(For use by New York Times News Service clients)
(For use by New York Times News Service clients)
c.2013 San Antonio Express-News
For print publication only
By Vicki Vaughan
San Antonio Express-News
SAN ANTONIO -- Before a North Dakota wheat farmer discovered an oil spill on his land on Sept. 29, the owner of the pipeline had used a high-tech device to detect problems on the line.
San Antonio-based Tesoro Logistics LP ran a robotic inspection tool known as a "smart pig" through the pipeline on Sept. 11. Smart pigs are inserted into pipelines to record information about the conditions of the pipe, including the thickness of its wall.
Tesoro reported that the device found "anomalies" in its North Dakota pipeline. Tesoro was awaiting the results of an analysis of the data when the leak was reported, a company spokeswoman said.
Seven month before the North Dakota spill, a pipeline owned by Exxon Mobil Corp. leaked 5,000 barrels of oil in a wetland and community in C entral Arkansas. Exxon had used a smart pig to detect problems a few weeks before the spill.
Exxon and Tesoro's use of smart pigs to examine pipe is common in the industry.
Federal data showed that smart pigs, which look like torpedoes, were used in 93 percent of inspections on hazardous-liquids pipelines last year, the Wall Street Journal reported.
However, while smart pigs have been effective in finding many imperfections, they aren't infallible. As Tesoro awaited the results of its smart pig test, its pipeline leaked 20,600 barrels of oil under the North Dakota field.
"Everybody thinks a smart pig is utopia, but it's really not, because it only shows you what has already happened," said Ed Ondak, a corrosion consultant in Littleton, Colo.
Smart pigs are likely to miss "very small pits and they won't pick up a coating scrape," Ondak said. Scrapes to coating can lead to corrosion, which can damage a pipe.
But the biggest challenge for smart pigs is detecting small cracks, said Chuck Morgan, executive director of engineering and technical services at NuStar Energy LP, a San Antonio-based partnership that owns 8,621 miles of pipeline.
Smart pigs use sensors and other tools that record irregularities that may point to corrosion, cracks, dents, gouges or other defects, experts said.
The data is logged into a computer and examined by a series of analysts, said Kevin Garrity, a corrosion engineer and the immediate past president of the National Association of Corrosion Engineers International.
But as the Tesoro leak showed, it takes time for data from smart pigs to be analyzed, and a spill may occur while the data is being examined.
"As is typical in smart pig test runs, the analysis identified areas appropriate for follow-up inspection," Tesoro spokeswoman Tina Barbee said in an email, referring to the North Dakota leak. "We conducted that follow-up and found no areas of concern."
Late last week, federal regulators said a lightning strike could have caused Tesoro's leak, but an exact cause of the damage won't be known for months.
At least once every five years, federal rules require companies to test their pipelines through "high consequence" areas, regions where a leak or spill could affect a populated or environmentally sensitive area or navigable waterway.
"Some operators run smart pigs more frequently," Garrity said.
On Thursday, the federal Pipeline and Hazardous Materials Safety Administration said it had ordered Tesoro Logistics to make safety improvements to its pipeline system in North Dakota where the leak occurred.
Tesoro performed more inspections and installed more leak-detection equipment, and then restarted the pipeline Friday.
Tesoro's Barbee said the company had agreed to the safety order. She said the company will add more devices "to continually monitor pressure and flow data to detect patterns that might indicate a leak."
"We will put systems and controls in place to identify and prevent this type of spill in the future," Barbee said.
Despite the smart pigs' blind spots, their use is a key part of maintaining pipeline safety, NuStar's Morgan said, adding that technological advances "are advancing every week."
NuStar's Mike Truby, senior vice president of operations, said the gathering and reporting of smart pig data, in particular, is evolving rapidly.
Through its use of smart pigs, NuStar can determine the location of a problem using global positioning system, or GPS, coordinates.
"It will show the orientation on the pipe, whether it's the top or bottom on the pipe and even the percentage of the deformation if it's a dent," Truby said.
That matters, he said, "when you're talking about lines 100 miles long and the report can put you within a foot or two -- or even within inches."
NuStar also has historical smart pig data that helps it zero in on possible problems.
If a problem is so small it's missed by a smart pig, a second inspection may point to a problem.
"As the sensitivity of the technology improves, you can see any trends," NuStar's Morgan said. "Is the corrosion growing or is it stable?"
http://www.phmsa.dot.gov 5/8 Pipeline regulator
https://www.tesorologistics.com 5/8 Tesoro Logistics