Install cable trays on the utility tunnel

Cable trays in utility tunnels provide organized, safe, and durable support for electrical and communication cables, ensuring compliance with fire and safety standards while facilitating maintenance and future expansion.

Planning and Design

Before installation, a pre-determined layout plan is essential. The system designer or engineer should consider tunnel geometry, cable types, load requirements, and clearances for other utilities. Early planning reduces errors, ensures proper support spacing, and allows for multi-layer cable routing if needed . Modular tray systems, such as ladder-type, wire mesh, or perforated sheet metal trays, are preferred for their flexibility in tight spaces, bends, and inclines .

Material Selection and Corrosion Protection

Tunnel environments are often harsh, with moisture, dust, and potential chemical exposure. Materials like hot-dip galvanized steel, stainless steel, or GRP (glass-reinforced polyester) provide corrosion resistance and long-term durability . GRP trays are halogen-free and self-extinguishing, offering additional fire safety benefits .

Mounting and Support

Cable trays are typically anchored to tunnel walls or ceilings using brackets, threaded rods, or strut systems. Center-hung supports allow easier cable deposition from both sides. Maximum support spacing is generally around 3.6 meters, with load capacities ranging from 318 kg to 340 kg per hanger . Adjustable brackets and fittings accommodate tunnel curves, inclines, and drops without custom fabrication .

Cable Organization and Safety

Proper separation of power, communication, and signaling cables is critical to prevent interference and ensure heat dissipation. Cable clamps, dividers, and multi-layer routing help maintain organization and load balance . Mesh trays provide excellent ventilation, reducing heat buildup for high-voltage cables .

Fire Safety and Compliance

Tunnels have limited ventilation, making fire safety crucial. Metal trays are non-combustible, and using low-smoke, halogen-free cables enhances safety. Systems should comply with standards such as IEC 60332, NFPA 130, EN 45545, and DIN 4102-12, ensuring that essential cables continue functioning during fire events . Firestop modules can be installed to prevent flame spread through walls or penetrations .

Installation Best Practices

• Use qualified personnel familiar with tunnel hazards and local electrical codes .
• Offload and store trays carefully to prevent damage; avoid using trays as lifting points .
• Install trays in a modular fashion, allowing for future expansion and maintenance .
• Ensure proper grounding and bonding of metal trays to prevent electrical hazards .

Maintenance and Future Expansion

Cable trays should be accessible for inspection, repair, and expansion. Modular systems allow adding or rerouting cables without major civil modifications . Early planning and high-quality materials reduce long-term maintenance costs and improve tunnel safety. By following these guidelines, cable trays in utility tunnels can provide efficient, safe, and durable cable management, meeting both operational and regulatory requirements.