How to mark lines on cable tray bends

Accurate marking of cable trays with bends requires using a square or template, maintaining minimum bend radii, and ensuring cable positions are preserved during installation.

Tools and Techniques for Marking

To mark cable trays, use a square that spans the tray width and gauge from one side rail to mark both flanges and the web of the tray. Marking can be done with a scribe, marking pen, or pencil. For bends, ensure the minimum permissible radius is maintained for the largest cable to prevent damage and maintain relative cable positions.

Field-cut trays can be marked using splice plates as templates. Drill jigs or short side rail pieces with factory hole patterns can serve as stops to ensure accurate hole placement for splice plates.

Cutting and Preparing Bends

After marking, cut the tray using appropriate tools depending on the material: Metal trays: hand-held hacksaw, circular saw with carbide-tip or diamond-dusted blade, hand-held band saw, or high-speed grinder for wire mesh. Fiberglass trays: circular saw with carbide tip or diamond-dusted blade. Ensure cuts are square to allow proper splice connections and smooth edges to remove burrs.

For bends, size them to maintain the minimum bend radius and preserve cable alignment.

Installation Considerations

Protect cut or drilled surfaces with zinc-rich paint or rust-proofing agents. Fix trays to supports and join adjoining lengths according to drawings, ensuring earth continuity links are correctly fitted. Apply finishes comparable to the rest of the tray and position joints as close to supports as practical.

Expansion connections should be included where trays cross building expansion joints.

Compliance and Safety

Follow IE

C 61537 and NEC guidelines for mechanical strength, electrical continuity, and grounding. Proper marking and bending ensure trays can handle cable loads, maintain electrical safety, and reduce the risk of system failures. By combining accurate marking, proper bend sizing, and careful cutting, cable trays with bends can be installed efficiently while maintaining cable integrity and compliance with safety standards.