Hi,
it may be worthwhile noting that this (admittedly simple) "rubber disk solution"
is only used on Bruker magnets - neither Oxford, Magnex or Jastec magnets employ
anything similar. Here one always slides the black ring nut and its O-ring (which
tightens the magnet's helium plug) over the helium transfer line. The nut is then
tightened after insertion of the transfer line in to the magnet. Some magnets even
come with two sets of nuts such that one nut can permanently stay on the transfer
line… This is also the much preferred way with helium recycling systems which
may have additional back pressure and is more prone to leak if the connection to
the transfer line isn't very tight.
Best regards
Bert
> Am 23.07.2024 um 19:28 schrieb Bob Berno <bberno_at_mcmaster.ca>:
>
> Hello Joe,
>
> I have sometimes seen a leak from the fill port under the black rubber disk
> on a few of our magnets, but not always.
> Once it starts to leak, there is no stopping it. The disk is just plain
> frozen in it's misshapen state, and will continue to leak until you are finished
> the fill.
>
> I came up with one "solution" I had to this for one particularly problematic
> magnet/transfer line combination:
> I speculated that the rubber disk was ever so slightly concave. So, I removed
> the disk from the stinger, flipped it over and then re-installed it. Since
> then, I have seen much less cold helium "plume" escaping from the fill port.
> Occasionally we will see some venting, but nothing like we had seen previously.
>
> Not only do we leave the large diameter one-way valve on the exhaust port,
> but we are also tied into a helium recovery system. So we have the additional
> back-pressure to deal with. So, I think this should work for your magnets as well.
>
> Good luck,
> Bob.
>
>
> On 2024-07-22 5:45 p.m., Joseph Dumais via groups.io wrote:
>>
>> As part of a recent console upgrade on our 600, I requested a new Helium
>> transfer line since we are pretty remote here and our other line has been
>> in user for 16 years. I wanted to have a backup on site. When we fill our
>> 600 we leave the Bruker supplied check valve on the exhaust port, it seems
>> to be a very low pressure check valve that seems to be functioning just fine
>> (no sticking detected and the pressure to open it is very low). The new
>> transfer line is of a corrugated outer layer versus the braided outer layer
>> on the older one. It is considerably lighter. For the magnet side of the
>> transfer line we use the rubber disk which Bruker provided to seal the upper
>> stack on both the older line and the newer transfer line. I checked the
>> stinger length below the rubber disk and it was set to a depth which was no
>> longer than it was on our older transfer line. As soon as we started to
>> fill the magnet there was a plume of cold gas escaping from between the top
>> surface on the upper stack and that rubber disk. It seemed like maybe there
>> was not enough weight to seal that gap? I tried to wrap it with thread
>> sealing tape but that was tough with the plume of cold gas coming out. I did
>> not want that part of the upper barrel to end up loaded with condensation.
>> In the end I decided to remove the check valve and that solved the issue.
>>
>> Has anyone else had this issue with the new transfer lines on one of the
>> magnets which has that check valve?
>>
>> We always remove the wider ring and take that "top hat" assembly off and=
>> do not use the smaller diameter opening. We could use the narrower part of
>> the cap if we had another one of those smaller diameter, knurled black caps
>> which could stay on the stinger. That would be more like what I was used
>> to on Oxford magnets.
>>
>> Joe Dumais
>
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