EMAIL:
wr@insulatedpipeline.com
wyy@insulatedpipeline.com
Published:2025-07-10 | Last Updated: 2025-07-10 Views: 1
.jpg "Steel Jacketed Steam Pipe")
(1) Definition
A Steel jacketed steam pipe, also known as a steel-clad steel direct-buried steam insulation pipe, is a pre-insulated pipeline specifically designed for transporting high-temperature steam. It features a structural design comprising an inner steel pipe, insulation layer, and outer protective steel pipe, offering excellent temperature resistance, pressure resistance, and mechanical strength, making it suitable for high-temperature and high-pressure steam transportation.
(2) Structural Composition
Inner Pipe (Working Pipe)
Primarily responsible for pressure-bearing and high-temperature steam transportation, typically made of seamless steel pipes or welded steel pipes, with materials such as carbon steel or alloy steel.
Insulation Layer
Commonly made of rigid polyurethane foam, rock wool, etc., to reduce heat loss.
Outer Protective Steel Pipe
Serves as a protective layer to prevent external groundwater and corrosive media from infiltrating, providing mechanical protection.
Corrosion-Resistant Layer
Epoxy or 3PE corrosion-resistant coatings are applied to the outer surface of the outer protective pipe to enhance corrosion resistance.
(3) Key Features
High-Temperature and High-Pressure Resistance: Capable of withstanding the operating environment of high-temperature steam transportation.
High Structural Strength: Steel-in-steel design adapts to harsh underground conditions and offers strong load-bearing capacity.
Long Service Life: Protection from the outer protective pipe and corrosion-resistant layer extends the lifespan of the pipeline system.
Easy Installation and Maintenance: Factory-prefabricated components require only welding connections on-site, enabling swift construction.
| Parameter Name | Parameter Content/Range | Description |
|---|---|---|
| Inner Pipe Outer Diameter | 25 mm – 1000 mm | Determined based on the flow rate and system design. |
| Inner Pipe Wall Thickness | 3.5 mm – 24 mm | Selected based on working pressure and standards. |
| Inner Pipe Material | Q235B, 20#, 16Mn, Alloy Steel | Common carbon and alloy steels, suitable for high-temperature and high-pressure applications. |
| Outer Sheath Outer Diameter | 125 mm – 1460 mm | Determined by the inner pipe, insulation layer, and clearance dimensions. |
| Outer Sheath Wall Thickness | 3 mm – 10 mm | Determined based on engineering design and protection requirements. |
| Outer Sheath Material | Q235B | Commonly used carbon steel spiral welded pipe or straight seam welded pipe. |
| Insulation Material | Polyurethane Foam, Rock Wool | Mainly used for thermal insulation. |
| Insulation Layer Thickness | 50 mm – 180 mm | Determined based on insulation calculations and design requirements. |
| Anti-Corrosion Layer Type | Epoxy Coating, 3PE Anti-Corrosion | Protects the outer sheath from corrosion. |
| Design Temperature | ≤ 350℃ | Applicable for high-temperature steam conveyance. |
| Design Pressure | ≤ 2.5 MPa | Designed according to engineering requirements and standards. |
| Length | 6 m / 9 m / 12 m / Custom Length | Standard lengths are available with customization options. |
| Service Life | ≥ 30 years | With proper design and construction, the service life can reach 30 years or more. |
| Execution Standards | CJ/T 163, GB/T 8163, etc. | Produced in accordance with pipe material, anti-corrosion, and insulation standards. |
Steel-in-steel steam pipes adopt a three-layer structural design consisting of an inner pipe for steam transportation, an insulation layer for thermal insulation, and an outer protective steel pipe for protection. The working principle is as follows:
(1) Inner Pipe for Steam Transportation
The inner pipe serves as the working pipe, carrying and transporting high-temperature, high-pressure steam. It is typically made of seamless steel pipes or welded steel pipes, which possess excellent high-temperature resistance and pressure-bearing performance.
(2) Insulation Layer for Thermal Insulation
The inner pipe is wrapped with a polyurethane foam or rock wool insulation layer to minimize heat loss during steam transportation, ensuring efficient heat transfer to the end-user while preventing deformation of the outer protective pipe due to heat exposure.
(3) Outer Protective Steel Pipe
The outer steel-clad steel protective pipe provides mechanical protection and waterproofing/corrosion resistance, withstanding soil pressure, groundwater erosion, and external impacts to ensure the overall structural stability and long-term operation of the pipeline.
(4) Sliding Design (Compensation Principle)
Steel-clad steam pipes typically feature sliding supports, guide supports, and fixed supports. When high-temperature steam transportation causes thermal expansion of the pipe, the inner pipe can freely slide within the outer protective pipe. Pre-installed compensators release stress, preventing thermal expansion from damaging the system.
