PU Foam Insulated Pipe
Factory-bonded pre-insulated steel pipe — 3PE carrier + rigid polyurethane foam + seamless HDPE jacket per EN 253 for district heating, cooling and energy networks down to -50 deg C and up to 120 deg C continuous.
PU Pre-Insulated Steel Pipe (Bonded Pipe-in-Pipe)
PU foam insulated pipe is a factory-bonded “pipe-in-pipe” system: an anti-corrosion coated steel carrier pipe surrounded by rigid closed-cell polyurethane foam and protected by a seamless high-density polyethylene jacket.
The three layers behave as one structure — the foam bonds to both the carrier and the jacket — eliminating voids and moisture paths. This is the standard solution for district heating and cooling networks in Europe, cutting heat loss by roughly 90% versus bare pipe and allowing direct burial without concrete works, per EN 253 / EN 13941.
Anti-corrosion base layer, spark-tested 100%
≥ 60 kg/m³ closed-cell, λ50 ≤ 0.033 W/(m·K)
Seamless moisture barrier, density ≥ 940 kg/m³
Technical Specifications & Performance
| Standard | Scope | Region |
|---|---|---|
| EN 253 | Factory-made bonded pipe systems for district heating (steel carrier + PU foam + HDPE casing) | Europe |
| EN 448 | Pre-insulated fitting assemblies for bonded pipe systems | Europe |
| EN 488 | Pre-insulated steel valve assemblies for district heating | Europe |
| EN 13941 | Design and installation of preinsulated bonded pipe systems | Europe |
| EN 14419 | Leak detection wire systems for bonded pipe networks | Europe |
| GB/T 29047 | Pre-insulated (PU foam + HDPE jacket) steel pipe for direct burial | China |
| CJ/T 114 | High-density polyethylene jacketed PU foam insulated pipe | China |
Carrier-pipe anti-corrosion layer is applied to EN 30670 / ISO 21809-1 (3PE or FBE) beneath the insulation.
| Parameter | Specification |
|---|---|
| Carrier Pipe OD | 21.3 mm – 1420 mm (1/2″ – 56″) |
| Carrier Pipe Types | Seamless, ERW, LSAW, SSAW |
| Carrier Steel Grades | API 5L Gr.B – X65 PSL1/PSL2, ASTM A53/A106, EN 10216, Q235B |
| Carrier Anti-Corrosion | 3PE (DIN 30670) or FBE, under the foam layer |
| Insulation Thickness | 25 – 140 mm (by DN and heat-loss design) |
| Standard Lengths | 6 m / 12 m (up to 16 m on request) |
| Service Temperature | -50°C to +120°C continuous, +140°C short-term peaks |
| Design Life | 30 – 50 years (EN 253 network design basis) |
| Layer | Material | Typical Thickness | Function |
|---|---|---|---|
| Layer 1 (core) | Steel carrier pipe with 3PE/FBE anti-corrosion | per carrier spec | Pressure containment and corrosion barrier |
| Layer 2 | Rigid polyurethane foam, closed-cell | 25 – 140 mm | Thermal insulation; λ50 ≤ 0.033 W/(m·K); density ≥ 60 kg/m³ |
| Layer 3 (jacket) | High-density polyethylene (HDPE), UV-stabilized | 1.8 – 12 mm by DN | Moisture barrier and mechanical protection; density ≥ 940 kg/m³ |
| Carrier DN | Carrier OD (mm) | Typical Foam (mm) | Typical Jacket OD (mm) |
|---|---|---|---|
| DN50 | 60.3 | 26 – 29 | 125 |
| DN100 | 114.3 | 36 – 40 | 200 |
| DN200 | 219.1 | 44 – 48 | 325 |
| DN300 | 323.9 | 42 – 46 | 425 |
| DN400 | 406.4 | 52 – 57 | 530 |
| DN500 | 508.0 | 64 – 69 | 655 |
| DN600 | 610.0 | 64 – 70 | 760 |
| DN800 | 820.0 | 70 – 76 | 980 |
| DN1000 | 1020.0 | 78 – 86 | 1200 |
Typical production series per EN 253 / GB/T 29047. Insulation and jacket dimensions are finalized by heat-loss and buoyancy calculations for each network.
| Property | Requirement | Test Method |
|---|---|---|
| Foam Density | ≥ 60 kg/m³ (core), ≥ 45 kg/m³ near ends | EN 253 / ISO 845 |
| Closed-Cell Content | ≥ 88% | ASTM D6226 / EN 253 |
| Thermal Conductivity | λ50 ≤ 0.033 W/(m·K) | EN 253 annex / ASTM C518 |
| Compressive Strength (10% deformation) | ≥ 300 kPa | EN 826 |
| Foam-to-Steel Adhesion (shear) | ≥ 120 kPa at 23°C | EN 253 |
| Jacket Penetration Resistance | per EN 253 class | EN 253 |
| Dimensional Stability | No degradation after 1000 h at 120°C? 160°C short-term | EN 253 type test |
| Carrier Anti-Corrosion Holiday Test | 100% of carrier length, 5 kV (3PE/FBE) | Spark test |
100% Production Testing (every joint)
| Test | Frequency |
|---|---|
| Carrier 3PE/FBE holiday (spark) test | 100% of carrier length |
| HDPE jacket pinhole (spark) test | 100% of jacket surface |
| Foam density at both pipe ends | Every joint |
| Jacket wall thickness & concentricity | Every joint, multiple points |
| Visual inspection of end seals | Every joint |
Batch / Type Testing
| Test | Frequency |
|---|---|
| Thermal conductivity (λ50) | Per foam batch |
| Compressive strength & closed-cell content | Per foam batch |
| Shear (adhesion) strength test | Per qualification / agreed lot |
| Dimensional stability type test | Coating system qualification |
Manufacturing Process
Factory-bonded pre-insulation process per EN 253 — anti-corrosion, foam injection and HDPE jacketing in one continuous line.
