Hello everyone,
Last August there was a useful email exchange here on the AMMRL about
repairing helium transfer lines. I have a related question.
Do any of you perform a preemptive pump-down of your transfer line(s),
or do you wait until you see signs that the transfer line has lost vacuum?
You can probably guess the reason I ask.
Last week we aborted a helium fill when I saw excessive frost/condensation
begin to form on the transfer line as we were cooling it down.
We aborted the transfer and then completed the helium fill using another
transfer line.
I brought the suspicious transfer line to the person in charge of our
helium recovery system to test. When he connected it to his pumping
station, he could tell that it had indeed lost vacuum. He left it
pumping overnight. Then on Friday morning he closed the valve,
disconnected the pump and let the transfer line sit over the weekend.Â
When he come in Monday morning, he found that it had maintained a good
vacuum over the weekend, so he doesn't think there is a leak, but that
it simply had lost vacuum.
To test that, this morning we did a scheduled helium fill of another
magnet to see how the freshly pumped transfer line performs.
The fill went smoothly enough, but we did see a small cold spot on one
of the welds (photo found at this link: https://photos.app.goo.gl/377BQgQZWrqyV4tj8 )
which we didn't see before.
Strangely, this is the newest of my transfer lines - about 4-years old.  Â
The second transfer line I used last week is more than 14 years
old and it has never been pumped down since we received it. And I have
two other transfer lines that are each more than 20-years old and seem
to be fine.
And so I ask if anyone performs a preemptive pump-down of your helium
transfer lines. If you do, how frequently do you do so? Every year?C2
Every five years? Or do you wait for the first signs that the transfer
line might be going soft?
Cheers,
Bob.
--
Dr. Bob Berno
Manager, NMR Facility
McMaster University, ABB-156
1280 Main St. West
Hamilton, ON L8S 4M1
T: 905-525-9140 x24158 or x24686
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Received on Thu Jul 11 2024 - 09:08:04 MST