Directly buried insulation spiral steel pipes can be buried in frozen soil layers of 0.6-1.2 meters (so people commonly refer to them as directly buried insulation pipes or prefabricated insulation pipes), reducing heat loss by more than 40% compared to ordinary pipelines. The working service life is more than 3-5 times longer than other insulation and anti-corrosion materials, and the service life can reach 30-50 years; The quality meets or exceeds the industry standards in China. Its complete insulation system has the characteristics of low overall project cost, short construction period, long service life, energy conservation, and environmental protection. The continuous operating temperature is 130 ℃, with a peak value of up to 150 ℃.

Classification of buried insulation spiral steel pipes:

1. Plastic sheathed steel insulation pipe: plastic sheathed steel insulation pipe is closely combined by high-density polyethylene outer pipe, polyurethane foam insulation layer and inner working steel pipe.

2. Steel sheathed steel insulation pipe: steel sheathed steel insulation pipe is composed of external protective steel pipe plus steel pipe anti-corrosion, polyurethane foam insulation layer and internal working steel pipe.

Polyurethane insulated buried pipes have become a relatively mature and advanced technology in some developed countries abroad. In recent years, Chinese heating engineering technicians have been promoting the development of domestic pipeline laying technology to a higher level by digesting and absorbing this advanced technology. The practical achievements in recent years have fully proved that the laying method of polyurethane insulation buried pipes has many advantages compared to traditional trench and overhead laying. This is also the intrinsic driving force behind the rapid development of polyurethane insulated buried pipes in China's heating engineering.