotary motion. The clean, dry, and processed gas required by this actuator is provided via a central compressed air station, which usually supports a range of pneumatic devices in a process system. Pneumatic actuators, in comparison to their electric counter parts,
are generally more durable, better suited for hazardous environments and less expensive. In addition, they often require less maintenance and provide higher torque in comparison to their size.