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Qualitative Risk Assessment for LNG Fuel

Using liquefied natural gas (LNG) as a vehicle fuel introduces certain potential safety hazards to fuel handlers, vehicle drivers and passengers, and the general public. In some regards, LNG is safer than propane or gasoline because it is flammable only within a narrow range of fuel/air ratio and it is less subject to accidental fire if vapors come into contact with a spark or flame. In the event of an accidental fire, methane tends to burn along a flame front rather than explode. Because it is lighter than air, methane tends to rise and dissipate instead of accumulating at dangerous concentrations the way gasoline and propane vapors do.

This is not to say that LNG use is without risks. Fires and explosions can occur under certain conditions. Furthermore, LNG is stored as a pressurized liquid at very low temperatures, at about -130 to -160 °C (-200 to -260 °F), so handling and use is subject to the general risks associated with any cryogenic fuel, including the risk of skin and eye burns on contact. Hazards such as these need to be identified and quantified in terms of the impact they will have on different applications and designs. Quantifying all of the risks associated with the use of LNG represents a significant task. A qualitative risk assessment reduces the effort and expense by focusing on only the important safety issues.

A qualitative risk assessment identifies different likely accident scenarios and determines the consequences that might affect general and public health and safety. This allows the quantitative work to be focused on only the most reasonable and likely safety concerns. The steps for this work are to collect from existing resources all of the phenomenological data on LNG into a single report, then identify all of the accident-initiating events using master logic diagrams, failure modes, effects analysis, and historical operating experiences.

We have conducted a qualitative risk assessment for LNG technologies related to transportation applications. The main product of the assessment is a report identifying the potential safety hazards associated with the use of LNG. We use the risk assessment at the INL to support integration of LNG-powered vehicles into our fleet, and to support research and development projects that design, test, and implement new LNG technologies.

The report is available to you below free of charge, subject to the following conditions:

  • You must include our disclaimer statement with all printed or file copies of the report
  • You may not claim ownership of the report
  • You agree to hold the report’s authors, the INL, the INL's contractor, and the U.S. Department of Energy harmless for the consequences of any use or misuse of the information provided in the report.

Qualitative Risk Assessment for LNG Fuel (13.0MB PDF)

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