FIRE SAFETY OF CNG BUSES – PROPER EXPERIENCES

Natural gas as engine fuel is a commercially very attractive option for medium and heavy duty vehicles. A combination of low gas price and incentives for environmentally friendly solutions are key arguments for bus fleet operators to convert to natural gas powered vehicles. From the second side, fuel can be dangerous if handled improperly. Gasoline and diesel are potentially dangerous fuels, but over time we are learned to use them safely. The same is true with liquefied petroleum gas and natural gas, as well as hydrogen. For commercial vehicles both, compressed natural gas and liquefied natural gas are equally relevant options. Recent fire accidents involving natural gas buses have shown that cylinders may explode through compliant with current UN ECE R110 regulation. Such a repeated scenario is certainly not acceptable having in mind the tremendous amount of energy released when a compressed cylinder burst. Recent accidents detailed in this paper highlights potential improvements in current natural gas buses fire safety concepts. Fire safety should not solely rely on cylinder behaviour when exposed to fire but also to additional and upstream fire safety barriers. Thermal fuses cannot be seen any more as an ultimate option to control cylinder burst in case of fire.