The polyurethane insulation pipe adopts a three-layer composite structure design, with each layer responsible for specific functions, jointly achieving efficient insulation, long-term durability, and safe operation.

As the core channel for medium transportation, working steel pipes are usually made of Q235B carbon steel, seamless steel pipes, or spiral welded pipes. The pipe diameter covers DN15 to DN3000, with a wall thickness range of 6-26mm, and can withstand working pressures of 0.1-5.0MPa. The surface of the steel pipe is treated with Sa2.5 level shot blasting and rust removal, and coated with anti-corrosion coating to ensure structural strength and sealing reliability during long-term transportation of hot water, steam or chemical media, in accordance with the requirements of GB/T 3091 and GB/T 9711.1 standards.

The insulation layer is composed of rigid polyurethane foam plastic, the density is controlled between 60 – 80 kg/m ³, the closed cell rate is not less than 90%, and some high-quality products can reach more than 95%. Its thermal conductivity is extremely low, ranging from 0.022 to 0.033 W/(m · K), resulting in only a quarter of the heat loss of traditional pipes. The temperature resistance range of this layer is -60 ℃ to 150 ℃, and the short-term peak can withstand high temperatures of 180 ℃. The compressive strength reaches 0.3-2.5 MPa, effectively blocking water vapor penetration, avoiding insulation performance degradation, and supporting the design life of the entire pipe for 30-50 years.

The outer protective pipe is made of high-density polyethylene (HDPE) material, with a density of ≥ 940 kg/m ³, a longitudinal shrinkage rate of ≤ 3%, and a moisture permeability rate of less than 1.5 g/(m ² · d). It has excellent impact resistance, chemical corrosion resistance, and environmental stress cracking resistance. The standard wall thickness is 2.0-6.0mm, and large-diameter pipes are correspondingly thickened to enhance mechanical protection. In elevated or highly corrosive environments, some products can use fiberglass or galvanized iron sheet as a substitute for the outer protective layer to enhance weather resistance.

The system can be equipped with leakage alarm lines, built-in copper core sensing wires, and linked with the monitoring platform to achieve precise positioning of leakage points within ± 1m, improving the efficiency of pipeline operation and maintenance. In terms of anti-corrosion coating, 3PE anti-corrosion or epoxy powder coating can be added according to the working conditions to enhance the resistance to acidic and alkaline substances in the soil. The connection method supports on-site welding or socket installation, with the latter equipped with rubber sealing rings for quick construction and maintenance.

When applied in the Linyi area of Shandong Province, special attention should be paid to the geological conditions of winter frozen soil depth (0.8-1.2m) and mixed clay sand soil. It is recommended to use insulation pipes with a closed cell rate of ≥ 93% and a density of ≥ 70 kg/m ³, with an outer protective pipe wall thickness of not less than 3.0mm, to resist soil stress and frost heave. Fine sand should be used for backfilling, and it is strictly prohibited for stones to directly contact the outer protective pipe to prevent mechanical damage.

All technical parameters comply with the national mandatory standard GB/T 29047-2021 and the urban heating industry specification CJ/T 114-2017. Internationally, ASTM C-591 and EN 14315-2:2013 are used to constrain the thermal conductivity and thermal resistance values, ensuring the compliance and reliability of the product in domestic and international engineering.