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CALGARY, Alberta (Reuters) - Two recent oil-train derailments in Canada have opened a new front on the debate over safety, highlighting how even shipments of Alberta's oil sands crude can contain components just as volatile as North Dakota's Bakken.
Although Canada is best known for producing viscous bitumen that is not prone to ignite on its own, it is often blended with as much as one-third super-light oil - known as condensate - before it is shipped in rail cars, injecting the same kind of volatile gases that can explode in derailments, industry experts say.
In the case of two fiery incidents in northern Ontario in recent weeks, the oil involved was synthetic crude from the Alberta oil sands, which is upgraded from raw bitumen, making it less stable.
Both Canadian National Railway trains were heading to a Valero Energy Corp's refinery in Quebec before they came off the tracks and burst into flames.
Ever since the Lac-Megantic disaster in Quebec, where a runaway train carrying Bakken crude erupted in a fireball in 2013, killing 47 people, worries about safety have been largely centered around light crude. In particular, Bakken has been the focus since its so-called "light ends," volatile gases with higher vapor pressure and low flashpoints, occur naturally.
But light ends are also present in the condensate used to dilute raw bitumen and some heavy crude. Even though the concentration in diluted bitumen, known as dilbit, is far less than in Bakken, the low flashpoint remains.
"Basically all the materials we are talking about - Bakken, West Texas Intermediate, some of the diluted bitumen blends coming out of Alberta - all have light boiling components that are flammable," said Dennis Sutton, executive director of the Crude Oil Quality Association.
(See related graphic on oil by rail incidents: here)
For Canada, the issue is not only the point at which diluted or synthetic oil sands crude might ignite, known as the flash point, but whether it would continue to burn once ignited, potentially setting off a series of blasts in adjacent tank cars.
Bakken crude is naturally rich in light ends so its flash point and fire point are roughly the same, says Andre Lemieux, secretary of the Canadian Crude Quality Testing Association (CCQTA), meaning if it ignites it will continue to burn.
However, the same is not necessarily true for crude being produced in and shipped from Alberta.
To complicate matters, there is no such thing as a typical Canadian crude. Different grades have different properties with light sweet crude streams tending to have lower flash points than undiluted heavy grades.
The concentration of light ends in dilbit vary depending on the quantity and quality of condensate added. Some shippers use semi-refined synthetic crude instead of condensate, to make a product called "synbit".
Synthetic crude presents a different challenge because as an upgraded product its flash and fire points may be quite different from crude oil.
One of the safer substances to transport by rail is raw bitumen from the oil sands, which in its undiluted state is the consistency of peanut butter and extremely difficult to ignite.
However, raw bitumen shipments require coiled and heated rail cars and additional infrastructure at rail loading and off-loading terminals, which not all shippers have access to.
Industry bodies including CCQTA and Transport Canada are now studying the flammability of various types of crude, and their results may have implications for how certain kinds of oil is shipped and how emergency services deal with crude train derailments.
Progress is likely to be slow, however. Researchers are developing new testing methods, since the existing United Nations methods for classifying dangerous goods transported by rail were originally developed for natural gas liquids like ethane and propane rather than mixed cargoes like crude oil.
"Ultimately the specific properties of crude oil and types of crude oil will become much more important as it relates to how material is transported," the CCQTA's Lemieux said. "But it will take a while."
Editing by Jonathan Leff and Diane Craft