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wr@insulatedpipeline.com
wyy@insulatedpipeline.com
Update time：2025-05-08
I Definition and Core Thermal Insulation Steel Pipe
i Structural Composition
(1)Working steel pipe layer
Seamless steel pipe, spiral welded pipe and other materials, the surface needs to be treated by shot blasting and rust removal, and coated with epoxy resin anticorrosive coating, used for the direct transmission of high-temperature steam, petroleum, chemical media.
(2) Insulation layer
Polyurethane foam: rigid closed-cell structure (density 60-80kg/m³), thermal conductivity as low as 0.033W/(m-K), applicable to the temperature range -185 ℃ ~ 150 ℃ (modified up to 180 ℃), through the high-pressure foaming process and the combination of steel pipe.
Other materials: such as aluminum silicate (high-temperature resistant type), glass wool (sound-absorbing and heat-insulating type), rock wool (fire-resistant type), etc., according to the working conditions to choose a different combination of materials.
(3) Outer protective layer
Commonly used high-density polyethylene (HDPE) or galvanized iron, thickness ≥ 2.5mm, with waterproof, soil corrosion resistance, mechanical impact resistance, etc. Some high-end models use FRP (FRP) to enhance weather resistance.
ii Functional Characteristics.
(1) Thermal performance: heat loss rate ≤ 2%, high efficiency heat insulation through the combination of aluminum foil reflective layer and inorganic insulation layer.
(2)Mechanical strength: can withstand 80kN/m² soil load, impact resistance of 50J/cm², direct burial without concrete support.
(3)Durability: Designed for 50 years, the anti-corrosion system includes cathodic protection and three-layer PE cold-wrapped tape sealing to prevent groundwater infiltration.
(jpeg).jpg "Thermal Insulation Steel Pipe")
iii Classification system
(1)According to sliding mode
Inner sliding type: the insulation structure is aluminum silicate, microporous calcium silicate and polyurethane layer in order from inside to outside, applicable to high temperature steam pipeline.
(2) External sliding type: the structure of glass wool insulation layer + air insulation layer is adopted, applicable to medium and low temperature medium transportation (-50-120℃).
(3)According to laying method
Directly buried prefabricated type: no pipe trench, directly buried, cost savings of more than 30%.
Overhead type: galvanized iron or glass fiber reinforced plastic is used for the outer sheath, which is suitable for special terrain such as river crossing and road crossing.
II Comparison table of high-quality and poor-quality steel pipe insulation
| Comparison Dimension | High-Quality Thermal Insulation Steel Pipe | Low-Quality Thermal Insulation Steel Pipe |
|---|---|---|
| Material and Structure | The steel pipe uses seamless steel pipe in accordance with GB/T 8163 or spiral welded pipe in accordance with GB/T 9711, with a wall thickness tolerance of ≤0.3mm. Blast cleaning to Sa2.5 grade, epoxy coating ≥300μm. Three-layer anti-corrosion system (steel pipe + polyurethane + HDPE). | The steel pipe uses straight seam pipe instead of seamless pipe, with non-uniform material. Surface with pitting and cracks, blast cleaning not up to standard. The outer protective pipe contains recycled materials or impurities. |
| Insulation Layer Performance | Polyurethane density ≥60kg/m³, closed-cell rate ≥88%, thermal conductivity ≤0.033W/(m·K). Compressive strength ≥0.3MPa, water absorption rate ≤10%. Service temperature above 120℃, service life ≥30 years. | Density ≤50kg/m³, low closed-cell rate (easy to absorb water). Insufficient compressive strength, deforms under pressure. Carbonizes at high temperatures, service life ≤10 years. |
| Outer Protective Layer Quality | HDPE outer protective pipe density ≥940kg/m³, tensile strength ≥19MPa, elongation at break ≥400%. Smooth surface without bubbles, uniform dispersion of carbon black. | Uses inferior PE material, density ≤900kg/m³. Rough surface, with depressions or impurities, prone to cracking. Carbon black clumps or unevenly distributed. |
| Testing and Certification | Provides national-level test reports (certified by CMA/CNAS). Complies with GB/T 29047-2012 standard, including full-range tests such as hydrostatic pressure, flaw detection, and thermal stability. | No test reports or forged data. Passed only by appearance inspection, lacks mechanical property tests. |
| Price and Cost-effectiveness | Higher purchase price (steel pipe is more than 30% more expensive than polyurethane pipe). Lower life cycle cost (maintenance costs reduced by 40%-60%). | Lower initial price (20%-50% cheaper than high-quality products). Frequent repairs during operation, total cost doubles. |
(jpeg).jpg "Thermal Insulation Steel Pipe")
III Application areas of insulated steel pipe
Centralized heat supply: main pipeline of urban heat network (temperature drop≤1℃/40km).
