San Bruno Pipeline Accident Update

Hi all,

Sorry for the long URL.

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Erik

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Erik
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Erik

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Erik

Erik, what software do you use that cplits URLS in this fashion? i

Reply to
Ignoramus21697

MT-NewsWatcher.

Erik

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Erik

Erik wrote in rec.crafts.metalworking on Tue, 14 Dec 2010 13:57:21 -0800:

Url reduced for you.

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dan

Erik wrote in rec.crafts.metalworking on Tue, 14 Dec 2010 14:04:58 -0800:

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Reply to
dan

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.

Steve

Reply to
Steve B

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 l "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....

Reply to
Jim Stewart

Steve, this is very useful to know. DO you know if that one "outside" weld that leaves a root inside, is done with one pass?

i
Reply to
Ignoramus21697

Send him this link (fast forward to about 1:10 for the good stuff) to see a graphic example of the power potential of compressed air or gas.

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Jon

Reply to
Jon Anderson

Here are your links, unbroken:

Reply to
Michael A. Terrell

Find yourself a copy of ASME B31.1-31.3 and read it, or at least the section on inspection.

Reply to
John R. Carroll

What percentage of that force is due to the truck rim flange and how much is due to the jet force of a puncture? That's more of a high-speed mechanical disconnect with mass vs a puncture.

Or would the pipeline be more of a half-circumference fracture which enlarged? How do they actually fail? Rustouts would be pinhole jets, but what happened here?

I dunno, but it feels like an apple/orange comparison here.

I can see that 400psi would blow out a lot of earth, but it doesn't seem strong enough to lift a long, heavy, rigid pipe + earth unless it had found a flame and exploded.

LJ--not an engineer.

-- Small opportunities are often the beginning of great enterprises. -- Demosthenes

Reply to
Larry Jaques

And where does the energy come from? All the energy released in the failure originates with the air pressure, the explosive nature of the failure is due to the strength of the materials being exceeded.

Well in a sense it is, but it does demonstrate the power of compressed air, or gas. There is a reason things like gas bottles are tested with water under pressure (hydrostatic) instead of compressed gas. Spring a leak with water, and pressure drops at once.

As for the explosion theory, where did the oxygen come from that would be needed for an actual explosion? I could see gas seeping through the earth catching fire and burning at the surface. But I can't see there being any significant oxygen, let alone an ignition source, around a buried pipe. Don't forget, there was a hell of a lot of volume of gas in that pipeline. It wasn't like the pressure suddenly dropped the instant the pipe began to fail. And, the earth is a lot heavier than the pipe. If the failure was at the bottom and there was enough force to move all that earth, moving the pipe as well is rather trivial.

Just my seat of the pants thoughts, worth half what ya paid for them...

Jon

Reply to
Jon Anderson

Well let's see. A 30 inch dia pipe would have 30 times 12 square inches or 360 sq inches per foot of length. That times 400 psi would be 144,000 lb of force per foot of length or 72 tons of force per foot of length trying to rupture the pipe. That might be strong enough to lift one foot of pipe and the earth above it.

Dan

Reply to
dcaster

Sonnofabitch...

I changed hundreds of split-rim logging truck tires in my misguided youth...

Reply to
Jim Stewart

My first truck had split rims originally and I changed my first set of tires myself. Dad showed me how and I didn't think it was any big deal. When he showed me how to insure the rim lock was seated, I didn't question it at all, just followed his example and had no problems.

But boy, when years later I read about a guy decapitated from a split rim coming apart, it sure sent a chill up my spine! Yeah, I was right on top of those suckers when airing them up...

Jon

Reply to
Jon Anderson

Yup, we had just a few rules, make sure the rim wasn't bent and that it seated properly, use a clip-on air chuck and then step back a few steps as it filled. We never had a problem.

I learned from my uncle and he had been a tire man for a good 20 years. He was pretty clear on stepping back as the tire filled.

Reply to
Jim Stewart

Certainly. I visited a pipe plant in W. Java that made spiral welded pipe ranging from 12 inch to 36 inch, with a maximum capacity of 48 inch. An Australian based company had built the plant and were in the start up phases when I was there. All of their pipe was welded single pass using a submerged arc system.

You could see the weld on both the inside and the outside and as I recollect that was the first stage in inspection - look to see if it was a continuous weld on both sides. Cheers,

John D. Slocomb (jdslocombatgmail)

Reply to
J. D. Slocomb

No, I really don't. What I find fascinating is inspecting small square or rectangular tubing. A welding crown is clearly visible on the inside, but how in the world do they get it in such a small space? I'd like to see it on How It's Made, or go to a factory for a tour.

Steve

Reply to
Steve B

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