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Overhead Utility Tunnel Pre-Insulated Pipe | Galvanized Metal Jacket System
Galvanized steel spiral-wound jacket, Class A fire rating, B1 flame-retardant PU option. UV-proof, 30-year outdoor corrosion resistance, rodent-proof. Heat loss only 25% of traditional pipes. Request free sample & quote!
- Overview
- Technical Specifications
- Application Scenarios
- Service & Support
- Recommended Products
Overview
Why Metal-Jacketed Pipes Are the Standard for Overhead & Tunnel
Standard HDPE-jacketed pre-insulated pipes are designed for direct burial — underground, protected from sunlight, with no fire safety requirements. Overhead utility tunnels, pipe galleries, and bridge crossings are a completely different environment: direct UV exposure, confined spaces with fire safety regulations, and mechanical vulnerability to impacts and pests. Metal-jacketed overhead pipes solve all three. The galvanized steel jacket is immune to UV degradation, can achieve Class A fire rating for tunnel safety, and provides mechanical protection that HDPE cannot match. Heat loss is only 25% of traditional on-site insulated pipes.
◆ Galvanized Steel Jacket — 30-Year Outdoor, Zero UV Degradation. HDPE jackets become brittle and crack after prolonged sunlight exposure. The spiral-wound galvanized steel jacket on our overhead pipes is completely UV-immune, corrosion-resistant (30 years without visual change outdoors), and mechanically robust against impacts, birds, and rodents. The threaded inner surface of the spiral-wound jacket creates a mechanical interlock with the PU insulation — bonding strength that HDPE relies on chemical corona treatment to achieve.
◆ Class A Fire Rating & B1 Flame-Retardant PU. Utility tunnels and pipe galleries have strict fire safety codes. Our overhead pipes use PU foam with B1 flame-retardant combustion performance. Combined with the non-combustible galvanized steel jacket, the system achieves Class A fire rating — eliminating the fire safety hazard that standard PU-HDPE pipes pose in enclosed tunnels. No smoke propagation, no flaming droplets.
◆ 3 Metal Options — Cost-Optimized Per Environment. Galvanized steel: most cost-effective, excellent corrosion resistance for standard overhead environments. Aluminum: lightweight, rust-proof, preferred for bridge crossings where weight matters. Stainless steel: ultimate corrosion resistance for chemical plants, coastal areas, and harsh industrial zones. We help you select the right jacket material for your overhead pipe environment and budget.
◆ Spiral-Wound Interlocking — Seamless Waterproof Seal. The spiral pipe rolling process creates a continuous helical jacket with tight interlocking seams. Unlike longitudinal-welded jackets that need full-length seam welding, the spiral-wound overhead pipe achieves a watertight seal through mechanical interlock. For extreme rain environments, waterproof sealant at seams ensures the PU insulation stays dry. No hot-melt patching required during installation.
◆ Sliding & Fixed Bracket System — Tunnel-Ready. Overhead pipes in utility tunnels need professional support systems. Our pipes are designed to handle mechanical loads on sliding supports and fixed brackets without crushing the PU insulation layer. The three-in-one bonded structure (steel-PU-galvanized jacket) distributes support loads evenly, accommodating thermal expansion while maintaining insulation integrity across the entire overhead pipe span.
