Getting fire testing standards right
Source: RTM Feb/Mar 17
Richard Nowell, rolling stock engineer at the RSSB, discusses the ‘EN 45545-2 Fire testing of materials and components for trains’, and how a new seat fire test standard has been drafted.
Fires on-board trains are thankfully rare, but a big part of that is down to the fact that the rail industry spends time and effort to reduce the risk.
The frequency of train fires is about a quarter of that seen 10 years ago, and the Safety Risk Model shows the risk at 0.03 fatalities and weighted injuries (FWI) per billion passenger journeys – that’s a pretty small risk.
Indeed, the risk from train fires has been even lower in recent years, largely due to the increased use of fire-resistant materials, so getting these materials right is paramount to improved safety. But fires can happen, and in the rare instance that one does break out, you don’t want it to spread.
The correct materials are particularly important for passenger seats. A carriage can have up to 80 seats or more, so the potential fire load could be considerable. To be soft, comfortable and stylish, seats could theoretically use a whole range of materials but these are fairly flammable and can give out large amounts of smoke and toxic fumes. For railway seats the materials used are carefully selected to control flame spread, heat release, smoke and toxic fumes within safe limits.
Requirements for this are set out in a European standard, ‘EN 45545-2 Fire testing of materials and components for trains’, which was published in 2013 and will soon be compulsory across Europe. Agreeing a standard of this sort is not easy; the work started over 25 years ago!
A common standard greatly simplifies procurement in the rolling stock supply chain, maximises product choice and eliminates unnecessary costs. In setting these harmonised requirements, it is important to ensure the right level of safety for people on-board a train and also comfort and durability.
As Britain’s rail industry membership body responsible for standards, we have engineers, risk modellers, human factors specialists and other widely experienced professionals to help inform standards and guidance which ultimately help our members, the rail companies actually running and supplying the railway, to meet their own obligations.
Alongside our members, we participate in specialist European ‘work groups’ and ‘taskforces’ that draft and update European standards and support the work with research. Our fire safety research showed that British standards aligned well with the new EN 45545-2 across the range of materials used in rail vehicles, except where seats were concerned, where there was a significant difference in the outcomes.
Indeed, when we fire-tested seats in trials to compare the testing methods in the British standard versus the new EN 45545-2, we found that it was relatively easy for any type of seat to pass the EN test, even for the most demanding category.
In response, our research looked at the EN test in detail and it was concluded the seats were not subjected to enough heat, and if the measurement of smoke was taken into account, a far better result could be obtained that was consistent with the British standard.
As a result, an EN taskforce was set up to produce a revised EN seat test. The group went back to the original seat fire scenario, a newspaper fire started by vandals. The result was that the representation of the newspaper fire was greatly improved by changing the burner hole pattern to optimise heat distribution and by operating with a higher heat output.
New seat fire test standard
A new seat fire test standard has been drafted. This gives a much more distinct performance ranking for the seats tested, and so will make it easier to set robust ‘pass-marks’ for the different categories of use. The test method is more clearly defined, has a more realistic heat input, smoke measurement is included, and test equipment, set-up and calibration procedures are more precisely defined.
The new test method is now subject to final discussion and a formal vote ahead of publication before the end of the year. When published, industry and its supply chain will have access to more consistent and more effective seat fire test methods that will apply equally across Europe.
In the short to medium term it’s not likely to radically change train seats, but it will make testing them more consistent and allow economies of scale because products will only need to be tested once rather than against many national standards. As experience is gained, the test criteria can be optimised using real-world data from GB and also the entire European network, further assuring safety that is at a practical and realistic level.
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