Hi all,
blockage of the nitrogen exhaust turret happened to me 2 - 3 times over 18
years in our 11.7 T Bruker magnet although it has a check valve.
As many others, I am refilling LN2 just prior to He fill and I am trying to
fill helium fast, i.e. in around 30 - 40 min (55-60 liters). I think that
the blockage occurred when helium fill was too slow and the magnet nitrogen
manifold became probably too cold.
Best regards,
Jan
---------------------------------------------------------
Jan Lang
Associate Professor
Charles University in Prague
Faculty of Mathematics & Physics
Department of Low Temperature Physics
V Holesovickach 2
CZ-180 00 Prague 8
Czech Republic
Tel.: +420 221912889
Fax: +420 221912567
http://nmr.mff.cuni.cz <
http://physics.mff.cuni.cz/kfnt/nmr/>
From: g-sukenick_at_ski.mskcc.org [mailto:g-sukenick_at_ski.mskcc.org]
Sent: Wednesday, August 24, 2016 9:22 PM
To: David.Richardson_at_ucf.edu; ammrl_at_ammrl.org
Subject: Re: AMMRL: RE: very scary nitrogen fill
David,
Older instruments do not use check valves and use latex or similar tubing
for exhausting nitrogen gas.
I have one 20 year old instrument with that setup, but I've never had ice
buildup inside.
I fill nitrogen before the helium fill and keep the tubing in good
condition.
Newer Bruker instruments have polyurethane tubing connected together with
push in fittings to form a system with a check valve.
The Bruker engineer showed me that at each fill the tubing needs to be
tested that they are securely in the fitting as they do come loose - and
when they are loose, you have an open system, and air can get in.
Cheers
George
From: David Richardson <David.Richardson_at_ucf.edu>
Date: Wed, 24 Aug 2016 13:42:35 +0000
To: AMMRL <ammrl_at_ammrl.org>
Subject: AMMRL: RE: very scary nitrogen fill
Hi all,
Is it not standard to put a check valve (or one-way valve/back-flow
preventer valve, whatever the appropriate name may be) on the nitrogen
exhaust? I have never worried about the negative pressure in the nitrogen
can during a helium fill because of the check valve, but with as long as
this conversation has gone on without mention of using a valve I am starting
to wonder if I need to consider the pressure despite using the valve.
David
David Richardson, Ph.D.
NMR Instrumentation Specialist
Chemistry Department
University of Central Florida
david.richardson_at_ucf.edu
407-823-2961
http://chemistry.cos.ucf.edu/nmr/
Received on Fri Aug 26 2016 - 11:50:22 MST