The important information in this chapter is summarized below.
Valve Actuators Summary
Manual actuators are the most common type of valve actuators. Manual actuators
include handwheels attached to the valve stem directly and handwheels attached
through gears to provide a mechanical advantage.
Electric motor actuators consist of reversible electric motors connected to the
valve stem through a gear train that reduces rotational speed and increases torque.
Pneumatic actuators use air pressure on either one or both sides of a diaphragm
to provide the force to position the valve.
Hydraulic actuators use a pressurized liquid on one or both sides of a piston to
provide the force required to position the valve.
Solenoid actuators have a magnetic slug attached to the valve stem. The force to
position the valve comes from the magnetic attraction between the slug on the
valve stem and the coil of the electromagnet in the valve actuator.