What is the appropriate thickness for cable trays with long spans

Long-span cable trays require increased material thickness and structural strength to safely support cables over extended intervals, typically guided by NEMA, NEC, and IEC 61537 standards.

Material Thickness and Duty Class

The thickness of cable trays is determined by the tray type, span length, and load requirements. Ladder-type or perforated trays designed for long spans (14–20 feet) generally require heavier gauge steel or aluminum to prevent excessive deflection and maintain structural integrity under full cable load and environmental factors such as wind or snow . Manufacturers provide thickness specifications based on duty class:

• Light-duty trays: Suitable for short spans and small cable loads; thinner material is acceptable.
• Intermediate-duty trays: Support moderate cable loads over medium spans.
• Heavy-duty trays: Required for long spans, high cable density, or industrial environments; thicker material ensures minimal sag and compliance with safety margins .

Span Considerations

Long-span cable trays are typically supported at 14 to 20-foot intervals, with 20 feet being common for industrial installations . As span length increases, tray thickness and side rail height must increase to maintain deflection limits and load capacity. Eaton's B-Line series demonstrates that long-span trays with continuous splice designs can support loads up to 10 lbs per foot at 20-foot spans while reducing the number of supports required .

Standards and Compliance

• NEMA and NEC: Provide guidelines for tray material, thickness, and load ratings in North America.
• IEC 61537: International standard specifying mechanical strength, deflection limits, and testing methods for cable trays. It requires manufacturers to provide test certificates confirming compliance with working load and safety margins .
• Galvanization and Coatings: Thickness of zinc coatings or other protective layers is also specified to ensure corrosion resistance, particularly for long-span trays exposed to harsh environments .

Practical Recommendations

1. Select tray thickness based on span and load: Longer spans require thicker side rails and base material.
2. Verify manufacturer specifications: Ensure the tray meets NEMA, NEC, or IEC 61537 load and deflection requirements.
3. Consider environmental factors: Corrosion, temperature, and vibration can affect long-span tray performance.
4. Use continuous splice designs: These improve strength and reduce deflection over long spans, minimizing the number of intermediate supports . By following these guidelines, long-span cable trays can safely support electrical, data, and instrumentation cables while maintaining compliance with industry standards and ensuring long-term reliability.