Petrochemical industry: oil pipeline in highly corrosive environment containing Cl->200ppm.
Municipal engineering: hot and cold water circulation system of underground comprehensive pipeline corridor.
IV Standard comparison table of insulated steel pipe in each country
| Country/Region | Standard Name | Main Content |
|---|---|---|
| China | GB/T 29047-2021 "High-Density Polyethylene Outer Sheath Rigid Polyurethane Foam Plastic Prefabricated Direct-Burial Insulated Pipes and Fittings" | Specifies the structure, performance requirements, and test methods for prefabricated direct-burial insulated pipes. |
| China | CJ/T 200-2004 "Technical Conditions for Prefabricated Direct-Burial Steam Insulated Pipes for Urban Heating" | Covers the manufacturing, inspection, and acceptance standards for prefabricated direct-burial steam insulated pipes. |
| China | CJ/T 114-2000 "High-Density Polyethylene Outer Sheath Polyurethane Foam Plastic Prefabricated Direct-Burial Insulated Pipes" | Provides technical requirements for the design, construction, and operation and maintenance of direct-burial steam pipelines. |
| USA | ASTM C165 "Standard Test Method for Measuring Compressive Properties of Thermal Insulation" | Tests the compressive properties of thermal insulation materials. |
| USA | ASTM C195 "Mineral Fiber Thermal Insulation Cement" | Specifies the requirements for mineral fiber thermal insulation cement. |
| USA | ASTM C303 "Test Method for Density of Rigid Cellular Plastics" | Tests the density of rigid cellular plastics. |
| USA | ASTM C335 "Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Guarded Hot Plate" | Tests the steady-state thermal transmission properties of materials. |
| USA | ASTM C449 "Mineral Fiber Water-Repellent Thermal Insulation and Edge Sealing Cement" | Specifies the requirements for mineral fiber water-repellent thermal insulation and edge sealing cement. |
| USA | ASTM C518 "Standard Test Method for Steady-State Thermal Transmission Properties by Means of the Heat Flow Meter Apparatus" | Tests the steady-state thermal transmission properties of materials. |
| USA | ASTM C547 "Mineral Fiber Preformed Pipe Insulation" | Specifies the requirements for mineral fiber preformed pipe insulation. |
| USA | ASTM C552 "Glass Foam Block and Pipe Insulation" | Specifies the requirements for glass foam block and pipe insulation. |
| USA | ASTM C591 "Unfaced Rigid Polyurethane Foam Thermal Insulation" | Specifies the requirements for unfaced rigid polyurethane foam thermal insulation. |
| USA | ASTM C592 "Mineral Fiber Blanket Insulation" | Specifies the requirements for mineral fiber blanket insulation. |
| USA | ASTM C612 "Mineral Fiber Block and Board Thermal Insulation" | Specifies the requirements for mineral fiber block and board thermal insulation. |
| UK | BS 5422:2023 "Specification for Thermal Insulation for Pipelines, Tanks, Vessels, Ductwork, and Equipment" | Specifies the performance requirements of thermal insulation materials for different operating temperatures. |
| UK | BS EN 448:2025 "District Heating Piping. Bonded Single Pipe Systems. Direct Buried Hot Water Networks. Factory-Made Pipe Components" | Specifies the requirements for factory-made pipe components for district heating piping, including steel service pipes, polyurethane thermal insulation, and polyethylene sheath. |
| EU | ISO 15516 "Moisture-Resistant Thermal Insulation Systems for the Petroleum and Natural Gas Industries" | Specifies the minimum requirements for moisture-resistant thermal insulation systems in the petroleum and natural gas industries, including application, testing, handling, storage, and transportation. |
| EU | ISO 8296 "Plastics. Films and Sheets. Determination of Wetting Surface Tension" | Specifies the method for determining the wetting surface tension of plastic films and sheets. |
| EU | ISO 16770 "Plastics. Polyethylene. Determination of Environmental Stress Cracking (ESC) by Full Notch Creep Test (FNCT)" | Specifies the determination of environmental stress cracking of polyethylene. |
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E-mail：wr@insulatedpipeline.com
E-mail：wyy@insulatedpipeline.com
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