Curved cable trays are measured by summing the straight tray lengths and the equivalent lengths of bends, using standard bend radii and fitting dimensions to calculate total tray run.

Understanding Curved Cable Tray Metering

When designing or installing cable trays with curves or bends, accurate metering ensures proper material estimation and installation planning. The total length of a curved cable tray is not simply the straight-line distance between start and end points; it must account for the geometry of bends and fittings.

Steps for Metering Curved Cable Trays

1. Identify Straight Sections Measure all straight tray segments between bends. These are added directly to the total tray length.
2. Account for Bends and Curves
   • Use the standard bend radius provided by the manufacturer or specified in IEC 61537 or BS EN 61537 standards .
   • For horizontal or vertical bends, the length of the tray along the curve is calculated as the arc length: $$L_{\text{bend}}=\theta \times R$$ where $\theta$ is the bend angle in radians and $R$ is the bend radius.
   • For 90° bends, the arc length is typically $\frac{\pi }{2}\times R$.
3. Include Fittings and Accessories
   • T-pieces, crossovers, reducers, and end closures have equivalent lengths that should be added to the total tray run .
   • Manufacturers often provide fitting length tables to simplify calculations.
4. Sum All Components Total tray length = sum of straight sections + sum of curved sections + equivalent lengths of fittings.

Practical Considerations

• Minimum Bend Radius: Ensure the bend radius meets cable manufacturer recommendations to prevent cable damage.
• Material Type: Steel, aluminum, or stainless steel trays may have different bend allowances due to rigidity .
• Installation Tolerances: Allow for slight adjustments during installation to accommodate alignment and support spacing.
• Compliance: Follow IEC 61537 or BS EN 61537 for mechanical strength, electrical continuity, and safety .

Example

For a cable tray run with:

• Two straight sections of 3 m and 4 m
• One 90° bend with a radius of 0.5 m
• One T-piece with an equivalent length of 0.2 m The total tray length is:

This method ensures accurate material estimation and proper installation planning for curved cable tray systems. By following these steps, engineers and installers can precisely meter curved cable trays, maintain compliance with standards, and avoid costly errors or rework.