Specifications of cable trays for engineering use

Engineering cable trays are standardized systems designed to support and route electrical cables, available in various types, materials, and finishes, and must comply with industry standards such as NFPA 70, NEMA VE, and ASTM specifications.

Types of Cable Trays

Cable trays are available in multiple configurations to suit different installation needs: Ladder Type: Features side rails with rungs for cable support, ideal for heavy-duty applications and long spans. Trough Type: Solid or ventilated bottom for medium-duty applications, providing partial protection to cables. Solid Bottom Type: Fully enclosed for maximum protection against dust, moisture, or mechanical damage.

Channel Type: U-shaped trays for smaller cable runs or specific routing requirements.

Wire Mesh/

Basket Type: Lightweight, flexible trays made from welded steel wire, suitable for light-duty and complex routing.

Materials and Finishes

Cable trays are manufactured from materials selected for mechanical strength, corrosion resistance, and environmental suitability: Galvanized Steel: Hot-dip or pre-galvanized for corrosion protection. Stainless Steel: Typically AISI 316L, offering high corrosion resistance, especially in chemical or marine environments. Aluminum: Lightweight with excellent corrosion resistance due to natural oxide layer, suitable for outdoor or humid environments.

Fiberglass Reinforced Plastic (FRP): Pultruded trays with high resistance-to-weight ratio and chemical resistance.

Standards and Compliance

Cable trays must comply with recognized standards to ensure safety and performance: NFPA 70 (National Electrical Code): Governs installation and grounding requirements.

NEMA V

E 1 & VE 2: Define metallic cable tray systems and installation guidelines.

AST

M Standards: Include A123, A653, A1011, A1008, and B633 for steel and zinc coatings.

U

L Listing: UL CCN CYNW for ladder cable trays, ensuring suitability as equipment grounding conductors.

C

E and RoHS Compliance: For European installations, ensuring safety, environmental, and chemical restrictions.

Dimensions and Load Ratings

Rung Spacing and Inside Depths: Vary by tray type and manufacturer; typically specified in product datasheets. Fitting Radii: Bends, elbows, and tees are designed to maintain cable integrity during routing. Load Capacity: Determined by tray material, span, and duty rating (light, medium, heavy), with manufacturer-provided safe working loads.

Accessories and Installation

Cable tray systems include a range of accessories for proper installation: Supports: Hanger rods, brackets, and clamps. Fittings: Tees, elbows, drop-outs, and expansion joints. Grounding and Bonding: Ensures electrical continuity and safety in accordance with NFPA 70.

Submittals: Shop drawings, product datasheets, and field quality-control reports are required for approval before installation.

Environmental and Safety Considerations

Corrosion Resistance: Material selection depends on exposure to moisture, chemicals, or outdoor conditions. Fire Resistance: Some trays are rated for fire performance, particularly in industrial or commercial buildings. Electromagnetic Performance: Metallic trays may provide shielding for sensitive data or power cables.

Engineering cable trays are thus a versatile, standardized solution for cable management, with specifications tailored to mechanical, electrical, and environmental requirements, ensuring safe and efficient routing of electrical systems.