By DANIEL GILBERT
Recent pipeline ruptures, including one at an ExxonMobil pipeline that caused a major oil spill in Arkansas last month, are raising fresh questions about the safety of pipes made decades ago using obsolete welding techniques.
Though the industry stopped making what is known as low-frequency, electric-resistance welded pipe by about 1970, it still accounts for more than a quarter of the 182,500 miles of liquid fuel pipelines across the US, according to federal data for 2011, the latest available.
The accidents come as federal regulators are examining whether state-of-the-art inspection methods are capable of detecting flaws in these old pipe seams. A US regulator has commissioned a study of old, substandard pipe that could help shape new rules.
In the Exxon rupture and another on a Chevron pipeline in Utah last month that spilled 600 bbl of diesel near the Great Salt Lake, segments of the pipes were made about 60 years ago by bending metal sheets to form a tube, then heating the edges with a low-frequency electric current to weld them lengthwise. Such welds can leave defects in seams that make them vulnerable to corrosion and cracks, risks that have been known for decades.
The Chevron pipeline appeared to split along the welded seam, according to federal regulators. A Chevron spokesman said while the investigation continues, "Initial indications are that the release may have been the result of a longitudinal seam failure in the pipeline."
The Exxon pipeline gushed about 5,000 bbl of crude into a residential neighborhood through a 22-foot, incision-like break.
"It clearly looks like a seam-type failure," Rick Kuprewicz, a pipeline-safety consultant, said after seeing photographs of the Exxon rupture.
Exxon spokesman Alan Jeffers said the company hasn't reached any conclusions on the cause of the pipeline failure and is awaiting a third-party review of the ruptured section, which was removed on Monday.
"If we felt there was a problem we would have done something else, but in hindsight clearly there was an issue," Mr. Jeffers said of the company's safety tests.
It isn't clear from federal records how often obsolete welds play a role in accidents. Of the 1,151 accidents on liquids pipelines since 2010 reported to federal regulators, 78% don't show what kind of weld was involved, and 85% don't show when the pipe was manufactured, according to a Wall Street Journal review of government data.
The Pipeline and Hazardous Materials Safety Administration says most of the accidents involved very small spills, or weren't related to pipe welds, so operators weren't required to furnish detailed information about them.
But the number of pipeline accidents has been rising; the 364 accidents on liquids pipelines last year were the most since 2008, but fewer than in 2002, according to federal data.
The threat of substandard welding "seems to be rearing its ugly head again," said Carl Weimer, a pipeline-safety advocate and executive director of nonprofit Pipeline Safety Trust. "The issue is how well are companies mitigating for that risk?"
A spokesman for the Association of Oil Pipe Lines says old pipe is safe as long as it is well-maintained, and that spills are relatively rare.
Federal regulators have questioned the adequacy of inspection methods that failed to reveal problems with these pipes before major explosions, including a 2007 blast in Mississippi that killed two people and injured seven.
The welds are such a concern that PHMSA, the pipeline regulator, in 2011 commissioned a $4.2 million, multi-year study of electric-welded pipes and how to prevent them from failing while in use.
Battelle Memorial Institute, which is conducting the study, has analyzed 280 cases in which electric-welded pipes failed between 1950 and 2005, including 55 failures while the pipe was in use. The nonprofit research group says the surest way to identify a weld defect is to pump water through the pipe at high pressure. Such tests are costly, requiring a company to shut down the line, and in some cases apparently led to failures when placed back in service, Battelle says.
The other chief testing method involves running a robotic device through the interior of the pipe to detect any anomalies. This device, commonly called a "smart pig," has at times failed to catch flaws that later resulted in a rupture.
"Neither of them is foolproof," said Brian Leis, a researcher leading Battelle's study. "Both are better than one."
Chevron last pressure-tested the pipeline that ruptured in Utah in 1987, and inspected it internally in 2009. Exxon conducted a pressure test on its Arkansas pipe in 2006, according to regulators. It conducted an internal inspection in 2010 that didn't find any significant anomalies, and another one in February, but hasn't received the results, regulators say.
By 1970, most pipe manufacturers began using a high-frequency current to weld, which produced seams less prone to fractures, according to a Battelle report submitted to federal regulators in September.
Last July, a pipeline carrying gasoline in southeastern Wisconsin split along an old electric-welded seam, spilling about 1,000 barrels and prompting the evacuation of two homes.
The operator, West Shore Pipeline, reported a second rupture in August on an similarly antiquated seam. It pressure-tested both pipelines more than a decade ago, and performed several different internal inspections on them between 2009 and 2012.
"We are continuing to consistently re-evaluate our programs, and consistently look to further test our lines to maintain them safely and operate them safely," said Patrick D. Hodgins, a spokesman for Buckeye Partners, which controls West Shore Pipeline.
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