UIC Leaflet 642: Fire Protection and Fire-Fighting Measures on Tractive Units

What is UIC Leaflet 642?

UIC Leaflet 642 is a safety-critical standard titled “Fire prevention and fire-fighting measures on tractive units.” In the high-stakes environment of railway operations, Tractive Units (locomotives and power cars) present unique fire risks due to the concentration of high-voltage electrical systems, fuel supplies, and heat-generating mechanical components.

The primary objective of UIC 642 is to create a “passive and active” safety net. It provides guidelines for Infrastructure Management and operators to ensure that if a fire starts, it is contained, detected, and suppressed before it threatens the Operational Safety of the train or the tunnels it traverses.

Passive Fire Protection: Design and Materials

The first line of defense according to UIC 642 is the physical design of the vehicle. This involves rigorous Material Science and structural engineering:

• Fire Barriers: Requirements for fire-resistant bulkheads between the engine room/high-voltage cabinets and the Driver’s Cab. These must provide a specific “fire rating” (e.g., E30 or E60) to allow time for the crew to stop the train safely.
• Non-Combustible Materials: Technical specifications for cables, flooring, and insulation. Materials must have low smoke toxicity and high resistance to ignition.
• Containment: Designing the Underframe and fuel tanks to prevent burning fluids from spreading along the track or dripping into the ballast.

Active Fire Protection: Detection and Suppression

UIC 642 mandates the “active” systems that must be present on modern Rolling Stock:

• Detection Systems: Strategically placed smoke, heat, or flame detectors that provide instant alerts to the driver. In automated systems, these may also trigger a “Power Cut-Off” to the traction motors.
• Fixed Extinguishing Systems: Requirements for automated suppression (such as fine water mist, CO2, or aerosol systems) in high-risk areas like the transformer room or diesel engine compartment.
• Portable Equipment: Standardized placement and types of fire extinguishers accessible to the driver and maintenance staff.

Operational Safety in Tunnels

A major focus of UIC 642 is “Running Capability.” In the event of a fire, the priority is to keep the train moving until it clears a tunnel or reaches a safe evacuation point. The standard defines:

• Redundancy: Critical control cables (for braking and throttle) must be fire-protected to ensure the driver maintains control even if a fire is active in one part of the unit.
• Ventilation Control: Automatic shutdown of fans and air intakes to prevent the “chimney effect” from feeding oxygen to the fire.

Comparison: Fire Protection Categories (UIC 642 vs. EN 45545)