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Jonas Brandt, Project Manager, SP Technical Research Institute of Sweden

“…working on improving fire safety on buses…”

Jonas Brandt, Project Manager, SP Technical Research Institute of Sweden

Jonas Brandt, Project Manager, SP Technical Research Institute of Sweden

Bus fires are a big problem in society. Statistics from Sweden show that 1% of all buses catch fire each year1. This incurs large losses to the carrier and insurance companies, but sometimes also large losses of lives. Examples of disastrous bus fires in recent years include Wuxi, China, in July 2010 (24 fatalities)2, Uttar Pradesh, India, in December 2008 (63 fatalities)3, Hannover, Germany, in November 2008 (20 fatalities)4, and Wilmer, USA, in September 2005 (23 fatalities)5.

A majority of the fires starts in the vehicle’s engine compartment1,6. This is explained by the high temperatures that results from strict regulations on noise and emission levels. In many cases poor maintenance is also contributing to the fires. Full scale experiments6 have shown that if a large fire breaks out in the engine compartment there are only ~5 minutes available for evacuation before the passenger compartment is filled with lethal levels of toxic gases.

Given the fact that most fires start in the engine compartment, adequate active fire protection systems for engine compartments are advantageous both in terms of passenger safety, carrier and insurance company economy, and general public resource management. Thus, various organisations have identified the installation of automated engine compartment extinguishers as an important fire-safety measure7-10. Furthermore, some insurance companies and individual carriers already require extinguishing systems in buses/coaches. However, there is still no legislative demand for this course of action, nor an international standard for testing automated bus engine-room extinguishing systems.

Since 2005, SP has been working on improving fire safety on buses using a holistic approach addressing various tools and issues such as statistics, risk analysis, material properties, as well as test methods for interior materials, fire partitions and suppression systems6,11-13. An example of the results from this work is the amendment of Reg No 11814,15 which was decided by the United Nations Economic Commission for Europe (UNECE) in 2011. In a joint document by France, Germany, Norway, and Sweden, presented at UNECE in 2010, fire suppression in engine compartments was pointed out as a prioritised issue16. Here we present a method for ensuring the performance of such systems.

Test method

Bus engine compartments may be designed in many different ways, but they have enough commonality to make a general test method useful1. Some of the factors affecting the fire and extinguishing processes include: The presence of a fan supplying oxygen; the presence of apertures; the presence of hot surfaces (and their temperature); the high working temperature in the engine compartment; the presence of several flammable liquids and other compounds; the risk of spray fire; the presence of complex geometries that may conceal fires; and the risk of re-ignition after extinction.

A test rig was developed to test and compare different fire suppression systems. Various fire sources were placed at various pre-determined positions in order to test different fire scenarios such as large fires, small fires, spray fires, hidden fires, and smouldering fires. The test method comprises a 4m3 enclosure with fan, apertures, engine mock-up, exhaust manifold and muffler mock-up (creating hot surfaces), and obstructions. This creates a generic cluttered space which reflects the environment found in real bus and coach engine compartments.

In order to fully characterise a suppression system it is tested against 10 different fire scenarios. The results are used to give an overall indication if the system has an acceptable performance, as well as to point out strengths and weaknesses of the system for different fire scenarios, driving conditions, and hazard levels (e.g. driving the bus in long tunnels).

References

  1. J. Brandt, M. Försth, Testing active fire protection systems for engine compartments in buses and coaches – a pilot study, SP Report 2011:22, Borås, 2011
  2. BBC Mobile, China bus fire kills 24 steel factory workers, 2010
  3. BBC Mobile, India bus fire toll rises to 63 in, 2008
  4. R. Damm, The Hanover bus fire and activities on improving fire safety in buses, FIVE – Fires In Vehicles, Gothenburg, 2010
  5. Highway Accident Report, Motorcoach Fire on Interstate 45 During Hurricane Rita Evacuation Near Wilmer, Texas, September 23, 2005, National Transportation Safety Board, 2007
  6. R. Hammarström, J. Axelsson, M. Försth, P. Johansson, B. Sundström, Bus Fire Safety SP Report 2008:41, Borås, 2008
  7. Svensk kollektivtrafik, Svenska bussbranschens riksförbund, Buss 2010 Branschgemensamma funktionskrav på bussar, in, 2010
  8. S.E. Sigfridsson, J. Mansfeld, Rapport RO 2000:01 Brand i en buss den 25 januari 1999 i Äskebacka, O län, O-01/99, Statens Haverikommission, 2000
  9. O. Lundström, J. Mansfeld, Rapport RO 2001:01 Brand i buss den 22 juli 1999 vid Glumslöv, M län, O-03/99, Statens Haverikommission, 2001
  10. L.-E. Sandin, Undersökning av olyckor och räddningsinsatser, Brand i bussar, Olycksplats: Boråstorpet, Hajom, Landvetter och Viskafors, Södra Älvsborgs Räddningstjänstförbund, 2009
  11. R. Hammarström, J. Axelsson, B. Reinicke, Fire Safety in Buses, WP1 report: Bus and coach fires in Sweden and Norway SP Report 2006:26, Borås, 2006
  12. P. Johansson, J. Axelsson, WP2 report: Fire safety review of interior materials in buses SP Report 2006:59, Borås, 2006
  13. M. Försth, H. Modin, B. Sundström, A comparative study of test methods for assessment of fire safety performance of bus interior materials, Fire and Materials, 2011
  14. M. Försth, A. Hagerupsen, J. Petzäll, Informal document No. GRSG-95-30: Ensuring fire safety in buses, in:  Working Party on General Safety Provisions, GRSG, UNECE, Geneva, 2008
  15. UNECE, Proposal for amendmens to Regulation No. 118 (Burning behaviour of materials), ECE/TRANS/WP.29/GRSG/2011/11, UNECE, Geneva, 2011
  16. Informal document No. GRSG-98-08: Fire Safety: Priorities of the joint action of France, Germany, Norway and Sweden, to amend Regulation No. 107 and Regulation No. 118 to enhance fire safety in vehicles of categories M2 and M3, in: Working Party on General Safety Provisions, GRSG, UNECE, Geneva, 2010

Biography

Jonas Brandt works as a Fire Protection Engineer and Project Leader at SP Technical Research Institute of Sweden in the Department of Fire Technology. As a former bus driver, Jonas has a special interest in the field of bus fire safety and has performed several full-scale bus fire tests and many laboratory tests of different fire suppression and detection system technologies.