Fire protection requirements for cable trays in Nepal

Cable trays in Nepal must be installed and fire-protected according to Nepal Standards (NS) and best practices, including proper firestopping, material selection, and layout to ensure safety and maintain functionality during a fire.

Regulatory Framework

In Nepal, electrical installations, including cable trays, are guided by Nepal Standards (NS) such as NS 29 for electrical systems, which outline safety, insulation, and installation requirements . While specific fire protection clauses for cable trays may not be detailed, compliance with NS ensures adherence to national safety norms. International standards and best practices are often referenced to supplement local regulations.

Firestopping and Penetration Protection

Cable trays passing through walls, floors, or slabs must be properly firestopped to prevent fire and smoke propagation . Key requirements include:

• Sealing Openings: All gaps around cable trays, busways, or trunking must be tightly sealed with fire-resistant materials such as fire-rated boards, firestop packs, firestop mastic, or mineral wool .
• Large Openings: Install a fire-resistant backing plate before sealing to ensure structural integrity.
• Gap Limits: The area between firestop packs and cables should not exceed 1 cm², and packing thickness should be at least 24 cm .
• Slab Penetrations: Provide 20–30 mm of firestopping at slab penetrations and install a fire-support plate at the top. Waterstops of at least 50 mm height are recommended at floor-level penetrations .
• Cover Plates: Use square, evenly painted cover plates to close openings, ensuring complete internal and external sealing.

Cable Tray Material and Installation

Fire protection also depends on tray material and installation quality :

• Material Selection: Indoor trays typically use painted steel or galvanized steel; outdoor or corrosive environments may require stainless steel, aluminum alloy, or fiberglass-reinforced plastic.
• Mechanical Strength: Trays must support the full cable load without deformation.
• Installation Accuracy: Horizontal deviation ≤2 mm/m, vertical deviation ≤3 mm/m; trays must be level, plumb, and securely mounted.
• Segregation: Power and signal cables should be separated to reduce interference and fire risk.
• Cable Arrangement: Cables should be laid neatly, parallel, and secured with ties or clips to prevent movement and damage.

Fire-Resistant Coatings and Tapes

Additional protection can be provided using fire-resistant coatings or tapes such as FLAMMOTECT-A or DG-CR 0.7, which:

• Prevent flame propagation along cable runs.
• Maintain cable functionality during a fire.
• Protect against environmental factors like moisture, UV, and chemicals .

Summary

To comply with fire protection requirements for cable trays in Nepal:

1. Follow Nepal Standards (NS) for electrical installations.
2. Ensure proper firestopping at wall, floor, and slab penetrations.
3. Select appropriate tray materials for the environment.
4. Maintain accurate installation and cable arrangement.
5. Consider fire-resistant coatings or tapes for enhanced protection. These measures collectively ensure safety, reliability, and continuity of electrical systems during fire events.