Requirements for laying cable trays in tunnels

Cable trays in tunnels must comply with international standards such as CEI 64-20 and EN 61537, using corrosion-resistant materials and ensuring proper load handling, separation, and fire safety.Regulatory StandardsCable trays for tunnels are typically required to meet CEI 64-20 standards for electrical installations in tunnels and EN 61537 for cable tray systems, ensuring mechanical strength, electrical safety, and durability . Many certified products also carry IMQ certification, confirming compliance with European safety and quality requirements . These standards cover aspects such as tray dimensions, load capacity, grounding, and electrical continuity .Material and Corrosion ResistanceTunnel environments are aggressive, with high humidity, dust, and potential chemical exposure. Cable trays are commonly made from 304 or 316L stainless steel, galvanized steel, or glass-reinforced polyester (GRP) to provide corrosion resistance and mechanical strength . Stainless steel with high chromium and molybdenum content enhances resistance to pitting and stress corrosion, while GRP offers a high strength-to-weight ratio and excellent corrosion resistance .Installation and Load HandlingCable trays in tunnels must support power, communication, and signaling cables with proper separation to prevent interference and ensure safety . Ladder-type or wire mesh trays are preferred for their modular design, allowing installation in tight spaces, bends, and inclines without modifying the tunnel structure . Trays are anchored to walls or ceilings using brackets or threaded rods, and rung spacing is typically 150–230 mm to maintain cable support and prevent sagging .Fire Safety and Electrical ConsiderationsCable trays must maintain electrical continuity and grounding to prevent short circuits and ensure safety during faults . Fire-resistant materials and covers are recommended to protect cables from heat and smoke propagation. Dual power supply systems, UPS, or generators are often integrated to maintain essential tunnel systems in case of power loss .Maintenance and AccessibilityProperly designed cable trays facilitate inspection, maintenance, and repair by providing organized routing and easy access to cables . Accessories such as clamps, dividers, and covers enhance protection and maintain separation between different cable types, reducing the risk of damage or interference .In summary, tunnel cable tray systems must combine compliance with international standards, corrosion-resistant materials, robust load handling, fire safety, and modular installation to ensure long-term reliability and safety in challenging underground environments .