Pneumatic actuator

rotarysingle-actingfor ball valves

Unlike linear pneumatic cylinders, rotary actuators perform a rotary movement by inserting compressed air into them. They are used in particular to open or close butterfly valves, ball valves, or mechanical parts that must make a quarter turn. The control is usually performed thanks to a 5/2-way Namur solenoid valve, or a particular type of valve suitable for being mounted directly on the actuator body. Rotary actuators can be double-acting or single-acting. The double-acting type receives air in both chambers (separated by an internal piston), when air is introduced on one side, rotation will be obtained, on the contrary, by introducing air on the opposite side, rotation will be carried out in the opposite direction, returning to the starting point. Single-acting rotary actuators are instead supplied with compressed air in a single chamber, while six springs are placed on the other. When the air enters the chamber, the springs are compressed by the force exerted on the piston. At the same time, the rotary movement will make a quarter turn. By removing the air supply, the preloaded springs will then return the actuator to its starting position. The single effect is usually used on valves when these must have normally open (NA) or normally closed (NC) functions.