Fireproof sealing thickness requirements for cable trays

Fireproof sealing inside cable trays typically requires a thickness of 20–120 mm depending on the material and fire rating.Recommended Thickness by Material1. Firestop Packs and Mineral Wool: For cable tray penetrations through walls or slabs, firestop packs or fire-resistant mineral wool should be installed with a minimum packing thickness of 24 mm, ensuring all gaps around cables are sealed tightly and no voids remain. The gap area between the packs and cables should not exceed 1 cm² to maintain fire integrity . 2. Intumescent Fireproof Pillows (e.g., AF BAGS): Intumescent pillows designed for cable tray penetrations can achieve fire protection with a sealing depth of 120 mm for cables up to 21 mm in diameter. These pillows expand under heat to seal the penetration and are suitable for walls, floors, and sandwich structures without requiring additional framing . 3. Fireproof Wraps (e.g., FireMaster Cable Tray Wrap): Fireproof wraps provide full encapsulation of cable trays. Installation requires overlapping adjacent blankets by at least 75 mm, with cut edges sealed using 100 mm strips. The wrap thickness is determined by the product specification, typically designed to withstand high temperatures up to 1200°C, and must be secured with stainless steel bands to maintain tight contact with the tray .Firestopping at Slab PenetrationsWhen cable trays pass through slabs, a firestopping layer of 20–30 mm is recommended, often combined with a fire-support plate at the top. For floor-level penetrations, a waterstop of at least 50 mm in height is also suggested to prevent fire and water ingress .Key ConsiderationsEnsure the sealing material is compatible with the fire rating required (e.g., EI 120, EI 240).Maintain tight and reliable sealing without visible cracks or voids.For large openings, install a fire-resistant backing plate before sealing.Follow manufacturer guidelines for installation sequence and material placement to facilitate maintenance . By adhering to these thickness guidelines and installation practices, cable tray penetrations can achieve effective fire containment and comply with safety standards.