Hello:
I am very pleased that so many people participated in this survey.
Here is the preliminary result. If I receive more responses, I will update this list in the future.
I am very interested to know whether anybody tried to recover the vacuum when boiloff was high.
If you did, did the boiloff rate decreased to normal after you pumped the magnet while the magnet was still at field?
Thanks,
Weixing Zhang
1983
300 MHz Oxford [sri.org] (original seal) Helium and Nitrogen boil-off is identical as the original specs.
360 MHz Oxford [uic.edu] resealed when updated 2001. works great no change in N2 or He boiloff
1984
500 MHz Oxford [berkeley.edu] installed 1984, at field since 1985, hold time and He boil-off rates have not measurably changed.
1985
500 MHz Oxford [chem.ucla.edu] dewar refurbished 1993
360 MHz Oxford [wisc.edu] obtained used in 85, rebuilt 1999; same as installed
500 MHz Oxford [wisc.edu] rebuilt 1999; same as installed
400 MHz Oxford [columbia.edu] All boil off rates are normal.
400 MHz Bruker [ucalgary.ca] Original seal
300 MHz Oxford [ineos.com] Reenergized for different reasons in 1995, 1996, and 2000; seals replaced on one of those occasions. Has high LN2 boiloff due to internal adjustments (not seal-related) but LHe boiloff is still in spec.
300 MHz Spectrospin [lubrizol.com] very similar He, N2 boil off as when installed.
500 MHz Oxford [ohio-state.edu] refurbished (due to a move) in 1998.
1986
500 MHz Oxford [chem.ucla.edu] dewar refurbished 1993
500 MHz Oxford [mbi.ucla.edu] refurbished 1993. The hold time/volume hasn't changed since 1993.
400 MHz Oxford [ineos.com] Original seal, Boiloff has not changed.
1987
400 MHz Oxford [berkeley.edu] hold time and He boil-off rates have not measurably changed.
500 MHz Oxford [uic.edu] resealed 1997, no change in N2 and He boiloff.
300 MHz Oxford [siu.edu] Since installation in 1987, cryogen consumption has not changed.
500 MHz Oxford [siu.edu] Since installation in 1987, cryogen consumption has not changed.
200 MHz Bruker [ut.ee] no remarkable cryogens consumption change
360 MHz Oxford binghamton.edu] boiloff is normal
600 MHz Oxford dual can [colostate.edu] still up
300 MHz Oxford [colostate.edu] went soft in 2009
300 MHz [iastate.edu] still has the same boil off rate.
250 MHz Bruker [ohio-state.edu] refurbished in 1998.
1988
300 MHz Oxford (chem.ucla.edu)
500 MHz Oxford [wisc.edu] ca. as installed (maybe slightly higher boiloff over last year)
500 MHz Oxford [uoregon.edu] boiloff remains about the same as when new
300 MHz Oxford [selcia.com] He boil-off rate did increase slightly about 5 years ago
1989
400 MHz Bruker [berkeley.edu] hold time and He boil-off rates have not measurably changed.
250 MHz Oxford [unm.edu] (moved and seals changed 1998) boiloffs are close to original
500 MHz Bruker [ucalgary.ca] Original seal
500 MHz Oxford [hawaii.edu] He and LN boil off rates have not changed in twenty years.
400 MHz Oxford [nmsu.edu] boil off rates for nitrogen (180) and helium (2-4) are normal.
360 MHz Oxford [uvic.ca] hold time and boil off rate do not seem to have changed.
1990
400 MHz, oxford [averydennison.com] boiloff same as usual with no big changes over the years
400 MHz Oxford [UTMB) no significant change on cryogen boil off
1991
250 MHz Oxford [unm.edu] boiloffs are close to original
2x 600 MHz Oxford [bms.com] no change in boil off rates
500 MHz Oxford [ineos.com] Original seal, Boiloff has not changed.
1992
300 MHz Bruker [berkeley.edu] hold time and He boil-off rates have not measurably changed.
270 MHz Oxford [memphis.edu] LN2 20% remaing after one week (vs. 35% in 1992).
LHe 30% remaining after 3 months (vs 35% in 1992)
400 MHz Bruker [South Africa] Helium consumption is still at 3% per week as it was in 1992.
600 MHz [spcorp.com]
500 MHz Oxford [unmc.edu] still stable at field
400 MHz Oxford [rz.uni-leipzig.de]
1993
500 MHz Bruker [chem.ucla.edu]
2x 300 MHz Oxford [wisc.edu] same as installed
500 MHz Bruker [mbi.ucla.edu] hold time/volume hasn't changed since it was installed.
1994
400 MHz Bruker [chem.ucla.edu]
300 MHz Bruker [unm.edu] boiloffs are close to original
300 MHz Bruker [poczta.fm] Boiloff is the same in 15 years.
500 MHz Bruker [columbia.edu] All boil off rates are normal.
1995
600 MHz Oxford [UTMB) no significant change on cryogen boil off
750 MHz Oxford [UTMB) no significant change on cryogen boil off.
400 MHz Bruker [uconn.edu] No change in boiloff in the last 8 years.
300 MHz Oxford [uoregon.edu] boiloff remains about the same as when new
1996
600 MHz Magnex [mbi.ucla.edu] hold time/volume hasn't changed since installation.
2x 300 MHz Bruker [columbia.edu] All boil off rates are normal.
600 MHz Oxford [uoregon.edu] boiloff remains about the same as when new
1997
600 MHz Oxford [bms.com] no change in boil off rates
600 MHz Oxford [stjude.org]
1998
500 MHz Bruker [unm.edu] boiloffs are close to original
600 MHz Oxford [stjude.org]
2000
600 MHz Oxford [wisc.edu] same as installed
2004
800 MHz US2 Bruker [mbi.ucla.edu]
400 MHz Bruker [poczta.fm]
300 MHz Bruker [uconn.edu] No change in boiloff.
500 MHz Bruker [uconn.edu] No change in boiloff.
600 MHz Bruker [uconn.edu] No change in boiloff.
******************** Other responses for my previous question *************
[dowcorning.com]
I have 4x magnets in my lab, two of which are 20+ years old. I've had seal work done on the other magnets in the lab when their vacuum's were called to question, but I've had no reason to question the vacuum's on the two older magnets to this point.
[chem.utoronto.ca]
We've just moved some magnets and had to make the same decision. We replaced the seals on an Oxford 500 that was installed in 1992. The seals on the magnet were ok, just hard, but the TMC leg seals failed after the move and had to be replaced. We also replaced the seals on a Bruker widebore magnet that was installed in 1996. There was significant corrosion and discoloring of the o-rings.
This is because condensate dripped off the N2 outlets and down the sides of the magnet on particularly hot and humid days
[umanitoba.ca]
I have one magnet that has been at field 25+ years. No noticeable change in boil-off. So it is possible that they can go a long time.
[sas.upenn.edu]
I have had several magnets at field without repair or seal replacement for 20 years .
[cornell.edu]
I have a 16 years old Oxford 500 and an even older Oxford 300 with original seals. The cryogenic performance of the 300 is still fine, the 500 is starting to evaporate He faster and as a result is evaporating N2 slower.
[harvard.edu]
We have three magnets that are 20 years old and they are still going just fine
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Received on Mon Jun 15 2009 - 11:11:52 MST