Material Selection Guide for Cable Tray, Metallic Tray Systems

This article is about Material Selection Guide for Cable Tray, Metallic Tray Systems for commercial buildings, plants and refinery projects as per international codes and standards.

Cable Tray General Requirements

Electrical materials shall be new and unused.

Electrical materials shall be in accordance with the Saudi Aramco-approved project-specific design drawings, diagrams, schedules, lists, databases, and associated documents.

Electrical materials shall be free of damage.

Electrical materials shall conform to all applicable requirements, standards, and specifications prior to release to be used as part of the work.

Electrical materials shall be identified by using tags, stamps, color coding, stencils or labels. The location and method of identification shall not affect the function or quality of the materials.

Electrical materials shall be traceable from the manufacturer and supplier through delivery, storage, fabrication, erection, installation, repair, modification and use.

Cable Tray Technical Specification and Requirements

Cable tray material shall be: a) copper-free aluminum (aluminum with a maximum of 0.4% copper) b) ladder type (two side-rail)

Aluminum cable tray shall: a) be designed, manufactured, rated, and tested in accordance with NEMA VE-1 b) tested to method A (Loading to Destruction) for determining the rated load capacity c) have minimum individual rung load capacity of 90 kg d) have manufacturer test report at cable tray material receiving area e) have flanged covers of minimum thickness of 1 mm

The manufacturer shall provide with each shipment of cable tray, product information that shall include the following:
(a) Table or chart clearly indicating the maximum rated simple beam loading in kilograms/linear meter and/or pounds/linear foot, and the maximum recommended distance in meters and/or feet between supports for each loading;
(b) Information on the alloys of aluminum or stainless steel
(NEC 110.3, NEMA VE-1 Sec.6.2)

            Dimensions of Ladder-type Trays

Cable tray shall conform to the following standard dimensions:

1. Lengths of Straight Sections
   a) 3m +/- 5mm
   b) 3.66m +/- 5mm
   c) 6m +/- 9mm
   d) 7.32m +/- 9mm
2. Widths -150, 225, 300, 450, 600, 750 and 900mm +/- 6mm.
   Overall widths shall not exceed inside widths by more than 100mm
3. Inside depths – 75, 100, 125 and 150mm +/- 10mm
4. Rung Spacing on Straight Sections -150, 225 and 300mm on centers
5. Fitting Radii – 300, 600 and 900mm
6. Degrees of arc for elbow – 30, 45, 60 and 90 degrees
   (NEC 110.3, NEMA VE-1 Sec.4.3)

Table 1
Load/Span Class Designations
Cable tray shall conform to the following class designations:

Dimensions and measurements marked on the product shall include SI units. Each straight section of cable tray and each fitting shall be marked in a permanent and readily visible manner with the following:
(a) the manufacturer’s name, trademark, or other recognized symbol of identification
(b) the word “Ventilated” or “Nonventilated,” as applicable
(c) the rated load/span as tested in accordance with Clause 5.2.
(d) type of material, such as stainless steel (including the type) or aluminum; as applicable
(e) cable tray sections and fittings shall be marked to show the minimum cross-sectional area in accordance with the NEC
(f) warning label that reads, “WARNING! DO NOT USE AS A WALKWAY, LADDER, OR SUPPORT FOR PERSONNEL. USE ONLY AS A MECHANICAL SUPPORT FOR CABLES, TUBING, AND RACEWAYS.”
(NEC 110.3, NEMA VE-1 Sec.6.1)

Cable tray systems shall not be subjected to physical damage. Cable tray shall be free from burrs or other sharp projections that could cause damage to the cable jacket during installation.  [NEC 392.4, 392.5 (B)]

Fasteners used for connection and assembly of a cable tray system shall be supplied according to the manufacturer’s instructions. Carbon steel fasteners shall be protected against corrosion by zinc electroplating in accordance with ASTM B 633. (NEC 110.3, NEMA VE-1 Sec.4.2.3 & 4.6)

Cable tray system shall be supplied with manufacturers standard fittings, clamps, hangers, brackets, splice plates, reducer plates, blind ends, connectors, and grounding straps.

All fasteners (i.e., nuts, bolts, washers, etc.) used to connect and assemble the cable tray system shall be 304 SS. In severe corrosive environments, 316 SS fasteners shall be used.

International Codes & Standards

1. NFPA 70 – National Electrical Code (NEC), 2008 Edition

2. SAES-P-104 – Wiring Methods and Materials, 13 January 2008

3. SAES-P-101- Regulated Vendors List for Electrical Equipment, 9 June 2007

4. NEMA VE1-2002 – National Electrical Manufacturers Association, Metal Cable Tray Systems