By Darren Engle
There are approximately 160,000 propane autogas vehicles on our nation’s roads and highways, making autogas the most widely used alternative fuel for transportation in the U.S. That is something to be proud of. So is its impressive safety record.
While vehicles fueled by propane autogas have a long history of performing safely under all operating conditions, some people have the perception that these vehicles are more dangerous than traditional gasoline- and diesel-powered vehicles. That perception is inaccurate.
When it comes to the transportation of children, school fleet directors know that propane autogas school buses are the safe choice. That’s because propane autogas school buses have bracket systems that help hold the fuel tank in place. In school buses, propane fuel tanks are located between the bus frame rails, providing added protection to the tank and thereby increasing the safety of the passengers.
School buses that run on propane autogas meet all conventional bus safety standards, plus additional standards required for alternative-fuel vehicles.
Propane autogas engine fuel systems in all types of vehicles are fitted with safety devices and shut-off valves that function automatically if the fuel line ruptures. All tanks are equipped with a valve — or combination of valves — in the liquid outlet connection that has manual shut-off, excess flow, and automatic closure features. The valve assembly prevents the flow of fuel when the engine is not operating, even if the ignition switch is in the ON position. The vehicle pressure relief valve must be vented to the outside of the vehicle, and all fittings must be vented to the outside if the tank is in an enclosed area, such as a trunk.
It’s Not Hollywood
Propane autogas tanks are 20 times as puncture-resistant as gasoline tanks, so they are more durable in a collision. They can also withstand up to four times as much pressure as a gasoline tank. Propane containers are much less vulnerable to puncture than moviemakers would have us believe. James Bond, for instance, causes an explosion by shooting a propane tank using his 9mm handgun in “Casino Royale.” But tests show that it doesn’t work that way in real life, as an episode of the television show “Myth Busters” makes clear (the segment is available for viewing on YouTube).
Another safety feature of propane autogas is that it requires a much higher temperature to ignite. Gasoline and diesel fuel will catch fire at temperatures as low as 495ºF, whereas autogas requires a temperature of at least 920ºF to ignite. The chart below illustrates the flammability range of propane autogas and other fuels.
Many organizations develop and implement codes, standards, and regulations for the safe use of vehicles that run on propane autogas. The regulations are constantly reviewed, updated, and improved to ensure that all new vehicles and vehicle technologies are as safe as possible.
The American Society of Mechanical Engineers (ASME) is responsible for rules governing vehicle tanks and piping. As an example, the tanks in all vehicles fueled by autogas are constructed from carbon steel in accordance with a code developed by ASME. The National Fire Protection Association also develops and implements codes and standards for propane autogas storage systems, dispensing stations, and vehicle systems.
Propane autogas is indeed a safe fuel when properly stored, transported, handled, and used. Several factors help ensure its safety: the fuel’s natural properties; the quality construction of fuel system components; stringent codes and regulations; and the industry’s extensive training and safety-awareness programs.
Darren Engle is director of marketing for Blue Star Gas, which serves Northern California, Oregon, and Washington. Blue Star Gas is advancing the use of propane autogas, and is a member of Alliance AutoGas. Engle serves as chairman of the Propane Education & Research Council’s Research & Technology Working Group, and travels the country training fleet managers of both private and public entities on the economic, safety, and environmental benefits of propane autogas.
Reprinted from Butane-Propane News April 2013