Fire resistance performance of fire-resistant cable trays

Fire-resistant cable trays are rated based on the duration they maintain circuit integrity under fire, commonly EI60, EI90, or EI120, with testing often following DIN 4102-12 or similar standards.

Understanding Fire Resistance Ratings

Fire-resistant cable trays are designed to maintain the functionality of electrical circuits during a fire, ensuring critical systems like emergency lighting, alarms, and smoke extractors continue to operate. The ratings indicate the duration in minutes that the tray system can withstand fire while preserving circuit integrity:

• EI60: Maintains integrity for 60 minutes; suitable for moderate-risk or secondary systems.
• EI90: Maintains integrity for 90 minutes; commonly used in industrial and infrastructure projects.
• EI120: Maintains integrity for 120 minutes; used for high-criticality systems or areas requiring extended operational continuity .

Standards and Testing

Due to the absence of a unified European standard for cable tray fire resistance, manufacturers often rely on DIN 4102-12, a German standard that tests the entire cable tray system, including cables, supports, and accessories, in a fire exposure oven. The test typically involves:

• Exposing the tray system to temperatures up to 1000°C.
• Testing durations of 30, 60, and 90 minutes to simulate different fire scenarios.
• Evaluating circuit integrity, heat transfer, and insulation performance . Other standards or local regulations may also be applied depending on the country, such as Czech or Slovak fire safety requirements .

Practical Considerations

• System-specific: Fire resistance applies to the tested assembly; “like-for-like” installation is critical.
• Cable compatibility: The tray rating depends on the type of cables installed (e.g., FP400, FP600, Firetuf).
• Installation: Accessories like fire-rated cable cleats can help preserve integrity during fire exposure .
• Risk-based selection: Higher EI ratings increase material thickness, detailing complexity, and cost, so selection should match project risk and operational requirements . In summary, fire-resistant cable trays are rated by the duration they maintain circuit integrity under fire, with EI60, EI90, and EI120 being common targets. Testing is typically conducted according to DIN 4102-12, ensuring that the tray system, cables, and supports can withstand high temperatures for the specified period, supporting safe shutdown and emergency operations.