Metal-Jacketed Overhead Pipe vs. Standard HDPE-Jacketed (Above Ground)
Feature |
Galvanized Metal Jacket (Sanjie) |
Standard HDPE Jacket (Buried Only) |
UV Resistance |
Immune — zero degradation in sunlight |
Becomes brittle, cracks in 2–5 years |
Fire Rating |
Class A (with B1 foam option) |
Combustible — not tunnel-rated |
Mechanical Protection |
Impact, bird, and rodent proof |
Easily damaged by impacts and pests |
Outdoor Corrosion |
30-year galvanized protection |
Degrades from UV + oxidation |
Bonding |
Spiral thread mechanical interlock + PU |
Chemical (corona treatment) bond only |
Installation |
No hot-melt patching needed |
Requires field joint heat-shrink |
Appearance |
Professional metallic finish |
Plain black plastic |
Temperature Resistance |
−50 to 120°C, no thermal stress |
Can deform above 80°C surface |
Condensation Control |
Metal jacket prevents external condensation |
Subject to external moisture |
Service Life |
30+ years overhead |
5–10 years above ground |
Technical Specifications
|
Parameter |
Standard / Value |
|
Working Pipe |
Seamless / Spiral Welded / ERW Steel (Sa2.5 blast-cleaned) |
|
Insulation |
Rigid PU Foam — density ≥60 kg/m³, ≤0.033 W/(m·K); B1 flame-retardant option |
|
Outer Jacket |
Galvanized steel spiral-wound pipe (Aluminum / Stainless steel optional) |
|
Jacket Process |
Spiral pipe rolling — threaded inner surface for mechanical PU bond |
|
Operating Temperature |
−50°C to 120°C (peak ≤130°C) |
|
Medium Pressure |
≤2.5 MPa |
|
Heat Loss |
25% of traditional on-site insulated pipes |
|
Outdoor Corrosion |
30 years without visual change (galvanized) |
|
Fire Rating |
Class A (with B1 flame-retardant PU) |
|
Service Life |
30+ years |
|
Laying Method |
Overhead / Utility tunnel / Pipe gallery / Bridge crossing |
|
Support System |
Sliding supports + fixed brackets (tunnel-ready) |
|
Standards |
ISO 9001 / GB/T 29047 |
|
Certifications |
ISO 9001 / ISO 14001 / CE |
|
Fittings |
Insulated elbows, tees, reducers, expansion joints, fixed brackets |
|
Packaging |
Steel end caps + weather-resistant bundling |
Application Scenarios
Urban Utility Tunnels & Pipe Galleries. The definitive solution for integrated underground utility corridors. Class A fire-rated overhead pipes with B1 PU eliminate the fire hazard that standard HDPE pipes pose in enclosed tunnels. Spiral-wound galvanized jackets provide professional appearance and 30-year corrosion protection in tunnel environments.
Bridge & Road Crossings. Lightweight aluminum-jacketed overhead pipes for bridge-mounted heating lines where structural load matters. UV-immune metal jacket requires zero maintenance compared to painted or wrapped alternatives. Sliding supports accommodate bridge deck movement without stressing the pipe system.
Industrial Plants & Power Stations. Stainless steel-jacketed overhead pipes for chemical plants, refineries, and coastal power stations where standard galvanized may not suffice. Impact-resistant jacket protects PU insulation in high-traffic industrial environments. Smooth metallic finish resists chemical splash and airborne contaminants.
District Cooling & Chilled Water. Metal-jacketed overhead pipes prevent condensation and insulate chilled water lines in data centers, commercial buildings, and campus cooling loops. The galvanized jacket acts as a vapor barrier, keeping external humidity from penetrating the PU insulation — a critical advantage over HDPE in high-humidity environments.
Exposed Pipe Racks & Outdoor Installations. Self-supporting overhead pipes on elevated pipe racks for long-distance heat transmission across open terrain. The galvanized jacket handles decades of rain, snow, and sun without degradation. Spiral-wound design accommodates thermal expansion without jacket cracking or joint separation.
Trusted Across 110+ Countries
Our metal-jacketed overhead pipes serve utility tunnel operators, EPC contractors, power plants, and industrial facility operators worldwide. As drafters of 8 national standards, we engineer every overhead pipe system for your specific environmental and fire safety requirements.
Service & Support
From jacket material selection (galvanized/aluminum/stainless) through support bracket engineering to fire safety certification, our team supports your entire overhead pipe project from design to commissioning.
|
Service Item |
Details |
|
Pre-Sales Consulting |
Jacket material selection, fire rating requirements, support bracket specification, thermal expansion analysis. |
|
Engineering Design |
CAD/PDF with support layout, expansion loop design, sliding/fixed bracket positioning, fire safety compliance. |
|
Free Samples |
At no charge. Customer covers freight. Cross-section for metal-PU bonding and jacket integrity verification. |
|
Production & QC |
Spiral-wound on automated lines. 100% tested for jacket interlock seal, PU density uniformity, and coating adhesion. |
|
Delivery |
7–14 days. EXW, FOB, CIF. Container-optimized with full support bracket and accessory kit. |
|
MOQ |
Flexible per project scope. |
|
Technical Support |
Installation supervision, support bracket alignment, expansion joint commissioning, fire safety compliance inspection. |
|
After-Sales Warranty |
30+ year comprehensive warranty. Dedicated team for overhead pipe maintenance and technical support. |
|
Payment Terms |
T/T, L/C at sight. Flexible for long-term partners. |
|
OEM / ODM |
Custom jacket material, B1/non-B1 PU, support bracket design, specification available. |
