Polyurethane thermal spiral pipe is divided into three layers from the inside to the outside: one layer of working steel pipe: according to the design and customer's requirements, seamless spiral welded pipe and straight welded pipe are generally selected. After the surface of steel pipe is processed by advanced shot blasting rust removal process, the surface roughness of steel pipe such as rust removal can be achieved. Two layers: polyurethane insulation layer: the rigid polyurethane foam plastic is injected into the cavity formed between the steel tube and the outer protective layer by polyurethane high-pressure foaming machine. It is commonly known as "tube in tube foam process". Its function is waterproof, 2 it is heat preservation, 3 it is to support heat network deadweight. When the conveying medium temperature: -50℃ - 120℃, choose rigid polyurethane foam plastic insulation layer. Three layers: high-density polyethylene protective layer prefabricated into a certain wall thickness of black (yellow) plastic pipe, its role is to protect polyurethane insulation layer from mechanical damage, second is anti-corrosion and waterproof.

The research and application of polyurethane foam thermal insulation spiral pipe have been paid more and more attention. After the 1970s, foreign countries generally attach importance to the production and application of insulation pipe, and strive to reduce energy consumption substantially, so as to reduce environmental pollution and greenhouse effect. Foreign insulation industry has a long history, and new insulation materials are constantly emerging. 1980 years ago, the development of thermal insulation pipe in China is very slow, one of the few insulation factory can only produce a small amount of directly buried insulating pipe underground, but China insulation industry after more than 30 years of efforts, especially after nearly 10 years of rapid development, many products from scratch, from single to diversity, from low to high quality, applied more and more common. Polyurethane is a commonly used thermal insulation material. Rigid polyurethane has many excellent properties and is widely used in the field of thermal insulation. About 49% of insulation materials used in developed countries are made of polyurethane, compared with less than 20% in China. Therefore, there is still a lot of room for the development of polyurethane insulation tubes in China.