I. Introduction to Steel-Jacketed Insulated Pipe
Steel-jacketed insulated pipe is a prefabricated insulated pipe system consisting of a working steel pipe, an inner anti-corrosion layer, a high-density polyurethane foam insulation layer, and a steel casing.
This pipe structure offers multiple advantages, including pressure resistance, thermal insulation, corrosion resistance, and resistance to mechanical damage. It is widely used for transporting hot water, steam, hot oil, and cryogenic liquids.
II. Steel jacketed steel insulated steel pipe structure
i. Working Steel Pipe (Inner Pipe)
Function: Withstands media pressure and transports hot water, steam, or chemical liquids.
Material Options: Carbon steel, low-alloy steel, or stainless steel.
Selection Tips: Low-alloy steel or stainless steel is preferred for high-temperature or highly corrosive media.
ii. Internal Anti-Corrosion Coating (Optional)
Function: Prevents media from corroding the inner pipe, extending pipe life.
Common Types: Epoxy coating, epoxy powder coating, or other anti-corrosion materials.
Selection Tips: High-temperature corrosion-resistant coating is recommended for pipes handling corrosive media or high-temperature steam.
iii. Insulation Layer (Inorganic Materials)
Material Types: Rigid insulation materials such as silicate wool, mineral wool, rock wool, and foam glass.
Function: Provides thermal insulation, prevents heat loss, and maintains stable medium temperature.
Thickness Range: Customizable based on design requirements, generally 20–100 mm.
Selection Tips: For high-temperature media, inorganic mineral wool or foam glass is preferred, as they offer excellent heat resistance and flame retardancy.
iv. Steel Casing (Outer Pipe)
Function: Protects the insulation layer and inner pipe from mechanical damage and environmental corrosion.
Material: Carbon steel or low-alloy steel, optionally coated or galvanized.
Selection Tips: Galvanized steel pipe is recommended for outdoor or complex construction environments; ordinary carbon steel pipe can be used for indoor environments.
v. Pipe End Protection and Joint Sealing
Function: Prevents moisture and dust from entering the insulation layer and maintains joint sealing.
Measures: Add protective caps, sealing sleeves, or flange connections to the pipe ends.
Selection Tip: For long-distance transportation or outdoor installation, ensure that pipe end protection is intact and joint sealing is reliable.
III. Implementation Standards for Steel-Jacketed Insulated Pipes
GB/T 14902 — Technical Specification for Steel-Jacketed Insulated Pipes (Chinese Standard)
GB/T 29766 — Technical Specification for Prefabricated Steel-Jacketed Insulated Pipes
ISO 13706 — Standard for Prefabricated Insulated Piping Systems
DIN 30670 — Standard for Prefabricated Steel-Jacketed Insulated Pipes (German Standard)
EN 253 — Standard for Prefabricated Hot Water and Steam Insulated Pipes (European Standard)
ASTM C585 — Standard for Prefabricated Insulated Pipes (American Standard)
IV. Steel jacketed steel insulated pipe operating temperature and pressure selection table
| Medium Type | Operating Temperature Range | Design Pressure Range | Recommended Inner Pipe Material | Recommended Insulation Material | Selection Notes |
|---|---|---|---|---|---|
| Hot Water | 0 – 120°C | 0.6 – 2.5 MPa | Carbon Steel | Inorganic Insulation (Silicate Wool / Mineral Wool) | Suitable for municipal heating and building hot water pipelines, conventional insulation thickness is sufficient. |
| Low-Pressure Steam | 120 – 200°C | 0.6 – 4 MPa | Carbon Steel / Low Alloy Steel | Silicate Wool / Mineral Wool | Suitable for low-pressure steam pipelines, insulation thickness can be calculated based on heat loss. |
| Medium-Pressure Steam | 200 – 300°C | 4 – 6 MPa | Low Alloy Steel | Silicate Wool / High-Temperature Mineral Wool | Medium-pressure steam pipelines require thicker insulation to control heat loss. |
| High-Pressure Steam | 300 – 450°C | 6 – 10 MPa | Low Alloy Steel / Stainless Steel | High-Temperature Mineral Wool / Foam Glass | High-temperature, high-pressure steam pipelines require insulation and steel jacket resistant to high temperature; inner pipe should be high-temperature alloy steel. |
| Cryogenic Liquids (e.g., Liquid Nitrogen, Liquid Oxygen) | -196 – 0°C | 0.6 – 1.6 MPa | Cryogenic Carbon Steel or Stainless Steel | Inorganic Cryogenic Insulation | Low-temperature media require steel pipes resistant to low temperatures and insulation materials that can accommodate thermal contraction. |
V. Procurement recommendations for steel jacketed insulated pipes
(1) Identify the medium and operating conditions
Determine the pipe material based on the medium being transported (hot water, steam, hot oil, chemical liquid, or cryogenic liquid).
