A few weeks after gas pipeline 132 in San Bruno split open and spewed a deadly geyser of flames, PG&E sent a robot with a camera through the out-of-service pipelines around the break, searching for other potential hazards that had existed in it without their knowledge.
And they apparently found plenty.
In one dramatic case, the pipe had been punctured and hastily plugged with a makeshift patch. In another, the pipe had been dented, causing a small split in a nearby seam. In several cases, liquid sat pooled in the pipe, a problem that could lead to corrosion.
In one instance, the robot illuminated a pipe that one expert suspected might have had the same basic fatal flaws as the one that ruptured.
Excerpts of the camera’s investigation were among hundreds of documents released this week by the National Transportation Safety Board at the start of a three-day hearing in Washington, D.C. It included pictures taken by the robot Versatrax 300 as it traversed about a mile and a half of pipeline 132 — a trek the technology could not have made while the pipeline was still in service.
The San Francisco Examiner consulted experts and asked them to interpret what the cameras found.
The most striking photo shows a large dimple surrounding a gouge in the pipe. UC Berkeley engineering professor Robert Bea speculated the puncture may have been inflicted by a construction crew doing other work near the pipe. The crew responsible apparently poured concrete on the puncture to stop it from leaking and then welded a patch from the outside.
“That method could be effective in a pipeline out in a pasture — if there are no animals around it — but if you get this in the middle of a neighborhood, it’s a big uh-oh,” Bea said.
Other pictures showed black spots on the edge of a weld and strange grooves on the pipe.
From Bea’s view, the most interesting photo showed a series of short sections of pipe welded together, just as the pipeline that exploded had been. Along the length of the pipe runs a black groove, much less tidy than seams in other photos.
“I think we could have a problem here,” Bea said. “It leads me to think the black line is a weld that has not been welded — there should be a weld filling up the space of that black line.”
Bea speculated that’s what the inside of the ruptured pipe looked like prior to explosion.
Bea and pipeline expert Richard Kuprewicz, who also reviewed the document, said PG&E would likely still be ignorant of these problems if the rupture hadn’t happened, and that is proof that PG&E should be required to conduct more-rigorous inspections of their pipes.
As it stands, PG&E tests the vast majority of its pipelines using a simple method that can only detect certain kinds of leaks and corrosion, but would miss virtually all the problems the camera caught.
PG&E spokesman Paul Moreno said the company is actively working to expand its ability to inspect its lines from the inside, and to verify the validity of the information it has about its pipes.
Kuprewicz said PG&E may be afraid of the expensive problems it will find if the utility uses rigorous testing methods.
“If they were to do the camera on other lines, what are they gonna find?” Kuprewicz said.