Control Valves are those who, driven by an external energy, interfere with the system by creating a pressure drop which controls a hydraulic variable (flow, pressure, level, …).
Control valves require auxiliary power to operate, manual, pneumatic or electric signal that comes from the control system and is connected to the valve through the actuator (there are also self-acting control valves that are driven by own medium). Control valves, in response to a control system signal, will open, close or keep the stroke in intermediate position. The valve obturator is pushed by the thrust of the actuator.
