Metal cable tray cable specifications

Metal cable trays are specified by type, material, finish, load rating, rung spacing, and compliance with standards such as NEMA VE 1 and UL 568.

Types of Metal Cable Trays

Metal cable trays come in several configurations to suit different applications:

• Ladder Tray: Features two side rails with transverse rungs; ideal for heavy power cables and long spans. Rung spacing typically ranges from 6 to 12 inches, with radius fittings often at 9 inches at the center of the tray width .
• Wire Mesh (Basket) Tray: Made of high-strength steel wire; suitable for light instrumentation and control cables, offering flexibility and ventilation .
• Channel Tray: Solid or ventilated bottom; used where aesthetics or electromagnetic interference protection is important .
• Solid Bottom Tray: Provides maximum protection against dust, moisture, and heat buildup; often used for sensitive instrumentation .

Materials and Finishes

The choice of material depends on environmental conditions and mechanical requirements:

• Galvanized Steel: Economical, corrosion-resistant; available in pre-galvanized or hot-dip galvanized finishes .
• Stainless Steel (AISI 316L): High corrosion resistance, especially in chlorinated or marine environments; includes molybdenum for enhanced durability .
• Aluminum: Lightweight, corrosion-resistant due to natural oxide layer; suitable for outdoor or humid environments .
• Pultruded Fiberglass (FRP): Offers high resistance-to-weight ratio and corrosion resistance, though less common for heavy power cables .

Mechanical and Electrical Specifications

• Rung Width and Spacing: Minimum cable-bearing surface is typically 7/8 inch with radius edges; spacing varies by tray type and load requirements .
• Load Ratings: Determined by span, material, and tray type; NEMA VE 1 provides load/span class designations .
• Splice Connections: Bolted type using high-strength steel splice plates; resistance of fixed splice connections should not exceed 0.00033 ohm for grounding purposes .
• Bend Radius: Minimum bend radius must be maintained to prevent cable damage, especially for fiber optic or instrumentation cables .

Standards and Compliance

• NEMA VE 1: Specifies manufacturing requirements for metal cable trays, including ladder, channel, solid bottom, and wire mesh types .
• UL 568: Covers construction and testing for continuous metal cable tray systems, ensuring safety and performance .
• NFPA 70 (NEC): Cable trays must comply with Article 392 for installation and grounding .
• CE Marking: Indicates compliance with European directives for mechanical and electrical safety .

Installation Considerations

• Ensure proper support spacing and secure attachment to prevent deflection or sagging.
• Maintain minimum bend radius and avoid overloading to prevent overheating or mechanical stress.
• Use covers or solid bottoms where environmental protection or electromagnetic shielding is required.
• Verify material and finish suitability for corrosive or outdoor environments. Metal cable trays are a versatile solution for routing power, control, and data cables, and proper specification ensures safety, durability, and compliance with electrical codes.