Article Overview
Cable tray bends must comply with minimum bend radius requirements, proper support placement, and strain relief measures to ensure safety and maintain cable integrity.
Minimum Bend Radius
When a cable tray changes direction, the internal radius of the bend should not be less than the minimum bending radius of the cables it carries, as specified by the cable manufacturer and relevant standards such as IEC 61537 . This prevents damage to the insulation and conductors and ensures long-term reliability.
Support Placement
Supports should be installed on either side of the bend to maintain cable alignment and prevent sagging or stress at the bend point . For long vertical runs, strain relief sections are recommended, typically involving a short horizontal offset of at least 2 cable diameters per section to relieve tension . For vertical runs exceeding 100 meters, additional tension-relieving measures, such as horizontal sections of at least 1 meter, should be incorporated.
Strain Relief and Flexible Systems
In flexible cable tray systems, where cables are not directly fixed, an initial offset or deflection (around 2%) is necessary to accommodate thermal expansion and prevent displacement from supports . Without this, expansion can cause cables to shift or overstress the tray system.
Compliance with Standards
Cable trays and bends should be installed in accordance with IEC 61537 (for metallic trays) or BS EN 61537 (for UK installations), which cover mechanical strength, electrical continuity, fire resistance, and compatibility with fittings and bends . Following these standards ensures safety, durability, and regulatory compliance.
Practical Recommendations
- Verify the minimum bend radius for each cable type before installation.
- Install supports close to bends to prevent sagging.
- Include strain relief sections for long vertical runs.
- Ensure bends and fittings are compatible with the tray system and meet IEC or national standards.
- Avoid using cable trays as walkways or for supporting personnel, as this can compromise safety and system integrity . By adhering to these guidelines, cable tray bends can be installed safely, maintaining both mechanical and electrical performance while complying with international standards.
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