Factory pre-insulated pipe with rigid polyurethane foam and HDPE jacket for district heating networks.
Pre-insulated pipe is a factory-made composite: a steel carrier pipe, a rigid polyurethane foam insulation layer, and a high-density polyethylene outer jacket. Because the sandwich is made in the factory under controlled conditions, the insulation performance on site is far more consistent than field-applied insulation.
Production starts with shot-blasting the carrier pipe, then centring it inside the HDPE jacket with spacers. Polyurethane is injected between the two and foamed in place, filling the annulus completely and bonding all three layers together — which is what gives the assembly its compressive strength and keeps water out.
For district heating networks we normally supply to GB/T 29047 or EN 253, choosing the insulation thickness from the design temperature, laying depth and allowable heat loss. Leak alarm wires can be laid into the foam so that insulation faults can be located from the ground without excavation.
The jacket also protects the foam during transport and backfilling. Where pipes are stored outdoors for long periods, we recommend an UV-resistant jacket grade or temporary covering.
| Carrier Pipe | Seamless / ERW / SSAW carbon steel, DN20 – DN1600 |
| Insulation Material | Rigid polyurethane foam (PUR) |
| Foam Density | ≥ 60 kg/m³ |
| Thermal Conductivity | ≤ 0.033 W/(m·K) at 50 °C |
| Water Absorption | ≤ 3% by volume |
| Closed Cell Ratio | ≥ 88% |
| Outer Jacket | HDPE, thickness per EN 253 / GB/T 29047 series |
| Max. Service Temperature | Up to 120 °C (continuous) |
| Alarm Wire | Optional, 2-core laid in the foam layer |
| Standard | GB/T 29047, EN 253, CJ/T 114 |
Every pipe passes through the same controlled route, with inspection points at each stage.
Remove rust and scale so the foam bonds to the steel surface.
HDPE jacket is extruded to size and corona-treated for better bonding.
Spacers keep the carrier pipe concentric so the foam layer is even all around.
Two-component PUR is injected at controlled ratio, temperature and pressure.
Foam cures, ends are trimmed and sealed with heat-shrink caps.
Thickness, density, conductivity and jacket appearance are checked per batch.
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