ISO 13857 Industrial Cable Tray Corrosion Resistant for Electric Power Projects

1. Functional Role of Industrial Cable Trays in Electric Power Projects:
BENDIN Industrial cable trays serve as the structural backbone for cable routing in electric power projects, performing several critical functions that directly affect system reliability, safety, and maintainability.

Mechanical support and load distribution. Cable trays carry the static and dynamic loads of power cables, control cables, and instrumentation cables across long horizontal and vertical runs. In power generating stations, trays must be designed to support both uniformly distributed cable loads and concentrated loads at support points. Typical specifications require a minimum uniformly distributed load capacity of 75 kg per metre run, with a concentrated load of 75 kg between supports. The tray structure—including side rails, rungs, and splice plates—must maintain structural integrity under these loads without excessive deflection.

Cable segregation and grouping. Power projects involve cables of multiple voltage classes and functions: high-voltage power cables, low-voltage control cables, and sensitive instrumentation cables. Cable trays enable physical segregation of these cable groups, which is essential for electromagnetic compatibility and fault isolation. Clause 6.4.3 of IEC 61537 requires that cable trays be installed so that cables of different voltage classes are properly separated. In practice, power cables are typically placed on upper trays while control and instrumentation cables occupy lower trays.

Heat dissipation and ventilation. Ladder-type cable trays, the most common configuration in power plants, provide open ventilation that prevents heat buildup from cable conductors. This is particularly important in high-current power circuits where conductor resistance generates significant heat. The open rung design allows convective airflow that extends cable insulation life and maintains ampacity ratings. Solid-bottom trays, while offering greater protection, limit airflow and may require cable ampacity derating when covers are used.

Grounding and fault current paths. Metallic cable trays in power projects serve as equipment grounding conductors when properly bonded and listed for that purpose. Cable tray systems must be bonded back to the power source, with both side rails of the tray bonded together at each section. For trays carrying cables above 240 V, the NRC requires grounding through a minimum of #2/0 AWG bare copper conductor routed with each tray, with every tray section bonded to this conductor. This grounding function is not merely a code formality—it provides a low-impedance fault current path essential for protective device coordination.

Routing flexibility and system expandability. Cable trays accommodate changes in cable routing direction through fittings such as horizontal bends, tees, crosses, and vertical risers. This modularity allows power project designers to plan cable routes that avoid structural obstacles while maintaining required bending radii for power cables. The tray system can also be expanded in future project phases by adding tray tiers or extending runs without disrupting existing cable installations.

2. Certification Requirements and Specifications by Region and Scenario
2.1 Global Certification Requirements for Cable Trays in Power Engineering
The following table summarizes the principal cable tray certification standards applicable to electric power projects across major global regions.

2.2 BENDIN Cable Tray Specifications in Power Systems
The following table presents the commonly specified dimensions, load classes, and material configurations for cable trays in electric power projects.

3. Key Considerations for BENDIN Cable Tray Selection and Installation in Power Projects:
3.1 BENDIN Tray Type Selection by Application Scenario
The choice of BENDIN tray type must match the specific environmental and functional requirements of each power plant area.

Ladder-type trays are the standard selection for outdoor areas, cable trenches, and high-heat zones in power stations. The open rung design provides superior ventilation, which is critical for maintaining ampacity of high-current power cables. Ladder trays are commonly installed in boiler areas, turbine halls, and switchyard cable routes. In nuclear power generating stations, ladder-type trays are predominantly used for both safety-related and non-safety-related cable routing.

Perforated trays offer a balance between ventilation and cable protection. The perforated bottom provides some mechanical protection while allowing heat dissipation and drainage. These are suitable for indoor cable galleries and control building areas where moderate protection is needed.

Solid-bottom trays with covers should be specified where electromagnetic interference shielding is required for sensitive instrumentation circuits, or where the environment contains conductive dust or corrosive vapours. However, solid-bottom configurations trap moisture and heat, so they are generally avoided in high-power cable routes unless specific protection requirements justify their use. When covers are used, cable ampacity derating must be applied according to NEC or IEC calculation methods.

