Pneumatic control valve refers to the air source as the power, the cylinder as the actuator, 4~20mA signal as the drive signal, and with the help of electrical valve positioner, converter, solenoid valve, holding valve and other accessories to drive the valve, so that the valve linear or equal percentage flow characteristics do adjustment action, In order to achieve the flow, pressure, temperature and other process parameters of the pipeline medium switching quantity or proportional regulation. Pneumatic control valve has the advantages of simple control, fast response, and intrinsically safe, and when used in flammable and explosive occasions, there is no need to take additional explosion-proof measures. Pneumatic control valve is usually composed of pneumatic actuator and regulating valve connection installation and commissioning, pneumatic actuator can be divided into single-acting and double-acting two, single-acting actuator has a return spring, and double-acting actuator has no return spring. The single-acting actuator can automatically return to the initially set open or closed state of the valve when the air source is lost or a fault occurs. Pneumatic control valve is divided into two types according to the action form, namely the so-called normally open type and normally closed type, the air opening or gas closing of the pneumatic control valve is usually achieved through the positive and negative action of the actuator and the different assembly methods of the valve structure.