Cable tray manufacturer s span standard

Cable tray support spans vary by tray type, load, and material, typically ranging from 6 to 20 feet for standard installations, with extra-long spans exceeding 20 feet.

Standard Span Classifications

Cable tray spans are generally classified based on the distance between supports:

• Short Span: Typically supported every 6 to 8 feet, used for non-industrial indoor installations .
• Intermediate Span: Supported every 10 to 12 feet, suitable for moderate loads and indoor applications .
• Long Span: Supported every 14 to 20 feet, often used in industrial or commercial settings where fewer supports are desired .
• Extra-Long Span: Exceeds 20 feet, commonly used outdoors to cross roads or reduce the number of expensive supports .

Factors Affecting Span

1. Tray Type and Material: Ladder, ventilated, solid-bottom, and wire mesh trays have different load capacities. Materials like aluminum, steel, or fiberglass influence allowable spans .
2. Load Class: Defined by NEMA or CSA standards, the load class (e.g., NEMA 12A, 12B, CSA C-3m, D-3m) determines the maximum support spacing for a given cable weight .
3. Environmental Conditions: Outdoor installations may require shorter spans due to wind, snow, or ice loads .
4. Tray Length and Splice Plates: The support span should not exceed the tray length, and typically only one splice plate is used per span to maintain structural integrity .

Standard Lengths and Installation Guidelines

• Standard straight tray sections are commonly 3 m, 6 m, 9.1 m, and 12.2 m, with some manufacturers offering lengths up to 40 feet .
• Support spacing is measured from the inside of one side rail to the inside of the opposite side rail .
• Proper selection of span ensures safe load distribution, minimizes deflection, and complies with NEC and CEC rules .

References to Standards

• NEMA VE 1: Specifies manufacturing requirements and load/span class designations for metal cable trays .
• UL 568: Covers performance requirements for fiberglass cable trays .
• CSA C22.2 No. 126.1: Harmonized with NEMA VE 1 for Canadian installations .
• IEC 61537: International standard for cable tray systems, including load and span requirements . By following these span standards and considering tray type, load, and environmental factors, engineers and installers can ensure safe, code-compliant cable tray installations.