Polyurethane insulation pipe - insulation material density 60kg/m3 to 80kg/m3 rigid polyurethane foam, fully fill up the gap between the pipe and the casing, and a certain bond strength, the steel tube, pipe and insulation jacket between the three form a solid whole. 
 Polyurethane foam has good mechanical properties and thermal insulation performance, usually under temperature 120 ℃, through modification or combination with other insulation materials temperature 180 ℃. Widely used for insulation of liquid gas pipeline network, pipeline insulation chemical engineering petroleum, chemical, centralized heating network, central air conditioning and ventilation pipes, municipal engineering. High-temperature heat pipe is buried prefabricated insulation performance, plus safe, reliable, low construction cost prefabricated insulation buried pipe. Effective solution to the urban central heating 80 ℃ -150 ℃ temperature input heat insulation buried pipe with a prefabricated insulation, lubrication and sliding the bare end of the water management problem. High-temperature pre-heat pipe buried not only the traditional trench and laying of pipe aerial difficult to match the advanced technology, practical performance, but also has significant social and economic benefits, but also heat energy effective measures. High-temperature heat pipes with prefabricated buried buried heat pipe technology, heat pipe technology development indicates that China has entered a new starting point. 
 Heat pipe is steel, glass and steel within the jacket, fiberglass shell composition is characterized by: including high-temperature insulation layer, the lubrication layer, flexible seal. Effective solution to this utility model of urban central heating 130 ℃ -600 ℃ temperature input heat insulation buried pipe with a prefabricated insulation, lubrication and sliding the bare end of the water management problem. 
 Heat pipe structure 
 High-temperature pre-buried heat preservation pipe mainly consists of four parts. 
 (1) steel work: According to the technical requirements of transmission media were used to seam steel pipe, seamless steel pipe, double-sided submerged arc spiral welded steel pipe. 
 (2) insulating layer: rigid polyurethane foam. 
 (3) protective shell: high-density polyethylene or fiberglass. 
 (4) leakage alarm line: high-temperature pre-heat pipe buried in the insulation layer near the pipe, buried the alarm line, once the pipeline somewhere leakage, conduction through the alarm line can be a dedicated instrumentation the alarm and shows the exact location of leakage and leakage of the size, in order to inform maintenance personnel to quickly deal with leaking pipe, to ensure the safe operation of heating network. 
 Characteristics of insulation pipe 
 High-temperature pre-buried heat preservation pipe - Benefits Features 
 A lower cost. 
 According to an estimate, dual control heating pipes, under normal circumstances can reduce the project cost of 25% (made of steel protective layer of glass) and 10% (high density polyethylene protective layer) around. 
 2 low heat loss and save energy. 
 Buried pipe insulation 
 Thermal conductivity W / mk 0.027-0.033 

 Heat pipe technology indicators 
 Technical performance unit technology 
 Capacity Kg/m3 45-60 
 Thermal conductivity W / mk 0.016-0.024 
 Temperature ℃ -90 - +120 
 Cell rate% ≥ 97 
 Water absorption Kg/m2 ≤ 0.2 
 Oxygen index h ≥ 26 
 Compressive strength Mpa ≥ 200 

 Insulation than other pipe materials used in the past is much lower, effective insulation increased by 4 to 9 times. Again its very low water absorption, about 0.2kg/m2. Low water absorption is due to the closed-cell polyurethane foam about 92%. Low thermal conductivity and low water absorption, insulation and the outside with a good waterproof high-density polyethylene or fiberglass protective shell, changing the traditional trench laying heating pipe "to wear wet jacket" situation, greatly reducing the heating pipes The overall heat loss, heat loss heating network is 2%, less than 10% of international standards. 
 Anti-corrosion, good insulation, long service life. 
 As the rigid polyurethane insulation foam pipe insulation tightly bonded in the steel skin, cut off from air and water infiltration, can play a good antiseptic. While its foaming holes are closed, water absorption is very small. High-density polyethylene shell, glass and steel shell have good anti-corrosion, insulation and mechanical properties. Therefore, work hard to be outside steel skin of air and water erosion. As long as the internal water pipeline deal, according to foreign materials, prefabricated high-temperature insulating pipe buried up to 50 years of life than the traditional trench laying, laying of overhead high life 3 to 4 times. 
 4. Small footprint, fast construction, favorable environmental protection. 
 Masonry buried heating pipes do not need huge trench, simply heat pipe buried underground, thus greatly reducing the project area to reduce about 50% of earth excavation, masonry and concrete construction to reduce the amount of 90%. Meanwhile, heat pipe trenching parallel processing and on-site, only on-site connection, you can shorten the duration of about 50%. 
 High-temperature pre-heat pipe buried 
 Insulating pipe safety system 
 Except for China, the production of buried pipe insulation, are equipped with leak alarm line, once the pipeline somewhere leakage, conduction through the police line, can be displayed in a dedicated instrumentation insulation pipe seepage, leakage of the exact location and the level of leakage size, to inform the inspection process quickly seepage leaking pipe, to ensure the safe operation of the heating pipe network. Domestic production of pipe insulation leakage current at the end set the alarm line, yet make up this gap. 
 In short, not only has the traditional heat pipe trench and laying of pipe aerial difficult to match the advanced technology, practical performance, but also has significant social and economic benefits, but also heat energy effective measures. The use of buried heating pipe technology, heat pipe technology development indicates that China has entered a new starting point. With this advanced technology to further improve and develop, instead of the trench and buried heating pipes overhead is imperative.