Cable tray expansion joint spacing between cable trays

Expansion joint spacing for cable trays depends on the tray material and expected temperature variation, typically 65 feet for aluminum and 128–130 feet for steel under a 100°F temperature differential.Material-Specific Spacing

• Aluminum cable trays: Require expansion joints approximately every 65 feet for a 100°F temperature change due to higher thermal expansion rates .
• Steel cable trays: Can have expansion joints spaced around 128–130 feet for the same temperature differential, as steel expands less than aluminum .
• Fiberglass trays: Typically allow longer spacing, up to 133 feet for a 70°C temperature differential .

Installation Guidelines

• Expansion joint splice plates: Use slotted holes to allow sliding; bolts should be finger-tightened and then slightly loosened to permit movement .
• Support placement: Supports should be located within 2 feet of each side of the expansion joint. The tray should not be clamped too tightly to allow free expansion and contraction .
• Anchoring: Anchor the tray at the midpoint between expansion joints using hold-down clamps, while other supports use expansion guides to allow longitudinal movement .
• Gap setting: The expansion gap is determined based on the expected maximum and minimum metal temperatures at the site. For example, a 50°F installation temperature with a 100°F differential may require a 3/8 inch gap between tray sections .

Practical Considerations

• Expansion joints are mandatory for outdoor trays or indoor trays with temperature swings greater than 30°C .
• Ignoring thermal expansion can lead to tray bending, bolt failure, or damage to cables .
• For long runs, always verify site-specific temperature extremes and adjust spacing accordingly, using linear interpolation if necessary for intermediate temperature differences . By following these guidelines, cable tray systems can safely accommodate thermal expansion and contraction, maintaining structural integrity and protecting installed cables.