Fabrication dimensions for vertical bends in cable trays

Vertical bends in cable trays require calculating the centerline radius, V-cut dimensions, arc length, and clearance based on tray width, cable diameter, and bend angle.

Key Parameters for Vertical Bends

1. Centerline Radius (CLR) The CLR is the radius along the centerline of the tray bend. Standard manufactured sizes are typically 12", 24", or 36" (300 mm, 600 mm, 900 mm), but the radius must also satisfy the minimum bend radius of the cables inside the tray. For example, power cables often require a bend radius of at least 12 times their outer diameter to prevent insulation damage (e.g., a 40 mm cable requires a minimum 480 mm radius) .
2. V-Cut Dimensions For sheet metal tray fabrication, a V-cut is made to allow the tray to bend vertically. The half-width and full-width of the V-cut are determined by the tray width and the bend angle. Tools like the Cable Tray Slope & Fabrication Calculator can provide exact V-cut dimensions, marking intervals, and slope lengths for angles such as 30°, 45°, or 60° .
3. Arc Length and Setback The centerline arc length is the linear length of tray material required to form the bend. The setback is the distance from the start of the bend to the point where the tray resumes its straight path. These dimensions ensure proper alignment and clearance for the cables .
4. Clearance and Offset When designing vertical bends, consider the vertical rise or lateral shift the tray must clear. For offset bends, calculate the horizontal run and vertical rise to determine the travel path and ensure the bend does not compress or damage the cables .
5. Cable Considerations Always account for the thickest cable diameter in the tray. The bend radius must comply with NEC, IEC, or NEMA standards and manufacturer recommendations to prevent cable stress or insulation failure .

Practical Fabrication Steps

1. Select Bend Angle and Type: Choose between a standard 90° vertical elbow, 45° bend, or custom angle.
2. Measure Tray Width: Input the physical width of the tray to determine V-cut dimensions.
3. Determine CLR: Ensure the centerline radius meets both structural and cable bend requirements.
4. Mark V-Cuts: Use calculated half-width and full-width dimensions to mark the tray for cutting.
5. Bend the Tray: Gradually bend along the V-cuts, checking that the arc length and setback match the design.
6. Verify Clearance: Ensure the bend allows sufficient space for all cables without exceeding bend radius limits.

Tools and References

• Cable Tray Bend Calculator: Calculates arc length, setback, chord, and offset distances for vertical bends .
• Cable Tray Slope & Fabrication Calculator: Provides V-cut dimensions, slope length, and on-site marking diagrams .
• Technical Guides: ABB and Legrand manuals provide material properties, bend radius recommendations, and installation best practices . By following these guidelines, vertical bends can be fabricated safely, ensuring structural integrity and compliance with cable bend radius standards.