Fireproof sealing thickness for cable trays

The recommended thickness of fireproof sealing inside cable trays is typically 120 mm for intumescent pillows and at least 24 cm for firestop packs, depending on the material and fire rating required.

Firestop Packs and Mineral Wool

For cable tray penetrations through walls, slabs, or shafts, firestop packs or mineral wool should be installed with a packing thickness of not less than 24 cm, ensuring that the gap area between the packs and cables does not exceed 1 cm². This ensures a tight, reliable seal without visible cracks or voids, which is critical for maintaining fire resistance and preventing fire spread along cable routes. Large openings may require a fire-resistant backing plate before sealing.

Intumescent Fireproof Pillows

Intumescent pillows, such as AF BAGS, are designed for cable diameters up to 21 mm and provide a sealing depth of 120 mm. These pillows expand under heat to seal the penetration and are suitable for walls, floors, and sandwich structures without requiring additional framing. They are certified under EN 1366-3 for fire ratings up to EI 240, making them suitable for high-performance fireproofing in industrial and commercial installations.

Slab Penetrations and Waterstops

At slab penetrations, a firestopping layer of 20–30 mm is recommended, often combined with a fire-support plate at the top. Additionally, a waterstop of at least 50 mm in height is suggested at floor-level penetrations to prevent water ingress while maintaining fire protection.

Material Selection and Installation

Common fireproof materials include fire-rated boards, firestop mastic, firestop packs, and fire-resistant mineral wool. The choice depends on the cable tray size, cable bundle diameter, and required fire rating. All gaps inside and around metal trunking must be sealed completely, and cover plates should be square, evenly painted, and properly installed to close the opening.

Summary

Firestop packs/mineral wool: ≥ 24 cm thickness, gap ≤ 1 cm²Intumescent pillows (AF BAGS): 120 mm sealing depth for cables ≤ 21 mmSlab penetrations: 20–30 mm firestopping, 50 mm waterstopInstallation: Tight, void-free, with backing plates for large openings Following these guidelines ensures compliance with fire safety standards and effective containment of fire within cable tray systems.