Fireproof sealing and fireproof board thickness for cable trays

Cable tray penetrations require fireproof sealing with fire-rated boards or firestop packs, typically 20–30 mm thick, combined with backing plates and intumescent materials to ensure complete fire containment.

Fireproof Sealing for Cable Trays

When cable trays pass through walls, slabs, or electrical shafts, all openings must be tightly sealed to prevent fire and smoke spread. Firestopping materials include fire-rated boards, firestop packs, firestop mastic, and fire-resistant mineral wool. The sealing must be continuous, without visible cracks or voids, and gaps around cables should not exceed 1 cm² . For large openings, a fire-resistant backing plate should be installed before sealing to provide structural support . Intumescent caulks or moldable putty can be used to seal cut edges and irregular gaps, expanding under heat to block fire penetration . UL-listed systems, such as 3M pillows or IC 15WB caulk, are commonly used to meet fire ratings for concrete or gypsum walls, with F-ratings ranging from 1 to 3 hours depending on the wall type .

Fireproof Board Thickness

For slab or wall penetrations, the recommended fireproof board thickness is generally 20–30 mm. This thickness ensures adequate fire resistance and structural integrity when combined with backing plates and firestop packs . Firestop packs should be arranged in an orderly sequence, and the total packing thickness must meet the design requirements to maintain the fire rating of the barrier .

Additional Considerations

• Tray Coatings: Fireproof cable trays may also have fire-resistant coatings to enhance durability and prevent fire spread along the tray itself. Coating thickness should comply with national safety standards and project specifications .
• Inspection: After installation, verify adhesion, uniformity, and fireproof grade of coatings and firestopping materials. Conduct tests such as combustion or endurance trials to ensure compliance .
• Maintenance: Regularly inspect for wear, corrosion, or degradation of fireproof materials to maintain long-term fire safety . By following these guidelines, cable tray installations can achieve effective fire containment, comply with safety standards, and ensure the protection of electrical systems in industrial and commercial buildings.