Cable tray gap treatment

Cable tray gaps should be managed using expansion joints, proper support, and bonding jumpers to accommodate thermal expansion and maintain electrical continuity.

Managing Cable Tray Gaps

Expansion joints are used to allow cable trays to expand and contract due to temperature changes without causing structural damage or misalignment. The gap between tray sections at expansion joints should be calculated based on the maximum and minimum expected metal temperatures of the tray during installation and operation. For example, a typical gap setting might be 3/8 inch, but this depends on the specific temperature range and material properties of the tray.

Installation Best Practices

Support Placement: Supports should be located within 2 feet of each side of the expansion joint splice plates. The tray should not be clamped too tightly to allow free movement along the expansion joint. Anchoring: Anchor the tray at the support closest to the midpoint between expansion joints using hold-down clamps, while other supports use expansion guides to allow sliding movement.

Avoid Over-

Clamping: Overly rigid clamping can prevent expansion, leading to bending, bolt hole elongation, or tray detachment in extreme temperature conditions.

Electrical Continuity

Bonding jumpers are installed around expansion joints to maintain electrical continuity. They should be sized to match the fault current capacity of the tray side rails or cross-section. If future upgrades are expected, jumpers should be sized to accommodate potential increases in protective device ratings.

Additional Considerations

Material Differences: Cable trays and supporting structures may have different thermal expansion rates, requiring tailored solutions for each installation. Standards Compliance: Follow IEC 61537 or relevant national standards to ensure mechanical and electrical safety, proper load handling, and compatibility with fittings and accessories. Thermal Expansion Planning: Consider seasonal temperature variations, especially for rooftop or outdoor installations, to prevent tray distortion or damage.

By following these practices, cable tray systems can safely accommodate thermal expansion, maintain structural integrity, and ensure reliable electrical performance.