PU insulated pipes have become a technology in some developed countries. Over the past decade, China's heating engineering technicians have, by absorbing and assimilating this technology, pushed domestic pipe-network laying technology to a higher level. More than ten years of practical experience have fully proven that PU Insulated Steel Pipe Manufacturer Compared with conventional trench and overhead laying, this laying method has many advantages. This is also the inherent driver of the rapid development of PU insulated direct-buried pipe in China's heating projects.

　　Advantages of PU Insulated Direct-Buried Pipe:

　　1. Lower project cost. According to calculations by relevant authorities, dual-pipe heating systems can generally reduce project cost by 25% (when FRP is used as the protective jacket) and 10% (when HDPE is used as the protective jacket).

　　2. Low heat loss, energy saving. Because the direct-buried pipe is made of PU foam, its thermal conductivity is: λ = 0.013–0.03 kcal/m·h·°C, far lower than other commonly used pipeline insulation materials, improving insulation performance by 4–9 times. In addition, its water absorption is very low, about 0.2 kg/m2. The low water absorption is due to the closed-cell ratio of PU foam being as high as 92%. Low thermal conductivity and low water absorption, together with HDPE or FRP protective jackets that provide a good insulation layer and external waterproofing, have changed the traditional heating-pipe laying practice of “wearing a wet cotton quilt” and greatly reduced overall heat loss of heating pipes. Heat-network heat loss is 2%, below the worldwide specification requirement of 10%.

　　3. Corrosion resistance, good insulation performance, and long service life. Direct-buried insulated pipe has an excellent anti-corrosion effect because the rigid PU foam insulation layer bonds tightly to the outer surface of the steel pipe and can isolate air and water. At the same time, its foam cells are closed and water absorption is low. The HDPE outer jacket and FRP jacket provide excellent corrosion protection, electrical insulation, and mechanical properties. Therefore the outer surface of the carrier pipe is virtually uncorroded by external air and water, provided that the water quality inside the pipeline is well treated. According to foreign data, the service life of PU insulated pipe can exceed 50 years, which is 3–4 times that of traditional trench installation and overhead laying.

　　4. Reduce land occupation, speed up construction, and protect the environment. Direct-buried heating pipe does not require construction of large trenches; the insulated pipe only needs to be buried underground, greatly reducing land use, cutting earthwork by about 50%, and reducing civil works and concrete volume by 90%. At the same time, insulated-pipe fabrication and on-site trenching proceed in parallel, and only field joints are required, which can shorten construction time by more than 50%.

　　5. PU insulated prefabricated pipes produced abroad are all fitted with leak-detection alarm wires. Once a leak occurs in some section of the pipeline, a dedicated inspection instrument can display, via the transmission wire, the exact location of water ingress and leakage, as well as the extent of the leak, so that inspectors can promptly locate the leaking section and keep the heating network in operation. Domestic insulated pipes are now being fitted with leak-detection alarm wires, though this still needs to be fully implemented. In short, PU insulated direct-buried pipe not only offers technical and practical performance that traditional trench and overhead piping can hardly match, but also delivers significant social and economic benefits, and is an energy-saving method of heat supply.