Ningbo Fangli Technology Co., Ltd. is a mechanical equipment manufacturer with nearly 30 years’ experiences of plastic pipe extrusion equipment, new environmental protection and new materials equipment. Since its establishment Fangli has been developed based on user’s demands. Through continuous improvement, independent R&D on the core technology and digestion & absorption of advanced technology and other means, we have developed PVC pipe extrusion line, PP-R pipe extrusion line, PE water supply / gas pipe extrusion line, which was recommended by the Chinese Ministry of Construction to replace imported products. We have gained the title of “First-class Brand in Zhejiang Province”.
The steel wire mesh skeleton polyethylene composite pipe is a three-layer integrated structure, the inner layer is high-density polyethylene material, the middle layer is a pressure bearing layer integrated by the steel wire mesh skeleton and special bonding resin, the outer layer is a high-density polyethylene protective layer, and the inner layer, steel wire mesh reinforcement layer and outer layer are integrally fused with the bonding resin of high-density polyethylene grafted with maleic anhydride, referred to as PSP composite pipe or SRTP pipe, as shown in Figure 1.
Fig. 1 structural diagram of steel wire mesh skeleton polyethylene composite pipe
Because its inner and outer layers are made of high-density polyethylene, it has the same characteristics as high-density polyethylene pipe, such as corrosion resistance, chemical resistance, light weight and good flexibility. Moreover, due to the reinforcement of high-strength steel wire mesh, its pressure resistance and resistance to rapid crack propagation are significantly enhanced compared with HDPE pipe. For example, the maximum pressure of PSP composite pipe below DN250 can reach 3.5Mpa, Moreover, the wall thickness of the pipe is significantly lower than that of HDPE pipe. The unique structure of PSP not only integrates the advantages of high strength of steel pipe and corrosion resistance of plastic pipe, but also overcomes the defects of easy delamination of metal plate skeleton reinforced plastic composite pipe. PSP composite pipe has high production efficiency, strong structural designability, and has the advantages of strong bearing capacity, good corrosion resistance, excellent wear resistance, high cost performance, light weight and convenient transportation and installation. Since its inception in the early 21st century, it has been used in municipal engineering, civil fire protection, oilfield water conservancy transportation, medical and chemical industry, agricultural water-saving irrigation, coal mining industry, slurry transportation engineering and submarine water conveyance engineering are widely used.
PSP composite pipe is produced by continuous extrusion method and steel wire continuous winding composite process. It is generally composed of core pipe extrusion, steel wire winding composite, rubber layer extrusion, outer layer composite, traction and length counting cutting. The reinforcement of PSP is high-strength copper plated steel wire mesh formed by dip angle staggered winding. The steel wire strength can reach 2000mPa, the dip angle of steel wire is generally 54.7 ° ~ 60 °, the number of steel wire layers is generally even, the winding direction of steel wire is left-hand and right-hand, and there is no need to weld between steel wire meshes, which greatly improves the production efficiency. Because there is no affinity between steel wire mesh and high-density polyethylene, it is necessary to use a maleic anhydride grafted high-density polyethylene resin between polyethylene and steel wire to realize multi-layer bonding, so as to achieve better interfacial peel strength. PSP composite pipes are usually connected by electric melting pipe fittings and metal flange or grooved pipe fittings by crimping mechanical connection. Generally, electric melting connection is mostly used below 2.5MPa, and metal pipe fittings are generally used for crimping connection in the field of high working pressure (above 2.5MPa).
According to the existing relevant standards, PSP composite pipes and fittings are applicable to the pipeline system with medium temperature ≤ 60 ℃. Generally, if the medium transmission temperature exceeds 20 ℃, corresponding pressure reduction coefficient shall be carried out to correct its nominal pressure, which is described in detail in the corresponding product standards. The temperature and pressure reduction coefficient of commonly used PSP composite pipes for water supply is shown in Table 1.
Table 1 applied pressure reduction factor of PSP pipeline
Temperature / ℃