Control valve is a Final control element .Final control elements are necessary to control the Process variable. Valves are used to control the flow of fluid in process system.
Main parts of Control valve are Valve Body and Actuator Actuators are used to position the valves. Actuator is a mechanism which moves or control a device such as a valve. 3 Basic types of Actuators are there
Pneumatic actuators use air pressure to produce motion to position a valve. Actuator that are powered by a pressurized liquids such as hydraulic fluid are called
Hydraulic actuators .Hydraulic actuators are more powerful. Electric Actuators use electricity to produce motion Electric actuator can be classified as two types - Solenoid actuators and Motor driven actuators One of the most common example for Pneumatic actuators are Diaphragm Actuators
Seat is the part of the valve that is steady / silent. Disc is a part which moves, serves as a flow controller. The disc will move upward so that it gives more room so that the fluid can flowing, moving downward when closing and pressing the seat with meetings.
The bonnet makes room for the disc to move up when valve in the open position. Whereas packing, functions as insulating material so that there is no fluid leakage through the stem
If we trace the valve from the bottom up after the seat, then the stem and handwell disc are all joined together. Stem-shaped stem which is partially threaded and partially not. Handwell is used by the operator to rotate the stem, so it can move the disc up and down.