By ALISON SIDER
An independent report found that a rupture in an ExxonMobil
pipeline that spilled thousands of barrels of oil in Mayflower,
Arkansas earlier this year was caused by defects dating back to
when the pipe was built in the 1940s, the company said.
An independent metallurgical laboratory looked at the section
of the pipe that ripped open in March, spilling an estimated
5,000 bbl of oil into a residential neighborhood in the small
town about 25 miles from Little Rock.
ExxonMobil said Thursday it is reviewing the results of that
assessment, which were provided to the company and the Pipeline
and Hazardous Materials Safety Administration (PHMSA) on
The Texas oil giant said that, according to the report,
hook-shaped cracks along the pipe's seams were the root cause
of the line's failure, not corrosion. The cracks are related to
an outdated welding process that is no longer performed on new
pipes, but that still affects thousands of miles of pipelines
in use across the US.
The lab also found that the pipeline's limited flexibility
contributed to the incident, ExxonMobil said. The report has
not been made public, and the PHMSA is still reviewing it, a
spokesman for the agency said.
The section of the pipe that ruptured is more than 60 years
old, but it passed a high-pressure test in 2006 and an internal
inspection in 2010 that sought to measure metal loss and other
anomalies, ExxonMobil said.
A spokesman for ExxonMobil said the full results of a more
detailed inspection the company conducted earlier this year are
not yet available. That inspection, called a transverse flux,
uses a magnetic field to find corrosion along seams. It can
also detect cracks and other defects, although not as reliably
as it can detect corrosion, according to the PHMSA.
After the results come out, the company will review whether it
needs to make changes to its pipeline integrity management
The type of cracks found to have caused the rupture in
Mayflower are associated with some types of an early welding
process called electric resistance welding, according to the
PHMSA. That process hasn't been used on new pipelines since
1970, but approximately 25% of the 182,500 miles of liquid fuel
pipelines across the US were welded that way, according to the
most recent federal data.
Other pipeline ruptures have been linked to electrically welded
pipe over the years, including a 2007 break in a liquid propane
pipe near Carmichael, Mississippi, which caused a fire that
killed two people.
In 2011, the PHMSA commissioned a study of how to detect
problems in these pipes and prevent them from failing while in
Arkansas and the US government have sued ExxonMobil for
allegedly violating pollution laws. The Arkansas attorney
general has not yet seen the testing results, a spokesman for
the office said.
Dow Jones Newswires