The most common valve operator is the ‘Hand-wheel’. Other methods of valve operation can be as follows :
A) A Diaphragm
Here, the valve is operated by an air powered diaphragm. These are called ‘Pneumatic Control Valves’.
The air powered actuator can also take the form of a ‘Piston’ rather than a diaphragm. The operation of the valve, depending on requirements, may be ‘Air to Open’ (AO) or ‘Air to Close’ (AC).
B) An Electric Motor
This is called a ‘Motor Operated Valve’ (MOV) and may be installed to allow valve operation from a remote location and may then be referred to as a ‘Remote Operated Valve’ (ROV).
C) A Solenoid
This method of valve operation is used for a small valve placed in an air supply line to a shut-down device.
The solenoid will be activated on an electrical signal from an automatic trip system and will open or close depending upon its function.