Fiberglass (FRP) trays are appropriate for highly corrosive environments such as coastal power plants or chemical plants, where metallic trays would require excessive maintenance. These must comply with UL 568 or equivalent nonmetallic tray standards

3.3 Structural and Load Considerations
Support spacing is the single most important structural parameter. Horizontal runs in power stations are typically supported at 1.5 m intervals, with some specifications permitting up to 2.0 m for channel-type supports. Vertical risers require closer support at 1.0 m intervals to prevent buckling and to secure cables against gravity. Cantilever arms for multi-tier installations should have a minimum vertical spacing of 300 mm to allow cable laying access and heat dissipation.

Load calculation must account for the cable weight, the tray self-weight, and any concentrated loads such as cable pull tension during installation. For power projects, the cable load should be calculated based on the actual cable schedule, not estimated. The NEMA VE 1 testing protocol requires a safety factor of 1.5 plus a 200 lb (91 kg) concentrated load applied at mid-span, which provides a defined margin of safety.

Spacing between trays in multi-tier arrangements should normally be maintained at 300 mm minimum for cable laying convenience and effective heat dissipation. In nuclear plants, where redundant train separation is critical, vertical separation between redundant tray groups may be specified at 1 ft minimum, with solid barriers required for closer spacing.

3.4 Grounding, Bonding, and Electrical Safety
Cable tray grounding in power projects is not optional—it is a fundamental safety requirement. Each continuous run of cable tray should be earthed at a minimum of two places, with the distance between earthing points not exceeding 30 m. A continuous ground conductor (typically 50×6 mm galvanized steel flat) should run along the entire length of each cable tray route, clamped to the tray at periodic intervals.

At splice joints, both side rails of the tray must be bonded together to maintain electrical continuity across the entire tray system. Bonding jumpers must be sized at minimum to meet the requirements for equipment grounding conductors. For trays carrying cables above 240 V, a #2/0 AWG bare copper conductor routed with each tray provides the primary grounding path, with each tray section bonded to this conductor.

The grounding integrity should be verified by resistance measurement from the ground wire at the end of each tray run to the station grounding grid, with recorded values confirming a low-impedance path suitable for fault current clearing.

3.5 Environmental and Corrosion Protection
Power plant environments vary dramatically in corrosivity. Outdoor switchyards, cooling tower areas, and coastal sites require hot-dip galvanized trays with coating thickness of 60–100 μm after fabrication. The HDG finish should comply with ASTM A123 or ISO 1461, with the coating applied after all cutting and fabrication to ensure complete edge coverage.

Indoor cable galleries and control buildings may use pre-galvanized steel (Z275 or G90 coating) as a cost-effective alternative where humidity is controlled. However, areas subject to washdown, chemical exposure, or high humidity should still specify HDG finish regardless of indoor location.

Stainless steel trays (typically 304 or 316 grade) are specified for the most aggressive environments, such as flue gas desulphurization areas or chemical storage zones. The higher material cost is justified by reduced maintenance and extended service life in these applications.

3.6 Installation Coordination and Practical Considerations
Cable pulling in trays should be performed using rollers to minimize stretching and insulation damage. Cables should be laid in an organized manner, with power cables separated from control and instrumentation cables. In horizontal tray runs, multicore power cables should be secured at intervals not exceeding 5 m; in vertical runs, securing at 1 m intervals is required.

Expansion joints must be provided at structural building joints and at intervals where thermal expansion of the tray could exceed the splice plate capacity. The tray system must accommodate the thermal expansion coefficient of the tray material over the temperature range expected in the installation environment.

Future capacity should be considered during tray sizing. A spare capacity of 25–30% above the initial cable fill is a common design practice in power projects, allowing for future cable additions without requiring tray replacement or parallel runs. This is particularly important for trays serving control systems that may be expanded during plant life extension projects.