Specifications and dimensions of fire-resistant partitions for cable trays

Fireproof partitions for cable trays are designed to prevent fire spread, typically using intumescent materials, fireproof boards, or modular fire-blocking sections, with dimensions tailored to tray size and UL-rated openings.

Materials and Construction

Fireproof partitions, also called fire-blocking sections, are commonly made from:

• Intumescent blocks and fireproof cloth combined with a metal frame coated with fireproof material for lightweight, modular designs .
• Traditional fireproof boards, fireproof mud, or fireproof bags, though these are heavier and may reduce heat dissipation .
• Moldable putty and pillows (e.g., 3M FSP-SLP-M) for sealing openings around cable trays, often used in combination with UL-listed caulks for enhanced fire resistance . These materials are selected for high flame retardancy, temperature resistance, corrosion resistance, and environmental durability, ensuring stability even under water exposure or rodent damage .

Dimensions and Sizing

The dimensions of fireproof partitions depend on the cable tray size and the required fire rating:

• Openings are typically 1.5 inches larger than the tray on all sides to accommodate firestop pillows or putty .
• Example: For a 4” x 12” tray, the recommended opening is 7” x 15” .
• Standard lightweight fire-blocking sections are compact and modular, with a single set weighing less than 5 kg, allowing easy installation and maintenance .
• UL-rated systems vary by wall type:
  • Concrete walls: 3-hour F-rating, 3/4-hour T-rating
  • Gypsum walls: 1–2 hour F-rating, 0–1/2 hour T-rating .

Installation Requirements

• Partitions must be firm, reliable, and smooth, with seams sealed using organic plugging materials .
• They should allow easy addition or removal of cables without damaging the tray structure .
• Proper spacing and support must be maintained to prevent cable deformation and ensure the minimum bend radius is respected .
• Fireproof partitions should be installed at strategic points, such as entrances to control rooms, distribution devices, or factory walls, to effectively isolate potential fire sources .

Key Considerations

• Compatibility with tray type: Ladder, solid-bottom, or ventilated trays may require different partition designs .
• Heat dissipation: Lightweight, modular partitions reduce heat accumulation, preventing cable insulation degradation .
• Regulatory compliance: Follow UL-listed systems and local fire codes to ensure the partition meets the required fire rating . By selecting the appropriate material, size, and installation method, fireproof partitions can effectively prevent fire spread, protect critical infrastructure, and maintain cable integrity in industrial and commercial settings.