Eastern Railroad Discussion > TSB of Canada Lac Megantic Derailment

My new Trains magazine (May 2014) reported that crude oil samples were taken from undamaged cars at the site of the Lac Megantic disaster and analyzed by the Transportation Safety Board of Canada. This analysis found that the flash point of the oil was below 23 degrees Celsius. This shows that the samples met the federal regulations for being classified as a flammable liquid of Class 3, Packing Group II. This means to me that concerns about highly volatile oil containing gases have no merit at least in this case.

The volatility is comparable to condensate or gasoline. The TSB also noted that the rapid release of large quantities of oil with high volatility and low viscosity were likely the major contributors to the fireball and pool fire that occurred after the derailment. To me this is a very odd and obvious statement for a national safety organization to make. This is pure speculation on my part, but I wondered if the last statement meant that liquid oil was escaping through a broken or open valve, ignoring ruptures for the present. Generally modern Hazmat tank cars are designed with low centers of gravity to keep the cars upright and are designed to contain the hazardous material in a derailment. I wondered if the design of the old cars considered that in a major derailment the tank car shell can separate from the trucks. The bottom of the tank car will then bounce along the ground, damaging or opening the bottom valve in a manner not considered in the design of the original tank cars. We should not forget that the tank cars at Lac Megantic came off a 10mph curve at high speed and rolled down a slope into the town.

Here's the report mentioned in the Trains article. It's on the TSB website. Although the final TSB report will cover many aspects of the examination, it seems that TSB is comfortable that: 1) the crude oil was properly labeled and classified, and 2) the volatility was similar to that of gasoline. The conclusions are in section 4 of the report.

One interesting aspect is the possibility there were two separate events. The derailment, and ripping open of several cars, and a fire in one or more cars. As oil gushed from several cars into pools on the ground, a small fire from one or more cars then ignited the vapours from the pool of oil, resulting in the fireball a few minutes after the derailment was observed. There's a flow chart in the report illustrating the process.

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4.3

The occurrence crude oil s properties were consistent with those of a light sweet crude oil, with volatility comparable to that of a condensate or gasoline product.

4.4

There was no indication that the occurrence crude oil s properties had been affected by contamination from fracturing process fluid additives.

4.5

The occurrence crude oil samples were taken at atmospheric pressure. This could lead to an underestimation of the crude oil s volatility due to evaporation loss of very light constituents.

4.6

The large quantities of spilled crude oil, the rapid rate of release, and the oil s high volatility and low viscosity were likely the major contributors to the large post-derailment fireball and pool fire.

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http://www.tsb.gc.ca/eng/enquetes-investigations/rail/2013/R13D0054/lab/20140306/LP1482013.asp

Thanks for bringing this to my attention. Crude Oil samplimg has to be carried out under controlled conditions in specialized closed sampling systems at the pressure in the tank car.. "Sampling at atmospheric pressure" as reported will not give representative samples if light ends are present. So forget my speculations they have no relevance. 64 pascalls is indeed a gasoline vapor pressure but I have some doubts now about the TSB conclusions.

I don't usually read Inside Climate News but this is as good an article as I've found regarding the volatility of Bakken crude oil:

http://insideclimatenews.org/news/20140305/oil-train-made-riskier-producers-deliberately-leaving-volatile-gases-crude-0



Allen