A device responsible for putting a mechanical device into action such as a valve. Single acting actuators act in only one direction such as in a spring and diaphragm actuator where the spring acts in a direction opposite to the diaphragm thrust. Double acting actuators have a power supply that acts to move the actuator in two normally opposite directions. Pneumatic actuators converts the energy of a compressible fluid, usually air, into motion. Vane actuators are typically fluid-powered devices where the fluid acts upon a movable pivoted member (the vane) to provide rotary motion to the actuator stem.