Diaphragm valve has simple structure, small fluid resistance and larger flow capacity than other types of valves of the same specification; It has no leakage and can be used to adjust the medium with high viscosity and suspended particles. The diaphragm isolates the medium from the upper chamber of the valve rod, so no packing medium will leak out. However, due to the limitation of diaphragm and lining materials, the pressure resistance and temperature resistance are poor, generally only applicable to 1.6MPa nominal pressure and below 150 ℃. The flow characteristic of the diaphragm valve is close to the quick opening characteristic, which is approximately linear before 60% of the stroke, and the flow change after 60% is small. Pneumatic diaphragm valves can also be equipped with feedback signals, limiters, positioners and other devices to meet the needs of automatic control, program control or flow regulation. The feedback signal of pneumatic diaphragm valve adopts non-contact sensing technology. The product adopts membrane type propulsion cylinder to replace piston cylinder, which eliminates the disadvantage that the piston ring is easy to be damaged, resulting in leakage and unable to push the valve open and close. When the air source fails, the hand wheel can be operated to open and close the valve.