Dear Karen Ann Smith,
We have one of the earliest vintages of the Bruker Prodigy Probe System and
we periodically see the same problem that you are experiencing, perhaps
about twice a year. We fill our Dewar as you described filling yours. If
your Dewar is like ours, there is no baffle that would obstruct passage of
a suitable plastic tube into the Dewar fill exhaust port when the tube is
clear. If you are not able to get a tube well into your Dewar you have a
blockage. Normally you can effectively force a tube through the LN2 fill
exhaust port well into the Dewar if not to the bottom of the Dewar. We
never actually measured how far a tube goes but when the blockage is
cleared the tube moves well into the Dewar with little pushes. We are
warned that a problem is building when the Dewar pressure displayed on the
Prodigy GUI Status tab during the LN2 fill gets much higher than normal,
whatever normal is for your system and at that point, we now preemptively
introduce a semi-rigid plastic tube into the LN2 Dewar exhaust port where
our blockages occur, and pass a N2 gas stream through the tube until the
blockage is clear.
The blockage will clear with room temperature LN2 but it works much faster
and we have seen no adverse affects when we heat the N2 gas stream before
sending it into the tube by passage through a copper coil heated with a
heat gun near the entrance to the liquid nitrogen Dewar exhaust port. It
usually takes us a half hour or so to clear the blockage. I am sure that
time can be improved but that is ok for us for now. I hope this works for
you and your system.
Francis Picart
NMR Coordinator
Stony Brook University
Department of Chemistry
100 John S. Toll Drive, Room 507
Stony Brook, New York 11794-3400
Francis.Picart_at_stonybrook.edu
(631)632-7991 Office
(631)632-7960 Fax
(631)632-9270 High Field NMR Suite
(631)632-1560 Center for Molecular Medicine (CMM)
(516)909-6459 Cellular Telephone
On Thu, Feb 15, 2018 at 1:47 PM, Karen Ann Smith <karenann_at_unm.edu> wrote:
> Resonators;
>
> For the second time in less than 6 months, we have had to abandon the
> liquid nitrogen refill of the prodigy dewar. As happened last fall, the
> nitrogen gas out port is clogged or blocked. Nothing comes out, which
> means that the overpressure valve is triggered as soon as we try to put
> liquid nitrogen in.
>
> Last time this happened, Bruker said to:
> warm up the probe
> disconnect all hoses from the dewar
> dump out any remaining nitrogen
> warm up the dewar completely
>
> Then, re-connect all hoses, refill the dewar, and cool the probe. This
> results in over 24 hours of down time.
>
> I tried running a hose with nitrogen gas into the out port. It will go in
> about 6 inches before it hits something. I don't know if that is ice or a
> baffle.
>
> Does anyone have any suggestions that don't involve a day of down time?
>
> Does anyone have any suggestions of how to prevent this from happening?
> (My TA runs gas thru the fill line, unscrews the black caps, puts the vent
> hose on the out, runs a bit more nitrogen, then attaches the fill line.)
> The out line is only open for a few seconds.
>
> thanks,
>
> kas
>
> --
> Karen Ann Smith Director, NMR Facility
> Group Leader, Analytical Chemistry Services
> Department of Chemistry and Chemical Biology
> Clark Hall MSC03 2060
> 1 University of New Mexico Albuquerque, NM 87131-0001
> karenann_at_unm.edu 505.277.4031 http://nmr.unm.edu
> Out of this world screensaver: http://setiathome.ssl.berkeley.edu
> "Stress is what you get when your job is worthwhile and interesting"
> from "Encounter at Tiber" by Buzz Aldrin & John Barnes
>
>
Received on Thu Feb 15 2018 - 12:59:10 MST