Cable tray cuts through bridge bend

Cable trays can safely navigate bridge-like bends by using proper cutting, bending, and support techniques while maintaining structural integrity and cable protection.

Planning and Marking the Route

Before cutting or bending a cable tray to pass through a bridge or curved structure, mark the tray route clearly. Identify the points where bends, sweeps, or level changes are required, ensuring the minimum bend radius accommodates the largest cable in the tray. Proper planning reduces the need for excessive field modifications and ensures cables maintain their relative positions on bends and sweeps.

Cutting Techniques

Wire mesh trays: Can be cut on-site using a bolt cutter, which forms a protective zinc layer on the cut ends. Rubber caps can be used to protect exposed edges. Ladder and solid-bottom trays: Use a band saw or circular saw with a blade suitable for the material (carbide-tipped for metal, diamond-dusted for fiberglass).

Smooth all cut edges to remove burrs and prevent cable damage.

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P or fiberglass trays: Cut in 300 mm increments for optimal strength, avoiding excessive heat to prevent resin damage. Always provide rigid support during cutting to prevent chipping or deformation.

Bending and Field Fabrication

Cable trays can be bent or swept on-site to navigate bridge structures: Wire mesh trays: Bends, tees, and crosses can be fabricated live at the project using bolt cutters and hand tools. Ladder trays: Use smooth radius fittings or fabricate bends carefully to maintain structural integrity and avoid sharp edges. General practice: Avoid bending at cut points or near holes to preserve torsional strength.

Safety and Protection

Always wear Kevlar gloves, eye protection, and appropriate PPE when cutting or bending trays. Remove burrs and sharp edges after cutting to prevent cable damage and injuries. Use splice plates or end caps to reinforce cut ends and maintain alignment.

Support and Installation

Ensure the tray is properly supported at intervals recommended for the tray type (typically 3–6 meters for ladder trays) to prevent sagging. For bridge-like spans, consider suspension or bracket mounting to maintain stability and allow for thermal expansion. Drill holes for splice plates using jigs to match factory hole patterns, ensuring secure connections.

Compliance and Standards

Follow National Electrical Code (NEC) Articles 318, 250, and 800 and NEMA guidelines (VE1, VE2, FG1) for cable tray installation, material selection, and field modifications. Proper adherence ensures safety, performance, and long-term reliability. By combining careful planning, proper cutting and bending techniques, protective measures, and adequate support, cable trays can safely navigate bridge bends while maintaining compliance and protecting the cables they carry.