Bad weld caused San Bruno pipeline explosion?

If the pipe is pressured to, say, 600 PSI, which is a nubmer that I saw here, then if it ruptured, it will be explosive. Then the mixture of gas and air would ignite. But just a pipe rupture with a compressible medium will be sort of explosive.

As opposed to what???

i

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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

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.

"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.

I'm betting on corrosion, Just like in Va. Look for Appomattox County Pipeline explosion

Just had a thought.

Maybe it was over pressured due to high demand. Yes I know it is 'summer' but the mornings and evenings have heavy fog banks there - that causes some to heat in those hours as well as cook.

Mart>> Erik writes:

Exactly. The break appears to be that jagged edge sticking up further back along the pipe section. There also appears to be a flange fitting* behind that, so its possible that the failure could be related to that.

*It could be the remains of a truck wheel for all I can see in this photo.

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.

Mart> "F. George McDuffee" wrote: (clip)A look into company records has found "no

Guy with back hoe nicks the pipe while doing work on other utilities, doesn't tell anyone and backfields the trench. Or just doesn't notice.

When I worked for the local power company, we had a back hoe operator digging near one of our main underground distribution lines (3 500 Kcmil alum 15 KV cables in PVC conduit), well marked. H said he thought he hooked a tree root, so he gave it a good tug. I pulled the cable off the connection where it went up a pole over a thousand feet away.

As opposed to what?

They do use plastic on the service laterals (about 50 PSI) to homes and small businesses. But the for the hich pressure stuff, steel is still used.

The transmission lines (this was one) are regularly inspected with instrumented inspection 'pigs'.

Natural gas (methane) is lighter than air. Propane is heavier. Still, I'd also suspect accumulated gas of some sort.

"Stormin Mormon" wrote: Natural gas (methane) is lighter than air. Propane is heavier. Still,

^^^^^^^^^^^^^^^^^^^^ What do you think of my post of 5:40 PM? It would explain how an explosive mixture could accumulate.

Whatever it was, there was quite an explosion. According to news reports the pipe line was buried 4 feet deep.

The blast, which erupted just after 6 p.m. on Sept. 9, threw a section of pipe 100 feet away?a section that National Transportation Safety Board investigators said might hold clues to what caused the blast that left a 167-by-26-foot crater.

The 28-foot length of pipe consisted of several smaller segments that were welded together in an unusual configuration. It also contained a long seam that ran the length of the pipe, the NTSB said.

Any air ordinance types that know how big a [fuel/air?] bomb would be required to blow a crater 167 X 26 X 4? foot deep and blast a piece of 30 inch steel pipe 28 feet long over

100 foot? Something rotten here....

Also does anyone know for sure what the line pressure was and how thick the pipe was? Some back of the envelope hoop stress calculations show there was little safety factor at even 600PSIG, if this was indeed 3/8 wall, and particularly if it has been buried for 50 years w/ no anti-corrosion coating/treatment. Was the line pressure recently increased?

-- 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).

"Ignoramus478" wrote

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

IIRC, high demand does not cause the supplier to increase pressure. The pressure is static.

Steve

fjo.124711$ snipped-for-privacy@en-nntp-08.dc.easynews.com...

Certainly, here in the UK, the pipeline network is used as a variable high pressure storage container ...

Certainly, here in the UK, the pipeline network is used as a variable high pressure storage container ...

reply: Then I did not recall correctly.

Steve

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.