A manufacturing defect, degraded coating and ineffective corrosion prevention system contributed to a fatal explosion and fire on Enbridge Inc.’s Texas Eastern Transmission (Tetco) natural gas pipeline near Danville, KY, the National Transportation Safety Board (NTSB) said Wednesday. .
The rupture of Tetco’s Line 15 in August 2019 and the ensuing fire killed one person and sent six people to hospital. The NTSB noted that the incident burned about 30 acres of land, destroyed five homes, and damaged 14 other residences. The accident also raised concerns in the market about potential limits to gas flows from the Appalachian Basin reaching the Gulf Coast.
Investigators concluded “that the combination of a pre-existing manufacturing defect – known as a hard spot – with degraded pipeline coating and ineffective cathodic protection, led to hydrogen-induced cracking at the outer surface of the pipe”.
Cathodic protection, aka CP, is an electrochemical method for controlling corrosion of pipelines and other metal surfaces.
According to the NTSB, Enbridge’s integrity management program contributed to the accident by not accurately assessing the condition of the 30-inch-diameter pipeline or estimating the risk of interactive threats.
The NTSB said its accident report concluded that “Enbridge underestimated the risk posed by hard points because its processes and procedures were inconsistent” with Pipeline and Hazardous Materials Safety Administration (PHMSA) guidelines, as well as “knowledge of the ‘hard spot threat interaction industry’.
To compensate for increased external corrosion, Enbridge and the system’s previous owners increased CP voltages on the affected segment of pipeline, investigators noted.
The NTSB report recommended six safety actions, three of which were directed at Enbridge and three at PHMSA, related to assessing the risks of changing gas flow, limits on analyzing line inspection data , threat assessments and threat interactions, and training and requalification practices.
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Quick review and response
“PHMSA will promptly review and respond to these recommendations,” a spokesperson told NGI. Pipeline failures like the Tetco incident “are not acceptable”.
Underscoring this, PHMSA “shares…the NTSB’s commitment to preventing pipeline accidents,” the spokesperson said. The representative added that the two federal entities have “a long history of cooperation and collaboration” to advance the safety, reliability and environmental performance of US pipelines.
“PHMSA continually seeks to leverage and evolve its oversight program, including changes to pipeline safety policies and inspection and enforcement approaches,” the spokesperson said.
One of the main tenets of PHMSA’s “monitoring program” is that pipeline operators should know and understand their pipeline systems and use appropriate technologies and procedures to address risks in order to prevent pipeline failures, while taking into account the inherent limitations of the technology,” according to the spokesperson.
“PHMSA prescribes in detail the factors that must be taken into account to mitigate risks and conducts inspections to ensure that adequate measures are taken and implemented effectively.”
Additionally, PHMSA’s research and development investments are intended “to leverage the best expertise in the world to help improve technology, in particular to improve detection methods relevant” to the Tetco accident.
“Enbridge takes these recommendations very seriously,” a spokesperson told NGI. “For more than three years since the incident occurred, we, in coordination with PHMSA and the NTSB, have worked diligently to understand the contributing factors to this incident and have made tremendous strides in modifying our procedures. , process and conducted thorough inspections in an effort to make our pipelines safer than ever.
The spokesperson said Enbridge “leverages technology, data and independent expert advice to ensure the effectiveness of our pipeline integrity management programs across all of our assets. And we will share these findings with our peers to focus on improving industry best practices and continuous improvement.