Cable tray systems typically use high-strength bolts such as hex head, carriage, or machine bolts, made from galvanized steel, stainless steel, or aluminum, sized according to tray type, load, and applicable standards like IEC 61537 and NEMA VE 1.

Common Bolt Types for Cable Trays

1. Hex Head Bolts – Widely used for connecting tray sections, supports, and splice plates due to their high torque capacity and ease of installation .
2. Carriage Bolts – Often used in ladder or channel trays where a smooth rounded head is preferred to avoid cable damage .
3. Machine Screws/Bolts – Used for lighter trays or accessories, typically with nuts and washers for secure fastening .
4. Self-Tapping Screws – Occasionally used for aluminum or thin-gauge trays where pre-drilling is not required .

Material and Corrosion Considerations

• Galvanized Steel Bolts – Common for indoor and outdoor installations; provide corrosion resistance per ASTM A123 or ASTM B633 .
• Stainless Steel Bolts (AISI 304 or 316) – Preferred in corrosive or marine environments for superior resistance to rust and chemical exposure .
• Aluminum Bolts – Used with aluminum trays to prevent galvanic corrosion and reduce weight .

Size and Strength Specifications

• Bolt diameters typically range from M6 to M12 (metric) or 1/4" to 1/2" (imperial), depending on tray width, load, and span .
• Length is selected to accommodate tray thickness, splice plates, and washers.
• Tensile strength should meet or exceed the tray manufacturer's recommendations, often grade 5 or 8 for steel bolts.
• Washers and lock nuts are recommended to prevent loosening due to vibration or thermal expansion .

Standards and Compliance

• IEC 61537 – Provides guidelines for mechanical performance, including bolt selection for load-bearing and deflection limits .
• NEMA VE 1 – Covers metallic cable tray systems and specifies fasteners for structural integrity .
• ASTM Standards – ASTM A123, A653, and B633 define coating, material, and corrosion resistance for bolts and tray components .

Installation Tips

• Ensure bolts are tightened to manufacturer-specified torque to prevent sagging or loosening.
• Use compatible materials to avoid galvanic corrosion (e.g., stainless steel bolts with stainless steel trays).
• For high-vibration environments, consider lock washers or nylon-insert lock nuts.
• Verify that bolt selection meets local electrical codes and safety standards for grounding and bonding if the tray is part of an earthing system .

By following these guidelines, you can ensure that cable tray installations are mechanically secure, corrosion-resistant, and compliant with international and national standards.