Monday, August 31, 2015

Great story on Tulane's NMRs during Katrina

Fascinating story by Bethany Halford on how Tulane chemists saved their NMRs from quenching during and after Katrina. This is just a little part of a great story: 
...Peel checked the NMRs’ cryogen levels and found that although the nitrogen needed topping off, the helium was still okay. Now the team had a decision to make: Keep the NMRs going, or discharge the magnets in a controlled manner and bring them up to room temperature. 
As long as the school had access to liquid nitrogen, which it did, they could keep the instruments running. But just because they had liquid nitrogen didn’t mean they’d be able to get it to the NMRs. Without electricity, the elevators didn’t work. During that visit, the team used a cherry picker to lift a tank of liquid nitrogen to a terrace with access to the 500-MHz instrument, but that was a solution no one saw as safe or sustainable. 
The team weighed its options. Discharging the magnets wasn’t a trivial operation. It would take some sort of power source—a car battery, for example. And without liquid helium on hand, they couldn’t be sure the magnets wouldn’t be damaged in the process.
After talking with the National Guard troops on campus, the team learned it could have access to portable, gasoline-powered generators. These could be used sparingly to run the elevators to deliver the liquid nitrogen. This, they decided, was their best option....
And this conclusion for which we can all learn from:
The chemistry department didn’t suffer any extensive losses to research. The biology department and researchers at the medical school were not so lucky. McPherson says he didn’t even think the story of the NMR rescue was noteworthy until he learned that every other university in New Orleans with superconducting NMRs had lost their magnets to quenches. 
As for lessons learned, the school now keeps a large stock of liquid nitrogen on hand during hurricane season, and it has a much more detailed emergency plan. Most faculty have an emergency contact number outside New Orleans and an additional e-mail account that’s not linked to Tulane.
Hardening facilities for natural disasters is probably not so high on folks' priority lists, but it definitely is worth some thought. 

17 comments:

  1. I wonder why each of those NMRs cost more that $1 million? Their website just lists a 400 and two 300s. Am I reading that wrong?

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  2. The numbers could be original prices rather than current values. A 400 MHz magnet that was years old a decade ago could have been originally purchased in that price range.

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  3. If I remember correctly, the combined purchase price + installation cost for new 400MHz used by synthetic group NMR is less than 500k. (It could be more if you have a fancy cryoprobe, also autosampler adds a little extra.) The overall cost of NMR facility is obviously a bit higher - you need to build the place to some specifications.

    When the eye of hurricane Wilma passed directly over the Scripps FL campus, we lost quite a bit of helium in our magnets - they went from 89% to 81% on that day. Most likely it was a rapid boil-off due to atmospheric pressure drop.

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  4. Isn't it pretty amazing that the nitrogen had boiled off completely but they didn't lose the helium in that heat?

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  6. I don't know if you are trolling or just little impaired: the dewar with liq. He (in which the superconductor sits) is cooled on the outside with liq N2, so as long as there is still some N2 left and the ambient pressure does not change, the He boil-off rate remains constant...

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  7. I am neither trolling nor impaired. I perform cryogen fills on NMRs frequently, so this article was especially interesting to me. It says that after the first 10 days there was no nitrogen left and that it was hot. I am amazed that they were able to get to the initial nitrogen fills before the magnets quenched. My understanding is that once the nitogen is gone, the helium boil-off is fast.

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  8. On second thought, maybe it isn't too surpising. They probably had a few more days before the helium was doomed.

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    1. The article says one magnet (with field lower than 500MHz) was completely without nitrogen, after 10 days since the last fill. It probably run out of N2 just the night before, judging from experience with Bruker and Varian 400MHz magnets, they can last 9 days between nitrogen fills.

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  9. I suppose the reason for my question is that I wonder how long could we go (in a dire emergency... I am certainly not willing to test this!) without nitrogen before the helium drops to a critical level. A few days? A week or even two? It is hot here, too.

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    1. increase from 22C to 32C is huge for our comfort but it is only a few% change of the temperature differential measured from -269C...

      If you are curious, you can do a simple experiment to estimate how long you could go without N2 - freshly just after the He fill, top off the liq. N2 and then watch every day the boil off rate carefully . If at day 10 the N2 boiloff drops from 170 to 0 and He boiloff suddenly increases from 12 to 60, you will know that your nitrogen just had run out, and you are losing helium five times faster than usual, and if the He boil-off stabilizes at this rate, you will need to re-fill He five times as often without nitrogen, and that would be 2-3 weeks in a normal case. (This is individual to each magnet.) But talk to your NMR people before you decide to perform this little experiment, since they may not like it

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    2. I am the "NMR people," however new. That makes a lot of sense, but I have no way to monitor boiloff quantitatively on most of these magnets. Only the most recently installed have working sensors. The strategy that has been passed down here is just to keep everything topped off all the time. We don't think nitrogen ever falls to less than half-full, and helium is topped off every six weeks. (We have quite a few elderly magnets.)

      Thanks for sharing. It is probably good to consider this now and not during an emergency.

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    3. there should be a little outflow meter with a tiny floating ball in it, on both the nitrogen and the helium outlets. (Normally, before you fill your nitrogen, every week or so, you would look up and log the reading in the book - to make sure there is no abrupt change)

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    4. Ah ha! I see! Forehead smack. :-)

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  10. Some of them don't seem to be working. The beads don't respond when tapped, and I don't see any valves that need to be opened. (I can't believe logging this hasn't been part of our protocol.)

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    1. well we used to log the reading of liq. He level meters before they quit... Both Bruker and Varian seem to have problem with quality of their He sensors.

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  11. That's what we do. On the instruments that have working sensors, we log the levels daily. Like you say, though, the older sensors have stopped working. Also, I think that we keep everything so full, the readings probably don't change much. Still, thanks for pointing that out. It's pretty easy to start recording the boiloff, too.

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