This is odd. I run a similar but smaller facility in New Zealand (3 tanks). If the nitrogen supply fails we have about 18-20 days worth left in the tanks before they run dry. Even then I had a staff member checking every couple of days over Christmas anyway. I wrote an R script to analyse data from the tanks https://rhizobia.nz/r/N2-tanks.html to get a good idea of usage.

Just strange to me that a much more well funded organisation didn't do better.

[–] jarfil@beehaw.org 1 points 9 months ago (2 children)

That's interesting. May I ask you a few questions?

Why are you storing in the gas phase?

Some temperature spiking is normal, but it should not exceed the glass transition temperature of about -130°C.

Glass transition of what, the samples? Sample containers? ...?

“one-fill all-fill” (OFAF) to work. OFAF fills all tanks sequentially once any one triggers the process.

What are the benefits of that?

From the usage graphs, why does it seem like Tank 1 is using the most nitrogen, even though Tank 3 is getting accessed the most? Shouldn't Tank 3 have higher losses?

[–] bevan 5 points 9 months ago

No problem, The gas phase avoids nitrogen liquid infiltration into our storage straws that could be imperfectly heat sealed. If only a tiny amount gets in this expands 700 times in volume to the gas phase when warmed up causing the straws to pop.

The key glass transition temperature is that of the samples, there will inevitably be some warming as the tanks are used and sample racks removed, but so long as the samples don't warm more than -130°C they won't experience any structural changes.

OFAF just saves liquid nitrogen, quite a lot is lost cooling down the pipes when doing a fill, so may as well fill all of the tanks while the supply pipe is cold.

I think there is an issue with Tank 1, perhaps the insulation is not as good as the other tanks. I am monitoring to make sure it does not get worse over time.

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