Spacing of Multi-layer Cable Tray Fixing Brackets

The spacing of multi-layer cable tray fixing brackets depends on cable type, tray material, load, and deflection limits, typically ranging from 1.2 to 2.5 meters, with adjustments for heavier or stiffer cables.General GuidelinesThe support spacing for cable trays is the distance between the centres of adjacent fixing brackets. Proper spacing ensures that the tray remains stable, prevents sagging, and avoids undue mechanical stress on the cables ( ). For multi-layer cable trays, the weight of multiple cable layers must be considered, as heavier loads reduce the allowable distance between supports.Factors Affecting Bracket SpacingCable Type and Weight: Heavier cables or those with stiffer sheaths (e.g., MDPE) can span longer distances without excessive sag, while lighter or more flexible cables (e.g., LSOH) require closer support ( ).Tray Material: Steel, stainless steel, or aluminum trays have different stiffness and load-bearing capacities. Stronger materials allow wider spacing, while weaker or ventilated trays may need closer supports ( ).Deflection Limits: The allowable sag is typically limited to 2–3% of the span length. Calculations using the Heinhold method or similar approaches can determine precise support distances based on cable and tray properties ( ).Environmental Conditions: External factors such as temperature, vibration, or exposure to corrosive environments may require reduced spacing to maintain structural integrity ( ).Typical Spacing RecommendationsStandard horizontal runs: 1.2–2.5 meters between brackets, depending on load and tray type ( ).Vertical risers or bends: Brackets should be closer, typically 1–1.5 meters, to prevent tray rotation or cable shifting ( ).Multi-layer trays: Consider cumulative weight; spacing may need to be reduced by 10–20% compared to single-layer trays ( ).Binding of cables: Cable ties within trays should be spaced no more than 1.5 meters apart to maintain order and prevent cable movement ( ).Installation Best PracticesEnsure trays are level and properly aligned before fixing brackets.Use fire-resistant or corrosion-resistant brackets where required.Maintain minimum clearances above and below trays for airflow and maintenance.Verify that the tray system complies with BS EN 61537 or relevant local standards ( ). By considering these factors, multi-layer cable tray systems can be installed safely, minimizing sag, mechanical strain, and potential damage to cables.