How to make underground cable trays

Building underground cable trays requires careful planning, trench preparation, proper tray selection, and protective layering to ensure safety, durability, and easy maintenance.Planning and DesignBefore starting, plan the cable tray route according to the site layout, electrical load, and clearance requirements. Consider the type of cables, expected load, and separation from other utilities. Review approved shop drawings to determine tray lengths, fittings, and support locations . Ensure all materials, including trays, ladders, and accessories, are inspected for damage and compliance with project specifications .Trench PreparationExcavation: Dig a trench along the planned route, typically 0.5 m wide and 1.5 m deep, depending on cable size and local regulations .Base Layer: Spread a 10 cm layer of sand at the bottom to provide a soft bed for the tray and cables, preventing mechanical damage .Tray Placement: Place the cable trays or troughs (cement concrete, stoneware, or cast iron) along the trench. Ensure they are level and aligned for smooth cable installation .Cable Tray InstallationTray Type: Choose between ladder-type, perforated, or solid-bottom trays. Ladder trays allow airflow and easy cable entry, while perforated trays are suitable for lighter loads .Supports: Secure trays with brackets or clamps, spaced 1.5 to 3 meters apart, depending on tray type and load .Alignment: Ensure trays are straight, level, and properly connected using fittings and connectors .Cable Laying and ProtectionLay cables carefully on the sand bed inside the tray, avoiding sharp bends or overlapping that could damage insulation .Cover cables with another layer of sand, then a protective layer of bricks or bituminous compound to prevent mechanical damage and moisture ingress .For additional protection, use bituminized paper and hessian tape on cable outer layers to prevent corrosion and electrochemical reactions .Final BackfillingAfter securing the trays and cables, backfill the trench with soil, compacting it carefully to avoid tray deformation .Ensure manholes or access points are installed at intervals to allow maintenance and cable pulling if needed .Safety and MaintenanceMaintain proper separation between power and communication cables to prevent interference.Ensure continuous operation of essential systems by considering dual power supply or UPS for critical installations .Regularly inspect trays and cables for damage, corrosion, or sagging, especially in underground environments . By following these steps, underground cable trays can be installed safely, efficiently, and in compliance with engineering standards, ensuring long-term reliability and ease of maintenance.