In the wake of an explosion this spring that ruptured a natural gas transmission pipeline in Westmoreland County, severely injuring one man and charring a quarter mile of land, Spectra Energy Corp. is planning to dig up hundreds of sites along a 263-mile stretch of the Texas Eastern pipeline running from Pennsylvania to New Jersey.
The four parallel pipelines that make up the system run from the Delmont Compressor station — a large complex a few miles from the site of the April explosion — to Lambertsville, N.J. The same type of tape coating that was found to have failed at the site of the April 29 explosion has been applied to hundreds of sites along those 263 miles, prompting the effort.
The assessment will be “thorough and conservative,” said Spectra spokesperson Creighton Welch, and will involve excavations, interior and exterior inspections, and reviewing inspection and construction records.
The Texas-based company hopes to return the system to full service by Nov. 1, in time for the winter heating season. The pipes carry natural gas — much of it produced in the Marcellus and Utica shales — to homes, industrial facilities and electric power plants in the Northeast.
Overall, the Texas Eastern system contains some 9,000 miles of natural gas transmission pipelines running from the Gulf Coast to the Northeast. There are more than 2,000 miles that travel through Pennsylvania, and 44 percent of those were installed before 1970.
‘History is a great teacher’
Major pipeline accidents, in the process of finding out what went wrong, often inspire operators and regulators to look at where circumstances might repeat.
“History is a great teacher,” said Nick Ashcraft, project manager at the Washington D.C.-based trade group, The Interstate Natural Gas Association of America Foundation. “We’ve improved the quality of the steel tremendously. We’ve improved coating, construction processes.
“Things have changed over the years. And incidents like these drive that change,” he said.
Pipeline design and construction methods have evolved over the decades that the Texas Eastern system was created, as have regulatory standards.
For example, the 30-inch pipeline that burst in Salem Township in April was put in the ground in 1981 and its welds were coated with a certain kind of tape no longer used in the field. A preliminary analysis of a weld that burst and another near it found they were corroded and that their tape coating appeared flawed.
But a test of the “cathodic protection system” on that stretch of pipe in April 2015 raised no red flags, Spectra confirmed.
Cathodic protection is another method of preventing corrosion on exposed pieces of metal by pumping electric current to them. All of Texas Eastern’s 9,000 miles are cathodically protected and all but 38 are coated, according to its 2015 annual report submitted to federal regulators.
The problem with tape and other older coatings systems is that they can become detached from the pipe and also act as shields for the electric current that’s intended to pick up the slack when coatings fail.
Spectra doesn’t know yet how long the coating flaws on the welds in Salem had been there. It’s also not confirmed whether corrosion under those flaws was the cause of the accident.
The root cause won’t be revealed until the full investigation by federal regulators is completed, which could take months or even years. But Spectra plans to release the results of its own preliminary investigations in late summer or early fall, Mr. Welch said.
Finding the best coating
The tendency of old coating methods to resist cathodic protection and mask flaws shielded by them is well known in the industry.
“Coatings have come a long way in the past 30 years, 40 years,” said David Wint, director of pipeline integrity for Audubon Field Solutions., an engineering firm, who is based in Tulsa, Okla.
In the 1950s and 1960s, it was typical to lay a rag under a pipeline and pour hot coal tar over it, then spread the tar around the surface of the pipelines. The practice was called “granny raggin,” he said.
Then came the age of asphalt, glass and felt, a coating that included asbestos. Asbestos is now known as a carcinogen, meaning pipes with those coatings now face an extra layer of hassle during repair.
“That was a little bit better,” Mr. Wint said. “However, based on my experience, they have a life of approximately 40 years.”
That practice lasted through the 1970s and early 1980s, when tape coatings came into fashion.
The current standard — fusion-bonded epoxy — doesn’t interfere with cathodic protection systems. The majority of the stretch of the Texas Eastern pipeline that burst in April was coated with fusion-bonded epoxy.
But the welds, which are done on site and typically have a different coating, were covered with tape, according to a preliminary report issued by federal regulators days after the April 29 blast. It’s not known how many other sections of the Texas Eastern system have the same coating profile but it is estimated to be in the hundreds.
In its intensive review over the next several months, Mr. Welch at Spectra said the company won’t be just focusing on tape-coated areas but will evaluate “areas based on a variety of characteristics, such as construction methods and inspection data.”
Last year, Spectra repaired 1,909 anomalies found on the entire Texas Eastern system across 17 states, according to data submitted to federal regulators.
It detected and repaired eight leaks, including four in Pennsylvania — one each caused by external corrosion, equipment damage, natural forces and other weather or outside forces.
Mr. Welch declined to provide a cost for the upcoming assessment. “While this is a significant part of U.S. energy infrastructure, we intend to be methodical in our evaluation and take the time we need to do a thorough assessment,” he said.
The company notified its customers that it will be reducing the pressure and the amount of gas that can travel through the system during the assessment process.
Anya Litvak: email@example.com or 412-263-1455.