Calculation of horizontal elbows in 800 cable trays

Horizontal elbows in an 800 mm cable tray are calculated using the offset distance, bend angle, and standard multipliers to determine the straight tray length between bends.

Understanding Horizontal Elbows

A horizontal elbow is a bend in a cable tray that changes the routing direction in the horizontal plane. These are used to navigate around obstacles, walls, or equipment while maintaining proper cable flow and avoiding sharp bends that could damage cables .

Steps to Calculate Horizontal Elbows

1. Determine the Offset Distance Measure the horizontal distance the tray must shift to bypass an obstacle. This is the straight-line distance between the start and end points of the offset .
2. Select the Bend Angle Common horizontal bend angles are 30°, 45°, 60°, or 90°. The choice depends on available space and installation requirements .
3. Use the Multiplier for Straight Tray Length Each bend angle has a standard multiplier to calculate the straight tray length required between bends:
   • 30° → multiplier 2.0
   • 45° → multiplier 1.5
   • 60° → multiplier 1.15
   • 90° → multiplier 1.0 Multiply the offset distance by the multiplier to get the length of the straight tray section between the two bends .
4. Calculate Number of Elbows For a single offset, two elbows are typically required (one at the start and one at the end). For multiple offsets or compound routing, repeat the calculation for each segment .
5. Check Minimum Bend Radius Ensure the bend radius meets the minimum requirement for the cable type to prevent damage. For large power or instrumentation cables, the radius is usually 6–12 times the cable diameter .

Example Calculation

Suppose an 800 mm wide tray must bypass a 1.5 m wide obstacle using 45° bends:

• Offset distance = 1.5 m
• Bend angle = 45° → multiplier = 1.5
• Straight tray length = 1.5 × 1.5 = 2.25 m
• Number of elbows = 2 (one at each end of the offset) This ensures the tray smoothly navigates the obstacle while maintaining proper cable spacing and bend radius.

Additional Considerations

• Tray Fill and Cable Spacing: Ensure the tray width (800 mm) accommodates all cables in a single layer with spacing for heat dissipation and future expansion .
• Mechanical Support: Brackets or supports should be installed near elbows to maintain structural integrity .
• Compliance: Follow IEC 61537 or NEMA standards for tray installation, including maximum span, load, and bend radius . By following these steps, you can accurately calculate the number, placement, and straight lengths for horizontal elbows in an 800 mm cable tray, ensuring safe and efficient cable routing.