Methods for sealing gaps in cable trays

Gaps in cable trays can be effectively sealed using firestop packs, intumescent mastics, mineral wool, and other fire-rated materials to ensure safety, prevent smoke or water ingress, and maintain system integrity.

Firestopping and Gap Sealing

Sealing gaps in cable trays is essential for fire safety and environmental protection. Openings where cable trays pass through walls, floors, or ceilings should be tightly sealed to prevent the spread of fire, smoke, and moisture. Common methods include: Firestop Packs: Pre-formed or loose mineral wool packs inserted around cables in the tray, often combined with a fire-resistant backing plate for large openings.

The packing should be dense enough to fill gaps completely, with no voids, and typically maintain a minimum thickness of 20–30 mm at slab penetrations. Intumescent Mastics and Sealants: These materials expand when exposed to heat, sealing gaps around cables and trays. They are suitable for both internal and external sealing and can accommodate multiple penetrations.

Intumescent gaskets or mastics are often applied around cable entries in equipment or accessories to maintain fire integrity. Mineral Wool with Fire-Retardant Coating: Soft penetration seals combine mineral wool of specific density with a fire-retardant coating, providing high fire resistance and moisture tolerance. The thickness of the coating depends on the cable type and configuration, with thicker layers required for metal conduits due to heat conduction.

Cement or Gypsum-

Based Plasters: For residential or low-movement applications, cement mortar, gypsum plaster, or vermiculite-based compounds can seal gaps up to 25 mm, providing fire resistance and structural stability.

Installation Considerations

Ensure tight and reliable sealing without visible cracks or voids. For large openings, install a fire-resistant backing plate before sealing. Maintain orderly placement of firestop packs and sealants to facilitate future maintenance.

Temporary sealing during construction can use removable pillows or sleeves, which should be reinstated with the same materials after alterations. Cover plates should be square, evenly painted, and properly dimensioned to close the opening.

Standards and Compliance

Firestopping systems should comply with EN 1366-3 for cable penetrations and be classified according to EN 13501-2. Always follow manufacturer guidelines and consult a competent authority for selecting materials suitable for the specific cable tray configuration and fire rating requirements. By combining these methods—firestop packs, intumescent mastics, mineral wool, and appropriate backing plates—gaps in cable trays can be sealed effectively, ensuring both fire safety and operational reliability.