Standard Dimensions of Fire Cable Trays

Fire-rated cable trays are designed to maintain cable function during fire, with specific dimensions, banding, wraps, and compliance to ASTM and API fire standards.

Standard Dimensions

Fire-rated cable trays follow standard dimensional ranges similar to conventional trays, including:

• Width: Typically 100 mm to 1220 mm, depending on cable load and application. Wider trays are used for high-density installations.
• Depth: Varies from 25 mm to 150 mm or more, ensuring adequate cable support and heat dissipation.
• Length: Standard tray sections are usually 3 meters long, but custom lengths are available.
• Material Thickness: Commonly 0.6 mm for corrugated aluminum sheeting used in fire protection, with stainless steel or galvanized steel for structural strength and corrosion resistance . Tray types include ladder, perforated, channel, and wire mesh, each with different depth and width considerations based on load, ventilation, and cable type .

Fire Protection Specifications

Fire-rated cable trays, such as FireMaster®, include the following features:

• Wraps: Cable trays are wrapped with fire-resistant material, typically one layer with 75 mm thickness, with 50 mm overlap at joints .
• Banding: Stainless steel banding straps, minimum 12 mm wide, are installed at 250 mm centers to secure the wrap and prevent slumping. Additional banding may be used at elbows and 90° bends.
• Mesh Lining: For open trays, mesh lining is used to support the wrap and maintain cable integrity during fire.
• Weather Protection: Corrugated aluminum sheeting (0.6 mm thick) may be used for outdoor installations .

Fire Testing and Standards

Fire-rated cable trays are tested to ensure performance under fire conditions:

• ASTM E1725-95: Measures response of electrical system components to heat or flame under controlled conditions.
• ASTM E119 and E1529: Provide cellulosic and hydrocarbon fire curves for testing.
• API 2218: References ASTM E1725-95 for petroleum and petrochemical plant applications, using hydrocarbon fire curves equivalent to UL 1709 . These standards ensure that cable trays maintain functionality, minimize toxic gas emission, and aid in safe evacuation during fire events.

Installation Considerations

• Ensure tight banding at all tray edges and overlaps.
• Maintain maximum strap spacing of 250 mm in the center of the tray.
• Use additional banding at bends and elbows to prevent wrap displacement.
• Select tray width and depth based on actual cable area and allowed fill percentage, typically 40% of usable tray area . By following these dimensions and specifications, fire-rated cable trays provide both structural support and fire protection, ensuring compliance with safety standards and long-term reliability.