As one of the main raw materials of coal to gas pipeline, plastic pipe has better performance. Compared with traditional metal pipe and cement pipe, plastic pipe has the advantages of light weight, corrosion resistance, low flow resistance, good comprehensive energy saving, convenient transportation and installation, long service life, etc. Application scope: plastic pipe material mainly used PVC (PVC), polyethylene (PE) and polypropylene (PP) and so on. Compared with other plastic pipes (such as PVC), HDPE (HDPE) pipes have the characteristics of low density, good toughness, corrosion resistance, good insulation, easy construction and installation. In municipal and building water supply and drainage, gas, heating and heating, wire and cable wiring, agricultural water-saving irrigation and other fields. HDPE pipe is a kind of thermoplastic resin with high crystallinity and non polarity. The application range of general PE pipe feed water pipeline is below 40 ℃, so it can not be used in hot water pipeline. The appearance of the raw HDPE is milky and translucent to a certain extent in the meager section. The PE tube material has excellent resistance to most domestic and industrial chemicals. Chemical corrosion occurs in certain chemicals, such as corrosive oxidants (concentrated nitric acid), aromatic hydrocarbons (xylene) and halogenated hydrocarbons (tetrachlorination) Carbon) The main features of HDPE pipeline are as follows: (1) toughness, good flexibility; (2) small friction coefficient, strong passing capacity; (3) convenient construction; (4) good chemical stability. Long service life; (5) proper flexure; (6) good resistance to rapid crack propagation; (7) low temperature resistance; (8) environmental protection in keeping with the requirements of the times. There are many methods for classification of HDPE pipes. It can be divided into water supply pipe, gas pipe, aluminum-plastic composite pipe, buried drainage pipe, agricultural irrigation pipe and electric casing according to the application field; according to the pressure, it can be divided into pressure. Force pipe and non-pressure pipe, feed pipe and gas pipe belong to pressure pipe category. In recent years, the density alone can not accurately reflect the essential properties of PE as pipe. At present, according to the long term hydrostatic strength of PE pipe, the current international classification method is divided into PE 32, PE 40 PE, PE 63.PE 80 and PE100. The pipes of PE 80 and PE 100 can be used to transport gas, while those below PE 63 are mainly used in hot water pipes and sewage pipes, irrigation pipes and so on.