Fireproofing and sealing of holes inside cable trays

Holes and penetrations in cable trays should be sealed using fire-rated materials such as intumescent pillows, mastics, or mineral wool to prevent fire and smoke spread while maintaining tray integrity.

Key Principles

Firestopping of cable trays is essential wherever cables pass through walls, floors, or ceilings. Openings must be tightly sealed to prevent fire propagation, smoke, and heat transfer, while allowing for maintenance and cable movement. The sealing process should ensure no visible cracks or voids, and large openings may require a fire-resistant backing plate before sealing.

Recommended Materials

Intumescent Firestop Pillows: Products like AF BAGS are designed for cable tray penetrations, expanding under heat to seal gaps and provide up to EI 240 fire resistance. They are suitable for small to large cable diameters and can be repositioned for maintenance. Firestop Mastics and Caulks: Intumescent mastics, such as IC 15WB Caulk, can seal cut edges and gaps around cables, providing a flexible, heat-activated barrier.

Mineral Wool and Fire-

Rated Boards: Non-combustible mineral wool or fire-rated boards can fill larger gaps, often combined with mastics or mechanical supports to ensure a complete seal. Metal Sleeves or Plates: For structural support and additional fire resistance, metal sleeves or cover plates can be installed over penetrations, especially in slab or wall openings.

Installation Guidelines

Measure and Plan: Determine the size and number of firestop products needed based on cable tray dimensions and cable diameters. Internal and External Sealing: Apply fireproof materials both inside and around the tray to ensure complete containment. Maintain Tray Integrity: Avoid damaging tray coatings or perforations; use fireproof trays only for flame containment, not unrelated functions.

Gap Management: Ensure gaps between firestop packs and cables do not exceed recommended limits (e.g., 1 cm²), and packing thickness meets product specifications. Inspection and Maintenance: Periodically check for corrosion, deformation, or compromised seals, and perform routine cleaning and fire resistance checks.

Regulatory Considerations

Firestopping must comply with local building codes and standards, such as BS 7671 and EN 1366-3, ensuring that penetrations maintain the fire-resistance rating of the surrounding structure. Temporary sealing during installation can use removable pillows or sleeves, with permanent sealing applied once cable routing is complete.

Practical Tips

Use perforated or wire mesh trays to improve airflow and reduce heat accumulation. Keep openings as small as practicable to minimize fire risk. Ensure segregation of power and signal cables to reduce interference and maintain safety.

Cover plates should be square, evenly painted, and securely fixed to close openings effectively. By following these guidelines, cable tray penetrations can be effectively fireproofed, maintaining both safety and compliance while allowing for future maintenance and modifications.