The pneumatic three-piece ball valves produced and sold by Huadian Pump Valve Company are divided into integral type, two-stage type and three-stage type. The valve body casting adopts the advanced technology imported from abroad, with reasonable structure and beautiful shape. The valve seat adopts elastic sealing structure, which is reliable in sealing and easy to open and close. The valve stem adopts an inverted sealing bottom-mounted structure, and the valve stem will not be flushed out when the valve cavity is abnormally pressurized.