Valve actuators are selected based on several factors, including the torque required to operate the valve and the need for automatic actuation.

Actuator types include that of manual handwheel, hand lever, pneumatic electric motor, solenoid, hydraulic piston and automatic actuator. All actuators except the manual handwheel and lever are adaptable to automatic operation.

Actuators are designed according to the torque of the valve, the function in which it will be used, or special requests from the customer.

Manual actuators can stop the valve in any position, although they do not allow automatic operation. The most common type of mechanical actuator is the handwheel, which includes handwheels fixed to the stem, hammer handwheels and handwheels connected to the stem through gears.

Flyers fixed to the stem provide only the mechanical advantage of the wheel. When these valves are exposed to high operating temperatures, valve seizure makes operation difficult.

If additional mechanical advantage is needed for a manually operated valve, the valve cap is equipped with manually operated reducers as shown in the image. A special wrench or a handwheel connecting to the pinion shaft allows the valve to be operated by one individual, even for valves that would normally need the help of several people. Because several teeth of the pinion are needed to produce one revolution of the valve stem, the operating time of large valves is longer. The use of portable air motors connected to the pinion shaft decreases valve operation time.

Electric motors allow manual operation (semiautomatic and automatic) of the valve. Motors are usually used to achieve the open-close function, although they can be adapted to place the valve on any point. The motor is connected through a gear train to reduce its speed and increase torque on the shaft. The direction of motor rotation determines the direction of disk movement.
Limit switches are normally provided to automatically stop the motor when the valve is fully open or fully closed and are actuated by valve position or motor torque.

Pneumatic actuators are provided for automatic or semiautomatic valve operation. These actuators translate pressure, into the movement of the valve stem through the action that is produced on the on a diaphragm or piston connected to the stem. Pneumatic actuators are used in butterfly valves for open-closed positioning where rapid action is required. When pressure closes the valve and spring action opens the valve, the actuator is called a reverse action. Duplex actuators have pressure from both sides of the diaphragm. Differential pressure across the diaphragm positions the stem valve. Automatic operation is provided when the pressure is controlled automatically. Semi-automatic operation is provided by manual switches for valve pressure control.

Hydraulic actuators provide semiautomatic or automatic valve positioning, similar to pneumatic actuators. These actuators use a piston to convert a signal pressure in the moving valve stem. Hydraulic fluids (water or oil) are fed to both sides of the piston.
Manual valves can also be used to control hydraulic fluid; thus, provide semiautomatic operation.

Solenoid actuators have a magnetic socket attached to the valve stem. The force to position the valve comes from the magnetic attraction the valve stem and the solenoid coil in the actuator.