Bad weld caused San Bruno pipeline explosion?



Still not enough zoom to get a good look at the weld or the structural failure zone.
Steve
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Lizzie, what my thinknig was, if the weld failed summarily, it would be a clean line like we saw on the photo.
If the pipe ruptured, it woud not look like a clean cutoff.
i
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Pipeline failures and ruptures mostly start at some weld point, and then like a weak spot in the paper, a tear follows along that. You will notice that all the photos seem to suggest a failure along a joint rather than out in undisturbed metal.
That is what is the problem. There are no real close ups, to show where failures occur in the adjacent metal, and the actual weld metal holds. In a real world, in a real weld, the weld is stronger than the surrounding metal, as proven again and again and again by destructive testing.
Steve
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@NOSPAM.478.invalid says...

The pipe may have ruptured along the heat-affected zone of a buttweld. The HAZ is typically more brittle and prone to failure than either the base metal or the weld itself. That could leave a pretty clean fracture line right along the toes of that old weld.
--
Tin Lizzie
"Elephant: A mouse built to government specifications."-Lazarus Long
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On Sat, 11 Sep 2010 14:08:39 -0500, Ignoramus1469

=========The news as it trickles out seems to be getting worse and worse.
http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2010/09/12/MNB91FCDGK.DTL <snip> NTSB investigators are looking to determine why a 40-foot section of pipe that was blown into the air by the original explosion appears to have been cut at some earlier point and rewelded in segments. <snip>
{Coincidentally, much of the PG&E data appears to have been "lost."}
<snip> Despite numerous reports that people in the neighborhood had reported the smell of gas in the days before Thursday's explosion, officials from Pacific Gas and Electric Co., which operates the 30-inch-diameter, high-pressure pipe, said Saturday that so far they have discovered no evidence that they received any calls.
A look into company records has found "no confirmed calls by residents in the vicinity within nine days" of the explosion, PG&E President Chris Johns said at a news conference. The utility also has no record of any construction work being done in the area by PG&E crews in the days before the blast. <snip>
-- Unka George (George McDuffee) .............................. The past is a foreign country; they do things differently there. L. P. Hartley (1895-1972), British author. The Go-Between, Prologue (1953).
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BTW, does anyone know the operating pressure of those lines?
Interesting .........
Citizen, "We called in and reported gas. I'm 67 years old and have smelled gas before."
PGE, "Yes, but can you PROVE it?"
Bet they tightened up security after that Erin Brockovich thing.
Steve
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So, maybe, my guess from just lopoking at the first photo, was right.
i

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I posted this earlier, and it has not appeared on my computer. I apologize if the rest of you are seeing it twice.
Here is what I think must have happened to produce the gas explosion. I don't have enough evidence to support this, except that no other scenario makes sense. We know that there were both gas and water pipes down there. After the explosion. the crater filled with water from the broken pipe. It's possible the water pipe was leaking before the explosion, creating an underground crater, which would have eventually led to a cave in, if the explosion had not occurred first. We know these things occur frequently. Now lets assume there was a gas leak in the pipe within that crater, causing it to fill with a combustible mix. Now all we need is an ignition source to complete the disaster. This could have come from a car exhaust or even a discarded cigarette, igniting the explosive mixture leaking up to the surface.
You can't explain that explosion by a ruptured pipe. That might produce a big flame, but not a crater-producing explosion, large enough to register on the seismographs
Some of the news media attributed the water in the crater to runoff from the fire hoses. That seems implausible, since we know there was a water main down there.
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Leo Lichtman wrote:

I'm betting on corrosion, Just like in Va. Look for Appomattox County Pipeline explosion
http://www.evfc160.com/main/article.php?story 090210194016157
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Steve W.
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Leo Lichtman wrote:

