Fundamentals and practice of CNG safety -

Transcription

1 Fundamentals and practice of CNG safety - Brief overview of CNG vehicle safety NGV 2010 International Conference and Exhibition 8 10 June 2010, Rome, Italy by Hien Ly CFS International NGV Consulting, Sydney, Australia

2 CNG vehicles have a good safety history Numerous studies have provided safety overview of CNG vehicles world wide and supported the use of CNG Arthur D. Little (1972), Los Alamos National Lab (1983), AGA (1987), New Zealand statistics (1987), Canadian survey (1989), New York State Government study (1989) Gaseous fuelled vehicles posed no greater safety risks than petrol and diesel vehicles CNG is less safe than petrol in an enclosed garage and in fuel line rupture scenarios

3 CNG vehicle safety issues (1) Safety characteristics of natural gas and CNG Standards and regulations Training Onboard fuel cylinders Vehicle gas system installation Vehicle operation and maintenance

4 CNG vehicle safety issues (2) Crash safety of gas system installation Fire safety of gas system installation Fire safety in road tunnels Safety against terrorist attack Recommended measures to improve safety

5 Fire protection Standard bonfire test (Powertech Labs, Vancouver)

6 Gunfire test

7 Bullet hole after gunfire test (source: Powertech Labs)

8 Drop test of CNG cylinder (source: Dynetek)

9 Composite impact damage after drop test (source: Dynetek)

10 Environmental exposure test (source: Dynetek)

11 Environmental test failure (source: Dynetek)

12 Importance of correct inspection procedure - Damage due to objects lodged between cylinder & mounting (Acurex Environmental, 1994) Dropped bolt damaged cylinder surface

13 Steel liner corrosion Type 2 cylinder with fibreglass reinforcement (corrosion would not be readily visible with carbon fibres)

14 Steel liner and stress corrosion cracking of composite Type 2 cylinder (Dimmick, 2009) SCC cracks in fibreglass reinforcement Philadelphia Gas Works, 2008

15 Explosion of LPG cylinder fitted to CNG vehicle Malaysia 2008 It is critically important for licensed CNG auto mechanics to be able to correctly identify the CNG cylinder to be installed - through cylinder stamping/labelling and production records

16 Protection of underfloor CNG bus cylinders Composite cylinders are not as damage tolerant as steel cylinders; their protection requirements may not be recognised by licensed technical personnel who were trained and licensed before composite cylinder problems became widely known

17 CNG piping - stress relief and mounting support Piping on converted CNG bus in New Delhi insufficient pipe clamps for support (source: Weaver, 2002)

18 Long CNG tube runs without mechanical support

19 Cylinder in close proximity to engine exhaust system

20 Contact between tubes to be repaired (Source: McGlinchey, NGV 2004)

21 Insecure cylinder mounting

22 Unprotected, protruding underfloor cylinder mounting relocation and mechanical guard required!

23 Incorrect installation of Type 4 cylinder (Dimmick & Adams 2009) (1) - Shielding of PRDs

24 Incorrect installation of Type 4 cylinder (Dimmick & Adams, 2009) (2) - Shielding of PRDs

25 Effect of PRD thermal shielding in vehicle fire Kuala Lumpur, April 2001

26 Steel CNG cylinder after failure

27 FM VSS CNG vehicle crash test for GVM up to 10,000 lb and all school buses (1) Frontal crash Rear crash (4000 lb moving barrier)

28 FM VSS 303 vehicle crash test (2) Side crash

29 Crash induced vehicle fires (petrol car) Fire after frontal impact (MVFRI 2006)

30 US CNG bus fire protection design (MARTA, Atlanta, Georgia, Jet flame direction is good, but still perilously close to inhabited building) What would have happened to the apartment building had the PRD not worked?

31 CNG vehicle fire Subang Jaya, Malaysia July 2009 Investigation in progress likely due to gas leak and ignition source(s) within car (no cylinder explosion)

32 Fire performance in real life installation can be different from bonfire performance of cylinder (Seattle Fire Department) (1) * Arson attack, Honda OEM Civic GX Seattle, 2007

33 Fire performance in real life installation can be different from bonfire performance of cylinder (2)

34 While composite was burned through

35 Cylinder valve showed no sign of heating or charring

36 CNG bus fire in depot Saarbrücken cken, Germany, 2003

37 Saarbrücken cken,, Germany, 2003

38 Saarbrücken incident (2003) (Left: partially melted PRD. Right: new PRD)

39 What happens to gas released from cylinder explosion? Modelling - Unconfined burning of flammable natural gas vapour cloud in free field (Univ. of Maryland, USA)

40 Santa Barbara CNG bus fire Feb 2008 Fire was successfully put out after 15 minutes no cylinder explosion

41 Safety examples CNG vehicles in road tunnels One - way tunnel tube

42 Large amount of smoke from CNG vehicle fire is similar to that from other vehicles despite CNG being a clean burning fuel due to non-fuel materials Smoke from CNG bus fire

43 Vehicles fire smoke in road tunnels CSIRO modelling (2007) (1)

44 Vehicles fire smoke in road tunnels CSIRO modelling (2007) (2) Extent of smoke along tunnel as function of time

45 CNG vehicle fire and explosion risks in public facilities Dealing with terrorist attacks Would CNG vehicles behave safely in a feasible terrorist attack? Glasgow Airport event of June 2007 is one example Catastrophic French bus fire in 2005 (Molotov cocktail lobbed into bus passenger cabin) is a powerful demonstration of the potentially lethal consequences Feasible terrorist attack scenarios should be examined and protective measures produced

46 Car bomb attack Glasgow Airport June 2007 What if this car bomb had been driven into a CNG vehicle of inadequate fire protection design?

47 Summary and conclusions

48 Status and perception of CNG vehicle safety Numerous studies have established that CNG vehicle safety is at least equivalent to petrol vehicles CNG vehicle safety incidents have received disproportionate publicity and concern due to their being novel and different Industry efforts in producing continuously improving safety standards, products and services are improving safety performance The industry s collective safety knowledge is significant and should be utilised to prevent and investigate failures

49 How to ensure CNG vehicle safety Compliance with standards and regulations is a basic requirement Adequate training and information to all involved Correct operation and maintenance Continuous learning from field observations and safety incidents both locally and globally

50 Examples of determinants of CNG vehicle safety CNG vehicle safety is strongly dependent on design, materials, installation, operating conditions and maintenance, not just the cylinder or other components in isolation CNG cylinder safety inspection must not be about the cylinders alone but also its installation, operating environment and feasible damage scenarios Fire protection and in-service damage prevention measures should be an important consideration in vehicle design All persons involved in CNG vehicle projects and operations should be given adequate, CNG specific training

51 Basic, specific short term measures (1) Training courses for CNG vehicle mechanics should contain specific measures against in - service damage, gas leaks in collision, fire safety CNG vehicle mechanics should update and use new CNG vehicle safety knowledge CNG vehicle fleet operators, service providers (e.g. gas cylinder inspectors), accident investigators, public transport facility operators, regulatory agencies and the emergency services should be given adequate training on CNG systems technical and safety characteristics

52 Basic, specific short term measures (2) Large CNG vehicle fleet operators should assess the safety of their vehicles with regard to arson or terrorist attacks, and devise effective countermeasures. Customers/owners of converted CNG vehicle certification (i.e. compliance check before road registration) should be given essential safety information such as the prevention/avoidance (operation and inspection method) of gas leaks and in-service degradation or damage, and vehicle safety in collision and fire

53 CNG training recommendations for various categories of staff * (US DOT) * Regulatory authority personnel need training as well