Steel sleeve steel prefabricated buried pipeline is the core specialized pipe material for high-temperature steam centralized heating network. It adopts a full steel sandwich structure of "inner working steel pipe+composite insulation layer+outer protective steel pipe", suitable for direct buried transportation of high-temperature media below 350 ℃. The core parameters fully comply with national industry standards such as GB/T 29046. The specific parameter specifications are as follows:

 Three layer core structure parameters

This is the most basic physical construction parameter of the pipeline, which directly determines the overall performance limit:

Internal working steel pipe: The mainstream use is 20 # seamless carbon steel pipe, with a conventional diameter covering DN200-DN1200, complying with GB/T 9711 standard, and designed with a maximum pressure rating of PN2.5MPa, suitable for the majority of municipal thermal pipe network conditions.

Composite insulation layer: adopt aluminum silicate+glass wool+optional nano aero gel multi-layer gradient structure, with thermal conductivity ≤ 0.03W/(m · K), closed porosity ≥ 97%, water absorption ≤ 0.2kg/m2, and no shrinkage and subsidence after long-term use at 350 ℃.

Outer protective steel pipe: Spiral seam submerged arc welded steel pipe is used, and the outer wall is treated with 3PE three-layer polyethylene anti-corrosion treatment. The overall soil corrosion resistance is greatly improved, and it can resist long-term erosion from groundwater and saline alkali soil after burial.

Core thermal performance parameters

Directly determining the transmission energy efficiency of the pipeline network is a key assessment indicator for high-temperature steam pipelines:

The heat loss rate is ≤ 25W/m ² (in accordance with the mandatory standard GB/T 29046), and under actual testing conditions, it can be as low as 18.7W/m ², reducing heat loss by more than 40% compared to traditional trench laying pipelines.

At a medium temperature of 350 ℃, the axial thermal displacement of every 100 meters of pipeline is ≤ 15mm, and the measured value can be controlled within 12.8mm, significantly reducing the damage of thermal stress to the pipeline structure.

Long term stable working temperature coverage of -90 ℃~+350 ℃, suitable for winter frozen soil environment in northern cold regions, fully meeting the demand for high-temperature long-distance steam transportation.

Structural safety and supporting component parameters

The core supporting parameters to ensure the long-term underground operation of the pipeline network without faults are:

The fixed joint adopts a double flange PN2.5MPa structure, equipped with a carbon steel reinforcement ring with a thickness of ≥ 20mm, which can completely offset the axial thermal thrust of the pipeline and avoid displacement and deformation of the pipeline network.

Compensators are selected based on thermal displacement: axial type for ≤ 50mm, hinge type for 50-200mm, and universal type for ≥ 200mm. UNS N06625 high-temperature alloy material is preferred for corrugated pipes, with a temperature resistance of up to 650 ℃.

The pipeline support adopts a broken bridge insulation structure, which reduces the thermal conductivity by 72% compared to ordinary steel supports. It can reduce the temperature difference of the thermal bridge at the support from 58 ℃ to 9 ℃, avoiding local heat concentration loss.

Triple waterproof sealing structure: the first stainless steel metal self-locking ring, the second temperature resistant -50~300 ℃ fluororubber sealing ring, and the third polysulfide sealant (displacement capacity ± 25%) completely prevent groundwater from infiltrating the insulation layer.

 Installation and lifespan parameters

Engineering landing parameters suitable for direct burial construction:

Conventional direct burial with a depth of 0.6-1.2 meters does not require the construction of dedicated trenches, resulting in a comprehensive engineering cost reduction of 10% -25% compared to traditional trench laying.

Under normal operating conditions, the designed service life can reach 30-50 years, far exceeding the service life of traditional overhead or trench laid pipelines.

An optional distributed fiber optic temperature monitoring system can be selected, with a temperature measurement accuracy of ± 0.5 ℃. It can provide 48 hour advance warning of pipeline leaks, insulation failures, and other faults, greatly improving the safety of pipeline operation.

This pipeline is currently the mainstream selection for high-temperature steam pipe networks for centralized heating in domestic cities, especially suitable for long-distance heat transmission scenarios in cold northern regions such as Shandong, with significant energy-saving and safety benefits.

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