The required sealing thickness for cable tray wall penetrations depends on the fire rating, cable type, and sealing system, typically ranging from 3 mm for coatings to 120 mm for intumescent pillows.

Fire-Rated Coatings

For soft penetration seals using mineral wool and fire-retardant coatings, such as PROMASTOP®-CC, the coating thickness varies by cable group and conduit type. Metal conduits, which conduct heat efficiently, require a thicker coating, for example, 3 mm dry film thickness instead of 1 mm for standard cables, to achieve proper insulation and fire resistance . The overall cross-section of the seal can be up to 3.75 m² in walls and floors, allowing large cable tray penetrations to maintain fire compartmentation .

Intumescent Fireproof Pillows

Intumescent pillows, such as AF BAGS, provide a sealing depth of 120 mm for cables up to 21 mm in diameter, suitable for walls, floors, and sandwich structures . These pillows expand under heat to fill gaps and maintain fire resistance up to EI 240 (EN 1366-3). The number and size of pillows are selected based on the cable tray dimensions to ensure complete closure of the penetration .

Firestop Packs and Mineral Wool

For larger openings or mixed penetrations, firestop packs or mineral wool are used. The packing thickness should not be less than 24 cm, and gaps between packs and cables should not exceed 1 cm² to ensure a reliable seal . Metal trunking and cable bundles must be sealed both internally and externally, often requiring a backing plate for large openings .

Practical Considerations

• Cable type and configuration: Different cable groups require different sealing thicknesses. Plastic conduits may need additional coating to compensate for melting during fire .
• Wall or floor thickness: Ensure the seal spans the full penetration depth.
• Maintenance access: Systems like intumescent pillows allow repositioning for cable changes without compromising fire protection .
• Standards compliance: Follow EN 1366-3 for testing and EN 13501-2 for classification . In summary, sealing thickness ranges from a few millimeters for coatings to over 100 mm for intumescent pillows or mineral wool packs, depending on the cable type, penetration size, and required fire rating. Proper selection ensures both fire safety and maintainability of cable tray penetrations.