The Control Valve is the key part of the control circuit. People who work at industrial field talk about control valves are actually referring to a complete assembly control valve. It usually includes the valve body, trim, actuators and a variety of other valve accessories. The actuator provide power to operate the valve, and it could be pneumatic driving, electric driving or hydraulic driving. And for accessories, according the control system to assembly sensor, valve positioner, transducer, air filter regulator, limit switches or handwheel etc.
There are two main types of control valve designed according to the function of the closing part: The sliding-stem control valve and the rotary control valve. Sliding-stem means the closure member action as a linear motion, but rotary valve use rotational motion to turn a closure member into and out of a seating surface.
Rotary type control valves include full-port ball control valve, segmented ball control valve, segmented V-notch control valve, butterfly control valve(conventional disk), eccentric butterfly control valve/high-performance butterfly valve, eccentric plug control valve.
Sliding-stem control valves include single-port globe type Valve, cage guided globe type, double-ported, three-way valve, angle type control valve.