Fireproofing cable trays sealing holes and cable tunnels

Fireproofing cable trays and sealing penetrations involves using firestop materials, coatings, and modular systems to prevent fire and smoke spread while maintaining cable functionality.

Fireproofing Cable Trays

Cable trays can be protected using intumescent coatings, fire-resistant tapes, or firestop wraps. Products like FLAMMOTECT-A and DG-CR 0.7 form a protective shield around cables, preventing flame propagation and maintaining functionality during a fire . These coatings also enhance resistance to environmental factors such as UV radiation, moisture, and chemicals, making them suitable for indoor and outdoor installations . For metal cable trays, firestop packs or mineral wool can be used to fill gaps and prevent fire spread along the tray .

Sealing Holes and Penetrations

When cables pass through walls, floors, or slabs, all openings must be tightly sealed with firestop materials. Key steps include:

• Install fire-resistant backing plates for large openings before sealing .
• Use firestop packs, mastic, or mineral wool to fill gaps around cables and trunking .
• Ensure gaps do not exceed 1 cm² and packing thickness meets design requirements .
• Cover plates should be square, consistent in size, and painted evenly to close the opening .
• Modular systems like Hilti cable transit frames create water-, smoke-, and gas-tight barriers for multiple cables .
• Products like 3M Fire Barrier Moldable Putty+ or IC 15WB Caulk can be used for outlet boxes and through-penetrations, providing intumescent protection that expands under heat to seal gaps .

Cable Tunnels and Shafts

For cable tunnels or electrical shafts:

• Firestopping should be applied after floor and wall finishes are completed and shaft doors are installed .
• Sequential installation is recommended: reserved openings → busway installation → distribution boxes → conduit → cable routing → grounding → waterproofing → firestopping .
• Mixed penetrations (cables, pipes, and conduits) require specialized multi-transit firestop solutions to prevent fire and smoke spread .
• Firestop collars and foam coatings can limit steel temperature rise and maintain compartment integrity for 60–90 minutes or more, depending on the rating .

Best Practices

• Always choose fire-rated materials compatible with the cable type and installation environment .
• Ensure installation is tight and free of voids to maintain fire resistance .
• Document and label all firestopped penetrations for inspection and maintenance.
• For retrofits, use mounting brackets or modular devices to allow easy addition of new cables without compromising fire protection . By following these methods and using certified firestop products, cable trays, holes, and tunnels can be effectively protected, ensuring compliance with fire safety standards and maintaining operational integrity during emergencies .