Anne,

I can tell you from my personal 10 years of university experience, I've nev
er seen this happen (that does NOT mean it won't or can't - just that I've 
not seen it).  I've had the tube break off (perhaps twice, but only once th
at I can for sure remember) right at the fill tube, though, and I can tell 
you I was far more concerned with the integrity of the can flange at that p
oint than whether or not I was getting liquid nitrogen on me (which I wasn'
t...)

That being said, there is a very good argument to be made for slow fills.

This tends to be more efficient, and permit a more complete fill (which eit
her translates into fewer fills if you fill at a specific level, or a large
r reserve if you fill on a specific time schedule).  If, as in our case, a 
graduate assistant or dedicated staff member is doing the fill, it does no 
good to rush the fill (vendors, on the other hand, have multiple deliveries
 to make in a single day and don't have the time to spare to do slow fills)
.

My vote is for the slow fill.

Brad Norwood

Bradley K. Norwood, PhD
Laboratory Director
Arista Laboratories
1941 Reymet Road
Richmond, VA  23237
(804) 271-5572 ext. 307
(804) 641-4641 (cell)
brad.norwood**At_Symbol_Here**aristalabs.com

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-----Original Message-----
From: DCHAS-L Discussion List [mailto:DCHAS-L**At_Symbol_Here**list.uvm.edu] On Behalf Of An
ne Skinner
Sent: Thursday, January 29, 2009 3:15 PM
To: DCHAS-L**At_Symbol_Here**LIST.UVM.EDU
Subject: [DCHAS-L] LN2 and NMR

We are involved in a discussion, rapidly getting acrimonious, about 
the best way to fill an NMR with LN2.  One faction wants to fill as 
rapidly as possible; the other very slowly.  The safety issue is as 
follows.  Eventually the rubber hose used in filling will split. 
When this happens, if the fill rate is rapid the LN2 will spatter 
around, possibly onto anyone supervising the fill, especially as they 
try to turn off the flow.  Has anyone any experience as to whether 
this is actually a threat?

Thank you --

Anne R. Skinner

-- 

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Dr. Anne Skinner
Chemistry Department, Williams College
47 Lab Campus Drive
Williamstown, MA 01267

anne.r.skinner**At_Symbol_Here**williams.edu
Phone:  (413) 597-2285
Fax No: (413) 597-4116

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