first of all, happy holidays...
secondly, i thought i had this summary posted a couple of months ago,
however, i just found it in the outbox of my email acount...
apparently, i did not hit "send" for some reason... i apologize and
hope no one is waiting for this summary... for the purpose of keeping
in the ammrl's archive for future reference, here it goes...
chen
***** forward message *****
Date: 27-Aug-2005 03:11:22 -0400
From: "Rainer Haessner" <rainer.haessner_at_ch.tum.de>
To: <dychen_at_bgnet.bgsu.edu>
Subject: Re: blockage in helium tank...
Sometimes there really is frozen air. This might or might be not
dangerous.
First have a look for the helium consumption. If this shows the normal
value, the solution maybe is easy.
As a very first attempt you can try to reach the bottom of your magnet
(metallic noise) with your dip stick. If you feel a rather soft
resistence
instead you nearly won. Using your helium transfer line you can blow
gaseous helium into the helium fill neck. This is not too
complicated, but call an engineer to get detailed explanatrions.
If you reach the bottom oif the magnet using the dip stick, then
maybe the other neck is iced. Replace the tow sealing by a glas
plate and have a look using a Maglight. You should see the connector
for the power rod. If you see ice, the situation is very complicated.
Even an experienced service ingenieur may fail to remove this ice
using gaseous helium, but there is no other way. By no means you
shoudl remove the helium by yourself at this side of your spectrometer.
Best regards
Rainer
Date: 27-Aug-2005 12:26:08 -0400
From: "Randy Winchester" <winchesr_at_gvsu.edu>
To: <dychen_at_bgnet.bgsu.edu>
Subject: Re:blockage in Helium Tank
Dear Chen:
Could you forward any replies you receive to me?
We also think that there may be a blockage in our Helium fill and I
would like to learn more about the best way to solve this problem.
Thank you,
Randy
Randy Winchester
Department of Chemistry
Grand Valley State University
Allendale, MI 49401
616-331-2387
616-331-3230 (fax)
winchesr_at_gvsu.edu
Date: 29-Aug-2005 08:45:48 -0400
From: "Morton, Martha" <martha.morton_at_uconn.edu>
To: <dychen_at_bgnet.bgsu.edu>
Subject: RE: blockage in helium tank...
Chen,
Could this be a helium gauge problem, rather than a blockage problem?
Warm helium gas is the way to go, if its a blockage.
Good Luck,
Martha Morton, University of Connecticut
Date: 29-Aug-2005 09:15:14 -0400
From: "charlie dickinson" <lcd_at_mail.pse.umass.edu>
Reply-To: <charlie_at_telemann.pse.umass.edu>
To: <dychen_at_bgnet.bgsu.edu>
Subject: Re: blockage in helium tank...
DYC
I have never had that happen. Please broadcast your solution as it
is the sort of thing I think we all worry about with every fill. Seems
to me you should psyche out specifically where a blockage could cause
your
symptoms before a He gas treatment.
Good Luck
Charlie Dickinson
U-Mass-Amherst
Date: 29-Aug-2005 11:36:43 -0400
From: "Klaas Hallenga" <hallenga_at_nmrfam.wisc.edu>
To: <dychen_at_bgnet.bgsu.edu>
Subject: blockage in helium tank...
Hi,
>From personal experience (30 + years in NMR labs) I must warn you
strongly against the procedure of blowing warm helium gas into the
filling tower of the Oxford magnet you have trouble with. We once
quenched a cryoshim doing this. A better procedure is to heat ( and I
mean really heat) a copper (or other non-magnetic) rod and push it
down the filling tower till it hits the blockage. While you do this
there also should be a gentle stream of helium gas blown into the open
tower to prevent more air from entering it. The rod will cool down
quickly and the procedure may have to be repeated several times.
Good luck.
Klaas Hallenga
Klaas Hallenga Ph.D.
Scientist NMRFAM National Magnetic Resonance Facility
At Madison
Dept. of Biochemistry phone: 608-262-0459
433 Babcock Drive fax: 608-262-3759
Madison, WI 53706-1544 email: hallenga_at_nmrfam.wisc.edu
Date: 29-Aug-2005 11:42:04 -0400
From: "Silverman, Bob" <BSilverman_at_mednet.ucla.edu>
To: "'dychen_at_bgnet.bgsu.edu'" <dychen_at_bgnet.bgsu.edu>
Subject: RE: blockage in helium tank...
