Weight requirements for fireproof cable trays

The weight of a fireproof tray-type cable tray depends on its material, dimensions, and design, typically ranging from 10 to 50 kg per meter for steel-based trays, with lighter options for aluminum or FRP.

Factors Affecting Weight

1. Material:

   • Mild Steel / Galvanized Steel: ~7,850 kg/m³
   • Stainless Steel (SS304/SS316): ~8,000 kg/m³
   • Aluminum: ~2,700 kg/m³
   • Fiberglass Reinforced Plastic (FRP): ~1,800–2,000 kg/m³

2. Tray Type:

   • Solid Bottom Tray: Heavier due to full sheet metal coverage.
   • Perforated Tray: Weight reduced by ~20% due to perforations.
   • Ladder Tray: Weight depends on side rails and rung spacing (typically 200–300 mm).
   • Wire Mesh Tray: Weight depends on wire diameter and grid spacing .

3. Dimensions:

   • Width, side height, and sheet thickness directly influence the tray's cross-sectional area and thus its weight.
   • Small increases in thickness (e.g., 1.6 mm to 2.0 mm) can increase weight by ~25% for the same profile .

4. Fireproof Coating:

   • Fireproof trays often include intumescent coatings or additional layers, which slightly increase the overall weight.
   • Periodic inspection is recommended to ensure coating integrity and maintain fire resistance .

Estimating Weight

The general formula for calculating tray weight per meter:

Weight (kg/m) = Cross-sectional metal area (m²) × Material density (kg/m³)

• For perforated trays, subtract the perforation volume (~20%) from the cross-sectional area.
• For ladder trays, include side rails and rungs in the cross-sectional area calculation.
• Multiply by the total length to get the total tray weight for structural support design .

Practical Example

• A 1-meter section of galvanized steel ladder tray with 100 mm side height, 50 mm rung width, and 2 mm thickness:
  • Cross-sectional area ≈ 0.002 m²
  • Weight ≈ 0.002 × 7,850 ≈ 15.7 kg/m
• Aluminum or FRP trays of the same dimensions would weigh significantly less, around 5–6 kg/m for aluminum and 3–4 kg/m for FRP .

Summary

The weight of fireproof tray-type cable trays varies widely depending on material, tray type, and dimensions. Steel trays are the heaviest, while aluminum and FRP offer lighter alternatives. Accurate weight estimation is essential for support structure design, load calculations, and safe installation, and can be calculated using the cross-sectional area and material density, adjusted for perforations and coatings. Regular inspection ensures fireproof coatings remain effective and do not compromise structural integrity .