I own some property that has one of these high pressure gas pipeline running along the very back of the property. When talking to the owner of a construction company I had doing some work who happened to have been the town fire chief some years earlier he told me that that pipeline had a blowout a 1/4 mile or so from my property one winter. The gas did not ignite in that case, however the blowout blew open a ~10' crater from just the gas pressure alone.
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Pete C. wrote:

The pipeline company that dropped the line through the upper end of our fire district has a seminar yearly on what we should do if there is a problem. One of the things they ask every year at the start of the meeting is "So what will you do if you discover a problem with the pipeline in your area?" My usual answer is "Drive like hell the other way....."
They show films of best and worst case stuff along with what we should do in each case. The Va. blast was in the last one I attended. The video they had and the close up shots of the effects from the blast get your attention.
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Steve W.

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IMHO, this post by Leo L and earlier post by Erik show considerable insight regarding what may have actually happened. I also previously assumed that a substantial mass accumulation of NG + air mixture that subsequently encountered an ignition source would have been required to result in an "explosion" adequate to eject the pipe section and create the observed crater. In this scenario, if the NG + air mixture was in a confined space (e.g., underground cavity), the "explosion" could have been a detonation, which creates a shock wave and very substantial overpressure. Otherwise, the "explosion" would have been a deflagration, which usually produces a milder overpressure.
But, I have a question for you welding experts: Is welded-seam pipe such as this gas transmission line usually installed (i.e., laid in the trench) seam up or seam down?
If it is seam-down, then perhaps the sequence of events was simply: pressure acting on weakened welded pipe seam causes section of pipe to split along seam (see photos); reaction forces associated with ~375 psi gas (latest PG&E estimate) escaping through rupture forces pipe up through 3 feet of dirt and breaks off at welded joints; huge mass of escaping gas mixes with air, a large region is in flammable range and eventually encounters ignition source (TBD), mixture ignites and flashes back; a huge escaping gas jet fed flame (torch like) persists for over an hour untill PG&E is able to shut off the gas (and it obviously persists somewhat longer as the pressure bleeds down).
Does this make sense?
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wrote:

