I. Introduction to Polyurethane Insulated Steel Pipes
Polyurethane insulated steel pipe is prefabricated, energy-efficient piping systems with a three-layer composite structure designed for underground installation. By allowing direct burial without the need for trench construction, they greatly reduce construction costs. These pipes are widely used in district heating, oil transportation, and other industrial applications.
II. Structure of Polyurethane seamless insulation steel pipe
(1) Working Pipe Layer (Inner Layer)
Made of high-quality seamless steel pipes
Directly transports hot water, steam, and other media
High-pressure resistant with strong load-bearing capacity
Inner walls can be treated for corrosion protection
(2) Polyurethane Insulation Layer (Middle Layer)
Hard foam formed on-site through foaming
Closed-cell rate exceeds 90%, waterproof and moisture-resistant
Thermal conductivity ≤ 0.033 W/(m·K)
Effectively reduces heat loss by 70%
This structure makes polyurethane insulated steel pipes the top-tier insulated steel pipes
(3) Polyethylene Jacket (Outer Layer)
Made of high-density polyethylene material
Thickness: 2.5–4.0 mm
Corrosion-resistant and resistant to soil acidity and alkalinity
Protects the integrity of the internal structure
III. Comparison Table of Insulated Steel Pipe Standards in Various Countries
| Standard Name | Country/Organization | Applicable Scope | Working Steel Pipe Requirements | Insulation Layer Parameters | Outer Sheath Parameters | Main Features |
|---|---|---|---|---|---|---|
| GB/T 29047-2012 | China | Continuous temperature ≤ 120°C, Peak ≤ 140°C, Pressure ≤ 2.5MPa |
• DN150 and below: Seamless steel pipe (GB/T 8163) • DN200 and above: Spiral welded pipe (GB/T 9711.1) |
• Closed cell rate ≥ 88% • Density ≥ 60kg/m³ • Compressive strength ≥ 0.3MPa • Water absorption rate ≤ 10% |
• Density ≥ 950kg/m³ • Carbon black content 2.5% ± 0.5% • Tensile strength ≥ 19MPa |
Compatible with European EN253 parameters, emphasizing high-temperature adaptability and mechanical properties of the outer sheath |
| CJ/T 114-2000 | China (Urban Construction) | Continuous temperature ≤ 120°C, Peak ≤ 140 |
• Same as GB/T 29047 steel pipe requirements • Seamless steel pipe in accordance with GB 8163 |
• Axial shear strength ≥ 0.12MPa • Closed cell rate ≥ 88% • Density ≥ 60kg/m³ |
• Environmental stress cracking resistance ≥ 200h • Elongation at break ≥ 350% |
Focused on urban heating projects, emphasizing the bonding strength and water resistance of the insulation layer |
| SY/T 0415-1996 | China (Petroleum Industry) | Petroleum and natural gas transportation |
• High-pressure seamless steel pipe • Spiral welded pipe (SY/T 5037) |
• High-temperature modification (≤180°C) • High closed cell rate design |
• Optional HDPE or fiberglass • Fiberglass has better temperature resistance (≤120°C) |
Targeted at chemical corrosion environments, supports fiberglass outer sheath, suitable for high-temperature oil transportation scenarios |
| EN 253 | Europe | Continuous temperature ≤ 120°C, Peak ≤ 140°C |
• Seamless/welded steel pipe (ISO 4200) • Corrosion protection requirements (ISO 21809) |
• Closed cell rate ≥ 90% • Density ≥ 60kg/m³ • Axial shear strength ≥ 0.12MPa |
• Uniform dispersion of carbon black • UV aging resistance |
Globally most widely used, emphasizing life prediction model (≥30 years), strict control of closed cell rate |
IV. Features of polyurethane insulation steel pipe:
High-efficiency insulation: polyurethane insulation steel pipes have low thermal conductivity and excellent insulation performance.
Waterproof and rust-proof: The high-density polyethylene outer protective layer provides waterproof and corrosion-resistant properties.
High strength: Polyurethane is tightly bonded to the steel pipe, offering strong compressive strength.
Easy Installation: Using the direct burial method, installation is simple and the construction period is short.
Long Service Life: Polyurethane insulated steel pipe under normal conditions, it can be used for over 30 years.
Environmental Friendliness: The materials are non-polluting and environmentally friendly.
Wide Application: Polyurethane insulated steel pipe suitable for heating, water supply, chemical, and other industries.
Excellent Low-Temperature Performance: Maintains superior performance even at low temperatures.
Low Maintenance Costs: The insulation layer protects the pipe, reduces corrosion, and lowers maintenance requirements.
