Polyurethane insulation pipe has become a mature advanced technology in some prosperous countries abroad. Over the past decade. It is pushing domestic pipeline network laying technology to a higher level. Over the past decade, the theoretical effect has proved that the laying method of polyurethane tyre thermal insulation buried pipe is better than the traditional trench and overhead laying method, and the national heating engineers and technicians have digested and absorbed this advanced technology. It has many advantages. This is precisely the internal power of the polyurethane thermal insulation directly buried pipe in the national heating project.
1. Reduce the cost of construction. According to the calculation of relevant departments, double-pipe heating pipeline can generally reduce the cost by 25% using FRP as maintenance layer and 10% using high density polyethylene as maintenance layer).
2. Low heat loss and energy saving. The thermal conductivity of the directly buried pipe is 0.0130.03kcal/mhoC, which is much lower than that of other commonly used pipes, and the thermal insulation effect is improved by 4-9 times. In addition, the water absorption rate is very low. The reason for the low water absorption of 0.2kg/m2 is that the closure rate of the polyurethane foam is about 92%. Low thermal conductivity and low water absorption, together with high density polyethylene (HDPE) or fiberglass reinforced plastics (FRP) maintenance shell with good insulation layer and external waterproof performance, have changed the situation of radical trench laying heating pipeline "wearing wet cotton jacket", greatly reducing the overall heat loss of heating pipeline, and the heat loss of heating network is less than 2% of the International 10% code request.
3. Anti-corrosion, good insulation performance and long service life. The directly buried insulation pipe is tightly adhered to the outer skin of the steel pipe because of the rigid polyurethane foam insulation layer, which can isolate the infiltration of air and water, and can play a good anti-corrosive effect. At the same time, the foaming holes are closed and the water absorption is very small. High density polyethylene shell and FRP shell have good anti-corrosion, insulation and mechanical properties. Therefore, the outer skin of working steel pipe is very difficult to be corroded by external air and water. According to foreign data, the service life of polyurethane thermal insulation pipeline can reach more than 50 years, which is 3-4 times longer than that of traditional trench laying and overhead laying.
4. It occupies less land, constructs quickly and maintains favorable environment. Directly buried heating pipelines do not need to build huge trenches. They only need to bury insulating pipes openly. Therefore, the construction area is greatly reduced, the excavation amount of earthwork is reduced by more than 50%, and the amount of civil construction and concrete is reduced by 90%. At the same time, the processing of insulating pipes and the excavation of trenches on site are stopped in parallel, and the construction period can be shortened by more than 50% with only the on-site joints.
5. Foreign consumer polyurethane insulation prefabricated pipes are equipped with leakage alarm lines. Once leakage occurs somewhere in the pipeline, through the transmission of the alarm lines, the exact location and degree of leakage of the insulation pipes can be displayed on the special testing instruments, so as to inform the inspectors to quickly dispose of the leakage pipeline section and ensure the safe operation of the heating network. At present, the leakage alarm line for domestic consumer heat preservation pipes has been set up, which needs to be filled in. In a word, polyurethane thermal insulation buried pipe not only has advanced technology and applicability which is difficult to compare with radical trench and overhead pipeline laying, but also has significant social and economic benefits. It is also a powerful measure for heating energy saving. The adoption of directly buried heating pipeline technology marks a new starting point for the development of heating pipeline technology in China. With the further improvement and development of this advanced technology, it is imperative to replace underground ditches and overhead by burying heating pipelines directly.
