Hi John,
75000 hours is pretty good for an outdoor air cooled compressor. Was
the cryoplatform running normally? If there's too much gunk in the
coldhead the coldhead can start to knock which is normally pretty noticeable.
When a compressor fails there's always chance of oil contamination. One
time I ran into this, I believe they used a UV light to see the oil
contamination--as I recall the oil fluoresced purple under the light. There
are a couple of places you can check--you can check the helium line from the
compressor at various points to see if there's oil present there (sometimes you
can even see the oil on the connector if there's a lot of it.) You can check
the output of the outdoor unit, the input and output of the indoor unit, and the
input to the cryoplatform. You could also check the input to the coldhead to
see if there's any evidence of oil in there. And if it's a Bruker cryoplatform
there is generally evidence of contamination in the log files that can be due to
oil or other things.
If the compressor oil has leaked out there's also a chance that whatever is still
in the system got overheated and gunked things up. If the oil has broken down
and started to pump hydrocarbons into the system then it likely needs decontamination
including a new adsorber in the indoor unit.
Anyway, that's my $0.02.
Cheers,Mike
On Tuesday, July 29, 2025 at 09:28:11 AM MDT, John H Grimes Jr. via groups.io wrote:
We have multiple cryoprobes that unfortunately use air cooled compressors.
One of our Sumitomo outdoor units recently shutdown. When I removed the
cover the pan under the helium capsule was full of oil. This is not surprising
given the age of the unit (~75,000 hours) and the fine Georgia summertime environment
in which it resides. We are lucky in that we just replaced FA-70 units on our
He liquefication system and I have an old one sitting around that was running when
it was disconnected last month. I want to swap it for the blown unit but do not
know if when a helium capsule blows, does it contaminate other parts of the system
with oil. Does anyone know if this is the case?
Thanks,
John
John Grimes
NMR Facility Manager
Complex Carbohydrate Research Center
University of Georgia
315 Riverbend Road, Athens, GA 30602
jgrimesjr_at_uga.edu
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Received on Tue Jul 29 2025 - 08:41:28 MST