Construction of Bottomless Cable Trays

Bottomless cable trays are open cable support systems designed to provide flexible routing, easy access, and efficient ventilation for electrical and communication cables.

Overview

Bottomless cable trays, also known as ladder-type or open mesh trays, are primarily used to support and organize cables in industrial and commercial installations. Unlike solid-bottom trays, they have no continuous base, allowing for better air circulation, heat dissipation, and easier cable installation or maintenance . They are suitable for high-density cabling, heavy-duty power cables, and environments where frequent cable changes are expected.

Materials and Corrosion Protection

Bottomless cable trays are typically fabricated from steel, stainless steel, or aluminum. Steel trays may be pre-galvanized or hot-dip galvanized to enhance corrosion resistance, while stainless steel (e.g., AISI 316L) provides superior protection in harsh or chemical environments . Aluminum trays offer a high strength-to-weight ratio and natural corrosion resistance due to the protective oxide layer . Material selection depends on environmental conditions, load requirements, and budget considerations.

Structural Components

A bottomless cable tray system consists of:

• Cable support lengths: Ladder sections or wire mesh panels that carry the cables.
• Fittings: Components such as horizontal and vertical bends, T-pieces, crossovers, and reducers to change routing direction or dimensions .
• Support elements: Brackets, hangers, and center suspensions that attach trays to ceilings, walls, floors, or steel structures .
• Accessories: End caps, splice plates, and grounding connections to ensure mechanical stability and electrical safety .

Installation Guidelines

1. Planning and Layout: Confirm tray routing, dimensions, and mounting heights according to approved drawings and standards .
2. Support Spacing: Install support brackets at intervals recommended by the manufacturer, typically every 1.5–3 meters for ladder trays, to prevent sagging and maintain load capacity .
3. Cable Placement: Lay cables evenly across the rungs, avoiding sharp bends or overloading any section. Maintain separation between power and communication cables if required.
4. Fittings and Connections: Use appropriate fittings for directional changes and secure all joints with bolts or clamps as specified by the manufacturer .
5. Grounding and Bonding: Ensure the tray system is properly grounded to prevent electrical hazards .
6. Inspection: Verify alignment, support integrity, and compliance with design specifications before energizing the system .

Standards and Compliance

Bottomless cable trays should comply with DIN EN 61537 for cable support systems and follow guidelines from the Cable Tray Institute (CTI) for installation, load ratings, and safety . Proper adherence ensures mechanical stability, fire safety, and long-term reliability.

Advantages

• Improved ventilation reduces heat buildup in power cables.
• Ease of installation and maintenance due to open access.
• Flexibility for future cable additions or modifications.
• Reduced dust accumulation in certain orientations, such as edge-wise installation . By selecting the appropriate material, support spacing, and installation method, bottomless cable trays provide a durable, efficient, and adaptable solution for industrial cable management.