Hi Dejian,
The valve should be the same effort to close that it was to open. It sounds like the valve was wet and the moisture froze in the open position so ice obstructed smooth operation. Never leave a rotary cryogen valve opened all the way against the stop. Any moisture can freeze the valve open. Always open it to the stop and then close it 1/4 to 1/2 turn so it cannot freeze the stop surfaces together.
Never open a wet cryogen valve. Dry it with a heat gun if necessary before you open it.
If there is a problem closing a cryogen valve, immediately open the dewar vent valve to relieve all pressure. With no internal tank pressure the flow will stop. Then you have no stress to go get a heat gun and thaw the valve.
Cheers, -Hirsch
Jerry Hirschinger, NMR Instrumentation Specialist
Purdue Interdepartmental NMR Facility
560 Oval Dr. West Lafayette, IN 47907-2084
Office: Wetherill 365A
Phone / Fax: (765) 494-5288 / 494-0239
Cellular: (765) 427-3034
-----Original Message-----
From: Ma, Dejian [mailto:dma6_at_uthsc.edu]
Sent: Tuesday, October 27, 2015 3:13 PM
To: ammrl_at_ammrl.org
Subject: AMMRL: Liquid valve is hard to turn off on the liquid nitrogen tank
Hello,
It maybe a trivial issue, but I didn't find any post on this issue before. The liquid valve on the LN2 tank we received this week became very hard to turn off after the LN2 refilling. I had to use a wrench to turn it off. Maybe the liquid valve is problematic. Is there anyway to know it before the refilling since it's not obvious when turning the liquid valve on. Thanks!
Not related to this, I read about the 'Bruker folders' discussion. Many of you know that the folder structure of the Bruker NMR data has been like it is for 20+ years, from previous XWinNMR to current TopSpin. It's actually kind of neat.
Dejian
University of Tennessee Health Science Center
Received on Wed Oct 28 2015 - 10:56:51 MST