Greetings fellow NMR users. I posted a few weeks ago about a problem
with ice in our fill-in port when we went to refill our NMR with liquid
helium. I just wanted to write back to the group, first of all to say
thanks for all your help, and secondly to recap the responses I
received.
We determined our issue arose from the o-ring used to seal off the
helium turret. During the last fill it had been replaced in the wrong
location, allowing air to leak into the turret. This was the the
primary suggestion made by the responders to check.
Additional suggestions for possible causes included a faulty one way
valve used to vent the Helium as well other possible sources of leaks.
Suggestions in regards to checking helium levels and filling made the
point to always make sure the ports to the helium tank are never
exposed for more than 5 seconds to open air. The easiest method to
"plug them up" temporarily would be to use Kimwipes.
As for removing ice once its in there, the best method is blowing warm,
dry helium gas on it at a very low pressure (<1psi). This should melt
the ice enough to clear the port for filling. The best tool for blowing
dry gas would be the transfer line used for filling as it is of an
appropriate diameter.
If you have any questions for me about other responses, or any further
ideas, don't hesitate to send me an email.
Thanks for all your help.
Scott Woltman
Graduate Student
Display and Photonics Lab
Brown University
Received on Mon Apr 11 2005 - 10:28:40 MST