Carrier Pipe Inspection
Steel pipes are checked for dimensions, surface condition and mill certificates before the line
3PE / FBE Anti-Corrosion
Carrier pipe is grit-blasted and externally coated with 3PE or FBE, then spark-tested 100%
Jacket Pipe Threading
HDPE casing pipe of the calculated OD is threaded over the anti-corrosion-coated carrier
End Containment Setup
Both ends are fitted with support rings and sealing frustum molds to center the carrier
Surface Preheating
The assembly is preheated to remove moisture and ensure foam adhesion to the carrier
PU Foam Injection
Two-component polyurethane is high-pressure mixed and injected into the annular space
Foam Curing & End Sealing
Foam cures inside the jacket; ends receive permanent sealing frusta for joint welding
Jacket Spark Test
100% of the HDPE jacket surface is holiday-tested to detect pinholes or thin spots
Density & Dimension Check
Foam density at both ends plus jacket thickness and concentricity are measured
Thermal Property Sampling
Thermal conductivity and compressive strength cubes are tested per foam batch
Marking & End Capping
Pipes are marked with DN, length and batch; ends are capped to keep the annulus dry
Packing & Dispatch
Pipes are strapped, loaded and dispatched with EN 253 conformity documentation
3PE vs PU Insulated vs Pipe-in-Pipe: Which Do You Need?
All three systems start from the same anti-corrosion base — the difference is what the pipeline needs beyond corrosion protection: nothing, heat retention, or full thermal containment under pressure.
| Criteria | 3PE Only | PU Pre-Insulated | Steel Pipe-in-Pipe |
|---|---|---|---|
| System Build-up | FBE + adhesive + PE | 3PE carrier + PU foam + HDPE jacket | Inner pipe + insulation + outer carrier pipe |
| Service Temperature | Up to 80°C | -50°C to +120°C continuous | Up to 250°C+ (steam) |
| Heat Loss | None (not insulated) | ≤ 80 W/m² typical at 50°C delta | Very low, by annulus design |
| Installation | Buried / above ground | Direct burial, no concrete works | Heavy; requires bulkheads and guides |
| Typical Use | Oil & gas transmission | District heating & cooling networks | Steam, EOR and HPHT flowlines |
| Relative Cost | $ | $$ | $$$$ |
Three-Layer Polyethylene
Anti-corrosion only, no thermal function. The workhorse for buried oil & gas lines up to 80°C where insulation is not required.
PU Foam Pre-Insulated
Carrier + rigid foam + HDPE jacket, factory-bonded per EN 253. Cuts heat loss by ~90% versus bare pipe and installs directly in native soil.
Steel Pipe-in-Pipe
Insulated annulus inside a load-bearing outer pipe. For steam, HPHT flowlines and road/river crossings where mechanical loads exceed jacket capability.
Applications
Wherever heat (or cold) must travel underground efficiently — municipal networks, oil gathering and temperature-controlled process lines.
District Heating Networks
Municipal hot-water transmission and distribution per EN 13941: low heat loss, direct burial without concrete, and EN 14419 leak-detection wires for network monitoring.
✓ λ50 ≤ 0.033 W/(m·K)
District Cooling & Chilled Water
Chilled water and low-temperature networks where the seamless HDPE jacket prevents ground-water ingress and surface condensation, keeping losses near zero.
✓ Zero-condensation jacket
Heated Crude Gathering Lines
Waxy or high-pour-point crude stays flowing: foam insulation holds product temperature between heating stations, cutting trace-heat demand dramatically.
✓ ~90% heat-loss reduction
Temperature-Maintained Process Lines
Chemical and food-grade transfer lines that must stay within a temperature window — the bonded system maintains stable wall temperatures year-round.
✓ Stable insulation performance
Direct-Buried Energy Corridors
Campus and industrial energy corridors where trench width, weight and installation speed favor bonded systems over concrete-encased alternatives.
✓ No concrete works needed
Leak-Detection-Ready Networks
Pipes supplied with integrated EN 14419 detection wires so operators can locate water ingress and foam damage along the whole network in real time.
✓ EN 14419 wires fitted
Frequently Asked Questions
Ready to Order PU Insulated Pipe?
Get a competitive quote within 24 hours. Send your DN schedule and heat-loss requirements — we will size the foam and jacket per EN 253.
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