In recent years, with some major cities prohibit the use of galvanized steel pipe as potable water, many cities began to promote PE water pipe. The PE pipe trenchless renovation of the old pipe and pipe laying of new residential areas hit an excellent opportunity. Accelerate the popularization and application of chemical building materials products and limits the pace of eliminating backward. In China's coastal areas, groundwater is high. Land humidity, you must use the seamless corrosion, and life expectancy is only 30 years, while the PE pipe can withstand a variety of chemical erosion of media, without preservative treatment. In addition, it will not promote algae, bacteria or fungal growth, the service life of 50 years. PE pipe is a pipe high toughness, high elongation at break, on the basis of differential settlement and dislocation pipe ability to adapt is very strong. Good shock resistance. Therefore, best suited to a seismic risk areas around the world, proved the best shock resistance PE pipe is a pipe. PE pipe welding to connect themselves (hot melt or fused). Essentially the interface to ensure the material, structure and identity of the tube itself, to achieve the integration of the connector and tubing. Its interface is higher than the tensile strength and burst strength of the pipe body, which can effectively resist the pressure inside the hoop stress generated by the axial stress. Therefore, with rubber ring like collusion or other mechanical joints compared, there is no danger of collusion distortions caused by the leak, sealing performance is very good. PE pipe and pipe wear comparative experiments showed that: it is four times the wear resistance of steel. Because PE pipe has the above advantages, such as corrosion resistance, toughness, hardness and softness, mounting pipe would like. It is more and more used in water supply systems. Such as transportation and installation, the traditional steel pipe, cast iron pipe, the length of not more than 10m, and especially small diameter PE pipe, and even coiled length can be freely controlled. Maximize the benefits of this is to reduce the interface. Is to reduce the frequency of occurrence of the accident, both safe and energy efficient. In addition. PE pipe can be inserted into the old pipe as intubation used to repair, update pipelines. Can also be used extensively for corrosive land, seismic areas, mountains, wetlands and other special sections of the pipeline. Another big advantage is that good economic returns. PE pipe in the pipe free excavation and renovation of old pipe, there is a high market share. PE pipes are often used in pipeline Free excavation. Since PE (PE) good overall performance, the production of composite pipe storage plastic composite pipe and plastic composite pipe) the main raw material. Composite pipe metal materials and pigments reasonable together, we can make full use of metal good mechanical properties and corrosion resistance of plastics, thus ensuring the safety and reliability of water supply network. Of course. Because the characteristics of the material itself polyethylene pipe, PE pipe also has some weaknesses, such as low intensity, encounter flint, metal collision squeeze, easy to cause pits until perforation; without flame retardant; There are restrictions on the maximum operating pressure; another, polyethylene pipe stacked high requirements, not long sun and rain, or easy to aging, reduce the service life. PE pipe system with hot-melt connection Butt (including saddle connection), and hot-melt socket connection. Melt socket connection for a relatively small diameter pipe fittings, because the small diameter thin wall pipe fittings, small cross-section, the use of docking difficult to ensure quality. Butt is suitable for relatively large diameter pipe fittings, socket connection material saving ratio, easy to manufacture, and because the cut in the oxidized surface layer before welding. Welding pressure can be controlled easier quality assurance. From the development trend of view, using the Butt is the mainstream. Fused connection including fused socket connection and fused saddle connection. Highlights of fused connection is reliable (reduce the human factor) and construction of high efficiency. Because fused pipe manufacturing techniques are required, the cost is higher, is mainly used in the early smaller diameter gas pipeline system. In recent years, as technology advances, fused connection is used widely. Not only applied to piping systems for water supply, and start applying to the larger diameter. PE pipe line expansion coefficient of steel, ductile iron pipes of 10 times, but the elastic modulus of polyethylene pipe is much lower than the metal pipe, polyethylene pipe indicating that although relatively high degree of expansion and contraction, but the stress generated by expansion and contraction are obviously very is small, so the polyethylene pipe laying overcome axial deformation caused by seasonal temperature measure is important. May be needed to control this retractable fixing methods are often simple and economical, it uses PE unique advantages-stress relaxation properties to control mechanical activity and deformation.