A 60-year-old coupling failed during a pipeline relocation project in January in midtown Tulsa, causing a loud explosion and evacuations of nearby neighborhoods.
Oklahoma Natural Gas acknowledged that “it failed to follow” its procedures in the construction project, according to a response letter in the Oklahoma Corporation Commission’s pipeline safety report released to the Tulsa World.
The Corporation Commission found there were two probable violations for ONG. One was a probable violation for failure to follow plans and procedures for the part in question and another probable violation was for failing to comply with specifications or standards for the project.
“ONG’s investigation determined that a recent pipeline construction project replaced part of an originally all-welded 16-inch pipeline installed in 1955,” ONG officials state in the letter to the Corporation Commission. “Although records existed, the project designers and reviewers failed to identify that two couplings had later been installed in 1959.”
Corporation Commission investigators defined the failure as a rupture due to a mechanical failure.
Project engineers failed to identify the two couplings when designing the project. ONG told OCC that the corrective actions taken included additional engineering reviews of projects and additional training for engineering personnel. Standards and specifications dictate that couplings should be reinforced in such projects.
The rupture occurred just after 3 p.m. Jan. 31 at a construction site in the 2200 block of South Memorial Drive. Residents and businesses were evacuated, and Memorial Drive was shut down for hours after the rupture. The gas flow was stopped upstream around 5:50 p.m.
The pipeline was operating at normal pressure, 230 pounds per square inch, according to the report. The rupture and explosion caused an estimated $369,000 in damage.
Investigators determined, roughly, what had occurred relatively early in the investigation. However, it was not reviewed and forwarded to ONG until late May, giving the company an opportunity to respond. ONG responded to the investigative report within three days.
Gas was shut off to the ruptured pipeline, and more than 50 Oklahoma Natural Gas employees were at the scene that night to restore service. No injuries were reported. Electric power was cut in the area temporarily that day to prevent electrical sources from igniting the gas.
“The safety of our customers and the communities we serve is our number one priority,” ONG said in a statement. “We cooperated with the OCC following this event and implemented additional reviews and training.”
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