Buried polyurethane insulation pipe wall smooth, good drainage performance, small fluid resistance, no scaling is compared to other pipeline big advantage, can greatly reduce the loss. At the same time, the linear expansion coefficient of large-diameter thermal insulation steel pipe is very small, which makes it very advantageous as the main water pipe, which greatly overcomes the defects of other plastics and ordinary pipes with large linear expansion coefficient. Large diameter insulation steel pipe is the traditional steel pipe, galvanized pipe upgrade type of cost-effective products. It has comprehensive characteristics, that is, high strength, high elongation, good low-temperature brittleness, small expansion coefficient, and plastic pipe corrosion resistance, wear resistance, low fluid resistance and other advantages. The mature technology of anti-corrosion and thermal insulation steel pipe belongs to a new type of water supply and drainage, anti-corrosion green large-diameter pipe, which is more and more widely adopted by various industries in China. In order to reduce the heat dissipation of the pipeline to the soil, the thermal insulation composite layer is added to the outside of the pipeline. The commonly used thermal insulation material is rigid polyurethane foam, and the applicable temperature is -185~120 ℃. This material is soft and soft. In order to improve its strength, a high-density polyethylene layer is added to the outside of the insulation layer to form a composite structure to prevent groundwater from penetrating into the insulation layer. High-pressure polyurethane foaming equipment is used to carry out shot blasting derusting treatment on the outer surface of the steel pipe and corona treatment on the inner surface of the outer protection pipe to improve the bonding performance of the insulation pipe. Insulation layer material for the density of 60kg/m3 to 80kg/m3 of rigid polyurethane foam, fully filled with the gap between the steel pipe and the casing, and has a certain bonding strength, so that the steel pipe, the outer casing and the insulation layer between the three to form a solid whole. Polyurethane foam has good mechanical properties and thermal insulation properties, usually temperature resistance of 120 ℃, by modification or combination with other insulation materials can be temperature resistance of 180 ℃.
