Hi Bob,
This is exactly what I experienced a couple of years back with the 300MHz HTL
at KDT. We decided to buy a new HTL. This one is now the back-up HTL but I
need to get it checked. I'll take it to J.K. Cryogenics (Newmarket, Ontario,
Canada) at some point.
As you already know, I got my 800MHz HTL pumped last winter (also at J.K.
Cryogenics) as it had lost its vacuum after 20 years. It works fine now. We
also bought a new HTL for the 800MHz (for a peace of mind) and now I have a
backup HTL for this magnet too.
Cheers,
Geneviève
***************************************
Geneviève Seabrook, PhD
Staff Scientist
NMR Research & Core Facility Manager
UHN, Princess Margaret Cancer Centre
Princess Margaret Cancer Research Tower (PMCRT)
4th floor, Room 4-902
101 College Street
Toronto, ONT, M5G 1L7
Mobile: 416-629-7391
Genevieve.Seabrook_at_uhn.ca
https://nmrcore.uhnresearch.ca/
-----Original Message-----
> From: main_at_ammrl.groups.io On Behalf Of Bob Berno
> Sent: Wednesday, July 10, 2024 4:49 PM
> To: main_at_ammrl.groups.io
> Subject: [External] [AMMRL] AMMRL: Helium transfer line gone soft.
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 just as we started cooling it down.
We aborted the transfer and then completed the helium fill using another
transfer line.
I asked the person in charge of our helium recovery system to test the
suspicious transfer line. 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. 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.
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 was wondering if anyone performs a preemptive pump-down of your helium
transfer lines. If you do, how frequently do you do so? Every year? 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 - 09:23:12 MST