What are the fire-resistant and flame-retardant materials used in cable trays

Fire-resistant cables maintain circuit integrity during a fire, while flame-retardant cables prevent fire spread along the cable path.

Key Differences

Flame-retardant cables are designed to limit the propagation of fire along the cable, reducing the risk of secondary fires and toxic smoke emissions. They are typically made with materials such as PVC or LSZH (Low Smoke Zero Halogen), which slow down flame spread and minimize smoke and corrosive gas production, improving visibility and safety during evacuation . These cables are suitable for general safety in public buildings, offices, and commercial centers, but they do not guarantee continued electrical operation once exposed to high temperatures . Fire-resistant cables, on the other hand, are engineered to remain operational during a fire, maintaining circuit integrity for a defined period (commonly up to 120 minutes). They use specialized insulation materials such as mica tape, cross-linked polyethylene (XLPE), ceramic composites, or glass fiber insulation. These materials can withstand extreme temperatures (up to 950–1000°C) without losing dielectric properties, ensuring that critical systems like fire alarms, emergency lighting, sprinkler controls, and public address systems continue functioning .

Common Materials

• PVC (Polyvinyl Chloride): Flame-retardant, widely used, but releases toxic gases like hydrogen chloride when burned .
• LSZH (Low Smoke Zero Halogen): Reduces smoke and toxic gas emissions, suitable for public spaces and critical infrastructure .
• XLPE (Cross-Linked Polyethylene): Provides thermal stability and flame resistance, often combined with LSZH or PVC jackets .
• Mica Tape: Mineral-based insulation used in fire-resistant cables to maintain circuit integrity under high heat .
• Ceramic or Glass Fiber Composites: Used in high-performance fire-resistant cables for extreme temperature endurance .

Applications in Cable Trays

• Flame-retardant cables are ideal for general cable tray installations where fire containment is the priority.
• Fire-resistant cables are essential in critical systems such as hospitals, tunnels, airports, data centers, and high-rise buildings, where maintaining power and communication during a fire is crucial .

Standards and Testing

Cables are tested and rated according to international standards to ensure performance:

• IEC 60332 / BS EN 60332: Flame propagation tests for single and bundled cables.
• BS EN 50200 / BS 6387: Fire resistance tests including flame, water, and impact exposure.
• IEC 60754 / IEC 61034: Evaluates acid gas emission and smoke density.
• NFPA 262 / CSA FT-6: Flame spread and smoke emission standards for flame-retardant cables .

Conclusion

For cable trays, select flame-retardant cables to prevent fire spread and reduce smoke hazards in general installations. Use fire-resistant cables when circuit integrity is critical during a fire, ensuring that emergency systems remain operational. Materials like LSZH, XLPE, mica tape, and ceramic composites provide the necessary performance, while compliance with international standards ensures safety and reliability.