The insulation pipe is suitable for conveying various media in the range of - 50 ℃ - 150 ℃. It is widely used in central heating, cooling and hot oil transportation, as well as thermal insulation and cold insulation projects in warm rooms, cold storages, coal mines, petroleum, chemical industries and other industries. Steel clad steel The thermal insulation structure of steel clad steel composite insulation pipe can be divided into two categories according to different sliding modes: 1. Internal sliding type: thermal insulation structure consists of working steel pipe, aluminum silicate, drag reduction layer, microporous calcium silicate, thermal insulation layer, stainless steel fastening steel strip, aluminum foil reflective layer, polyurethane insulation layer, outer steel pipe, and external anti-corrosion layer. The inner sliding thermal insulation steel pipe is composed of steel pipe conveying medium+composite silicate or microporous calcium silicate+rigid polyurethane foam+outer steel pipe+anti-corrosion protective layer of glass fiber reinforced plastic shell. The thermal insulation treatment technology of various pipe fittings nodes is mature and the quality is reliable. 2. External sliding type: the thermal insulation structure consists of working steel pipe, glass wool thermal insulation layer, aluminum foil reflective layer, stainless steel fastening steel strip, sliding guide bracket, air insulation layer, external protective steel pipe, and external anti-corrosion layer. polyurethane The polyurethane insulation pipe is divided into three layers from the inside to the outside: Thermal insulation pipe Thermal insulation pipe First floor: working steel pipe floor Seamless steel pipe, spiral steel pipe and straight seam steel pipe are generally selected according to the design and customer requirements. After the steel pipe surface is treated by advanced shot blasting, the steel pipe rust removal grade can reach Sa2 in GB8923-1988 standard, and the surface roughness can reach R=12.5 μ m in GB6060.5-88 standard. The second layer: polyurethane insulation layer: It is made by injecting the original liquid of rigid polyurethane foam into the cavity formed between the steel pipe and the outer protective layer with a high-pressure foaming machine, which is commonly known as "pipe in pipe foaming". The third layer: high-density polyethylene protective layer: Prefabricated into black or yellow polyethylene plastic pipes with a certain wall thickness. Its function is to protect the polyurethane insulation layer from mechanical hard objects, and to prevent corrosion and water. All directly buried insulation pipes produced outside China are equipped with leakage alarm lines. Once leakage occurs somewhere in the pipeline, through the conduction of the alarm line, the exact location and degree of leakage of the insulation pipe can be displayed on the special detection instrument, so as to notify the leakage inspector to quickly deal with the leaking pipe section and ensure the safe operation of the heating pipe network. The leakage alarm line has not been set for the insulation pipes produced in China, which needs to be filled in. In a word, insulation pipe not only has advanced technology and practical performance that traditional trench and overhead laying pipeline cannot match, but also has significant social and economic benefits, which is also a powerful measure for heat supply and energy conservation. The use of directly buried heating pipeline technology marks that China's heating pipeline technology has entered a new starting point. With the further improvement and development of this advanced technology, it is imperative to directly bury heating pipelines instead of trench and overhead.