Robert Heller  wrote:   
   > At Thu, 24 Jul 2014 23:22:00 +0000 (UTC)  wrote:   
   >   
   >>   
   >> The car is spec'ed to carry non-pressurized flammable liquids. The same car   
   >> spec is required for crude oil, ethanol, gasoline, and other flammable   
   >> liquids. It wasn't necessarily designed with any particular commodity in   
   >> mind.   
   >   
   > My understanding about the recent "crude oil" derailments / fires is not a   
   > matter of "flammable liquids", but due to the fact that the crude oil in   
   > question contains flammable *gases* (eg propane and butane) desolved in the   
   > crude oil.  Different grades of crude oil have differing amounts of   
   > 'petrolelum gas' (propane and butane) and the current batches being shipped   
   > have partitularly high amounts of these gases.   
      
   When you dissolve a gas in a liquid, you get a liquid. "Gas" and "liquid"   
   describe physical states, not chemical composition.   
      
   When you put a liquid in a tank, some of the liquid will evaporate. Exactly   
   how much depends on the temperature, volume of the empty space, etc., as   
   well as chemical composition. So yes, if Bakken crude contains a higher   
   proportion of lighter hydrocarbons than other crude oils, it would form   
   more volatile vapors. But, when you put gasoline, ethanol, or jet fuel in a   
   tank, you still get volatile vapors through exactly the same evaporation   
   mechanism. Google TWA Flight 800 for an example of volatile jet fuel vapors   
   forming in a tank.   
      
   So in regulatory terms, what your concerned about is how much the liquid   
   tends to give off vapors that will ignite when mixed with heat and air.   
   That property is measured as the "flash point", which is a property of the   
   liquid. I'm the case of crude oil, the flash point will vary depending on   
   the mix of hydrocarbons (including dissolved propane) present, so it   
   captures the extra explosiveness of certain crude oils quite effectively.   
   The Lac Megantic oil was found to have a low flash point.   
      
   If the flash point of a liquid is below a certain value, then it will be   
   classified as a "flammable" liquid. A flammable liquid just means anything   
   that is loaded, transported, and unloaded in the liquid state, and that has   
   a sufficiently low flash point. Liquified natural gas is a flammable   
   liquid, too.   
      
   The hazmat regulations use flash point to determine the "packing group" of   
   a flammable liquid. The packing group classification doesn't depend on the   
   chemistry, only of the flash point. The packing group is then used to   
   determine additional packaging and transportation requirements. In the   
   current version of the federal regs, however, it does NOT affect the type   
   of tank car needed. So, the current regulations do allow for Bakken crude,   
   ethanol, gasoline, and other more-volatile liquids to move in the same spec   
   tank car as stabilized crude, heavy crude, etc. (LNG has different   
   requirements because it is pressurized, not because of its low flash point   
   per se,)   
      
   The new regulations would create more stringent requirements for Packing   
   Group I, the flammable liquids with the lowest flash points. Based on the   
   reporting in the popular press, my understanding is that this would apply   
   to any Packing Group I material regardless of commodity, which I think   
   would include most denatured ethanol.   
      
   Dan   
      
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