An air actuated diaphragm valve is a special type of cutting valve that emerged in the 1920s. Its actuating part is a diaphragm made of soft material, which separates the valve body cavity from the valve cover cavity and the driving components, hence the name "air actuated diaphragm valve." The distinctive feature of the air actuated diaphragm valve is that the diaphragm isolates the lower valve body cavity from the upper valve cover cavity, thus protecting the valve stem and valve disc, etc., above the diaphragm from medium corrosion. It eliminates the need for packing seal structures and prevents medium leakage. The structural characteristic of the air actuated diaphragm valve is that a set of thin hemispherical metal diaphragms are fixed within the valve body, acting as a barrier between the valve stem and the fluid. The valve is closed by pressing the valve disc against the valve seat with the valve stem head and the metal diaphragm. The valve opens when an internal spring raises the valve stem, lifting it away from contact with the diaphragm, causing the valve disc to rise. Since the stroke of the valve equals the stroke of the diaphragm, the characteristic lift of this valve is much smaller than that of general valves.