Cable tray installation in cable tunnels

Cable trays in tunnels are installed using modular support systems anchored to walls or ceilings, ensuring safe, organized, and fire-resistant cable routing.

Planning and Preparation

Before installation, detailed planning is essential. This includes reviewing approved shop drawings to determine tray layout, lengths, and locations, and verifying that all materials meet project specifications and are free from damage. Early planning reduces errors and ensures proper load distribution, corrosion protection, and fire safety compliance.

Support and Mounting Systems

Cable trays are typically mounted using brackets, threaded rods, or anchor channels attached to tunnel walls or ceilings. Support systems such as U, I, or STRUT profiles provide flexibility for different tunnel geometries, including bends, slopes, and inclines. Multi-layer routing is possible with cable support troughs, allowing separation of power, communication, and signaling cables.

Tray Types and MaterialsLadder-type trays: Suitable for heavy cables and long spans, providing mechanical strength and ventilation. Wire mesh trays: Offer excellent ventilation and flexibility for tight spaces and curved tunnel sections. Perforated sheet metal trays: Provide additional mechanical protection and fire safety.

Materials are chosen based on environmental conditions. Stainless steel is preferred in road tunnels to resist corrosion from chlorides and moisture, while coated steel or galvanized trays may be used in less aggressive environments.

Installation Procedure

Material Handling: Store trays horizontally on flat surfaces with timber supports at regular intervals to prevent deformation. Anchoring: Secure brackets or rods to solid tunnel surfaces, ensuring alignment with the planned route. Modular Assembly: Connect tray sections using compatible fittings, allowing adjustments for bends, slopes, and drops without modifying the tunnel structure.

Cable Bundling: Use cable clamps or dividers to organize individual cables or bundles, maintaining separation for safety and load balancing. Fire Safety: Install firestop modules or covers where required to prevent fire propagation and maintain functionality of emergency systems.

Maintenance and Expansion

Properly installed trays facilitate inspection, maintenance, and future expansion. Modular designs allow easy addition of new cables without disrupting existing installations. Regular checks ensure corrosion protection, mechanical integrity, and compliance with fire safety standards.

Key Considerations

Ensure mechanical stability to withstand dynamic loads, especially in railway tunnels. Maintain adequate ventilation to prevent overheating of cables. Follow standards and regulations such as DIN 4102-12 for fire resistance and BS EN 61537 for tray systems.

Plan for multi-layer routing to separate power, communication, and signaling cables safely. By following these methods, cable trays in tunnels can be installed efficiently, safely, and with long-term durability, ensuring reliable operation of electrical and communication systems.