Steve B wrote:
wrote in message
...
Hi all,

Sorry for the long URL.

http://latimesblogs.latimes.com/lano...sections-of-se
am-on-exploding-san-bruno-pipeline-were-welded-only-on-outside.html

Erik

I copied and pasted this url, and it worked for me. The second one you
posted said OOPS, broken.

This is interesting.

VERY FEW pipelines are welded both inside and outside. Most are just welded
on the outside, that being a confusing term. They are welded FROM the
outside, but the root pass penetrates into the inside of the pipe a tiny
bit, and joins the root of the two pieces together. Very few pipelines are
welded on the inside because it interferes with the cleaning devices run
through them. That would be for the welds that join the two pieces of pipe
together.

The article was about the absence of longitudinal welds, that is the welds
running from end to end, made when the pipe was rolled into a tube, and the
edges joined along their two longitudinal edges. The welds are then
finished so fine that it is difficult to find the weld. Apparently, the
sections of pipe had longitudinal welds that had inside and outside welding,
but some were missing the internal half of the weld. There would be major
inconsistencies if they were present in some sections, and not in others, or
were intermittent, as from a malfunctioning welding machine. I would
suggest that they were made with an automated welding device, perhaps using
the SAW technique. (Submerged Arc Welding)

It will be interesting to follow this. This particular fact of the
investigation is one that I would have never guessed. I always said I'd
wait for the final report, and this isn't even the final report, but it DOES
provide some of the actual facts of the metallurgical forensic
investigation.

There was also an interesting inconsistency between
the LA times article and the NTSB report. The NTSB
says..

"The rupture created a crater approximately 72 feet
long by 26 feet wide. A pipe segment approximately 28
feet long was found about 100 feet away from the
crater. The released natural gas was ignited sometime
after the rupture; the resulting fire destroyed 37 homes
and damaged 18. Eight people were killed, numerous
individuals were injured, and many more were evacuated
from the area. "

Whereas the LA times says...

"The powerful blast occurred after a major transmission
line running under a hillside neighborhood began leaking
large volumes of gas. When the gas ignited, it blew a
28-foot section of the pipe out of the ground and set
fire to more than 50 homes, 37 of which were completely
destroyed."

Early on, I tried to convince a cow-orker that a 30"
pipe pressurized to 400 psi would be quite capable
of heaving itself out of the ground and 100 feet away
just by the pressure of the gas released through a
failed weld. He wouldn't believe me....