High density polyurethane foam steel pipes

Published:2025-04-08 | Last Updated: 2025-06-12    Views: 24

I. What is high density polyurethane foam steel pipe insulation?

High-density polyurethane foam insulated steel pipes technology is a mature and widely used advanced pipeline insulation solution in developed countries abroad.

In recent years, my country's heating engineering technicians have successfully promoted the development of this technology in China through in-depth research and practice, and significantly improved the overall technical level of pipeline laying.

This solution with insulated steel pipe as the core (its working layer often uses straight seamless steel pipe or high-performance alloy steel pipe) integrates many significant advantages: simple and fast construction, excellent insulation and energy-saving effect, excellent anti-corrosion performance, overall light weight but high strength, and also has flame retardant, cold-resistant, waterproof (non-absorbent) and other characteristics.

II. High-density polyurethane foam steel pipe material implementation standards:

i. Working steel pipe

DN ≤ 150 mm: seamless steel pipe must be used, and GB/T 8163 "Seamless steel pipe for conveying fluids" must be implemented.

DN ≥ 200 mm: spiral welded pipe can be used, and GB/T 9711.1 or SY/T 5037 (petroleum and natural gas industry transportation steel pipe standard) can be implemented.

Pretreatment requirements: The surface of the steel pipe must be shot blasted to Sa2 level (GB/T 8923) to ensure that there is no oil or rust to enhance the adhesion of the insulation layer.

ii. Outer sheath (high-density polyethylene, PE)

GB 13018-91 "Limit Deviation of Outer Diameter and Wall Thickness of Polyethylene (PE) Pipes" must be implemented, requiring density ≥950 kg/m³, carbon black content 2.5%±0.5% (UV resistance), and tensile strength ≥19 MPa.

iii. Key technical parameters of the insulation layer of Polyurethane foam thermal insulation steel pipe

The following are the core performance requirements that the insulation layer must meet, formulated in accordance with GB/T 29047-2012 and CJ/T 114-2000:

III. Polyurethane insulation pipe specification table

IV. Application fields of direct buried polyurethane insulated steel pipe

i. Urban heating

a. Efficient insulation: significantly reduce heat loss and ensure stable heating.

b. Long life: underground service life can reach 30-50 years.

ii. Industrial field

a. Oil and gas: resistant to harsh environment, ensuring stable medium transportation.

b. Chemical industry: strong corrosion resistance, protecting the medium from pollution.

c. Food and medicine: hygienic and environmentally friendly, meeting the needs of steam transportation.

iii. Municipal engineering

a. Heating and water supply: The insulation layer of thermal insulated steel pipes protects the pipes, extends their service life, and helps with municipal infrastructure construction.

V. Storage method of insulated steel pipe

i. The ground should be level and free from hard impurities such as gravel.

ii. Placement site should be dug drainage ditch, the site should not accumulate water.

ii. The stacking site should be set up with pipe supports, and the outer protection pipe should be 150mm above the ground. 

iv. The stacking height of the insulation pipe should not be more than 2 meters.

v. Insulation pipe shall not be subject to sunlight, rain and soaking, open storage is appropriate to cover with a tarpaulin, stacking should be away from heat and fire sources.

VI. Which layers does the polyurethane insulation pipe consist of?

Detailed explanation of the three-layer structure (working steel pipe → insulation layer → outer protective pipe).

i. The first layer: working steel pipe

Optional materials: seamless steel pipe, spiral welded pipe, straight seam welded pipe, PPR pipe, fiberglass pipe

Function: conveying fluid medium (hot water/steam/chemical medium), taking on the core role of pressure bearing and corrosion resistance

ii. The second layer: polyurethane insulation layer

Molding process: through a high-pressure or low-pressure foaming machine, the polyurethane raw material is injected into the interlayer of the steel pipe and the outer protective pipe for foaming and curing at one time

Core characteristics: rigid closed-cell foam structure to achieve efficient thermal insulation (thermal conductivity ≤ 0.033W/m·K)

iii. The third layer: high-density polyethylene (HDPE) outer protective pipe

Dual core functions:

Physical protection: resist underground mechanical impact and rock extrusion

Environmental protection: waterproof and moisture-proof + chemical corrosion resistance, ensuring the 50-year life of the insulation layer

V. Table of uses and applicable standards for polyurethane insulated steel pipes