The Texas Eastern pipeline explosion that injured one man, damaged several homes and disrupted gas flows to the Northeast last week involved a pipeline that federal investigators said had corroded in at least two places.
The U.S Department of Transportation’s Pipeline and Hazardous Materials Safety Administration cautioned that “the cause of failure is unknown at this time, and the investigation is ongoing,” in a document on Wednesday.
A preliminary investigation into the April 29 blast, however, revealed corrosion along two welds. One was located right where the pipeline ruptured and another was in a section of the pipe excavated after the accident.
“The pattern of corrosion indicates a possible flaw in the coating material applied to girth weld joints following construction welding procedures in the field at that time,” the agency wrote.
Although sections of pipelines are typically coated by the manufacturer, weld joints are coated onsite and likely with a different material.
The 30-inch diameter pipeline that ruptured in Salem on Friday was installed in 1981 and was tape coated, said Creighton Welsh, a spokesman for Spectra Energy, which operates the Texas Eastern system.
“Tape coating was an accepted and preferred method of coating the pipeline weld joints,” he said. Tape coating refers to the method of coating, rather than the type of material used.
As part of a corrective action order issued to the company, the federal pipeline regulator laid out a plan that Spectra must follow before it can put that section of its pipeline back into service.
It includes excavating and examining the joint welds on additional sections of the affected pipeline and the three other lines all within 25 feet of each other that make up the Texas Eastern system in that area.
The ruptured pipe, 25 feet of which shot up in the air during the explosion and landed some 100 feet away, has been sent out for metallurgical analysis.
Richard Huriaux, a consulting engineer, and former director of regulations and technical standards at PHMSA, said welding procedures and coating quality have improved significantly over the years.
But he warned against investing in the preliminary analysis.
“Corrosion is the second-largest cause of failure,” Mr. Huriaux said. But “the fact that they found some corrosion nearby is neither here nor there at this point.”
Investigations into accidents such as this can take months or years and often amend, if not altogether reverse, a preliminary finding.
“It’s a hint, but it’s not a determination,” he said.
Two weld cracks found on the Texas Eastern pipeline last year, one in Tennessee and another in Texas, are still under investigation.
A crack in a girth weld in Texas was discovered by company employees in Texas in November when a leak was detected from that pipeline.
In December, a landowner in Tennessee reported a leak to the company on a 30-inch line. When the company excavated the pipe, it found a crack in the girth weld.
According to federal data, there have been 62 incidents on Texas Eastern’s 9,000-mile system in the past 30 years, ranging from internal corrosion to barges crashing into transmission lines.
A lightning strike hit a compressor station in Perry County in 2000. A plane crashed into a pipeline in New Jersey in 2003. Off the coast of Louisiana, a shrimping net pulled loose a section of a pipeline connected to Texas Eastern’s system in 1995. More common, however, are instances when someone detects a leak, and the company discovers corrosion, or an unrelated party is digging in the ground and dings the pipeline.
Closer to home, a fire broke out in 2006 at the Delmont Compressor Station, a large complex of tanks and pipes that process natural gas in Delmont, after a small gas leak in one of the compressor cylinders ignited.
The pipeline that exploded last week was inspected from the inside in 2012 and the results of that inspection found nothing that had to be repaired or replaced before the next scheduled inline inspection, in 2019.
“We also conduct routine field surveys of the corrosion prevention systems, including bimonthly inspections,” Mr. Welch said.
The pipeline was operating within its allowable pressure last week. The company registered some pressure drops before the explosion, Mr. Welch said. He did not have further details.
A pressure drop sometimes is an indication of a leak or other problems.
The gas that feeds that section of the system flows from the Delmont Compressor Station, which is about a mile from the explosion site. Just before the break, some 1.3 billion cubic feet of gas was coming through there daily, roughly equivalent to 7 percent of the volume flowing out of the entire Marcellus Shale field each day.
Within an hour after the explosion, the compressor station shut down so as to prevent feeding the ruptured line. The shutdown provided one bookend that isolated the gas flow, while a site 15 miles away served as the other.
The compressor station remains closed, but Spectra’s top officials told analysts during a company earnings call Wednesday morning that they don’t expect the halt on the system to be a “long-term issue with respect to flows.”
There are many pipelines in the area, said Gregory Ebel, Spectra’s CEO, and the industry is adept at finding workarounds.
As for Spectra, Mr. Ebel said that “all things taken in, we would not expect any material impact financially from the incident.”
Anya Litvak: alitvak@post-gazette.com or 412-263-1455.
First Published: May 4, 2016, 7:41 p.m.
Updated: May 5, 2016, 3:43 a.m.
