Pneumatic flange butterfly valves, based on imported advanced technique, adopts fine J shape elastic seal ring and triple offset multilayer metal hard sealing structure. Applicable temperature belows 425℃. It is widely used to regulate flow or closure medium in metallurgy, petroleum, power and other industries. The valve utilizes triple offset sealing structure. Valve seat and disc made of stainless steel with different hardness, have good corrosion resistance and long service life. The valve has bi-directional sealing, according to GB/T13927-92 pressure test standard.