Parts for coaches of passenger train made using Ashland's HETRON® FR resin. (Pictures courtesy of Temoinsa, Spain.)
Parts for coaches of passenger train made using Ashland's HETRON® FR resin. (Pictures courtesy of Temoinsa, Spain.)

Partly driven by the rapidly rising cost of hydrocarbon fuels, the global mass transit industry is showing renewed growth. Fabricators that supply composites to the mass transit industry are also experiencing substantial growth, but that growth can often be quite challenging due to the myriad fire retardant (FR) regulations country by country around the world.

Advantages

Composites used in the construction of passenger rail cars, locomotives and people movers are not new. The first use of composite materials in public transportation dates back more than 25 years. Composites were recognised then for their design flexibility and performance advantages over metals and wood. Advances in resin and fabrication technology since that time have led to additional qualities that now position composites as the materials of choice for manufacturing mass transit vehicles. In addition to design flexibility, composites deliver significant weight savings and require considerably less maintenance when compared to other materials of construction. One of the biggest areas of focus for train manufacturers is the issue of flame spread, smoke and toxicity (FST) because these materials are inherently combustible.

Fire codes

It is important to have standards to protect rail system passengers. Many countries have developed fire codes for these types of vehicles. Nearly every country currently uses different test methods with different requirements. Most of the flame spread and smoke tests cannot be correlated. Composite materials may meet the highest classification in one test, but not in another.

The United States, for instance, has fire retardance regulations for passenger trains travelling between cities described in 49 CFR part 216 et al. There is a second voluntary standard for intercity trains referred to as Docket 90. The US National Fire Protection Association also has a fire code for mass transit vehicles called NFPA 130. All of these standards have flame spread and smoke requirements to protect passengers from fire hazards and give them enough time to evacuate cars safely. The flame spread test is based on the ASTM E162 radiant panel test and the smoke test is based on ASTM E662 smoke density. The requirement for all vehicle walls and ceilings is a maximum flame spread of 35 and maximum smoke density at 90 seconds of 100 and a maximum smoke density at 4 minutes of 200. Some of the car manufacturers have more stringent requirements and include a smoke toxicity test requirement as well.

Currently in Europe, each country has its own test procedures and requirements for rolling stock. There is a new mandatory Technical Specification for Interoperability (TSI) for the European rail system. This is managed by the European Railway Agency. The TSI for railway rolling stock has adopted the national fire code standards from Britain, France, Italy, Poland and the new version of German DIN 5510-2. Any train that has met any of these standards can cross the European Union (EU) borders. Each of these norms use a different test for flame spread and smoke opacity measurement. There is not a good correlation between the tests. A composite system may meet the test requirement for one country but not another country. If a rolling stock vehicle is to be used in only one country then it must meet the requirements of that country.

Unified standards

The EU has started projects to develop European unified testing standards for the railway industry. The FIRRESTAR (fire standard research in railways) project was conducted to define the needs for a unified FR norm in Europe. The EU committee put together to develop the unified standards decided to base this future standard on 'F' = flame spread, 'I' = ignitability, 'R' = rate of heat release, 'S' = smoke opacity, 'T' = toxicity of smoke, called the FIRST concept.

After the FIRST concept was introduced, a long process was started to develop the European Railway standard EN 45545. This is being done by the joint working group under the responsibility of CEN TC 256. Each country has at least one representative on the working committee. There have been many discussions between national representatives because of the different approaches and test methods, especially for the selection of a smoke toxicity method. This has been ongoing for more than 10 years.

In 2006, the CEN TC 256 committee decided on some drastic changes in the norm. This would have eliminated many materials that are currently being used and result in no apparent improvement in fire safety. The committee made additional refinements to the norm that were more realistic and that resulted in three levels of hazard classifications – HL1, HL2 and HL3. The HL1 classification is the least stringent and HL3 is most stringent.

The EN 45545 standard will also have four operating categories of vehicles and four design categories that will require different hazard classifications depending on the operating and design category of the vehicle. The flame spread test is based on the IMO radiant panel test ISO 5658-2. The heat release is measured using ISO 5660-2 cone calorimeter. Smoke opacity is measured by EN ISO 5659-2 and smoke toxicity is measured using EN ISO 5659-2 with FT-IR used to measure toxic smoke components. A Technical Specification, TS 45545, should be published in August 2008 that will list all test data collected. Publication of TS 45545 will allow the (12 month) review process to reach its final stages thus paving the way for full acceptance on EN 45545. If all goes as planned, EN 45545 may be implemented by 2010.

The implementation of this new norm will make it easier for rolling stock manufacturers, fabricators and resin manufacturers to get the fibre reinforced plastic (FRP) systems approved for use in all of Europe. Instead of having to get the FRP tested and approved in every country, it can be done with one certification to this new norm and be accepted in all EU countries.

Some Asian nations typically adopt FR standards from either the EU or the US. But they may adopt their own FR standards in the future (such as the already existing TB/T3138-2006 in China). The final decision is sometimes left up to the design firm in charge of building the railway system (eg. Bombardier, Alstom, Kawasaki, or Siemens), which would generally use the standards of their own countries.

Ashland's fire retardant MODAR® and HETRON® resins have been used to build rolling stock, locomotives and people movers all over the world. There are FR resins designed for specific fabrication techniques, such as hand lay-up, spray-up, resin transfer moulding, vacuum infusion and pultrusion, that can meet all local FR requirements.

The requirements of the new EU standard can be met with FRP systems and will not prevent the use of these materials in the future. In fact, with the harmonisation of FR standards in Europe and the rest of the world it is anticipated that it may make it easier to get FRP materials approved for use in rolling stock in the future. It will be also be easier to get new materials approved since only one test standard has to be met rather several different ones.