A flow control valve is used to regulate or monitor the flow of a liquid through a system. Usually that system is industrial or has an industrial purpose. They can also be used to measure the amount of fluid running through a system. They do this in many ways and make use of several other mechanisms that tell the valves when to open and close.

A flow control valve can respond to certain pressure changes. When the pressure in a system rises to a certain level, a flow control valve will open or close, depending on what its purpose is. This relieves or reduces pressure in one part of the system to maintain a balance with the other parts of the system.

Flow control valves sometimes use a device to open the valve. This device is often operated by hydraulic mechanisms. When the flow valve senses a pressure change, it is the actuator that opens the valve. Some flow control valves do not use any other device to open and close. These are called automatic control valves. When pressure drops or rises, it provides enough force to open the valve automatically.