A fire in an underground tunnel can be devastating, but the development of a flexible fire-retardant coating for suspension fittings and anti-vibration components could provide those vital few minutes which delay the release of toxic gases, smoke, flame and heat, allowing the driver to get the train and passengers to a station for evacuation.
Safety in the event of fire is essential in the rail industry, something which became even more important following the King’s Cross Station fire of 1987. In urban areas, however, railway tracks often run below the ground, and there is not enough space for the heat and smoke to rise above the passengers. Furthermore, the risk of rapid spread of fire is increased through convection and radiative feedback.
Most underground transit systems have relatively short distances between stations – on the London Underground, for example, a train is on average no more than four minutes away from a station. Therefore, if there is an onboard fire, train drivers are required wherever possible to drive the train to the nearest station before evacuating. As a result, measures need to be in place to buy time.
The most important elements in minimizing the risk of an underground tunnel fire are limiting the use of combustible materials and, when such materials are essential, treating them with effective fire retardants, explains Trelleborg.
For the past 10 years, and with the help of a SPARK award which is designed to link larger UK companies with universities, engineers at Trelleborg have collaborated with university researchers to develop a new solution – a flexible coating for all primary and secondary suspension fittings and anti-vibration components, called DragonCoat.
A flexible coating for flexible components
A flexible coating designed to be applied to flexible components, DragonCoat is said to be exceptionally durable, fire retardant and, under certain circumstances, self-extinguishing.
Roy Holroyd, Trelleborg’s global market manager rail, explains: “Our solution is a polymer-based fire-retardant coating that can be applied to suspension components. The extreme flexibility and durability of DragonCoat ensures that it maintains its integrity despite constant movement of suspension components. It has a life expectancy that matches that of the suspension component, and it is also highly resistant to environmental factors – rain, snow, heat, cold and the materials used in under-train cleaning. DragonCoat provides those vital few minutes of delay in the release of toxic gases, smoke, flame and heat, allowing a train driver to get the train and passengers to a station for evacuation and also providing a delay that allows firefighters safer access to the source of the fire.”
Bill Mortel, director of advanced technologies for Trelleborg’s industrial antivibration systems, added: “Although many of the natural and rubber components used in primary and secondary suspension components don’t cause fires, they are essentially fuels that will feed a fire. DragonCoat has no effect on the performance of a natural rubber spring; in fact, it enhances a component’s oil resistance. Combined with Trelleborg’s Metacone and Chevron primary suspension springs and the hourglass secondary suspension springs, we can deliver a long-lasting product that makes a real contribution to fire safety on railway systems.”
According to the company, DragonCoat has been approved for an EU patent, and the reaction to its launch at InnoTrans 2012 was very positive from both train operators and builders.