Branch cables in vertical shaft cable trays must be installed with careful mechanical support, proper cleating, and adherence to safety standards to prevent cable damage and ensure long-term reliability.

Key Considerations for Vertical Shaft Installations

Safety and Risk Management: Installing cables in vertical shafts is inherently dangerous due to the weight of the cables and the risk of free fall. Only trained professionals should perform these installations, and fail-safe mechanisms such as secondary steel wires or synchronized cable pushers should be used to prevent accidents . Cable Routing and Configuration: Vertical shaft installations can be either rigid (straight) or flexible/snaked. Rigid installations are simpler and generally preferred for ease of laying, while snaked configurations can reduce stress on the cable during thermal expansion and contraction . Proper snaking also helps prevent conductor elongation and insulation cracking due to thermal cycling. Mechanical Support and Cleating: Cables must be supported at regular intervals using spring-loaded or high-tensile cleats to prevent downward movement. The cleats should be designed to accommodate the cable's weight and thermal expansion. For branch cables, ensure that the tray and cleat spacing maintain the minimum bend radius and avoid closed loops of ferromagnetic steel when using metal supports . Cable Tray Selection and Installation: Use cable trays that match the load and environmental conditions. Ventilated or solid-bottom trays can be used depending on heat dissipation requirements. Branch cables should be fixed at regular intervals, and cable fill should not exceed 40% of tray capacity to prevent overheating . Proper identification and spacing of branch cables are essential for maintenance and safety. Thermal and Mechanical Considerations: Vertical shaft installations must account for thermal cycling, which can cause relative movement between the cable core and sheath. High tensile strength cables, steel wire armoring, or integrated pulling members can help maintain integrity. Avoid excessive bending and ensure that the cable is laid in an organized manner to minimize stress . Compliance and Standards: Follow relevant standards such as BS EN 61537 for cable trays and BS 6946 for channel support systems. Ensure that all components are compatible and tested together as a system to withstand forces generated during short circuits or other operational loads .

Best Practices Summary

• Plan the installation carefully, considering cable weight, bend radius, and thermal expansion.
• Use rigid or snaked configurations based on cable type and shaft height.
• Install spring-loaded or high-tensile cleats at regular intervals.
• Ensure cable fill does not exceed 40% of tray capacity.
• Implement fail-safe mechanisms to prevent cable free fall.
• Maintain proper spacing and identification for branch cables.
• Verify compliance with relevant standards and manufacturer recommendations. By following these guidelines, branch cables in vertical shaft cable trays can be installed safely, minimizing mechanical stress and ensuring reliable long-term operation .