| Inner Pipe Outer Diameter (mm) | Inner Pipe Wall Thickness (mm) | Outer Sheath Outer Diameter (mm) | Insulation Layer Thickness (mm) | Common Lengths (m) |
|---|---|---|---|---|
| 25 | 3.5 | 125 | 50 | 6 / 9 / 12 |
| 32 | 4.0 | 132 | 50 | 6 / 9 / 12 |
| 40 | 4.0 | 140 | 50 | 6 / 9 / 12 |
| 50 | 4.5 | 172 | 60 | 6 / 9 / 12 |
| 65 | 5.0 | 188 | 60 | 6 / 9 / 12 |
| 80 | 5.0 | 220 | 70 | 6 / 9 / 12 |
| 100 | 6.0 | 240 | 70 | 6 / 9 / 12 |
| 125 | 6.0 | 280 | 80 | 6 / 9 / 12 |
| 150 | 7.0 | 305 | 80 | 6 / 9 / 12 |
| 200 | 8.0 | 355 | 90 | 6 / 9 / 12 |
| 250 | 9.0 | 425 | 100 | 6 / 9 / 12 |
| 300 | 10.0 | 480 | 100 | 6 / 9 / 21 |
| 350 | 11.0 | 560 | 120 | 6 / 9 / 12 |
| 400 | 12.0 | 610 | 120 | 6 / 9 / 12 |
| 500 | 14.0 | 720 | 130 | 6 / 9 / 12 |
| 600 | 16.0 | 860 | 140 | 6 / 9 / 12 |
| 700 | 18.0 | 1010 | 150 | 6 / 9 / 12 |
| 800 | 20.0 | 1160 | 160 | 6 / 9 / 12 |
| 900 | 22.0 | 1310 | 160 | 6 / 9 / 12 |
| 1000 | 24.0 | 1460 | 180 | 6 / 9 / 12 |
(1) Determine the operating medium and conditions
Conveyed medium: Confirm whether the conveyed medium is high-temperature steam. Steel-in-steel pipes are generally suitable for steam conveyance at temperatures ≥150°C.
Design temperature: Select appropriate materials and insulation thickness based on the conveyance temperature. Steel-in-steel steam pipes can withstand temperatures exceeding 350°C.
Design Pressure: Select the inner pipe wall thickness based on system pressure. Common ranges are 0.6 MPa to 2.5 MPa; higher pressure ratings may be required as needed.
(2) Select inner pipe specifications and material
Specifications: Determine the inner diameter based on steam flow rate and pipeline design calculations.
Material:
Common: Q235B, 20#
High-temperature and high-pressure conditions: 16Mn, Q345B, alloy steel (e.g., 12Cr1MoVG)
Wall thickness: Select based on working pressure and standards, refer to GB/T 8163 or relevant pressure pipeline standards.
(3) Determine the thickness and material of the insulation layer
Material: Rigid polyurethane foam, rock wool, or composite insulation materials.
Thickness: Determine based on design heat loss requirements, commonly 50–180 mm; the larger the pipe diameter, the thicker the insulation layer.
(4) Select the specifications and material of the outer protective pipe
Material: Q235B spiral welded pipe or straight seam welded pipe, with sufficient mechanical strength.
Corrosion protection requirements: Select epoxy, 3PE, or other corrosion-resistant coatings based on soil conditions to enhance corrosion resistance.
(5) Expansion joint design
Calculate thermal expansion based on pipeline length and temperature changes, and install bellows expansion joints or design internal pipe sliding supports to prevent thermal stress from damaging the system.
(6) Confirm supply length and connection method
Standard lengths: 6 m / 9 m / 12 m, custom lengths available upon request.
Connection methods: Welded connection or flanged connection, depending on on-site construction conditions.
(7) Reference Standards
Manufacturing standard: CJ/T 163-2008 “Technical Specifications for Prefabricated Steam Insulated Buried Pipes”
Design standard: GB 50264-2013 “Design Specifications for Thermal Insulation Engineering of Industrial Equipment and Pipes”
.jpg "Steel Jacketed Steam Pipe")
(1) What is the maximum temperature that steel-in-steel steam pipes can withstand?
The design temperature is typically ≤ 350°C. Specially designed alloy steel inner tubes can withstand higher temperatures.
(2) What is the service life of steel-in-steel steam pipes?
Under proper design specifications, construction standards, and operational maintenance, the service life can exceed 30 years.
(3) What is the primary insulation material for steel-clad steel steam pipes?
Polyurethane foam or rock wool is primarily used as insulation material, offering excellent thermal insulation properties.
(4) Why does the outer protective steel pipe require corrosion protection?
The outer protective pipe is directly buried underground and must undergo corrosion protection treatment (e.g., epoxy coating, 3PE corrosion protection layer) to prevent soil moisture corrosion and extend service life.
(5) Does the steel-clad steam pipe require expansion joints?
Yes, high-temperature steam pipes undergo thermal expansion and contraction, so bellows expansion joints or sleeve expansion joints must be designed. Alternatively, thermal stress can be released using a combination of “sliding supports + fixed supports.”
(6) What are the common connection methods?
Welding connection (most commonly used, with reliable sealing)
Flange connection (easy to disassemble and maintain, suitable for valve connection points)
(7) What standards are followed in production?
CJ/T 163-2008 “Technical Specifications for Prefabricated Buried Insulated Steam Pipes”
GB/T 8163-2008 “Seamless Steel Pipes for Conveying Fluids”
GB 50264-2013 “Design Specifications for Thermal Insulation Engineering of Industrial Equipment and Pipelines”
(8) In which industries are steel-jacketed steam pipes applicable?
Widely used in urban centralized heating networks, industrial steam transportation, power plant thermal systems, petrochemical industries, and other fields.
(9) What parameters need to be provided when placing an order?
Conveyed medium, temperature, pressure
Pipe diameter, length
Inner pipe material requirements
Insulation layer material and thickness
Outer protective pipe corrosion protection requirements
Scan wechat
Tel：+86 15383177997
E-mail：wr@insulatedpipeline.com
E-mail：wyy@insulatedpipeline.com
Address：Chengnan Development Zone, Yanshan County, Cangzhou City, Hebei Province, China
技术支持：沧州利畅网络
