Monday, July 7, 2014

Experts say dilbit could have caused Mayflower, Arkansas oil spill

From:  Tree Hugger

Chris Tackett (@ChrisTackett)

September 20, 2013

exxon pegasus pipeline cut photo

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.  MORE

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