Consider the operating temperature and design pressure to ensure that the inner pipe and insulation layer can withstand long-term operating conditions.
(2) Select the appropriate inner pipe material
Carbon steel: Suitable for normal temperature hot water and low-pressure steam pipelines.
Low alloy steel: Suitable for medium and high temperature steam and hot oil pipelines.
Stainless steel: Suitable for corrosive media, low temperature liquids or special chemical pipelines.
(3) Confirm the insulation material and thickness
Select insulation materials (inorganic materials such as mineral wool, silicate wool, or foam glass) based on temperature and heat loss requirements.
Long-distance transmission or high-temperature and high-pressure pipelines require thicker insulation to ensure energy-saving effects.
(4) External protective pipe material and protection requirements
Galvanized steel pipes or coated steel pipes are recommended for outdoor pipes to enhance corrosion resistance.
Ordinary carbon steel or anti-corrosion coated steel pipes can be used for indoor pipes.
(5) Pipe Specifications and Length
Outer diameter, inner pipe wall thickness, insulation layer thickness, and outer protective pipe wall thickness must be consistent with the design drawings.
Standard lengths of 6m and 12m are available, and custom lengths can also be selected for project-specific installation.
(6) Implementation standards and quality requirements
Common standards: GB/T 14902, GB/T 29766, ISO 13706, DIN 30670, EN 253, ASTM C585.
When purchasing, manufacturers are required to provide material certification, factory inspection report, and anti-corrosion test report.
(7) Transportation and Storage
Install protective caps on the pipe ends to prevent damage to the insulation layer.
Avoid stacking or prolonged exposure to sunlight and rain to ensure that the pipes arrive intact on site.
(8) Supplier Selection
We prioritize experienced manufacturers to ensure consistent product specifications, materials, insulation, and outer casing quality.
We support customized services and can provide piping solutions tailored to project conditions.
VI. Frequently Asked Questions (FAQ) about Purchasing Steel-Sheathed Insulated Pipes
Q1: How do I choose the inner tube material for steel-jacketed insulated pipe? What are the differences between different media?
A1: The inner tube material should be selected based on the media temperature and corrosiveness:
Transporting hot water or low-pressure steam → Carbon steel pipe (Q235, 20#) is sufficient;
Transporting medium- to high-temperature steam or hot oil → Low-alloy steel (such as 15CrMo, 12Cr1MoV) is sufficient;
Transporting corrosive chemicals or cryogenic liquids → Stainless steel (304, 316L) is suitable.
It is recommended to confirm the media composition and operating conditions before purchasing, so that the manufacturer can recommend the optimal material accordingly to avoid over- or under-design.
Q2: What material is used for the insulation layer of steel-jacketed insulated pipes? How is the thickness determined?
A2: Steel-jacketed insulated pipes typically use inorganic insulation materials, such as silicate wool, mineral wool, or foam glass.
The insulation layer thickness should be determined based on the temperature of the conveying medium, the ambient temperature, and the allowable heat loss:
Hot water system: generally 30–60 mm;
Medium- and high-temperature steam: 60–120 mm;
High-temperature steam or hot oil: 120 mm or more.
When selecting a pipe, it is recommended that the manufacturer perform a heat loss calculation based on the project parameters. This will provide a more accurate insulation effect and significantly improve energy savings.
Q3: Does the outer steel pipe require corrosion protection? What types of corrosion protection are available?
A3: Yes, the outer steel pipe must be treated with corrosion protection. Common corrosion protection methods include:
Epoxy coal tar coating (economical, resistant to wet soil environments);
Polyethylene (PE) coating (suitable for long-term buried pipes);
FBE epoxy coating (high-temperature resistance and excellent water resistance);
Galvanized steel pipe (suitable for open-air or less corrosive environments).
The type of corrosion protection affects the pipe’s service life and maintenance costs and should be selected based on the installation environment.
Q4: When purchasing steel-jacketed insulated pipe, how can I assess the manufacturer's product quality?
A4: To determine a manufacturer’s reliability, focus on three key factors:
Complete test reports: This includes reports on the raw material, insulation density and thermal conductivity testing, weld X-ray inspection, and corrosion protection layer inspection reports.
Procedure: Does the manufacturer have equipment for automatic welding, insulation molding, and automatic anti-corrosion coating of outer sheaths?
Project references: Does the manufacturer have successful case studies of municipal heating or industrial steam projects?
In addition, sample pipes can be inspected on-site to check for tight insulation, full welds on outer sheaths, and proper sealing of ports.
Q5: What precautions should be taken during the transportation and installation of steel-jacketed insulated pipes?
A5:
Before transportation, seal both ends to prevent dust and moisture.
Use lifting straps during loading and unloading, and avoid rolling or impacting.
Store pipes flat on site, away from direct sunlight and rain.
After welding, promptly repair the insulation and anti-corrosion coatings at the joints.
After installation, perform a system insulation integrity check to ensure there are no cracks, hollows, or water seepage points.
