Dear group,
OK, I think I mostly know what happened. There was actually a partial
blockage on the vent side. At the time that I wrote, it had just
happened and the radiator that I have on the vent side was still frozen
from the fill, so I hadn't actually checked whether that side was
blocked. And nitrogen had been shooting out that side very hard all
through the fill so I assumed it was clear.
But now it's clear that it was partly blocked during the fill. That must
have led to pressure building up inside the nitrogen dewar. I cleared it
and refilled nitrogen this morning. Everything behaved completely
normally, so hopefully it will be OK.
Two things I don't understand though: the first is the cycling of the
pressure when I removed the filling hose from the fill port yesterday.
It was truly amazing to see. It cycled between almost no flow at all to
erupting like a geyser over a period of about 20 seconds, and continued
for 6-8 cycles before it started to wind down.
The other thing is the change in sound that I heard during the fill
yesterday. In retrospect it really seems like that could have been the
blockage forming. Is that possible?
Anyway, I will pay closer attention to sound changes in the future.
Thanks in advance for any information.
-Robert
-------- Forwarded Message --------
Subject: very scary nitrogen fill
Date: Tue, 09 Aug 2016 15:56:48 -0700
From: Robert Peterson <peterson_at_mbi.ucla.edu>
To: AMMRL <ammrl_at_ammrl.org>
Dear group,
I just had a very disturbing experience just after filling nitrogen. The
system is a Bruker 600 - Magnex magnet, installed in 1996.
I filled nitrogen, and it took much longer than usual. It took about 90
minutes, while it usually takes ~40. Also, during the fill there was a
change in the sound the fill made - it suddenly became louder and
higher. The fill did finish eventually (liquid came out). After it
finished, there was a very strong outflow from the vent port - almost
like I was still filling. After it had gone on like this for a few
minutes, I double checked to make sure the tank was closed (it was).
(The magnet has 3 nitrogen ports. One is occupied by the nitrogen
sensor, and the other two are used for filling and venting during the fill.)
After a few minutes (while it was still venting like crazy), I removed
the filling hose from the magnet: nitrogen came blasting out harder and
harder until _liquid_ nitrogen was blasting out so hard it was hitting
the ceiling 5 feet above and splashing down on me. Then it gradually
calmed down until only gas was coming out relatively slowly. Then the
pressure got higher and higher until again liquid was shooting out. The
full cycle took maybe 20 seconds. This continued for 2-3 minutes. After
maybe 6 or 8 of these cycles it started getting less intense and a few
minutes later it had stopped. 10 minutes later it seemed completely normal.
Both of my open nitrogen ports are clear. Nothing was different with my
nitrogen dewar (low pressure - 22psi). The magnet is still a magnet, and
the lock was stable even while the nitrogen was blasting out.
Does anyone know what could cause this? I will post a summary or an
explanation.
thanks,
-Robert
--
-----------------------------------------------
Robert Peterson, Ph.D.
Facility Manager - NMR Technology Center
UCLA-DOE Institute for Genomics and Proteomics
UCLA Dept. of Chemistry and Biochemistry
phone: (310)825-1816
fax: (310)825-0982
peterson_at_mbi.ucla.edu
-----------------------------------------------
Received on Wed Aug 10 2016 - 06:16:53 MST