Calculation of pipe well cable tray supports

Cable tray support in a pipe well is calculated by determining the tray type, measuring the tray length, evaluating cable load, and applying support spacing formulas according to standards.

Step 1: Identify Cable Tray Type and Specifications

Determine the type of cable tray (ladder, perforated, wire mesh, or channel), its dimensions, and material. These factors influence the load capacity and the recommended support spacing . For example, wire mesh trays typically have shorter allowable spans than ladder trays due to lower rigidity.

Step 2: Measure Tray Length and Layout

Measure the total length of the cable tray within the pipe well, including straight sections, bends, tees, and vertical changes. Each section should be considered separately for support placement .

Step 3: Determine Support Spacing

Support spacing depends on the tray type, cable load, and installation standards. Typical spacing ranges from 1.5 to 3 meters for straight runs, with closer spacing required for heavier loads or bends . Supports should also be placed within 610 mm (24 in.) of splices and at every change in direction or elevation .

Step 4: Calculate Support Quantity

Use the formula: Support Quantity = (Total Tray Length ÷ Support Spacing) + 1 For example, a 20-meter tray with 2-meter spacing requires: 20 ÷ 2 + 1 = 11 supports .

Step 5: Calculate Load on Each Support

Determine the cable load per foot or meter using the cable specifications and tray fill ratio. For example, if a tray carries 49 cables at 20 lb/1000 ft, the load per foot is 0.98 lb/ft. Then calculate the weight on each support: Weight of span = Load/foot × Span length Weight on support = Weight of span ÷ 2 . This ensures that each support can safely carry the load between adjacent supports.

Step 6: Consider Environmental and Safety Factors

Cable trays in pipe wells may be exposed to moisture, vibration, or other mechanical forces. Use corrosion-resistant materials and follow standards such as IEC 61537 and NEC Article 392 for installation, ensuring supports are rated for the expected load and environmental conditions .

Step 7: Adjust for Bends and Vertical Changes

Additional supports are required at bends, tees, and vertical transitions to prevent sagging and maintain stability. Each section should be evaluated individually for load and spacing . By following these steps, you can calculate the number of supports, their placement, and the load each support must carry, ensuring a safe and compliant cable tray installation in a pipe well.