A valve is defined as the device that is used to control the flow of the liquid and they have a variety of functionalities in order to cater to these needs. The functionalities include opening, closing and partially blocking the various passageways of the liquids. The flow control valves are used to regulate the course or the pressure of the liquid through them. These valves are generally controlled by independent devices such as a flow meter or a temperature gauge which produces some control signals.

Most of the times, the flow control valves are fitted with the actuators and positioners. For instance, in industries, the pneumatically actuated flow control valves with positioners are used extensively for control purposes. In this type of valves, pressurized gas is used to control the flow. There are also other types of valves that have also been put to use in industries to some extent. This may include modified ball valves and butterfly valves.

Automatic control valves

The flow control valves can also be equipped with hydraulic actuators which are also known as hydraulic pilots. And the control valves equipped in this way are also called the automatic control valves. Unlike the pneumatic actuators for control valves, the hydraulic actuators work by responding to the changes in the pressure in order to open or close the valves automatically. Such automatic control valves do not need any external power supplies. This implies that the valves are opened or closed with the help of the fluid pressure alone. These automatic control valves may also include back pressure sustaining valves, pressure reducing valves, relief valves and altitude valves in addition to the flow control valves.

Uses

The first major use of the flow control valves is in controlling the operation of the steam turbines. Nowadays these control valves are designed to be used in other applications also. For instance, the flow control valve can be used in conjunction with the vertical turbine pumps or submersible pumps for its advantages such as good liquid injection rates, absence of sand lock, wear resistant properties and variety of injection rates.