The pipe has a valve at its base called the blow-out preventer which is supposed to seal off the flow entirely. At the moment, this doesn't appear to have been fully closed again probably due to the damage caused by the sinking platform.
I'm sure there will be lessons learnt from this incident.
...but that would require flow, right? (that is, closing of the flow too fast will basically lead to a shockwave rupturing the pipe).
In this case, the pipes were basically being used as pressure vessels (I believe it was quoted in the media that pressure in one of the pipes was 105bar/1,500psi or so before the leak sprung).
With nothing but static pressure, I have a hard time seeing how such a pipeline may be sabotaged in SW alone - doubly so as it, as far as I can tell from media reports, really is the proverbial dumb pipe - valves and thingamajigs at either end, but the pipeline itself is essentially just a pipe with no shutoff valves throughout. (Which, in itself I find hard to believe, so I probably had better dig a little bit more!)
Are there not valves along the pipeline to seal off sections? I've done some small amount of work on above ground gas pipelines and I feel like the majority of the pipeline would be undamaged, assuming the valves were closed in a reasonable time.
That's actually why I looked this up in the first place. I think it's just air from what I could gather. The three sections of the pipe are laid on the seafloor like this (with the open end staying out of the water): https://www.wermac.org/nordstream/html_img66.html.
And then those three sections are welded together using an "air-tight habitat" surrounding them.
From what I've heard salt water getting into the pipe could make it really difficult to repair, and it might have to be scrapped altogether.
A blocked pipe alone doesn't cause it to burst. It has to be combined with something that causes the pressure to increase, like perhaps a breakdown product that produces gasses?
It was intended to be airgapped, but we're talking about a pipeline that is several thousand miles long, with many pumping stations and delivery terminals. All it would take is one of the SCADA systems at one of those locations to suddenly open a valve and dump petroleum out into the environment to cause a disaster.
Or worse - rapidly open & close valves in rhythm, and the water hammer effect (the inertia of the petroleum in the pipeline) would cause the pipeline to destroy itself. The repair costs would be astronomical - you'd naturally have to repair the damaged sections, but then also re-test all the welds to see if any had been weakened by the pressure pulses.
Yeah, this seemed like the biggest killer, besides inertia and politics.
My friends and I were wondering aloud if you could put a slight bow in the pipe - so instead of expanding lengthwise, the pipe might raise and lower at certain places. Of course, none of us are engineers in that sense.
I'm surprised a 3" water main stopped it, pipes in general are typically made of very soft, low quality steel. It probably just ran out of energy after flying through everything else.
The plug wasn't welded, it simply screwed into existing pipe threads replacing an overpressure valve.
One possibility is that it's not actually being used for anything. A broken pipe could leak that much water, and depending on the local geology it might reach the water table without anyone noticing.
My understanding is (although it may not apply to this particular pipeline) that they shut some of the pipes off depending on the degree of arbitrage between the two ends. I met someone who wrote code to do this once (although I think it was a petroleum pipe to a refinery.)
Understood! Does this mean that this leak will affect the whole pipe or can it be isolated? I assume it will perhaps not crush, but at least fill up with water.
I'm sure there will be lessons learnt from this incident.
More info here: http://news.bbc.co.uk/1/hi/world/americas/8651333.stm
reply