These notes came from the 48 ENC, when we had 3 years less information about cold probes.
We all maintain spectrometers, mostly without contracts. If you have a repair on a cold/cryoprobe, it will be costly!
Do you pay for it in contract $ or in repair $?
Summary from the Cold Probe Discussion at AMMRL’s meeting (48th ENC).
These notes depict each major component of the cold probe/cryoprobe systems
1. Vacuum pumps: The Varian turbo pumps, that are on Generation 1 and 2 probes, should have the TIP seals changed every six months. Otherwise they will start pulling the load and will gradually wear out. Ion pumps are very reliable and have lifetimes of around 5 years if used properly.
2. Cold Head (CCC): Use grade 6 helium (highest purity available) and watch how you change tanks. The molecular sieve bed can be contaminated causing blockages that will reduce cooling performance. Cold head service can be pushed until the cold head dies at the risk of several months of down time, because engineers aren’t readily available. Plan ahead! MD10’s can go 2 years or more.
3. Cryobay Helium Compressor: It is recommended to change the charcoal filters for oil scrubbing about every 6 months on Leibert compressors. They have an approximate lifetime of about 5 years under optimal working conditions. Both Varian and Bruker have moved to Sumitomo helium compressors/cold heads on their latest cryogenic systems.
4. Electrical Outages: Several people have bypasses until backup generators start. Put the cold probe on emergency circuits and use UPSs for sites that have lots of electrical storms.
5. Heat exchangers and water chillers– Copper tubing on Haskris chillers will corrode over time specially if DI water is used. Opt for stainless steel if possible. Many people are using water-water heat exchangers. Filters in this case need to be monitored carefully. Water–air heat exchangers can work well depending on your site.
6. Boiloff from liquid N2 of the magnet can be used as your emergency eject air. See Jerry Hirshinger’s diagram.
7. $$$$$: Most of us didn’t project the long-term costs of running these probes. Cold head service and probe repair are expensive and you have to plan your budget accordingly. The general consensus was to push vendor maintenance back, but keep logs on your system.
Martha Morton, Ph. D.
Chemistry NMR Lab Director and
BBC NMR Facility Scientist
University of Connecticut
55 N. Eagleville Road, Unit 3060
Storrs, CT 06269-3060
(860)486-4069 (860)486-2981 (FAX)
________________________________________
From: Gregory Heffron [Gregory_Heffron_at_hms.harvard.edu]
Sent: Tuesday, June 23, 2009 10:38 PM
To: 'Mary Howe'; ammrl_at_ammrl.org
Cc: 'Jim Loo'
Subject: AMMRL: Another Cold Probe survey
Hi Mary,
I think the biggest issue is “the possibility of long term contamination”. Running the coldhead longer than recommended before replacing it carries the risk that somehow the system may get contaminated. It is not clear what that means exactly, but it can happen to either a Varian or Bruker system. Removing the contamination if it happens is tricky and also expensive.
I would strongly recommend the cryoprobe service contract. I am not a fan of console service contracts, but I think the cryo one is money well spent. One probe failure plus the annual coldhead service can easily exceed the price of the contract.
I think that the 7700-CS system is now superior to the Bruker one. From what I know it is more robust, and less likely to fail.
Good luck,
Greg
-----------------------------------------------------------------
Gregory J. Heffron
Director, Harvard Medical School NMR Facility
Harvard Medical School
240 Longwood Ave.
Boston, MA 02115
Phone: 617-432-1812
Fax: 617-432-4383
________________________________
From: Mary Howe [mailto:howe_at_chemistry.ucsc.edu]
Sent: Tuesday, June 23, 2009 5:48 PM
To: ammrl_at_ammrl.org
Cc: Jim Loo
Subject: AMMRL: Another Cold Probe survey
Another Survey:
The 600MHz Varian 7700-CS Cold Probe system on our Inova 600 has been working for about a year. Among other factors, the 7700-CS Closed-Cycle Cryogenic System boasts a new robust CryoBay.
We would like to get feedbacks from those who own the Varian 7700-CS Cold Probe system (or Bruker equivalent). Do you have a Service Contract for the whole cryo system or just the Cold Head? What problems are you experiencing?
Our understanding is Cold Head maintenance (cleaning) implies complete Head replacement. That being the case, why not just operate the system for 2 years or until the Head fails? It doesn’t cost any more – we checked. And if it hasn’t failed after two years, then the Cold Head and the Oil Absorber can be serviced at the same time. The down side of this scenario is the Probe must be returned to Varian. Institutions that are able to absorb being without the Cold Probe for a month or so could potentially save a bunch of money. A full Service Contract costs about $30,000.00 dollars/year.
We will post summaries.
Mary Howe
NMR Facility
UCSC
Santa Cruz, CA
Received on Wed Jun 24 2009 - 08:13:12 MST