1. Outer Protective Steel Tube. It protects the thermal insulating layer from the erosion of the groundwater, supports the working steel tube and bears certain external loads to ensure the normal operation of working steel tube.
2. Anticorrosion Coating. It provides protection for the outer protective steel tube from corrosion to extend the service lifetime of the outer protective steel tube.
3. Drag Reduction Layer. It is for guaranteeing the working steel pipe moves freely when facing the thermal expansion and cold contraction.
4. Polyurethane Foam Layer. It plays the role of keeping the temperature of medium and ensuring the surface of the outer protective steel tube maintaining normal temperature.
5. Barrier and Reflective Layer. The barrier ensures that the organic foam material won't enter into the inorganic rigid high temperature resistant layer. The reflective layer reflects part of the heat of the high temperature resistant layer.
6. Working Steel Pipe. The delivered medium flows normally in the working steel tube.
7. Inorganic Rigid Thermal Insulating Layer. It is high temperature resistant and can ensure the temperature of the interface located between the organic thermal insulating layer and the inorganic rigid thermal insulating layer. The foam is also guaranteed without carbonization.