Control of flow of process and utility streams is achieved with the help of a control valve. Input to control valve is provided by a sensing device which measures the process parameter to be controlled like Level,
Temperature, Flow, Pressure etc. Sensing devices send their input first to microprocessors which then converts it to appropriate signal to control valve.
Body of the control valve is mostly similar to conventional globe valve. It can be flanged, Socket Welded, Buttwelded, Screwed etc. depending on the applicable piping material specification. Instead of a operator like handwheel, they have a diaphragm actuator which operates on pneumatic pressure. Some control valves are specified for both manual and automatic operation. In such case, they are equipped with a handwheel as well as a diaphragm actuator.
Youtube Videos
Best Control Valve Video
https://www.youtube.com/watch?v=-ES_3m5x94I&width=320