Pneumatic valve is an important device of industrial pipeline system automation, which installs pneumatic actuator on the basis of ordinary valve and drives the actuator by air source pressure. 
Pneumatic valves can be used to control the flow of various types of fluids, such as air, water, steam, various corrosive media, mud, oil, liquid metal and radioactive media. 
The working principle of the pneumatic valve is to use compressed air to promote the movement of several groups of combined pneumatic pistons in the actuator, transfer the force to the crossbeam and the inner curve track, drive the hollow spindle to rotate, and the compressed air disc is transmitted to each cylinder. Change the inlet and outlet position to change the rotation direction of the spindle, according to the requirements of the rotating torque required by the load (valve), the number of cylinder combinations can be adjusted to drive the load (valve) to work. 
In addition, the pneumatic valve daily maintenance and maintenance is also very important, regular inspection, the main inspection items are: (1) sealing surface wear. 
(2) trapezoidal thread wear of valve stem and stem nut. 
(3) whether the packing is out of date and invalid, if there is any damage, it should be replaced in time. 
(4) after valve maintenance and assembly, the sealing performance test should be carried out.