Can fire cable trays be used to install low-voltage electrical shafts

Effective fire protection for cable trays in low-voltage electrical shafts combines proper firestopping of penetrations with targeted suppression systems to prevent fire spread and ensure safety.

Firestopping Requirements

Cable trays passing through walls, slabs, or entering electrical panels must be tightly sealed with firestopping materials to maintain compartmentation and prevent fire propagation . Key practices include:

• Material Selection: Use fire-rated boards, firestop packs, firestop mastic, or fire-resistant mineral wool. Firestop packs should be installed in an orderly sequence, with gaps around cables not exceeding 1 cm² and packing thickness of at least 24 cm .
• Large Openings: Install a fire-resistant backing plate before sealing to ensure structural integrity and fire resistance .
• Slab Penetrations: Provide 20–30 mm of firestopping at slab penetrations and install a fire-support plate at the top. Waterstops of at least 50 mm height are recommended at floor-level penetrations .
• Sealing Quality: Ensure all gaps inside and around metal trunking are sealed both internally and externally, with cover plates square, consistent, and evenly painted .
• Maintenance Considerations: Electrical shafts should be designed to allow easy access for cable routing, maintenance, and future modifications without compromising firestopping .

Fire Suppression for Cable Trays

Cable trays are prone to fire hazards due to electrical faults, overheating, and external ignition sources. Fires can escalate rapidly, especially in confined shafts with limited ventilation . Effective suppression strategies include:

• Direct Low Pressure (DLP) Systems: These systems use a heat-sensitive detection tube along the cable pathway. When exposed to high temperatures, the tube ruptures, releasing a clean extinguishing agent directly at the fire source .
• Advantages of DLP Systems:
  • Rapid Response: Immediate activation minimizes fire spread.
  • Targeted Suppression: Direct application ensures efficient control.
  • Minimal Downtime: Only the affected section requires replacement, allowing quick restoration.
  • Compliance: Systems can meet industry standards and regulations .
• Design Considerations: Customize layout to cover all potential fire risk areas, select appropriate clean agents, integrate with existing fire detection systems, and schedule regular inspections and maintenance .

Best Practices

• Maintain proper cable spacing and tray layout to reduce heat accumulation and fire risk .
• Use ventilated or solid covers depending on heat generation and environmental conditions .
• Ensure routine inspection and replacement of firestopping materials after any cable modifications to maintain compartmentation .
• Consider preformed firestop elements for areas with frequent cable updates to simplify maintenance and improve safety . By combining robust firestopping at penetrations with targeted suppression systems, low-voltage cable trays in electrical shafts can be effectively protected, reducing fire risk, ensuring operational continuity, and complying with safety regulations .