Dear all,
I got a dozen of answers. I attach below short excerpts from them, not
ordered for contents but ordered for coming in into my mailbox.
To summerize:
there are *two goups of user of nearly equal size*.
The user of first group state: what quality you use does'nt play any role.
The slight impurities will remain in the dewar (cooling trap), nobody
knows, how others handle this dewars (ice from other gas!). The dewars
have to be warmed up time by time for make them clean.
The impurities going into the magnet are much greater by other souces,
e.g. opening the magnet flange.
So: take the cheapest gas available, don't waste money!
The user of the second group are afraid to make any error. They won't ne
guilty in case of accident.
So: take highest quality available.
Thank you all for your answers!
Matthias
Now in detail:
----------------------
-----------------------
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99.996% should be more than fine. You'll get way more undesirables just
from having the magnet's helium system open for a short time.
Bill
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I only use what Bruker recommended: He gas Praxair 5N-99.999% ultra high
purity 5.0
Genevieve
------------------------------
I use the best grade I can buy from the local gas supplier, 99.999 % (N5).
In an environment where one shares delivery dewars with other users ...
I think that one has a responsibility to make sure that
what goes into the dewar as a pressurizing gas doesn't contaminate
Regards,
Craig.
-------------------
I normally use Airgas UHP helium: I think this is 99.999%
Phil.
---------------------------
We have been using what is called "balloon grade" He for years with no
problems. According to Praxair, it is 99.995%.
Jane
----------------------------------
We use zero or 5th grade from Airgas.
Ana.
---------------------------------------------
You only need the industrial grade Helium gas tank. You use the gas to
internally pressurize the liquid Helium tank.
Don't waste your money buying the expensive one.
Simon
--------------------------------------
We use Grade 4.5 (99.995%) to pressurise supply dewars.
The gas used to pressurize the supply dewar does not even enter the magnet
unless the supply is emptied.
If it does empty, the impurities entering the magnet are several orders of
magnitude fewer than those entering simply because the magnet is open to
atmosphere.
Cheers, -Hirsch
-----------------------------------------
We use 99.999% (five 9s) quality helium gas, but I am confident that
99.996% is sufficiently pure for this purpose.
Bob.
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ich verwende seit Urzeiten He 4.6, also 99.996%, Auch bei allen unseren
Installationen hat
Bruker immer solches Helium verwendet
(i.e. he used 4.6-He for very long times, even Bruker did - M.F.)
Kristian
--------------------
We use UHP Helium gas from Trigas.
Chuck
------------------
I never actually gave it any thought. I think the risk of getting
water/ice in the magnet is greater from having ice on the transfer line
when you insert it or having the vessel open to atmosphere for too long.
Cheers,
Mark
-------------------------
We are not using 5th degree
Alvicler
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I have been using standard grade helium fro > 25 years with no problems
(yet!)
Alan
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Wir benutzen Gasflaschen, die grundsätzlich für die Chromatographie
bestimmt sind, die 99.999 % sind.
Ich habe unser Lieferer (Messer) gefragt, er sagte für uns würde auch
99.996 % genügen,
(i.e. they use high grade for convience, but 99.996 would be sufficient -
M.F.)
Svetlana
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Just to be sure we use 99.999%
Fred
------------------------------------
Helium gas 99.996 is perfectly fine for pressuring Liquid He
container.
We had used same grade for more than 10 years.
we have devised another mechanism to pressurize the
container. We are using Hot water bag....
Manoj
-----------------------------------
4.6 is to much enough...
Rainer
Received on Mon Oct 06 2014 - 00:39:32 MST