More about Flow Control Valves

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Used to regulate fluid pressure and flow rate, flow control valves are used in a wide range of systems. A basic flow control valve consists of a changeable aperture that opens to increase flow rate or closes to slow flow rate. In many systems, such as a hydraulic circuit, the flow directly affects the function of actuators; to a degree, therefore, these actuators are controlled by the flow control valve (pump output, temperature and other factors also affect flow).

The types of flow control valves available include ball, diaphragm, needle, butterfly and plug valves. Ball valves are among the simplest control valves, as they consist merely of an inner ball attached to a handle. As the handle is turned a quarter turn, a hole through the center of the ball is aligned with or turned perpendicular to the valve openings, thereby permitting or shutting off flow. Butterfly valves accomplish a similar result with an opening and closing internal metal plate, also attached to a turning mechanism. Needle valves are typically more precise, and allow for greater flow control. These valves use an adjustable needle and valve stem to restrict or permit fluid flow. By controlling the amount that the needle obstructs the flow of fluid, an operator can control the flow rate.

One of the main advantages to a control valve is that it provides an inexpensive solution to many flow control concerns. Unfortunately, this is also at the expense of efficiency, since pressure is lost across a partially obstructed valve. Also, basic flow control valves are not wholly reliable, as flow rate can change even given a static valve position. This can be due to system pressure and temperature factors, as temperature can change fluid viscosity and therefore affect flow rate. Both pressure and temperature factors can be addressed in valve selection, however, although effective solutions involve increasingly complex control valves.

Materials used in the manufacture of flow control valves are brass, carbon steel, stainless steel, zinc and synthetics. Flow control valves are every bit as useful in pneumatic circuits as they are in hydraulic and liquid systems. They can be used to control the rate of compressed air, oil or virtually any other fluid; a wide variety of manual and automated systems are available, and these can be easily integrated into existing control systems.