Fireproofing and sealing requirements for cable trays and shafts

Cable trays and shafts must be firestopped using approved materials and methods to prevent fire and smoke propagation, ensuring all gaps are sealed and penetrations meet design and UL-rated standards.General Firestopping PrinciplesCable trays, busways, and cables passing through walls, slabs, or shafts must have all openings tightly sealed with firestopping materials according to design requirements. Sealing must be reliable, without visible cracks or voids, and allow for maintenance access. Large openings require a fire-resistant backing plate before sealing, and all gaps around metal trunking must be sealed both internally and externally .Materials and ProductsCommon firestopping materials include:Fire-rated boards and fire-resistant mineral wool for packing large gaps .Firestop packs and firestop mastic for smaller penetrations, ensuring the gap area between packs and cables does not exceed 1 cm² and packing thickness is at least 24 cm .Intumescent caulks (e.g., IC 15WB) and moldable putty (e.g., 3M FSP-SLP-M) for sealing around cable trays and outlet boxes .Fire protection coatings and tapes (e.g., FLAMMOTECT-A, DG-CR 0.7) to prevent flame propagation and protect cables from environmental factors like UV, moisture, and chemicals .Installation RequirementsSequence: Install busways → distribution boxes → conduits → cables → grounding → waterproofing → firestopping .Slab penetrations: Provide 20–30 mm of firestopping, install a fire-support plate at the top, and ensure waterstops at floor level are at least 50 mm high .Tray layout: Align with building structure, avoid unnecessary crossings, and segregate power and signal cables to reduce interference .Cover plates: Must be square, consistent in size, evenly painted, and used to close openings .UL Ratings: Use UL-listed systems for walls and slabs, e.g., concrete walls with 3 HR F-rating or gypsum walls with 1–2 HR F-rating, depending on the application .Maintenance and ComplianceEnsure all gaps are sealed and firestop packs are placed in an orderly sequence .Verify that fireproofing materials are compatible with environmental conditions (indoor, outdoor, corrosive, or high-humidity areas) and mechanical loads .Regular inspections should confirm that seals remain intact and that any modifications or additional cables are properly firestopped using approved methods . By following these guidelines, cable trays and shafts will maintain fire integrity, prevent smoke and flame spread, and comply with safety standards for industrial, commercial, and critical infrastructure installations.