Flow Control Valves are used to regulate the flow of fluids. Control of flow in hydraulic systems is critical because the rate of movement of fluid-powered machines or actuators depends on the rate of flow of the pressurized fluid. They are used in a variety of industries. In this article, well explain the operation of two common types for oil and gas producers. Control valves normally respond to signals generated by independent devices such as flow meters or temperature gauges. Flow Control Valves are very useful.