Specifications and dimensions of fire-resistant partitions for cable trays

Fireproof partitions for cable trays typically require a minimum packing thickness of 24 cm, with gaps around cables not exceeding 1 cm², and openings sized slightly larger than the tray dimensions to accommodate firestop materials.

Key Dimension Guidelines

Packing Thickness: Firestop packs or fireproof partitions should have a minimum thickness of 24 cm to ensure adequate fire resistance and isolation of the cable tray section. Gap Area: The gap between firestop packs and cables should not exceed 1 cm² to prevent fire and smoke penetration. Opening Size: For retrofit or new installations, the opening should be approximately 1.

5 inches larger than the cable tray on all sides. For example, a 4” x 12” tray would require a 7” x 15” opening to accommodate firestop pillows or putty. Waterstop at Slab Penetrations: At floor or slab penetrations, a waterstop of at least 50 mm in height is recommended, along with 20–30 mm of firestopping material and a fire-support plate at the top.

Material Considerations

Common fireproof partition materials include: Fire-rated boards and firestop packs for easy installation and good fire resistance. Intumescent caulks or putty (e.g., 3M FSP-SLP-M pillows or FSP-MPS moldable putty) that expand under heat to seal gaps. Fire-resistant mineral wool or coatings for additional protection and heat dissipation.

Installation Tips

Ensure all gaps inside and around the tray are sealed completely, both internally and externally. Use cover plates that are square, consistent in size, and evenly painted to close openings. For large openings, install a fire-resistant backing plate before sealing to maintain structural integrity.

Maintain orderly placement of firestop packs to facilitate inspection and maintenance.

Practical Example

For a 4” x 12” ladder tray, the recommended fireproof partition opening would be 7” x 15”, using medium self-locking firestop pillows and two sticks of moldable putty per opening. This ensures compliance with UL-listed firestop systems and provides a 1–3 hour fire rating depending on wall type. By following these dimension and installation guidelines, fireproof partitions can effectively prevent fire spread along cable trays, maintain system safety, and comply with industry standards.