Polyurethane insulated pipes generally consist of a three-layer structure, arranged from the outside inward as follows: The first layer: high-density polyethylene, fiberglass-reinforced plastic, or steel pipes are used as the protective casing. The second layer: a rigid polyurethane foam insulation layer made from isocyanate and formulated polyether. The third layer: welded or seamless steel pipes are selected according to the technical requirements of the conveyed medium. When the pipeline is installed directly underground or laid in trenches, an epoxy powder coating (FBE), three-layer polyethylene coating (3LPE), or three-layer polypropylene coating (3LPP) can be applied to the steel pipe surface as an anti-corrosion protective layer to enhance the corrosion resistance of the steel pipe and extend the service life of the pipeline. Polyurethane insulated pipes offer the advantages of light weight, high strength, thermal insulation, flame retardancy, cold resistance, water resistance, and simple, rapid installation. They have been widely used in construction, transportation, petroleum, chemical, electric power, refrigeration, and many other fields.