IMHO, this post by Leo L and earlier post by Erik show considerable insight regarding what may have actually happened. I also previously assumed that a substantial mass accumulation of NG + air mixture that subsequently encountered an ignition source would have been required to result in an "explosion" adequate to eject the pipe section and create the observed crater. In this scenario, if the NG + air mixture was in a confined space (e.g., underground cavity), the "explosion" could have been a detonation, which creates a shock wave and very substantial overpressure. Otherwise, the "explosion" would have been a deflagration, which usually produces a milder overpressure.
But, I have a question for you welding experts: Is welded-seam pipe such as this gas transmission line usually installed (i.e., laid in the trench) seam up or seam down?
If it is seam-down, then perhaps the sequence of events was simply: pressure acting on weakened welded pipe seam causes section of pipe to split along seam (see photos); reaction forces associated with ~375 psi gas (latest PG&E estimate) escaping through rupture forces pipe up through 3 feet of dirt and breaks off at welded joints; huge mass of escaping gas mixes with air, a large region is in flammable range and eventually encounters ignition source (TBD), mixture ignites and flashes back; a huge escaping gas jet fed flame (torch like) persists for over an hour untill PG&E is able to shut off the gas (and it obviously persists somewhat longer as the pressure bleeds down).
Does this make sense?
reply: I am busy and have far far far too many other things to do, so I'll just be lazy and wait for the reports from the people who are actually touching the evidence, examining it, and who know about such things.
I could be spending all that time analyzing fishing.
Steve
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I think it does make sense. Except that I suspect more corrosion occurs at the bottom of a gas transmission pipe regardless of where the seam is located.
I can remember my father telling about a part time gas line inspector who was inspecting a gas line on a Sunday. He called in and reported that there was a right smart leak in the pipe. The dispatcher was not sure what the inspector meant by a right smart leak. Was it worth getting a crew out to fix it on a Sunday? Or was it something that could wait until Monday? The inspector kept saying it was a right smart leak and he reckoned they might want to get a crew out there. When the crew arrived at the location of the leak, they found that the leak had blown out three joints of pipe. But there was no fire.
I can not recall how big the pipe was or the pressure, but think it may have been something like a 12 inch pipe and 600 lb pressure.
Dan
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"over-oaked" wrote: If it is seam-down, then perhaps the sequence of events was simply: pressure acting on weakened welded pipe seam causes section of pipe to split along seam (see photos); reaction forces associated with ~375 psi gas (latest PG&E estimate) escaping through rupture forces pipe up through 3 feet of dirt and breaks off at welded joints; huge mass of escaping gas mixes with air, a large region is in flammable range and eventually encounters ignition source (TBD), mixture ignites and flashes back; a huge escaping gas jet fed flame (torch like) persists for over an hour untill PG&E is able to shut off the gas (and it obviously persists somewhat longer as the pressure bleeds down). (clip) ^^^^^^^^^^^^^^^^ If my conjecture about leaking water producing an underground cavity us correct, then let me add some thoughts to what you have said here. If water leakage washed away the soil around the gas pipe, it would have left it unsupported, so it would sag under its own weight. This would create bending stress in the pipe shell, superimposed on the hoop stress due to pressure. This combination of stresses would be acting on a pipe which is already near the end of life from corrosion. This could be the reason for the gas leak which many people smelled, and which ultimately led to the explosion.
IOW, it's likely not a coincidence that the leakage happened just where the cavity was.
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I find it really hard to understand that PG&E could not turn off the gas. I heard the valve was to close to the fire... But what about the next one.
There should have been one on each end - isolation valves as they call it.
Sounds as if they didn't want to cut off another neighborhood but just burn the gas until the main regulator tank pressure dropped.
If I was there and in charge or semi-so - cut off the far end to cut off the local - get the fire off and then get PG&E re-light the pilots on the ok section.
Now just who will pay for the gas ? - I bet the customers in the long run.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net "Our Republic and the Press will Rise or Fall Together": Joseph Pulitzer TSRA: Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Originator & Charter Founder IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com /
On 9/18/2010 10:01 PM, Leo Lichtman wrote:

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My logic says there is some sort of a device that, whenever there is a drastic drop in pressure, which would happen in a rupture, that there are automatic shutoffs on the pipeline.....................? No one needs to "shut it off". Just like happens with an electric grid. When there is something way amiss sensored by the monitors, it just shuts itself off.
Steve
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"F. George McDuffee" wrote: (clip)A look into company records has found "no confirmed calls by

^^^^^^^^^^^^^^^^^^^ If he's telling the truth, it shows that the citizen reports were not taken seriously. When the NTSB carries out a full investigation, I hope they interview the PG&E employees who might have investigated the complaints from the neighborhood.
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I hope they interview the neighborhood members themselves. Their bills might show calls to the gas company help line - e.g. cell phone calls and some home bills will do that.
Maybe a time and date will bring the 'angry customer call - no issue' out into the light.
Martin
Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net "Our Republic and the Press will Rise or Fall Together": Joseph Pulitzer TSRA: Endowed; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal. NRA Second Amendment Task Force Originator & Charter Founder IHMSA and NRA Metallic Silhouette maker & member. http://lufkinced.com /
On 9/12/2010 7:46 PM, Leo Lichtman wrote:

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http://www.csmonitor.com/USA/2010/0911/What-caused-deadly-San-Bruno-fire-Investigations-underway
'I was not there', and I have no information to contribute. I have learned to wait for the investigation report before forming an opinion as to the real cause of any incident/accident or of the completeness or reliability of the investigation.
However speculation can sometimes be fun and an interesting exercise, if nothing else it requires us to have an open mind and to resist jumping to conclusions as often times 'things are not what they first appear'.
http://www.henrymakow.com/was_san_bruno_explosion_a_plan.html
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