Steel sleeve insulated steel pipe

Published:2025-06-26 | Last Updated: 2025-06-26    Views: 2

I. What is steel sleeve insulated steel pipe?

A steel sleeve insulated steel pipe is a type of prefabricated insulated steam pipe specifically designed for high-temperature steam transportation.

Its structure consists of multiple layers, including a working pipe, insulation layer, air layer or sliding layer, and outer protective pipe.

Compared to ordinary insulated steel pipes it has stronger high-temperature resistance and mechanical strength, making it suitable for steam pipeline systems buried underground.

II. Steel sleeve insulated steel pipe structure composition table

III. Features of Steel-in-Steel Insulated Steel Pipes

(1) Excellent High-Temperature Resistance  

Steel-in-steel steam insulated pipes utilize high-performance insulation materials and high-temperature-resistant steel, enabling them to sustain steam temperatures of 350°C or higher for extended periods. This meets the high-temperature transportation requirements of various industrial and urban heating systems.

(2) High Structural Strength and Adaptability to Complex Operating Conditions  

The double-layer steel structure design features an inner pipe responsible for bearing steam pressure and an outer steel pipe providing mechanical protection. The overall structure has high rigidity, capable of withstanding underground soil pressure and external mechanical loads.

(3) Low heat loss, significant energy-saving effects

The high-quality high-density insulation layer within the pipeline effectively blocks heat conduction and radiation, significantly reducing heat loss. As a key representative of high-temperature pre-insulated pipelines, steel-clad steel steam insulation pipes enhance the thermal efficiency of the entire steam transportation system through scientific design of insulation thickness and multi-layer structure, thereby reducing energy consumption and operational costs.

(4) Strong corrosion resistance and long service life  

The outer steel pipe surface is coated with advanced corrosion-resistant coatings (such as 3PE epoxy coal tar asphalt coating), effectively resisting corrosion from groundwater, acids, alkalis, salts, and other corrosive media, ensuring the pipeline's durability and longevity.

(5) Sliding structure design accommodates thermal expansion and contraction

The internal design includes a reasonably structured sliding layer or guide layer, providing sufficient space for thermal expansion and contraction. This allows the inner pipe to freely expand and contract with temperature changes, preventing insulation layer cracking or pipe deformation caused by thermal expansion and contraction.

IV. Specification and parameter table for steel-clad steel insulated steel pipes

V. Main Applications of Steel Sleeve Insulated Steel Pipes

(1) Urban Central Heating Systems  

Used in urban heating networks for steam supply pipelines, reducing heat loss and improving transportation efficiency.  

(2) Underground Direct Burial Installation  

Serves as pre-insulated steam pipelines for direct burial, featuring one-time forming and rapid construction, with seamless integration between the insulation layer and outer protective layer.

(3) High-Pressure Steam Transportation in Power Plants  

Utilizes a double-layer insulated steel pipe structure to stably transport high-temperature, high-pressure steam to turbines.

(4) Process Steam Piping Networks in Chemical Plants  

Used in distillation, heating, and other process stages, offering excellent corrosion resistance and insulation performance.

(5) Combined Heat and Power (CHP) Projects  

Transports waste heat steam to centralized heating networks, achieving waste heat recovery and comprehensive utilization.

(6) Large Industrial Parks and Desalination  

Provides a stable and efficient steam heat source in processes such as hydrogen production and multi-stage flash distillation of seawater.

VI. Main Quality Inspection Items and Methods for Steel Sleeve Insulated Steel Pipes

Raw Material Inspection: Verify the material certificates for the inner and outer pipes, test the chemical composition and mechanical properties, and ensure compliance with standards.

Dimension and Thickness Measurement: Use calipers and ultrasonic thickness gauges to quickly measure the thickness of the inner pipe, insulation layer, and outer protective pipe, ensuring compliance with design tolerances.

Weld Inspection: Perform magnetic particle, penetrant, or ultrasonic testing on spiral or straight welds to identify cracks and incomplete fusion defects.  

Corrosion Protection Layer Inspection: Measure the thickness of the epoxy coal tar asphalt or 3PE coating and visually inspect for bubbles or peeling.

Insulation layer testing: Test thermal conductivity and compressive strength to confirm uniform insulation layer thickness.  

Vacuum dehumidification test: Vacuum or nitrogen-blow the insulation cavity (if present) to confirm tight sealing and no moisture accumulation.  

Hydrostatic pressure test: Apply 1.5 times the design pressure for 5 minutes with no leakage.

Heat loss measurement: Measure surface temperature at specified temperature or use a heat flux meter to ensure heat loss is within acceptable limits.  

Direct burial performance testing: Simulate underground conditions to test the waterproofing, corrosion resistance, and compressive strength of the outer casing, suitable for pre-insulated steam pipelines.  

Appearance and markings: Visually inspect the surface for smoothness and no damage, verify markings, serial numbers, and inspection reports are complete.

VII. Quality Inspection Standards for Steel-Clad Insulated Steel Pipes

VIII. Steel-in-Steel Insulated Steel Pipe Construction Convenience

i. Factory Prefabrication

All layers (inner pipe, insulation layer, outer protective pipe) are formed in one piece at the factory, eliminating the need for on-site layered wrapping.

ii. Quick Connection

Using socket or flange connections, on-site alignment is simple, with fewer welds and higher welding efficiency.

iii. Reduced On-Site Work

No on-site pouring or spraying of insulation or anti-corrosion layers is required, significantly reducing construction processes.

iv. Short Installation Cycle

Prefabricated pipe fittings are directly laid, with on-site work limited to bracket fixation and joint treatment, ensuring fast installation and short project duration.

v. Labor Savings

Simplified on-site construction processes require minimal worker skill levels, enabling efficient completion by small teams.

vi. High adaptability

Pipe lengths and elbows can be customized to order in the factory, allowing flexible on-site assembly and reducing cutting and rework.

vii. Environmental friendliness and cleanliness

No large amounts of insulation dust or waste residue on-site, minimizing construction disturbances and secondary pollution.

viii. Easy quality control

Critical processes are completed in a controlled environment, with on-site inspection limited to joint verification and sealing, ensuring more reliable quality.