How much cable tray should be used for cable tray bends

The number of cable trays required for bends depends on the bend type, radius, and tray width, with pre-fabricated bends or multiple straight sections used to achieve the desired curve.

Understanding Cable Tray Bends

Cable tray bends are used to change the direction of a cable run while maintaining proper support and avoiding excessive stress on cables. Common bend types include 90° inside/outside elbows, 45° sweeps, offsets, and 180° turnarounds. Each bend may require either a pre-fabricated bend fitting or a combination of straight tray sections bolted together to approximate the curve .

Number of Trays for a Bend

• Pre-fabricated bends: Manufacturers offer bends in various radii (e.g., 12”, 24”, 36”, 48” for a 6” tray). Using these bends typically counts as one tray section per bend, simplifying installation and ensuring proper cable radius .
• Field-fabricated bends: If straight tray sections are cut and bolted to form a bend, multiple straight trays may be needed to approximate the curve. The exact number depends on the desired bend radius and the length of each straight section. Smaller radii require more sections to maintain a smooth curve .
• Bend radius considerations: The centerline radius of the bend should accommodate the cable type and service state (fixed, pull, or temporary lay-in). Using a calculator or manufacturer guidelines ensures the bend does not crowd cables or exceed minimum radius limits .

Practical Recommendations

1. Use pre-fabricated bends whenever possible to reduce labor and maintain proper cable bend radius.
2. Check cable fill and bend take-up using a cable tray bend calculator to ensure the bend does not exceed allowable cable stress or crowding .
3. For complex routing or offsets, calculate the required straight tray lengths between bends to maintain smooth transitions and proper support .
4. Follow manufacturer and NEC guidelines (NEC 392.18) for field bends, ensuring that bolted straight sections do not compromise cable integrity . In summary, each bend typically requires at least one tray section, either as a pre-fabricated fitting or multiple straight sections to form the curve. The exact number depends on the bend radius, tray width, and cable type, and using calculators or manufacturer specifications helps optimize the layout and maintain safe installation.