Sealing the back of a cable tray can be achieved using fireproof pillows, silicone or polyurethane sealants, or specialized weatherproofing systems to create a secure, dustproof, and fire-resistant barrier.

Fireproof Sealing

For fire-rated applications, intumescent fireproof pillows such as AF BAGS are highly effective. These are placed inside a non-combustible fiberglass casing and expand under heat to seal cable tray penetrations, providing protection up to EI 240 depending on the product and wall thickness. To use, measure the cable tray width, select the appropriate number and size of pillows, and insert them to completely close the penetration. They are repositionable, allowing for maintenance or cable modifications without compromising the seal .

Weatherproof and Dustproof Sealing

For outdoor or exposed installations, weatherproofing systems like GRP sealants or WSP weatherstops can be used. WSP units consist of a steel frame with water-resistant pads coated in silicone-based sealant, creating a weathertight barrier around the tray. These systems accommodate any cable size and quantity, are corrosion-resistant, and can be installed before or after the tray and cables . GRP weathering systems use a fiber-reinforced, cold-applied liquid that adapts to any penetration size and can be tinted to match building aesthetics .

Sealants for Non-Fire Applications

For interior or non-fire-rated walls, silicone or polyurethane sealants are suitable. Prepare the area by cleaning debris, then apply the sealant around the cables using a caulk gun. For larger gaps, insert a backing rod first to provide support. Smooth the sealant to prevent water pooling and allow it to cure fully before disturbing the cables. For exterior walls, creating a drip loop in the cable before sealing helps prevent water ingress .

Cable Entry Systems

For multiple cables or high-density installations, cable entry seals such as single-entry or multi-entry grommets and plates can be used. These provide a neat, strain-relieved, and sealed entry point, reducing leak paths and simplifying maintenance .

Best Practices

• Ensure the sealant or system is compatible with the wall or floor material.
• Maintain proper fire ratings if required.
• Allow sealants to fully cure before handling cables.
• Consider accessibility for future cable maintenance.
• Use appropriate mechanical support to prevent stress on cables. By combining fireproof pillows, sealants, and entry systems as needed, you can achieve a secure, weatherproof, and fire-resistant seal at the back of a cable tray.