Polyurethane Insulation Steel Pipe

Published:2025-04-04 | Last Updated: 2025-06-12    Views: 27

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I. What is polyurethane thermal insulated steel pipe?

i. Definition of Polyurethane Insulated Steel Pipes

Polyurethane insulated steel pipe is a composite pipe. It combines the strength of steel pipe with the thermal insulation properties of polyurethane foam.

ii. Main Applications

This pipe is primarily used for transporting fluids that require thermal insulation or heat insulation. Common examples include hot water, steam, and certain chemical media.

iii. Core Structure (From Inner to Outer Layers)

a. Working Steel Pipe

This is the innermost layer.

Its primary function is to transport fluids.  

Common materials include seamless steel pipes, spiral welded steel pipes, or straight seam welded pipes.  

These materials have high strength and typically also exhibit good corrosion resistance.  

b. Polyurethane Insulation Layer  

This layer is located between the working steel pipe and the outer protective pipe.  

The material is polyurethane foam.

Polyurethane foam is produced through the reaction of isocyanate and polyether polyol, followed by foaming.  

It is filled into the interlayer via high-pressure injection.  

This results in a continuous and dense insulation layer.  

Its key advantage is an extremely low thermal conductivity, typically ≤ 0.03 W/(m·K).  

Therefore, it provides excellent thermal insulation performance.  

c. Outer Protective Pipe

This is the outermost layer.  

Its primary function is to protect the internal insulation layer.  

It prevents the insulation layer from mechanical damage and resists corrosion from external environments.  

Common materials include high-density polyethylene (PE), fiberglass-reinforced plastic (FRP), or steel pipes.  

These materials typically have anti-aging, waterproof, and moisture-resistant properties.

II. The Five Core Advantages of Polyurethane Insulated Steel Pipes

Polyurethane foam pre-insulated steel pipes (also known as polyurethane insulated pipes or prefabricated insulated pipes) combine the strength of steel pipes with the excellent performance of polyurethane foam. Their core advantages are as follows:

i. Excellent insulation and significant energy savings

Polyurethane rigid foam has an extremely low thermal conductivity (≤0.03 W/m·K).

The insulation layer provides seamless coverage, effectively preventing cold bridge effects.  

Compared to traditional insulation materials, pre-insulated pipes achieve energy savings exceeding 30%.

ii. Durable, pressure-resistant, moisture-proof, and weather-resistant  

The steel pipe shell combined with a high-density outer protective layer has high compressive strength (≥200 kPa).  

The closed-cell structure of polyurethane foam has a low water absorption rate (<3%).  

Polyurethane insulated pipes are suitable for underground humid environments, resistant to corrosion, and do not crack.  

They have a wide operating temperature range (-50°C to 150°C).

iii. Lightweight and easy to install, saving time and labor

The insulation layer of polyurethane foam pre-insulated steel pipes is 40% thinner than traditional glass wool, saving underground space.

As pre-insulated pipes, they can be directly buried and laid without complex on-site insulation construction, eliminating the need for additional maintenance.

Significantly shortens the construction period by over 30%.

iv. Environmentally friendly, safe, and durable

Uses fluorine-free environmentally friendly foaming technology.

Polyurethane insulation pipe materials are non-toxic and pollution-free.  

Excellent flame-retardant performance (Class B1).  

Complies with national standards (e.g., GB/T 31404-2015).  

v. Convenient maintenance, economical and efficient  

The pre-insulated pipe has a stable structure and can be repaired under temperature and pressure without shutting down the pipeline.  

Overall maintenance costs are significantly reduced (approximately 60%).

III. Related parameters of polyurethane insulated steel pipes

i. Technical Specifications Comparison Table

ii. Application Scenarios

iii. Production Standards and Specifications Table

iv. Performance Comparison Table (with other insulated pipes)

IV. Comparison of Industry Application Scenarios and Benefits

V. Polyurethane Insulated Steel Pipe Export Standards 

i. International Common Standards 

(1) Pipe Standards 

Working steel pipe needs to comply with API 5L (oil pipeline pipe) or ASTM A53/A106 (seamless/SSAW steel pipes) to ensure that the chemical composition and mechanical properties are up to standard.

EN 253 is commonly used in the European market, covering the overall prefabrication requirements for the working steel pipe, polyurethane insulation and polyethylene outer protection pipe.

(2) Performance of the insulation layer 

Density ≥ 60kg/m³, closed cell rate ≥ 88%, thermal conductivity ≤ 0.033W/(m-K) (50 ℃ test conditions).

Compressive strength ≥0.3MPa (10% deformation conditions), water absorption ≤10% (boiling water immersion for 90 minutes).

(3) Requirements for outer protection pipe 

High-density polyethylene (HDPE) density ≥940kg/m³, tensile strength ≥19MPa, elongation at break ≥350%.

Anti-corrosion coating needs to comply with DIN 30678 (polyethylene anti-corrosion layer) or GB/T 23257 (domestic equivalent standard).

ii. Special Requirements for Target Markets 

(1) European Market 

EN 253 certification is mandatory, focusing on continuous operation temperature (140℃), peak temperature (150℃) and 30-year service life verification of the insulation pipe.

CE certification and proof of environmental compliance (e.g. fluorine-free foaming process) are required.

(2) North American market 

Conform to ASTM standards, such as ASTM C177 (thermal conductivity test of insulation materials), ASTM D1621 (compressive strength test).

The outer protection pipe needs to pass UL certification (flame retardant performance) and NACE anti-corrosion standard.

(3) Middle East and Southeast Asia market 

Emphasis on high temperature resistance performance (some projects require resistance to 180 ℃), need to provide third-party test reports of modified polyurethane insulation.

Adapt to high saline and alkaline environment, the outer protection pipe needs to be certified by ISO 21809-1 (anti-corrosion coating).

iii. Export Quality Control Points

(1) Production Standard 

Adopt GB/T 29047-2012 (domestic) or EN 253 (international) for prefabrication, and ensure that the factory passes ISO 9001 quality management system certification.

The surface treatment of steel pipe needs to reach Sa2 grade descaling (GB/T 8923), with roughness R=12.5μm. 

(2) Testing and Acceptance 

Each batch of products needs to be provided with third-party testing report, containing key parameters such as axial shear strength (≥0.12MPa) and melt index (0.50~0.70g/10min).

Implementation of layered compression test: working pressure 1.5 times the steady pressure for 30 minutes without leakage.

(3) Marking and packaging 

The outer protection pipe is labeled with material, specifications, implementation standards, production date and manufacturer information, in line with the labeling regulations of the target country.

Use moisture-proof packaging during transportation, and install protective caps on the pipe ends to avoid mechanical damage to the insulation layer.

iv. Avoidance of common export risks 

Risk of poor quality raw materials: Refuse to use TDI waste or recycled materials, and ask suppliers to provide test certificates of MDI purity ≥ 98%.

Construction suitability: confirm the target country's burial depth standard (e.g. European requirement ≥1.5 meters) and welding process (e.g. ASME B16.5 flange connection) before export.