The control valve plays a very important role in the automatic control of modern chemical plants. The production of these plants depends on the correct distribution and control of flowing liquid and gas. These controls, whether it is energy exchange, pressure reduction, or simple container feeding, require certain final control components to be completed. The final control element can be considered as the “physical force” of automatic control. The final control component completes the necessary power amplification between the low energy level of the regulator and the high energy level required to perform flow fluid control. Regulating valve is the most widely used type of final control component. Other final control components include metering pumps, regulating baffles and louvered baffles (a variant of butterfly valves), variable pitch fan blades, current regulating devices, and motor positioning devices different from valves. Although regulating valves are widely used, other units in the regulating system probably do not require as little maintenance work as it does. In many systems, the operating conditions such as temperature, pressure, corrosion and pollution that the regulating valve is subjected to are more serious than those of other components. However, when it controls the flow of process fluid, it must operate satisfactorily with minimum maintenance. The regulating valve plays a variable resistance role in the pipeline. It changes the turbulence of the process fluid or provides a pressure drop in laminar flow, which is caused by changing the valve resistance or “friction”. This pressure reduction process is commonly referred to as “throttling”. For gases, they are close to an isothermal adiabatic state, and the deviation depends on the non ideal degree of the gas (Joule Thomson effect). In the case of liquids, pressure is consumed by turbulence or viscous friction, both of which convert pressure into heat energy, resulting in a slight increase in temperature. The common control circuit consists of three main parts, the first part is the sensitive component, which is usually a transmitter. It is a device that can be used to measure the adjusted process parameters, such as pressure, liquid level, or temperature. The output of the transmitter is sent to the regulating instrument – the regulator, which determines and measures the deviation between the given or expected value and the actual value of the process parameter, and sends the calibration signal one by one to the final control element – the regulating valve. The valve changed the flow rate of the fluid, achieving the expected process parameters. In the pneumatic regulating system, the pneumatic signal output by the regulator can directly drive the spring diaphragm actuator or piston actuator to make the valve act. In this case, the energy required to determine the valve position is provided by compressed air, which should be dried in outdoor equipment to prevent freezing and purified and filtered. When a pneumatic control valve is used in conjunction with an electric regulator, an electric pneumatic valve positioner or an electric pneumatic converter can be used. The compressed air supply system can be considered in the same way as a fully pneumatic control system. In terms of regulation theory, the regulating valve has both static and dynamic characteristics, so it affects the success or failure of the whole control circuit. The static characteristic or gain term is the flow characteristic of a valve, which depends on the size of the valve, the combination structure of the valve core and seat, the type of actuator, the valve positioner, the pressure before and after the valve, and the properties of the fluid. Technical parameters of pneumatic control valve Nominal pressure: PN1.6-32.0Mpa Working temperature: -100-1000 ℃ Nominal diameter: DN8-600mm Connection method: flange, thread, welding Material: 304, 316, 304L, 316L, SS316, WCB, CF3, CF8, cast steel, cast iron, ductile iron, forged steel, stainless steel, etc.