Experts say dilbit could have caused Mayflower, Arkansas oil spill
According to experts in the failure of oil and gas pipelines, there are a handful of factors that can contribute to a pipeline rupture, like the one on Exxon Mobil's Pegasus pipeline that spilled toxic diluted bitumen or dilbit from the Canadian tar sands into a Mayflower, Arkansas lake and subdivision.
Those factors include pressure swings within the pipe, reversing the direction of the flow of oil, the quality of the original pipe construction and a build-up of hydrogen atoms inside tiny cracks in the pipe.
Elizabeth Douglass reports at The Arkansas Times that all of these factors were in play in the Pegasus pipeline rupture.
Some operators may change their pumping pressures and their cycles to accommodate customers or to push more crude through the pipe faster, which generates more fees. Exxon, for example, increased the amount of dilbit flowing through the Pegasus by 50 percent in 2009. To accomplish that without installing larger pipe, Exxon had to send oil through the pipe faster, either by adding pumping stations or increasing the overall operating pressure, or a mix of the two.
Three years earlier, in 2006, Exxon also reversed the direction of the pipeline's flow, a move that would automatically alter the impact of pressure cycles by changing where the highest and lowest pressures hit along the pipeline.
Big changes in the internal pressure cause pipe to repeatedly flex, and that can cause special problems in crack-prone vintage pipes like the Pegasus. Exxon's pipe was doubly challenged, however, because its pipe was known to be exceptionally brittle around the seams. Brittleness can cause pipes to fracture instead of flex, just as the way wire will break after being bent back and forth repeatedly
And pipeline experts suspect the makeup of the tar sands oil or dilbit Exxon was transporting played a role, as well...