Hello everyone,
My apologies for this late summary of the comments I have received. I'd like to thank everyone for their contribution and will post further summaries if more information comes in.
The original question was if people recover helium gas while they are filling their NMR magnets and to my surprise a great deal of respondents said yes. Here at the University of Alberta we have never recovered during helium fills, but the installation of new recovery technology and a new liquefier coupled with ever increasing prices makes the idea of this type of recovery more attractive.
Of the 13 responses that I had 6 stated that they did have helium recovery and re-liquefaction facilities, and that they did recover helium vented during liquid helium transfers. Statements overwhelmingly support the practice and observe no adverse effects to the magnets. One comment cited the need for manostats on systems connected to recovery lines. This will eliminate possible recovery line pressure fluctuations from affecting NMR operation. Usually manostats are placed on systems 600MHz and above, but it may be necessary to apply them to all systems if they are on a recovery line. I have heard from Varian/Agilent that they would recommend manostats on magnets connected to recovery lines.
With recovery lines attached to the helium manifold the traditional observation of the helium plume, getting larger and producing a 'flame' is lost. A couple of practices used in 2 locations were put forth. One facility used pressure gauges and the amount of air condensing on the recovery line as an indicator. No mention of the type of line that was used for recovery. Another facility used CF-25 1" metal flex line, however they did not comment on what visual cues they used to conclude the fill was finished. Most likely they would observe similar air condensation on the line. A third facility used DN-25 flange 25mm i.d. for recovery. To observe when the transfer was complete they used a manometer. (30-70mbar during the fill and 80-100mbar when the fill was complete). We'll probably do something similar.
Another issue I had regarding helium recovery was that researchers in our Chemistry Department were told that they would void their warranty if they hooked their new Bruker magnets up to helium recovery. This idea isn't terribly outrageous. I imagine that a poorly designed or maintained recovery system could absolutely pose a threat to an NMR magnet. It would be up to the supplier to inspect the system during their site evaluations and determine whether the recovery system is appropriate or not. Simple relief valves and back flow preventers would eliminate most problems I imagine. In general all respondents were surprised at this stance by Bruker citing that they have extensive helium recovery within their own plants and have also worked side by side with users who actively recover helium during installations. Another respondent indicated that Varian had this stance at his facility. It was also recognized that NMR suppliers are going to have to accept helium recovery very soon if they do not already. Institutions and individual users are investing in recovery and re-liquefaction and it will be the norm in major institutions in the future.
There was a question about the system we are getting here at the University of Alberta, so here you are;
Model L1410 Helium Liquefier
Data Acquisition Package
Expansion Engine Maintenance Kit for 2" Engine
Expansion Engine Maintenance Kit for 3" Engine
Piping Kit: L1410 to RS Compressor
1400 Series Remote Delivery Tube (RDT)
Transfer Line
Cryogenic Absorber
RS Helium Compressor
Acoustic Blanket for RS Helium Compressor
Absorber Maintenance Kit for Model RS Compressor Module
500 SCF Helium Recovery Gas Bag
250 Gallon Vertical Tank
Model 50B Helium Recovery Compressor
Piping Kit: Model 50B Helium Recovery Compressor
Helium Purity Monitor
12-Station Manifold Assembly
Model 500 Helium Automatic Purifier
In conclusion we've just finished a complete helium application survey for the University of Alberta. The study was to confirm that our existing system will be able to handle helium recovery for all of campus and not adversely affect any applications tied into the system. The recovery line will operate at 2 inches of water column (0.0721PSI, 4.97mBar) nominally. We are interested to see how the pressure rises in the system if NMR helium transfer gas is added. As stated before we haven't captured transfer helium gas before and will be interested in seeing if effects helium applications up and down the recovery line.
If anyone has any more questions or comments please contact me.
I will keep everyone updated,
Sincerely,
Deryck Webb
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Deryck Webb - Business and Technical Manager
NANUC - Canada's National High Field NMR Centre
Room 103 Email: deryck_at_nanuc.ca
NANUC Bldg. Phone: (780) 492-8530
University of Alberta Fax: (780) 492-9174
Edmonton, Alberta Cell: (780) 707-0857
Canada T6G 2E1 AIM: derycknmr
http://www.nanuc.ca
Received on Mon Nov 29 2010 - 12:11:13 MST