November 29, 2016 | Desmog Blog | In July 2015, a train carrying Bakken crude oil derailed in Culbertson, Montana resulting in an oil spill of 35,000 gallons — more than the contents of a full rail tank car.
But unlike all of the other Bakken train accidents where large amounts of oil were spilled something odd happened. There was no explosion or fire.
So what was different about the accident in Culbertson, Montana?
One potential explanation was that the oil was significantly less volatile than the oil involved in other Bakken accidents that resulted in fires and explosions. The Federal Railroad Administration told DeSmog that two samples of the oil were taken and the Reid vapor pressure for those samples were 8.73 psi and 9.23 psi.
Reid vapor pressure is used to quantify the volatility of substances like crude oil and gasoline. If there are more natural gas liquids in the crude mixture — like propane and butane — it will have a higher Reid vapor pressure (RVP).
In comparison, the oil involved in the massive fire and explosion in Mount Carbon, West Virginia had an RVP of 13.9 psi according to the Wall Street Journal. Samples taken from the train derailment and fire in Lynchburg, Virginia averaged RVP values over 14 psi.