Polyethylene, or PE, is one of the most widely used plastics since the invention of petrochemical products by human beings. Since the 1980s, it has gradually attracted people's attention due to its good physical properties, corrosion resistance, long service life, low price and convenient installation and maintenance. With the continuous research and development of PE materials, PE materials such as PE80 and PE100, which are suitable for gas pipeline transportation, have emerged.

　　With the popularization and application of PE gas pipelines in China in the mid-1990s, people gradually realized the advantages of PE ball valves in terms of performance and price, and gradually began to use PE ball valves instead of metal ball valves. In the late 1990s, China began to develop and produce its own PE ball valves. Up to now, it has been able to produce 32 ~ 315 mm standard valves and single and double relief valves in batches and apply to PE gas pipe network widely in China.

　　The medium pressure PE valves in gas pipelines generally include dn40, dn50, dn63, dn90, dn110, dn160, dn200 and dn250 in terms of types and diameters. According to size, it can be divided into small polyethylene valves (below SD63) and large polyethylene valves (above SD63, including SD63). Small polyethylene valves generally do not have relief ports, and large polyethylene valves can be provided with one or two relief ports according to different needs. With regard to material grade, it is divided into PE80, PE100, etc. As for function, it is generally divided into standard ball valve, single relief ball valve and double relief ball valve.