What size should the cable tray bolts be

Cable trays typically use M8 high-tensile bolts with nuts and washers, with 8 hardware sets per joint for standard GI or perforated trays.

Bolt Types and Sizes

For standard perforated or GI cable trays, the following specifications are commonly used:

• Bolt Size: M8 (metric 8 mm diameter) high-tensile bolts .
• Length: Minimum 75 mm for wall-mounted supports; length may vary depending on tray thickness and support structure .
• Hardware Sets: Each joint between two cable tray sections typically uses 8 sets of bolts, nuts, and washers when using coupler plates .
• Nut Type: Serrated flange locknuts are recommended for splice connections to prevent loosening .
• Washers: Flat washers are used to distribute load and protect the tray surface. High-strength washers are preferred for structural integrity .

Splice and Coupler Plates

• Splice Plates: Made of high-strength steel, meeting ASTM A1011 HSLAS, Grade 50, Class 1 .
• Bolt Arrangement: 8 bolts per splice plate for standard straight sections; wedge lock 4-bolt or 2-bolt KwikRail connections are UL-classified as equipment ground conductors .
• Rung Spacing: Straight sections typically have rungs spaced 6, 9, or 12 inches apart; radius fittings use 9-inch spacing at the center .

Installation Notes

• Wall-Mounted Supports: MS angles (50 x 50 mm, 6 mm thick) are fastened with M8 bolts at ~1-meter intervals .
• Bridge Supports: MS C-channels (150 x 75 mm, 5.7 mm thick) welded to angles use high-tensile bolts for tray attachment .
• Insulation: G-10 or FRP sheets may be used at supports to isolate the tray from metal structures, with M8 bolts securing the insulation .
• Material Considerations: Bolts and hardware should match the tray material (galvanized steel, stainless steel, or aluminum) to prevent galvanic corrosion .

Summary Table

These specifications ensure mechanical stability, electrical continuity, and compliance with UL/NEMA standards for cable tray installations . Proper selection of bolt type, length, and material is critical for safe and durable cable management systems.