|Railway tunnel fires can be more dangerous to life than road tunnel blazes |
Fire prevention is the single most important issue for railway tunnel fires safety. The potential consequences of fire, both materially and in human life often exceed road tunnels accidents. While the technology and solutions are available to reduce incidences of serious situations, the issue and danger still remains. The question is how we can manage it effectively.
Ali Aleali, of fire detection solutions providers FireVu, looks at the issues.
It is 20 years ago today, as I write this article, that the Channel Tunnel opened.
In the past two decades it has experienced several incidents of fire, three of which were notable and caused substantial damage. The most serious, the 2008 fire, resulted in £60 million worth of repairs being undertaken and 6 month’s disruption to services that cost Eurotunnel an estimated £185m in lost revenue. The 2008 fire does not stand out as a particularly large or destructive fire despite the costs cited.
The Channel Tunnel fires do press the point though that even new state of the art tunnels are not immune from the threat and occurrence of serious fires.
Railway tunnel fires can be more dangerous to life than road tunnel blazes, providing generally less favourable opportunities for escape than road tunnels. The smaller cross section of a railway tunnel leads to a more rapid spread of fire, stronger convective heating and a lower smoke stratification that rapidly affects breathing and visibility.
These factors came into tragic play at the funicular railway at Kaprun in 2000, where 155 passengers lost their lives. The ventilation rapidly pushed through toxic smoke that overwhelmed passengers in a matter of a few minutes.
Improving safety in railway tunnels
There have undoubtedly been improvements in railway fire prevention measures and action in the past decade.
Passenger trains are generally less combustible, with lower heat release rates from passenger rolling stock specifications. In the 7/7 bombings on London Underground the trains smoulded rather than burned and the loss of life was not due or exacerbated by flammable materials in the carriages.
|Passive fire prevention can minimise fire damage to infrastructure|
Goods trains have also benefited from measures to reduce incidences of fire such as the compartmentalisation of wagons, the control of combustible material and fixed fire suppression. And the implementation of regular fire drill test procedures has improved fire safety levels for both goods and passenger trains.
However, the very nature of tunnel fires and the loads being carried ensures that the issue will never be eliminated and we cannot be complacent.
Passive fire prevention can minimise fire damage to infrastructure, with options ranging across micro mono-filament polypropylene fibres added to the concrete mix of wall linings, fire resistant panels and cementitious coatings.
There is a range of active fire suppression solutions available such as sprinklers, standpipes and hydrants, water curtains and water mist that can be combined to passive fire prevention measures.
Underpinning the active suppression is fire detection technology, with solutions such as video smoke detection triggering the key systems.
Legislation and railway tunnels
In April 2014, EU Directive 2004/54/EC came into effect for road tunnels for all 28 EU member states, an area with a population of over 500 million that generates 20% of global wealth.
In terms of fire detection monitoring, the new directive means systems need to be implemented for tunnels over 500m long, with video detection systems being mandatory for tunnels longer than 3,000m.
The same uniform regulations do not exist for rail tunnels despite the dangers outlined above.
The NFPA 130 does not cover the issues of fire safety in tunnels. The EU’s technical standard “Safety in Railway Tunnels” is a framework standard rather than a specification.
Research and the identification of suitable regulations continue to be pursued by The International Tunnelling Association’s Committee on Operational Safety of Underground Facilities.
Global or indeed European wide railway tunnel safety regulations are not shared.
It all boils down to a need for a co-ordinated approach, as shown for road tunnels, for railways.
Railway fires, thankfully, are not everyday events. Yet, there impact on life and property can be immense and therefore measures have to be considered against the potential affects of a fire. Isn’t it time that fire detection and prevention for railway tunnels is not one of chance?