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Update San Bruno Fire

by D. Boyer

If you follow the url provided it will take you to my Youtube playlist that contains eye witness video of that disaster.
My thoughts and prayers go out to the families affected.
The NTSB has just released a report about the piece of pipe that failed and caused the San Bruno gas pipeline explosion.
The conclusion is "No external corrosion."

"NTSB Advisory
National Transportation Safety Board
Washington, DC 20594
December 14, 2010
This is an update on the continuing investigation of the natural gas pipeline rupture and explosion that
killed eight people in San Bruno, Calif., on September 9, 2010.
The investigative group conducting the metallurgical examination of the pipe is chaired by the National
Transportation Safety Board and includes technical experts from the Pipeline and Hazardous Materials
Safety Administration (PHMSA), the California Public Utilities Commission (CPUC), and Pacific Gas
& Electric (PG&E). This group is in the midst of an exhaustive evaluation of the ruptured pipe pieces.
What follows is factual information that has been developed at this early point in the investigation.
PG&E survey sheets and charts for the rupture location indicate that the pipeline was constructed of 30-
inch-diameter seamless steel pipe (API5L Grade X42) with a 0.375-inch thick wall. Evidence obtained
so far, however, indicates the pipeline in the area of the rupture was constructed, at least in part, with
seam-welded pipe.
After the ruptured pipe surfaces were thoroughly surveyed, all of the asphalt coating was removed and
the pipe was cleaned to allow for visual inspection and nondestructive testing (NDT) of the surfaces.
The condition of the welds was evaluated by visual inspection, x-ray radiography, and magnetic
particle inspection to document any defects or irregularities in the material. Pipe thickness surveys
were conducted using ultrasonic thickness testing. Additionally, the pipe pieces were laser scanned for
complete dimensional documentation.
The fracture surfaces of the ruptured pipe pieces were examined using low-magnification optical
microscopes. Samples were then cut from the ruptured pipe pieces for detailed metallurgical
examination. The fracture surfaces were examined under both high-magnification optical microscopes
and scanning electron microscopes to identify and document specific fracture features. Metallurgists
are currently in the process of using this information to determine the direction of crack propagation
and the fracture origin and failure mechanisms.
Investigators found that while the longitudinal seams on some of the pipe segments were fusion-welded
from both inside and outside the pipe, some were fusion-welded only from the outside of the pipe. In
order to understand this variance, investigators are in the process of researching pipe welding standards
and practices in effect at the time the pipeline was installed in 1956.
The outer surfaces of the ruptured pipe pieces revealed no evidence of external corrosion. No dents,
gouges, or other physical indications consistent with excavation damage were observed. Additionally,
no physical evidence suggests that a pre-existing leak occurred in the ruptured pipe pieces.
The following laboratory work is ongoing:
• Chemical compositional analysis and mechanical property testing of samples taken from the
ruptured pipe pieces.
• Evaluation of environmental factors at the accident site.
The investigation is still in an early phase and there is much factual information to be developed before
the Safety Board is positioned to determine the probable cause of the accident.
Other areas that investigators are examining include pipeline control and operations, regulation and
oversight, human performance, survival factors, and pipeline maintenance and records.
Additional factual updates will be provided and distributed via media advisory as investigative
information is developed.

Preliminary Report issued on 10/13/2010
Launch of investigation
NTSB Media Contact: Peter Knudson
peter.knudson [at]
(202) 314-6100
NTSB Home | << Back to Press Releases Page << | News & Events
§The failed piece of pipe.
by D. Boyer
28-foot-long ruptured section of pipeline at laboratory facilities at the NTSB Training Center, Ashburn,
§Police scanner recording snippet
by D. Boyer
Listen now:
Copy the code below to embed this audio into a web page:
This is a snippet of the police scanner chatter when the blast occurred.
This recording is for mature audiences only.
It includes the discovery of the blast by multiple counties, some of which are miles away. It also includes the confusion about the location, and includes dispatch announcing there is a plane down. It also includes the report that several house's and blocks are on fire. The rest of the scanner recording which I did not include in this snippet is the discovery that there is no water supply.
§The pdf of the NTSB report
by D. Boyer
I attached a pdf file of the NTSB investigation report.
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