1. PE-RT Ⅱ plastic pipe: the thermal conductivity is about 0.4 w / m · K; The medium temperature is 75 ℃; Temperature resistance: - 40 ℃ - 110 ℃, - 70 ℃ embrittlement; Density 0.947g/cm ³。
2. polyurethane foam insulation: density 60kg/m ³； The temperature of conveying medium is - 50-140 ℃; After the certification of CCOT, the temperature resistance is 140 ℃.
3. High density polyethylene outer pipe: the density is more than 940kg / m ³； The tensile yield strength shall not be less than 19mpa; The elongation at break shall not be less than 350%.
At present, the operating pressure and temperature of secondary heating pipe network in China are basically below 0.8MPa and 85 ℃. Considering the corrosion, connection and cost of steel pipe and the suitability of plastic pipe, PE-RT II heat-resistant polyethylene pipe is used instead of steel pipe to prefabricate three in one hot water insulation composite pipe.
(1) The thermal conductivity of PE-RT II pipe is 1% of that of ordinary steel pipe, and the thickness of insulation layer can be reduced under the same service conditions.
(2) The heat loss rate is low, and the temperature drop per kilometer is less than 0.1 ℃.
(3) The thermal expansion coefficient of the three-layer material is similar, so it is not easy to "delamination".
(4) It is easy to connect and can be connected by hot melting and electric melting. It is easy to construct, convenient to maintain and low in construction cost.