Instructions for Longitudinal Fixing of Cable Trays

Longitudinal fixing of cable trays involves securing the tray along its length using appropriate supports, fasteners, and spacing to ensure stability, load-bearing capacity, and compliance with standards.

Key Principles

1. Support Spacing: Cable trays must be supported at regular intervals along their length to prevent sagging and maintain structural integrity. Typical support spacing depends on tray type and material:

• Ladder trays: 1.5–3 meters (5–10 feet) for steel or aluminum trays
• Solid-bottom trays: 1–2 meters (3–6 feet) depending on load and tray width
• Mesh trays: 1–2 meters (3–6 feet) for light instrumentation cables 2. Mounting Methods: Longitudinal fixing can be achieved using:
• Wall brackets or ceiling hangers: Attach trays to walls, ceilings, or structural beams using threaded rods, clamps, or strut channels .
• Strut channels: Provide adjustable support and allow alignment along the tray length.
• Direct bolting: For short runs or where structural members are available, trays can be bolted directly to supports. 3. Alignment and Leveling: Ensure trays are level and aligned along the entire run. Misalignment can cause stress on joints and fittings. Use laser levels or string lines for long runs . 4. Expansion and Contraction: Allow for thermal expansion, especially for long runs of metal trays. Expansion joints or slight gaps at fixed points prevent buckling or deformation . 5. Fastening and Hardware:
• Use compatible fasteners (bolts, nuts, clamps) recommended by the tray manufacturer.
• Ensure all fasteners are tightened to prevent movement but avoid over-tightening, which can deform the tray .
• For heavy loads, consider additional longitudinal supports or intermediate hangers. 6. Safety and Compliance:
• Follow relevant standards such as BS EN 61537, Canadian Electrical Code (CEC), or local building codes .
• Do not use cable trays as walkways or ladders. They are designed solely for cable support.
• Ensure grounding and bonding of metallic trays to prevent electrical hazards. 7. Installation Sequence:

1. Plan the tray route and mark support locations.
2. Install wall brackets, ceiling hangers, or strut channels at specified intervals.
3. Place the tray sections on supports and align longitudinally.
4. Connect tray sections using manufacturer-supplied fittings.
5. Secure trays with bolts, clamps, or fasteners along the length.
6. Check alignment, level, and spacing before loading cables. By following these steps, longitudinal fixing ensures that cable trays remain stable, safe, and compliant, providing reliable support for electrical and communication cables over their entire length .