Chen, we had this done to our 360 MHz Spectrospin magnet several years
ago.
We called Bruker in to do it since I was uneasy about a procedure I had
never done before. There was no problem and it only took a few minutes
of
helium blowing to clear the ice. If your helium level is high (60%
sounds
good), then it should not be a problem to do this yourself using a
very low
flow of helium gas.
Bob Silverman
UCLA Pharmacology NMR Facility
Date: 29-Aug-2005 13:43:21 -0400
From: <Jerry_Dallas_at_BERLEX.COM>
To: <dychen_at_bgnet.bgsu.edu>
Subject: Re: blockage in helium tank...
Chen:
The procedure is delicate because you must attempt to warm the
reservoir and sweep out ice/sludge with warm He gas while minimizing
the
impact on the magnet. You are risking a quench although you have no
choice.
Expect to receive a burst of cold gas at any moment. Wear protective
gloves, eye wear and a face shield. You will consume several cylinders
of
He gas and the process will take a long time. The first item to check
is
whether the baffle is frozen in place in the port where the quench
plug has
been inserted into the magnet energization socket. If this is frozen it
must be thawed by removing the the small brass pressure relief valve
at the
top of the baffle and inserting a metal tube which will fit inside the
the
core of the baffle assembly. As I recall a He flutter tube is about the
right diameter. An alternative is a large guage stainless syringe
needle
about 3' in length. Keep a slight positive flow of room temp He gas
flowing
through the tube as you insert it deeper into the baffle assembly. You
may
find that the tube is blocked and you will need to melt through the
blockage. Just keep it moving up and down so that it does not become
frozen
in place. In my hands this process took more than a week and strained
my
patience. When it finally does melt through then you may discover that
you
will push ice/sludge in the reverse direction toward the He fill port.
If
you warm the baffle sufficiently from the inner core out then the
baffle
can finally be removed. Having removed the baffle, then you must
continue
to spray warm He gas on the quench plug area where ice has been most
likely
to collect. For this you may use a larger diameter stainless tube such
as
the liquid nitrogen L tube ( used during the magnet energization
process to
insert liquid nitrogen into the He reservoir for precooling ).
Then you should be able to focus on the opposite side of the can.
Break the dogbone assembly into two sealed parts. Rubber stoppers work
if
you have nothing else available. Insert the stainless L tube into the
fill
port with no opportunity for gas to escape veritcally. Measure the
tube in
advance to be sure that you just reach the very top area of the He
reservoir. Keeping a positive flow of warm He gas flowing through this
tube
you want to sweep out the top area of the magnet can gently and push
any
residue back toward the baffle port---- up and out of the dogbone
assembly.
This process gets a little scary because you need to allow the liquid
He
level to drop very low--near quench conditions. You may need to stop
the
process and fill the He to 40% and then resume the flushing process
again.
When you sense that you are finished then attempt a complete liquid He
fill
and see what level you achieve. If you recover fully then I would wait
until the next He fill to reinstall the baffle tube. In fact, I have
left
my baffle tube out for the past 3 years with no ill effects. Magnet
engineers tell me that it is common to find the baffle tube frozen in
place
and they are accustomed to removing it.
Your predicament sounds worse than most. It is particularly
bothersome that you can fill to no more than 60% now. You may be
required
to quench the system anyway. Then you might as well warm the magnet
completely, install new O-rings and and then completely re-install the
magnet. In the event of quench or deliberate magnet shutdown, be sure
to
remove the probe, the room temp shims and the upper stack assembly
before
the bore tube begins to ice up. Otherwise you may damage the RT shims.
best of luck,
Jerry Dallas
Biophysics
Berlex Biosciences
Richmond, CA
Date: 29-Aug-2005 15:31:57 -0400
From: "Dave Scott" <scott_at_iastate.edu>
To: <dychen_at_bgnet.bgsu.edu>
Subject: Re: blockage in helium tank...
Chen,
I guess that you've got to figure out where the ice
is before trying to melt it. They are usually in the
fill port, but I suppose it could be in the top manifold
or the charging port. You could probably use a thumping
tube to figure out where it is blocked.
