Characteristics and principle of pneumatic control valve?

The working principle of pneumatic control valve is simply realized by compressed air. In practical application, it is of great significance to understand the working principle of pneumatic control valve.

Pneumatic control valve is one of the industrial process control instruments widely used in petroleum, chemical industry, electric power, metallurgy and other industrial enterprises. Usually, pneumatic actuator, valve and positioner are connected, installed and debugged to form pneumatic control valve.

Working principle of pneumatic control valve:

Pneumatic control valve takes compressed air as the power source and cylinder as the actuator. It drives the valve to realize on-off or proportional adjustment with the help of electric valve positioner, converter, solenoid valve, position keeping valve and other accessories, and receives the control signal of industrial automation control system to complete the adjustment of various process parameters such as flow, pressure and temperature of pipeline medium. Pneumatic control valve is characterized by simple control, rapid response, intrinsic safety and no need for additional explosion-proof measures.

Therefore, sometimes gas-operated valves are also called unable to close FC. The action direction of closed air is just the opposite to that of closed air. When the air pressure increases, the valve moves in the closing direction; When the air pressure decreases or does not decrease, the valve will be opened or fully opened. ThereFOre, it is sometimes called unable to open fo. The air opening or closing of pneumatic control valve is usually realized by the positive and negative actions of actuator and different assembly methods of valve state structure.

valve positioner

Valve positioner is the main accessory of control valve, which is widely used with pneumatic control valve. It receives the output signal of the regulator, and then controls the pneumatic regulating valve with its output signal. When the regulating valve acts, the displacement of the valve stem is fed back to the valve positioner through the mechanical device, and the valve position state is transmitted to the upper system through the electrical signal.

Valve positioner can be divided into pneumatic valve positioner, electric valve positioner and intelligent valve positioner according to its structure and working principle.

The invention can increase the output power of the regulating valve, reduce the transmission lag of the regulating signal, accelerate the moving speed of the valve stem, improve the linearity of the valve, overcome the friction of the valve stem and eliminate the influence of unbalanced force, thus ensuring the correct positioning of the regulating valve.

Pneumatic control valves can be divided into two types: air-open type and air-closed type. Air-open type means that when the air pressure on the membrane head increases, the valve moves in the direction of increasing opening, and when the upper limit of input air pressure is reached, the valve is in a fully open state. On the contrary, when the air pressure decreases, the valve moves in the closing direction, and when there is no air input, the valve is completely closed.