How to effectively use fireproof putty for cable trays

Applying fireproof putty to cable trays involves cleaning the area, placing firestop pillows or backing, molding the putty around cables, and ensuring a tight, UL-compliant seal.

Step-by-

Step Procedure1. Prepare the Installation Area Ensure that the cable tray is installed and all cables are routed properly. The surrounding wall or slab finishes should be complete, and any shaft doors or openings should be in place.

Clean the surfaces around the penetration to remove dust, grease, or debris, which ensures proper adhesion of the fireproof putty. 2.

Install Fire-

Resistant Backing (if needed) For large openings, place a fire-resistant backing plate or mineral wool to fill the majority of the gap. This provides structural support and ensures the putty will remain in place. 3.

Position Firestop Pillows (Optional) If using firestop pillows, place them in an orderly sequence around the cables. The gap between the pillows and cables should not exceed 1 cm², and the packing thickness should meet the manufacturer's specifications, typically at least 24 cm for larger penetrations. 4.

Apply Fireproof Putty

Take the moldable fireproof putty (e.g., 3M FSP-MPS) and cut or portion it as needed. Mold the putty around each cable or bundle, pressing it firmly into gaps and voids. Ensure the putty adheres to both the cable surfaces and the surrounding wall or tray edges.

For multiple cables, apply putty in layers to completely fill the opening, avoiding air pockets. 5. Shape and Smooth the Surface Use a putty knife or gloved hands to smooth the surface, ensuring a uniform seal.

The putty should cover all exposed edges and conform to the contours of the cables and tray. Avoid leaving cracks or voids, as these compromise fire resistance. 6.

Install Cover Plates (if applicable) For wall or slab penetrations, place a square, fire-rated cover plate over the sealed opening. Ensure it is properly aligned, painted if required, and securely fastened to maintain the integrity of the firestop system. 7.

Inspect and Verify Compliance Check that all gaps are sealed, the putty is continuous, and the installation meets UL-listed system requirements. For larger or non-standard trays, consult the manufacturer or obtain an engineering judgment letter to ensure compliance. 8.

Maintenance and Future Access Fireproof putty can often be reused or adjusted if additional cables are added. Keep documentation of the installation for future inspections and maintenance. By following these steps, you ensure that the cable tray penetration is properly firestopped, reducing the risk of fire spread and maintaining compliance with safety standards.