I remember using a copper tube to introduce the helium
gas and using a heat gun on the tube to make it hot
helium gas.
hth,
dave scott
iowa state university
Date: 31-Aug-2005 11:08:36 -0400
From: "Jerry Hirschinger" <hirsch56_at_purdue.edu>
Reply-To: <hirsch56_at_purdue.edu>
To: <dychen_at_bgnet.bgsu.edu>
Subject: RE: blockage in helium tank...
Hi Chen,
Sorry I did not get back to you sooner, but I was out sick for 2 days.
One
should never blow warm helium gas into a magnet to remove ice unless
they
know for sure where the ice is. I suggest inspecting the fill port
visually. One can do this by placing a glass or other clear plastic
over
the fill port. The glass will stop air from entering the port and
making
fog. Look down into the port with a flashlight to see where the ice
is. To
remove ice, direct warm helium gas at the blockage using the 'L' tube
for
the magnet. One can warm the helium above RT using a heat gun directed
at
the tube. Use a low rate of flow to give the helium a chance to do some
work before it blows back out. There is a good chance the magnet will
quench, so be very careful to protect your face and body from escaping
cold
gas.
A caution; your LHe level monitor might be in error due to the ice.
Don't
be surprised if the level is much lower than you expect. I would have
enough LHe on hand to fill the magnet, both for this reason and in
case of a
quench. If it quenches, allow the spewing gases to die down, reseal the
manifold, and refill LHe immediately.
Once you get the blockage cleared, you must also find the leak which
allowed
air in to make the ice. Seal up the manifold and use a bubble test
solution
to find the leak.
If you cannot remove the blockage, try filling into the other port,
taking
care not to damage the e-stick connection pins at the bottom.
Good luck, Jerry
Jerry Hirschinger, NMR Instrumentation Specialist
Purdue Interdepartmental NMR Facility
560 Oval Dr. West Lafayette, IN 47907-2084
Office: Wetherill 365A
Phone / Fax: (765) 494-5288 / 494-0239
Cellular: (765) 427-3034
Date: 1-Sep-2005 03:15:18 -0400
From: "Dr. Julien Furrer" <julien.furrer_at_urz.uni-heidelberg.de>
Reply-To: <julien.furrer_at_urz.uni-heidelberg.de>
To: <dychen_at_bgnet.bgsu.edu>
Subject: Re: blockage in helium tank...
Hello,
we had here in Heidelberg the same problem and could also only fill to
75%.
Bruker Germany told us to open the helium refill port and with a thin
metal bar (like a transfer line) to push or remove the eventual ice
blockage in the helium tank.
After that, we could again refill without any problem
best regards
Dr. Julien Furrer
Ruprecht-Karls-University Heidelberg
Organic-Chemistry Institute
NMR Group
Im Neuenheimer Feld 270
D-69120 Germany
Tel: +49 (0)6221 548431
Fax: +49 (0)6221 544205
Email: julien.furrer_at_urz.uni-heidelberg.de
Date: 22-Sep-2005 09:06:16 -0400
From: "jr385274" <Jan.Runsink_at_rwth-aachen.de>
To: <dychen_at_bgnet.bgsu.edu>
Subject: Oxford300 Magnet
dear Dr Chen,
during my holliday you posted a question on AMRL concerning some kind
of
blockage in the helium tank of your 300MHz Oxford Magnet. We have four
nonshielded normal Oxford Magnets, a 500 (1991) a 400 (1997) two 300
(1994 and 2001), all with different type of Varian consoles. The
newest
300 magnet has an electronic device at the side of the heliumport to
measure the liquid He level. The first three magnets are easely filled
thill the liquid helium is coming out of the exhaust port, but the
newest 300 Magnet does have a blockage during Helium filling. We need
maximum He-gas flow (10 lpm) and maximum pressure (> 2.5 psi) and
still
we never see liquid helium coming out of the exhaust port. We just
stop
after half an hour. After a while the meter will give a measure. One
time it was 90%, the last time it said 100%, but I am not satisfied
with
this situation. My questions to you are: what happened in the mean
time?
Did you need to blow helium gas in the magnet with the flutter tube?
Do
you have also this electronic device? The Varian Service gave me some
suggestions but with the remark if somethings goes wrong it will
quench.
So before doing anything it would be good to learn from your
experiences.
with most regards,
Jan Runsink
Organic Chemistry RWTH-Aachen (germany)
***** end of message *****
Received on Wed Dec 21 2005 - 09:12:57 MST