chemrox
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dewar syphon
I have an 8L dewar for liq N2 etc. Was made for DOE. Came without the syphon. I need one. Has anyone here made such a thing?
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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-jeffB
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I work at an MRI lab, and when folks there need to transfer LN2 (from the large rolling dewars), they use a simple, uninsulated metal wand and
Tygon(?) tube. There's some loss while the tube cools down, of course, and the rubber hardens during transfer, but it's apparently not worth it to
use any kind of insulated tube. For the liquid helium, they have a wand and tube with evacuated jacket.
I don't know how much loss there is due to evaporation in the uninsulated transfer tube, but I'm guessing that it's small compared to the loss from
cooling down the smaller (destination) dewar.
I have a dewar in the 8L range that has lost its vacuum. Before I discovered that it was dead, I had figured that I'd just do transfers by pouring
into a funnel.
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chemrox
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Please send me a PM with a little more data on the wand. This was the kind of thing I was looking for.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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ftirinih
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Pump the dewar down?
| Quote: | Originally posted by -jeffB
I work at an MRI lab, and when folks there need to transfer LN2 (from the large rolling dewars), they use a simple, uninsulated metal wand and
Tygon(?) tube. There's some loss while the tube cools down, of course, and the rubber hardens during transfer, but it's apparently not worth it to
use any kind of insulated tube. For the liquid helium, they have a wand and tube with evacuated jacket.
I don't know how much loss there is due to evaporation in the uninsulated transfer tube, but I'm guessing that it's small compared to the loss from
cooling down the smaller (destination) dewar.
I have a dewar in the 8L range that has lost its vacuum. Before I discovered that it was dead, I had figured that I'd just do transfers by pouring
into a funnel. |
Just how would you restore the vacuum? Is that a usual thing to do?
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The_Davster
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At work we have an improvised one made of a couple copper pipes through a large rubber stopper. One copper pipe extends to the bottom of the dewar,
and leaves the stopper terminating in a spout. The copper pipe is insulated before the spout with some sort of packing foam ducttaped on. The other
copper pipe does not extend far into the dewar, only a couple inches, and the part outside is hooked up to a bottle of nitrogen. Turning on the
nitrogen gas blows liquid nitrogen out the other pipe after the pipe cools down.
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chemrox
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There's a fluid hardware company up the street that wants to hep with this and the welding gas company has lots of cheap N2 liq. There's a built in
pressure relief tube at the top. It would just take a piece of flex tubing and a clamp to be functional The hole from the top of the dewar is about
1.5 cm and is threaded. So maybe all we need to do is get the right thread, make a curved copper pour tube and equip the pressure release line.
There is a separate pressure inlet but for N2 I don't feel it's really needed. Maybe the best thing wouild be to build a cradle for the vessel to
ease the pouring operation. I'm kind of getting that idea from the feedback here.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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