Spray Polyurethane Insulated Pipe with Wound HDPE Jacket

Spray Polyurethane Insulated Pipe with Wound HDPE Jacket is a pre-insulated direct-buried pipeline system designed primarily for hot-water transmission and district heating networks. The system consists of a high-strength steel carrier pipe, a rigid polyurethane (PU) insulation layer and a high-density polyethylene (HDPE) outer protective jacket.

The pipe is manufactured using an automated online spray-and-winding process. After surface preparation and shot blasting, polyurethane is directly sprayed onto the steel pipe using high-pressure equipment, where it rapidly reacts and forms a uniform insulation layer. HDPE is then extruded and continuously wound around the PU insulation layer to form the protective outer jacket.

This integrated forming process provides improved uniformity of insulation thickness and density, reliable adhesion between layers and stable overall product performance. The system is suitable for conveying media with a long-term operating temperature up to 120°C and occasional peak temperatures up to 140°C.

Key Advantages

High Insulation Uniformity — Automated online spraying provides consistent PU insulation thickness and density.

Reliable Layer Adhesion — Active PU reaction and controlled surface preparation promote strong bonding between the steel pipe, insulation and outer jacket.

Stable Product Performance — Controlled production parameters provide good consistency in insulation density, thickness, thermal conductivity and compressive strength.

Adjustable Insulation Thickness — Insulation thickness can be automatically controlled according to project requirements.

High-Performance HDPE Jacket — Wound HDPE provides good toughness, scratch resistance and mechanical protection for the insulation layer.

Lower Material Consumption — The wound-jacket structure can reduce outer-jacket thickness while maintaining required protective performance.

Good Mechanical Performance — Reduced outer-jacket thickness can help limit shrinkage, deformation and thermal stress.

Automated Production — Online forming improves production efficiency, dimensional consistency and product quality stability.

Comprehensive Quality Control — Carrier pipe, raw materials and finished insulated pipes can be inspected through the company's integrated testing capabilities.

Manufacturing Process

1. Surface Preheating

Qualified steel pipes are preheated before shot blasting to remove surface moisture and maintain the steel surface temperature at least 3°C above the dew point.

2. Shot Blasting

The steel pipe is treated by internal and external shot blasting to remove mill scale, oil and other contaminants. The surface preparation reaches Sa 2.5, with an anchor profile of approximately 50–100 μm.

3. High-Pressure PU Spraying

Rigid polyurethane raw materials are applied to the prepared steel surface using high-pressure spray equipment, forming a uniform and high-density thermal insulation layer.

4. HDPE Winding

HDPE is extruded into sheet form and continuously wound around the PU insulation layer to form the protective outer jacket.

5. Quality Inspection

Finished pipes undergo inspection before marking and release, including dimensional, insulation and relevant performance checks according to project and applicable standard requirements.

Applications

District Heating · Hot Water Transmission · Municipal Heating Networks · Long-Distance Heat Transmission · Industrial Thermal Pipelines · Direct-Buried Heating Systems · Energy Infrastructure

Typical Advantages

Uniform PU Insulation · Reliable Layer Adhesion · Automated Online Forming · High-Performance HDPE Protection · Direct-Buried Installation · Stable Thermal Performance