In a cable interlayer, electrical (power) trays are typically positioned above instrumentation (signal/control) trays, maintaining proper spacing to minimize interference and allow heat dissipation.

Layering and Separation

Electrical on Top, Instrumentation Below: In multi-layer cable tray systems, power cables are generally installed on the upper trays, while sensitive instrumentation and control cables are placed on lower trays. This arrangement reduces the risk of electromagnetic interference (EMI) from high-current power cables affecting low-voltage signal cables . Layered Separation: Strong current and high-voltage cables should be physically separated from low-current instrumentation cables. Industry standards recommend a minimum vertical and horizontal spacing of 300 mm (12 inches) between power and control trays. Where space is limited, metal partitions or dividers can be used to prevent interference .

Tray Types and Material Considerations

Tray Types: Common tray types include ladder trays, perforated trays, solid-bottom trays, wire mesh (basket) trays, and channel trays. Ladder trays allow good ventilation and easy cable installation, while solid-bottom trays provide maximum protection from dust and moisture. Wire mesh trays are suitable for data and low-voltage cables, and channel trays are used for sensitive or small instrumentation cables . Material Selection: Materials such as steel, aluminum, or coated metals are chosen based on environmental conditions, load requirements, and corrosion resistance. Aluminum offers excellent corrosion resistance, while galvanized steel provides mechanical strength and durability .

Routing and Maintenance

Optimal Path Planning: Cable trays should follow the shortest practical route between equipment, minimizing bends and junctions. Multi-level layouts or bridges can prevent crossovers and congestion, making maintenance easier . Service Access: Ensure trays are accessible for routine inspection, troubleshooting, and future cable additions. Avoid placing trays too close to structural obstructions, pipes, or ventilation ducts .

Heat Dissipation and Environmental Factors

Ventilation: Power cables generate heat, so trays should allow air gaps for heat dissipation. Perforated or ladder trays are preferred for high-current cables to prevent overheating . Environmental Protection: In humid or high-temperature areas, use corrosion-resistant materials and provide additional spacing. In hazardous zones, fire-retardant trays or coatings may be required .

Summary

For a cable interlayer arrangement:

• Place power trays above instrumentation trays to reduce EMI.
• Maintain minimum spacing of 300 mm or use partitions if necessary.
• Select appropriate tray types based on cable type and environmental conditions.
• Plan straight, accessible routes to simplify maintenance.
• Ensure adequate ventilation and consider fire and corrosion protection. This approach ensures safe, efficient, and maintainable cable tray systems in multi-layer installations .