How to calculate the cable tray hanger rod

Cable tray support hanger rods are calculated by determining the total load on the tray, dividing it among the number of supports, and selecting rod size based on material strength and safety factors.

Step 1: Determine Cable Tray Load

Calculate the total weight of the cable tray system, including:

• Cable tray weight (based on type and material)
• Cables weight (sum of all cables laid on the tray)
• Additional components (angles, fittings, junction boxes) For example, a 1.5 m cable tray with 17 cables weighing 25.7 kg and GI angles weighing 5.8 kg results in a total load of 51.1 kg .

Step 2: Decide Support Spacing

Support spacing depends on tray type, load, and installation standards. Typical spacing ranges from 1.5 to 3 meters for straight trays . Use the formula to calculate the number of supports: Support Quantity = Total Tray Length ÷ Support Spacing + 1 For a 20 m tray with 2 m spacing: Support Quantity = 20 ÷ 2 + 1 = 11 supports .

Step 3: Calculate Load per Rod

Divide the total load by the number of hanger rods supporting the tray. For example, if 4 rods support a 51.1 kg load: Load per rod = Total Load ÷ Number of Rods = 51.1 ÷ 4 = 12.775 kg per rod . Convert kilograms to Newtons for structural calculations: Force (N) = Mass (kg) × 9.81 m/s² 12.775 kg × 9.81 ≈ 125.4 N per rod.

Step 4: Select Rod Diameter

Choose a rod diameter based on material yield strength and calculated load. For steel rods, check the manufacturer's technical data sheet for yield strength (e.g., 8 mm rod with 475.63 N/mm²). Ensure the rod can safely carry the load with a safety factor (commonly 1.5 to 2) applied . Example:

• Load per rod: 125.4 N
• Safety factor: 1.5 → Required capacity = 125.4 × 1.5 ≈ 188.1 N
• Compare with rod tensile capacity to confirm suitability.

Step 5: Consider Standards and Installation

Follow relevant standards such as NEMA VE-1, IEC 61537, BS EN 61537, and local building codes . Include considerations for:

• Concentrated loads (e.g., maintenance personnel)
• Environmental factors (wind, vibration, corrosion)
• Proper mounting and alignment of rods and brackets

Step 6: Verify and Document

• Check calculations for each tray section, including elbows and tees
• Document rod size, spacing, and load calculations for client approval
• Use software tools if available for large-scale projects to improve accuracy . By following these steps, you can ensure that cable tray support hanger rods are correctly sized and spaced, providing safe and reliable support for the cable system.