Federal regulators are citing potential integrity threats at dozens of points along the trans-Alaska pipeline.
The U.S. Pipeline and Hazardous Materials Safety Administration proposed a list of corrective measures in a March 13 letter to Tom Barrett, president of Alyeska Pipeline Service Co.
The agency began an investigation after a stray piece of metal, 10 inches in diameter, was discovered on Sept. 8, 2013, inside a valve at the Valdez Marine Terminal at the end of the 800-mile pipeline.
Alyeska traced the piece back to milepost 385, about 70 pipeline miles north of Fairbanks.
There, in 2012, Alyeska had installed a domelike “encapsulation” over an unused air vent that had posed a risk for oil leaks.
As it turned out, the encapsulation proved faulty, dislodging the metal piece that then traveled down the pipeline.
PHMSA is concerned that numerous other encapsulations installed on the pipeline might also be faulty.
‘Full confidence’The agency issued a “notice of proposed safety order” calling for Alyeska to monitor the encapsulations, to test some of them, and to fix any problems. The proposed order sets deadlines to complete much of the work by the end of September.
Alyeska, however, can try to negotiate terms with PHMSA.
The company is in the process of responding to the proposed safety order, Alyeska spokeswoman Michelle Egan told Petroleum News on April 9.
She noted that the stray metal incident did not result in an oil spill or a pipeline shutdown, and that Alyeska “took immediate steps” to repair the failed encapsulation at milepost 385.
“Extensive testing and investigation is ongoing and Alyeska is operating (the system) with full confidence in pipeline integrity,” Egan said.
In its proposed safety order, PHMSA laid out the preliminary findings of its investigation.
In August 2012, Alyeska encapsulated what was described as “a construction-era high point vent” at milepost 385. The pipeline in that area runs above ground.
The job involved welding the encapsulation to the pipeline, and filling it with epoxy.
An analysis showed that as the epoxy cured, pressure built up inside the encapsulation, and this resulted in a “punch-out” of a piece of the steel pipeline wall. This piece, called a coupon, entered the oil stream and rode to Valdez.
The safety order reveals that Alyeska work crews found a small oil leak from the encapsulation the day after it was installed.
Alyeska secured the milepost 385 site by installing a “full-encirclement, pressure-containing sleeve” on the pipeline, PHMSA said.
Dramatic lab testThe safety order also describes a rather dramatic laboratory experiment to simulate the pipeline failure. About 3½ hours after epoxy was poured into an encapsulation installed on a mock-up section of 48-inch pipe, the encapsulation “bulged and then failed during the curing process.”
Pipeline wall material and epoxy shot into the mock-up, and the “explosion” resulted in a lab safety incident that itself required an investigation, PHMSA said.
The concern now is the condition of about 90 other encapsulations Alyeska installed over vents and drains between 2010 and 2013, the agency said.
Concerns include cracking of the pipe underneath the encapsulations, and internal pressure in the encapsulations as a result of epoxy curing or crude oil leakage, PHMSA said.
“Despite significant field testing to date, PHMSA believes Alyeska still has not fully addressed the integrity conditions at all of the other encapsulation sites,” the agency’s proposed safety order says. “Alyeska proposed a plan to address many of our remaining integrity concerns through additional field testing ... but that testing cannot be accomplished until weather and site conditions improve.”
PHMSA is proposing a list of corrective measures. These include developing a protocol for increased monitoring of the encapsulations, conducting ultrasonic and other field tests, and relieving encapsulation pressure.
Anchorage-based Alyeska operates the pipeline on behalf of the owners, including BP, ConocoPhillips and ExxonMobil.
The line has been moving Alaska North Slope crude since 1977.
Barrett, the Alyeska president, formerly headed PHMSA.