Yes, the sensor problem in itself is only an inconvenience, but it points to a leak which must be eliminated.
The operating model Greg suggests is viable, but only after stopping the leak which enabled ice to accumulate in the first place. Most NMR helium sensors use the same neck as LHe fills, so ice building around the sensor eventually blocks LHe fills also. Mostly ice builds at the nearest cold surface to the leak, so an iced sensor usually indicates a leak in the sensor electrical connector or the sensor seal, or elsewhere on that side of the helium manifold.
Helium leaks in the manifold plumbing are pretty easy to find using some tape and shopping bags, or by using bubbles. Tape a bag around each fitting of interest, and see if the bag inflates. If you want to use a bubbling leak detector liquid, that also can work to locate the leak.
Cheers, -Hirsch
-----Original Message-----
From: Heffron, Gregory J. [mailto:gregory_heffron_at_hms.harvard.edu]
Sent: Tuesday, February 03, 2015 1:14 PM
To: ammrl_at_ammrl.org
Subject: RE: AMMRL:
Hi,
The best way to deal with such an issue is to have a professional look at it. If there is a risk of a quench by playing around with it, you can simply operate the system without a helium sensor. We have done this with 3 magnets for more than 20 years without any issues. The meter is only a convenience. You could do the following rather than risk a quench:
1. Fill the magnet dewar until it is clearly full.
2. Monitor the boil-off with an accurate gauge and leak-free tubing.
3. Fill the dewar when the boil off indicates that you have lost the amount of helium at which you would normally do a fill. You can be conservative and add 10% or so to it.
If you faithfully monitor boil-off, which one should routinely do anyway, you should not have any issues and can exist very much as you have since the magnet was installed. If you have any concerns, do the right thing and have a professional look at it.
Good luck,
Greg
Gregory J. Heffron
Director, NMR Facility
Harvard Medical School
240 Longwood Ave.
Boston, MA 02115
Ph:617-432-1812 Office
617-335-2929 Cell
617-432-4383 Fax
________________________________________
From: Hirschinger, Jerry D [jerryh56_at_purdue.edu]
Sent: Monday, February 02, 2015 2:46 PM
To: ammrl_at_ammrl.org
Subject: RE: AMMRL:
One must usually de-ice the sensor in place. It is likely frozen into a block of ice which extends to other mechanical components of the helium vessel. Additionally, most magnets do not have enough overhead clearance to remove the sensor. It is the longest component of the magnet, and is installed before the magnet is raised upon its legs. Quenching a magnet during ice removal is a necessary risk.
Cheers, -Hirsch
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
-----Original Message-----
From: Jordi Redondo [mailto:jredondo_at_eqesteve.com]
Sent: Monday, February 02, 2015 5:42 AM
To: Zhao, Chunqing
Cc: ammrl_at_ammrl.org
Subject: RE: AMMRL:
Hi,
We have a similar problem some months ago in an Agilent system, and it provoked a quench, since the helium level was much lower than the level reading. The Agilent engineer concluded that the sensor had some ice on it and for that reason the reading was wrong. So, I suggest you to call your local engineer to remove the sensor and clean it.
Best regards,
Jordi Redondo
Spectroscopy Manager
Esteve Química
R & D Dept.
Barcelona
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CONFIDENCIALIDAD: La información contenida en este mensaje es confidencial y para uso exclusivo del destinatario. Si ha recibido este mensaje por error, le agradeceremos nos lo indique y proceda a su eliminación. Para mas información sobre protección de datos personales visite www.eqesteve.com/lopd.
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De: "Gudzon, Ana" <Ana.Gudzon_at_Covidien.com>
Para: "Zhao, Chunqing" <nelson.zhao_at_unf.edu>, "ammrl_at_ammrl.org"
<ammrl_at_ammrl.org>,
Fecha: 30/01/2015 19:01
Asunto: RE: AMMRL:
Maybe your helium sensor is frozen or you got some ice on the sensor or inside the . Bruker has a program that send some electrical impulses that it melts. I am not sure about Agilent instrument.
From: Zhao, Chunqing [mailto:nelson.zhao_at_unf.edu]
Sent: Thursday, January 29, 2015 9:21 AM
To: ammrl_at_ammrl.org
Subject: AMMRL:
Hi All:
Our Aglient 500 VNMRS system (2007) helium level reading does not change for the past several days. It did not change even I put the meter in the fill mode for 5 min. Any idea what I should do.
Thanks,
Nelson Zhao
Analytical Facility Manager
Chemistry Department
University of North Florida
Building 50/3610
1 UNF Drive
Jacksonvill, FL 32224
Ph. 904-620-1962
Fx. 904-620-3535
© ESTEVE (2015) & CONFIDENCIAL
CONFIDENCIALIDAD: La información contenida en este mensaje es confidencial y para uso exclusivo del destinatario. Si ha recibido este mensaje por error le agradeceremos nos lo indique y proceda a su eliminación.
CONFIDENCIALITAT: La informació continguda en aquest missatge és confidencial i per a ús exclusiu del destinatari. Si ha rebut aquest missatge per error li agrairem ens ho indiqui i procedeixi a la seva eliminació
Received on Wed Feb 04 2015 - 12:22:05 MST