How cable trays cross bridges

Installing cable trays across bridges requires careful planning, proper support spacing, load calculations, corrosion protection, and adherence to industry standards to ensure safety and durability.

Planning and Design

Before installation, plan the cable tray route carefully, considering bridge structure, clearance, and environmental exposure. Review the Bill of Quantities (BOQ) to ensure all tray components meet the weight and size requirements for the project . Determine the total cable weight per meter to select the correct tray thickness and support brackets . Ensure the route allows for safe access, maintenance, and separation from other utilities .

Selecting the Right Tray Type

Choose a tray type suitable for bridge crossings:

• Ladder trays: Provide airflow and easy cable entry, ideal for heavy or high-voltage cables .
• Perforated trays: Suitable for lighter loads and allow drainage .
• Solid-bottom trays: Protect cables from debris and weather exposure .

Consider material selection for corrosion resistance, such as galvanized steel, stainless steel, or aluminum, especially in outdoor or humid environments .

Support and Load Considerations

• Support spacing: Typically 1.5 to 3 meters apart, depending on tray type and load. Shorter spacing increases rigidity, while longer spacing requires stronger trays .
• Maximum load per hanger: For center-hung supports, typical limits are 318–340 kg (700–750 lbs) with a maximum spacing of 3.6 meters .
• Sag prevention: Ensure supports are properly aligned to prevent bending or sagging, which can damage cables .
• Environmental loads: Account for wind, ice, and snow when calculating tray and support strength .

Installation Steps

1. Mark the route on the bridge structure, ensuring clearance and alignment.
2. Install supports (brackets, hangers, or center-hung systems) at calculated intervals. Ensure they are level and securely anchored to the bridge structure .
3. Assemble trays using connectors and fittings, aligning them straight and level. Avoid sharp edges that could damage cables .
4. Lay cables carefully, maintaining proper separation and avoiding overfilling the tray. Use banding or cable ties to secure bundles .
5. Grounding and bonding: Ensure the tray system is properly grounded according to local electrical codes .
6. Inspection and testing: Verify alignment, support integrity, and cable placement before final commissioning .

Safety and Standards

Follow relevant standards such as IEC 61537, NEC Article 392, and local building and fire codes . Only use components designed and tested together to ensure system integrity . Avoid using cable trays as walkways or supports for personnel, as this can cause injury and damage the system .

By following these steps, cable trays can be safely and efficiently installed across bridges, ensuring long-term durability, cable protection, and compliance with industry standards.