Valve Actuators Glossary of Terms

Actuator Electric or manual rotary device used to open and close a valve, gate or damper
Declutch A mechanical mechanism to disengage an actuator from the load
Direct mounting The actuator is mounted directly onto a valve without any intermediate adapter plate or kit
Dual acting A pneumatic actuator that can operated in both directions by air
Fail safe Typically a mechanical device that returns an actuator to a safe position in the case of a power failure
Gear operator A term for a valve actuator
Handwheel A wheel manually operated by hand to open or close an actuator
Input torque The rim effort times the handwheel radius
Limit switch A limit switch is an electromechanical device with contacts that interrupt a circuit when tripped
Mechanical advantage Mechanical advantage is a measure of the force amplification achieved by the actuator
Mounting kit A bracket or plate to adapt an actuator to a valve
Multi turn A type of rotary actuator that turns more than one complete revolution
Output torque The input torque multiplied by the mechanical advantage
Position indicator A mechanical device on the actuator that provides a visual indication of the valves open/close position
Quarter turn A type of rotary actuator that turns only 90 degrees
Rack & pinion The type of gearing used in pneumatic actuators
Ratio Number of turns on the input divided by the number of turns on the output
Rim effort The amount of force applied to the radius of the handwheel by the operator, typically in pounds
Self locking Gearing within an actuator that is designed such that it cannot be driven backwards from the load side
Solenoid valve An electromechanically operated valve controlled by an electric current
Spring return A pneumatic actuator that can be operated in one direction with air and the other direction by means of springs
Stem The shaft on a valve is also referred to as the stem
Top works The mounting details on the top of a valve, typically the stem size and mounting bolt hole pattern
Torque Force times radius
Valve operator A term for a valve actuator