Dear Brian,
We have a Bruker Biospec 70/30 with an ultrashielded refrigerated magnet that was installed in 2003. At first, we had terrible problems with the refrigeration system - the cold head and/or compressor had to be replaced about six times before we got a combination that worked for more than one year. Fortunately, each replacement was covered under warranty because failure occurred prior to one year of service. Once that settled out, the system ran pretty reliably, requiring an overhaul about once every two years. We could not afford the annual service contract for the refrigeration system so, instead, we had to raise about $35K for each overhaul. The overhaul generally involves swapping out the cold head, which required ramping down the magnet. Fortunately, these magnets do not have superconducting shims and so it is relatively simple to ramp them down and up as needed for service. After one overhaul, there was a slow leak in the helium lines which required adding ultrapure helium gas every six months or so. This is not difficult and you can do it yourself if you have the right regulator and fittings. Overall, the biggest problem by far has been providing the Cryomech compressor with reliable water cooling. Due to the low reliability and performance of our old building's chilled water system, we used a dedicated Thermo Neslab HX300A chiller to provide chilled water to the Cryomech. This worked well for several years but then the HX300A became unreliable, too. Ultimately, we had to use tap water instead until we moved the magnet to our new building, where chilled water is more reliable. Nevertheless, I invested in an automatic fail-over system which switches from building chilled water to city water in case of inadequate flow rate and/or temperature. This has worked quite well so far after an initial period of fine-tuning. In addition, the Cryomech compressor has always been supplied with electric power (208 volts three phase 40 amps) from a large uninterruptable power system (UPS). In the new building, this UPS is further backed up by a generator and automatic transfer switch (ATS). I hope this information has been helpful. Please let me know if you have any questions.
Best regards,
Ken.
Kenneth W. Fishbein, Ph.D.
Facility Manager, MRI Section
National Institute on Aging
National Institutes of Health
251 Bayview Boulevard
Suite 100, Room 04B120
Baltimore, MD 21224
(410) 558-8512
FAX: (410) 558-8376
Kf31x_at_nih.gov<mailto:Kf31x_at_nih.gov>
________________________________
From: Brian Breczinski [bbreczin_at_bucknell.edu]
Sent: Friday, September 20, 2013 4:01 PM
To: ammrl_at_ammrl.org
Subject: AMMRL: maintenance times and costs for closed-system He refrigeration cryostats
Hello spinlanders,
I'd like feedback from anyone who has a magnet that uses a helium refrigeration system rather than the usual helium and nitrogen boiloff cooling of the superconducting magnet. We're specifically interested in an fMRI system such as the Bruker ClinScan 70/30, but I would appreciate information from anyone who has such a system for NMR as well.
What I want to know is, how often does the system require maintenance, and (approximately) the cost of such a service visit. If you have a service contract, the cost of that would also be informative.
Thanks
Brian Breczinski
NMR, Computer & Instrumentation Specialist
Bucknell University
Received on Mon Sep 23 2013 - 10:02:18 MST