Improved vehicle protection will boost tunnel safety
Published: 11 January, 2010
With all the attention focused on tunnel fire prevention and firefighting, it is easy to lose sight of the fact that if fewer vehicles caught fire, the problem would be greatly diminished. Nick Grant, EMEA Vice President and General Manager of Firetrace International, explains.
Without in any way suggesting that there should be an easing of the efforts to make road tunnels safer, the statics and casualty figures could be drastically improved if, at the same time, vehicles using tunnels – particularly heavy goods and passenger-carrying vehicles – had more effective fire protection.
While not all tunnel fires start with a vehicle fire, a significant number do. Take, for instance, the Mont Blanc tunnel fire a decade ago that resulted in death of 39 people. The inferno started with smoke seen coming out of the cab of a truck pulling a trailer containing margarine. Once the fire had spread to engulf the high-fuel-load of the margarine, the die was cast. But, what if the fire had been extinguished before it had the opportunity to spread? Instead of making worldwide headlines, the fire would have generated hardly a ripple of interest.
According to the findings of an NFIRS [National Fire Incident Reporting System] / NFPA research study, mechanical and electrical failures or malfunctions account for 75 percent of fires in on-highway vehicles. In 60 percent of the cases, the most common location for the outbreak of a fire is in or around the engine compartment, the running gear or wheel areas. So, on the reasonable basis that the tunnel environment does not make a vehicle inherently more or less susceptible to fire, improving the fire protection of engine and generator compartments can only improve tunnel fire safety.
Of course, protecting an engine compartment is a specialist task with a number of critical factors that, in the past, have seen many solutions fall short of reliable. The first consideration is the nature of these fires. In addition to the vehicle’s fuel and the risk of fuel-line ruptures, there are any number of flammable liquids present throughout an engine compartment, such as hydraulic, brake, transmission and power-steering fluids, plus combustible accumulated grease on the engine block, for which frayed or damaged electrical wiring can easily provide the ignition source.
The second consideration is airflow in and around an engine compartment when a vehicle is in motion. This can seriously impair the performance and reliability of traditional detection and suppression techniques because heat and flame typically rise from the source of a fire and may be propelled away from the sensing device, delaying its activation. Indeed, leaving an engine compartment fire unchecked while the vehicle is travelling at speed provides the fire with additional oxygen. This has the potential to accelerate its spread to engulf the driver’s cab and the goods being transported, as happened in the catastrophic Mont Blanc tunnel fire.
To overcome these challenges it is essential for the solution to be automatic, fast acting and self-seeking. It also needs to be immune to vibration and shocks. Firetrace, for example, is a UL listed, FM approved and CE marked tube-based system that comprises an extinguishing agent cylinder that is attached to proprietary Firetrace Detection Tubing via a custom-engineered valve. This polymer tubing is a linear pneumatic heat and flame detector that was specially developed to deliver the desired temperature-sensitive detection and delivery characteristics.
This leak-resistant tubing is routed throughout the engine or generator compartment. Immediately a fire is detected the tubing ruptures and automatically releases the suppression agent, extinguishing the fire precisely where it starts and before it can take hold. The tubing is placed both above and behind the potential source of fire to ensure that the airflow actually helps in the direction of the heat and flames.
