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A control valve, also known as a regulating valve, receives a control signal from a control unit and uses power to adjust the flow rate of the fluid. A control valve generally consists of an actuator and a valve. Based on the power source used by their actuators, control valves can be divided into three types: pneumatic control valves, which use compressed air as a power source; electric control valves, which use electricity as a power source; and hydroelectric control valves, which use the pressure of a liquid medium such as oil as a power source. Additionally, depending on their functions and characteristics, there are also hydraulic control valves, solenoid valves, electronic control valves, intelligent control valves, and fieldbus-type control valves. The selection of the valve body type for control valves is diverse; common types include straight-through single-seat, straight-through double-seat, angle, diaphragm, low-flow, three-way, eccentric rotary, butterfly, sleeve, ball, and others. When making a specific selection, the following factors can be taken into consideration: 1. The shape and structure of the valve core are primarily determined by the desired flow characteristics and the unbalanced forces involved. 2. Wear resistance: When the fluid medium is a suspension containing high concentrations of abrasive particles, the internal materials of the valve must be hard. 3. Corrosion resistance: Since the medium is corrosive, it is advisable to choose valves with a simple structure. 4. Temperature and pressure of the medium: When the temperature and pressure of the medium are high and subject to significant fluctuations, it is necessary to choose valves whose valve core and seat materials are less affected by such temperature and pressure changes. 5. Prevent flashing and cavitation; flashing and cavitation occur only in liquid media. In actual production processes, flashing and cavitation can cause vibrations and noise, reducing the service life of valves; therefore, when selecting valves, it is necessary to prevent flashing and cavitation from occurring. Selection of the actuator for control valves: For the proper operation of a control valve, the actuator used must be capable of generating sufficient output force to ensure a tight seal as well as the proper opening of the valve.