Bad weld caused San Bruno pipeline explosion?

It probably is. Gas runs at very low pressures of a few PSI in the home, in the teens and twenties in larger lines. I don't recall where I read that...OK, this one says 200-1,500psi in the mains.

guess I was misled earlier.

That's the bad part. They didn't catch it before it blew.

I'm interested in seeing a closeup of the inside and outside (and welds) of the pipe.

-- Not merely an absence of noise, Real Silence begins when a reasonable being withdraws from the noise in order to find peace and order in his inner sanctuary. -- Peter Minard

"F. George McDuffee" wrote

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

"Larry Jaques" wrote>

Wall thickness for a particular job is dictated by multiple parameters, pressure being right in there towards the top.

Steve

1000psi, 30". The photo showed one end of the pipe (thrown many feet from the crater by the explosion) with one end as if it had been cut cleanly perpendicular to the pipe (a factory end, if you wish); the other end was harder to see in the photo, but looked torn and mangled.

The gas wasn't required to be odorized, and PG&E hasn't confirmed whether it was or not. 1000PSI bursting will create quite the mess even if the pipeline had been charged with air.

scott

It's 3/8". (.375).

It's a transmission line, not a distribution feeder, so it was buried deeply.

scott

54 years ago, when this line was installed, they were used.

scott

So, maybe, my guess from just lopoking at the first photo, was right.

i

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

>

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.