High Reliability: Can be equipped with a leakage detection system to ensure safe operation.
V. Applications of Polyurethane Foam Insulation Pipe:
Urban Heating Systems: Used in centralized heating pipelines to ensure efficient heat transfer and minimize heat loss.
Oil and Natural Gas Transportation: Long-distance pipeline transportation, providing insulation and freeze protection to ensure stable energy transmission.
Chemical Industry: Transporting chemicals and organic substances to prevent contamination.
Food and Pharmaceutical Industry: Transporting liquids and gases while maintaining stable temperatures to ensure quality.
HVAC Systems: Cooling and hot water transportation to enhance energy efficiency.
Industrial Fluid Transportation: Reducing heat loss, suitable for liquid and gas transportation.
Low-Temperature Transportation: LNG pipelines to ensure low-temperature transportation.
Construction sector: Exterior wall insulation, cold storage, and pipeline insulation.
Water conservancy and mining: Frost-proof and corrosion-resistant pipeline systems.
Geothermal and hot spring transportation: Long-distance transportation to meet insulation requirements.
Polyurethane foam-insulated steel pipes are widely used across multiple industries, while high-temperature insulated steel pipes are particularly important in the petroleum and chemical transportation sectors.
VI. Insulation steel pipe performance parameter table:
| Parameter Name | Unit | Parameter Value | Description |
|---|---|---|---|
| Thermal Conductivity | W/(m·K) | ≤0.024 | The low thermal conductivity of polyurethane foam insulation ensures excellent thermal insulation performance. |
| Water Absorption Rate | % | ≤0.2 | The low water absorption rate of polyurethane foam ensures good waterproof performance. |
| Compressive Strength | MPa | ≥0.3 | Polyurethane foam has a high compressive strength. |
| Closed Cell Rate | % | ≥95 | The high closed cell rate of polyurethane foam ensures excellent thermal insulation and waterproof performance. |
| Density | kg/m³ | 30-80 | The density range of polyurethane foam. |
| Temperature Range | ℃ | -196~150 | Polyurethane insulation can withstand extremely low and relatively high temperatures. |
| Service Life | Years | 30-50 | The long service life of polyurethane insulated steel pipes under normal operating conditions. |
| Corrosion Resistance | - | Good | The outer jacket and corrosion-resistant layer effectively prevent the corrosion of steel pipes. |
| Outer Jacket Density | kg/m³ | 940-960 | The density of high-density polyethylene outer jacket. |
| Outer Jacket Tensile Strength | MPa | ≥19 | The tensile strength of the outer jacket. |
| Outer Jacket Elongation at Break | % | ≥450 | The elongation at break of the outer jacket. |
VII. Polyurethane foam thermal insulation steel pipe quality inspection report:
| Inspection Item | Inspection Content | Inspection Standard | Notes |
|---|---|---|---|
| Appearance Quality | Smooth and flat surface, free from bubbles, cracks, dents, and impurities | Visual Inspection | Surface quality directly affects the service life of the pipe. |
| Dimensional Accuracy | Outer diameter of steel pipe, wall thickness, insulation layer thickness, outer diameter and wall thickness of outer jacket | GB/T 29047-2012 | Dimensional deviations must be controlled within the standard range. |
| Insulation Layer Performance |
Density ≥60 kg/m³ Closed cell rate ≥88% Thermal conductivity ≤0.033 W/(m·K) Water absorption rate ≤10% (100℃ boiling water, 90 minutes) Compressive strength ≥0.3 MPa (at 10% deformation) |
GB/T 29047-2012 | Insulation performance is a core indicator. |
| Outer Jacket Performance |
Density ≥950 kg/m³ Tensile strength ≥19 MPa Elongation at break ≥350% Longitudinal shrinkage rate ≤3% |
GB/T 13018-91 | The outer jacket must have good mechanical properties. |
| Corrosion Resistance | Thickness, adhesion, and corrosion resistance of the anti-corrosion layer | GB/T 8923.1 | The anti-corrosion layer protects the steel pipe from corrosion. |
| Temperature Resistance |
Continuous operating temperature ≤120℃ Peak operating temperature ≤140℃ |
GB/T 29047-2012 | Suitable for a variety of temperature scenarios. |
| Mechanical Strength | Shear strength ≥0.12 MPa (at 23±2℃) | GB/T 29047-2012 | Ensures the pipe is not damaged during construction and operation. |
| Durability | Service life ≥30 years | GB/T 29047-2012 | Long-term stable performance. |
| Non-destructive Testing | Radiographic testing, ultrasonic testing | NB/T 47013.2-2015 | Ensures the internal quality of the polyurethane insulated steel pipe. |
