Quarter turn or rotary operation is one of the two main structural forms for valves, and includes mechanisms for operating butterfly, ball and plug valves as well as the quarter turn air damper. They operate by inducing a 90° or quarter turn movement and can be actuated by electric, hydraulic or pneumatic power. Quarter turn actuators are commonly found for automating air dampers and 90° valves in the water treatment, chemical, pharmaceutical, and food and beverage industries.
Hydraulic and pneumatic quarter turn actuators are more versatile than electrically powered ones, and can be used where no source of electrical power is readily available. They are simpler, more reliable have a vast torque range and can withstand a lot of mechanical abuse. Almost all pneumatic quarter turn actuators use a cylinder with a mechanism that converts its linear motion to a 90°output motion, although some vane-type actuators can also be used to operate a quarter turn valve.
Quarter turn actuators can be configured for single and double action, with double-acting actuators using the air supplied to different inlets to open or close the valve. Some single-action types may alternatively be opened or closed by an air-pressure spring providing the necessary movement. Pneumatic actuators typically employ solenoid control valves mounted on the actuator, and may incorporate adjustable position switches for additional flexibility. This type of quarter-turn actuator has a compact, simple design, which is suitable for both low and high temperature ranges and for most process industry tasks.