Bad weld caused San Bruno pipeline explosion?

Scrith, perhaps? Hard to find, really hard to weld....& is it DOT-approved?

Traditionally, service lines are 0.5 {yes one half) psi. More recently, they may be 40 psi with a regulator at the meter. In house is still 0.5.

A transmission line such as this is 1000-2000psi.

You can be sure it was there decades before the subdivision. Pipelines stay put; the suburbs grow...

And other schemes.

Further, it would be wrapped to insulate it from ground, and cathodic protection current applied. IOW, there's a DC source, a sacrificial anode, and electroplating. Any place scraped SHOULD be protected by that, at least short term.

Steve -

Remember this is California - the place that refuses to build another power line through a bottle neck and run the wires almost to melting. The sag is measured and then they start to blackout someone.

The gas line from Texas goes through southern Ca. Another line was refused to be allowed to be built - the first one wanted all and more money.

So another line wasn't brought in to help in the usage.

I highly suspect that these local branch lines into a high use area are to small and as you pointed out to old. Some of these areas are power base politics - e.g. don't dig up my street...

So all they can do on electric - raise voltage to get more power through and with gas - raise pressure. The higher pressure fills the local storage tank (those with floating tops) and keeps them filled as needed.

Infrastructure racked by side slips and bending lands must be maintained at all times else failure is to be expected.

Mart>> Just had a thought.

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.

Still not enough zoom to get a good look at the weld or the structural failure zone.

Steve

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?

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

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

"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.

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.

Mart> "over-oaked" wrote: If it is seam-down, then perhaps the sequence of events

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

'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'.

Good luck with that. The people doing the scraping may be unaware that they've nicked it (to a backhoe, it feels like a rock). And some people may not want to admit it. Or be aware of the consequences.

Back in my days with the power company, we'd share a right of way with a number of pipelines. And the off roaders loved the rights of way as well. There were a few places where people had rutted the roads down to the pipes and continued to drive over them until the wrapping was completely gone. To them, its just like crawling their Jeep over a log.

Yeah - that "Underpants Bomber" around last Xmas was a setup, to give Obama an excuse to escalate the Cheney+Bush war on Freedom.

Thanks, Rich

You're sort of new to this whole Internet thing, aren't you?

;-)

here is a more recent speculation by the same author

I read through both, and didn't mention any plane or missile parts being found. There was some talk of 10 55 gal. barrels being removed.

My first impression of the drone theory is that even with high ordinance stuff, shrapnel is blown for miles, and any part of any drone/plane that would have been found would have made the finder an instant celebrity. If there were many pieces found, there would have been a bidding war on them. So far, I see none have come forth. An area that large in a population center would retain a lot of pieces. I don't know the address of the explosion, but San Bruno is what I would call dense, even if the house were on the border of the water or the uninhabited part of the peninsula west of

1. Drawing a five mile radius half circle with its center at 285 and 92 covers a LOT of densely populated space, the other half of the circle going onto what looks like hilly coastland.

When I lived in La Marque, Texas, a friend of mine had a piece of jagged plate steel about the weight of five or six silver dollars. The ships that blew up in 1948 were at Port Rd., Texas City, 4.55 miles from his house according to Google Earth. John said the shrapnel had enough velocity to pierce their front wall and landed in the living room. There must have been many thousands of such pieces within a five mile radius or more of the San Bruno blast if it was an aircraft. I believe an ad in San Bruno would bring out a lot of pieces, and maybe they did recover pieces they found or that were turned in. I think in densely populated California some would have landed in plain sight. And the explosive force on a drone would not vaporize a lot of the titanium components, or even hardly damage some of them. The F 18 mentioned has a lot of thick titanium that surely would survive a jet fuel fire spread over an area.

I don't buy the conspiracy theory, but it makes good Hollywood.

Steve

I find this to be very interesting, and ask myself the same question, what are the chances that the location of the blast was accidental?

Assuming you mean 280 and 92, that 5 mile half-circle is quite lightly populated relative to, say, the City. Large lots, large houses, big parks and exclusive neighborhoods.

scott

The chances are as near to 100% as possible.