Spacing between long-span cable trays

For long-span cable trays, support spacing typically ranges from 1.5 meters to 3 meters for standard spans, while extra-long spans can exceed 6 meters, depending on tray type, load, and environmental conditions.

Standard and Long-Span Support Guidelines

For typical horizontal cable tray runs, the support span—the distance between supports—generally ranges from 1.5 meters to 3 meters. This spacing ensures structural stability, prevents sagging, and allows for maintenance access and heat dissipation . The exact distance depends on factors such as cable weight, tray material, and type of installation.

Extra-long spans are used in outdoor or special installations where supports are costly or difficult to place. These spans can range from 20 to 40 feet (approximately 6 to 12 meters) . In such cases, the tray strength must be designed specifically for the chosen support span, and splice plates should be carefully positioned to maintain structural integrity. Only one splice plate is recommended per support span to avoid weakening the tray at connection points .

Factors Affecting Support Spacing

1. Tray Material and Design: Steel, aluminum, or fiberglass trays have different load capacities and stiffness, affecting maximum span .
2. Cable Load: Heavier cables or bundled installations reduce allowable span due to increased sag and stress .
3. Environmental Conditions: Outdoor trays exposed to wind, ice, or temperature variations may require closer supports to maintain safety .
4. Deflection Limits: The allowable sag or deflection is typically limited to a small percentage of the span (e.g., 2%) to prevent mechanical strain on cables .
5. Standards Compliance: NEMA VE-1/VE-2, BS EN 61537, and BS 6946 provide guidance on support spacing and installation practices .

Practical Recommendations

• Match tray length to support span to control splice locations and maintain structural integrity .
• Use appropriate hardware such as splice plates, bolts, and hangers rated for the load and environmental conditions .
• Consider future maintenance: Adequate spacing allows for inspection, cable replacement, and heat dissipation .
• Parallel trays: Maintain at least 0.6 meters horizontal separation for maintenance access and airflow, and 0.5 meters between power and signal trays to reduce EMI .

By carefully considering these factors, long-span cable tray installations can achieve both structural reliability and operational efficiency, minimizing the risk of sagging, cable damage, or system failure.