Control valves regulate and control the flow, pressure, the temperature of a flowing fluid, such as gas, steam, water, or the chemical mixture by opening or closing internal passages. They control the amount of flow in processes. The valve stem moves, altering the size of passage, and this increases, decrease or holds steady flow.
Valve actuator is the element to open and close a valve . It is a must element for any valve .
There are mainly four types of actuators: manual, pneumatic, hydraulic, and motorized (electric ).