--Apple-Mail-20--112230430 Content-Type: text/plain; charset=WINDOWS-1252; format=flowed; delsp=yes Content-Transfer-Encoding: quoted-printable Hi everyone and Happy New Year, Because we use our own dewars which are never warmed up we = always use =20 UHP helium to avoid any buildup of contaminants in the helium dewar. Deryck Webb = --------------------------------------------------------------------------= ---------- Deryck Webb - NMR Technologist NANUC - Canada's National High Field NMR Centre Room 103 Email: deryck@nanuc.ca NANUC Bldg. Phone: (780) 707-0857 University of Alberta Fax: (780) 492-9174 Edmonton, Alberta Cell: (780) 707-0857 Canada T6G 2E1 AIM: derycknmr http://www.nanuc.ca On Dec 26, 2007, at 1:43 PM, Jane Strouse wrote: > Dear AMMRLers, > > I indirectly received the message below from someone who was =20 > pretty embarrassed about having used the wrong gas to pressurize the =20= > storage dewar for helium fills. I thought I would relate my =20 > experience with this sort of thing. Quite a number of years ago, I =20= > found that the people working for me had been using nitrogen gas. I =20= > have no idea how long this had been going on or how it happened that =20= > we ended up with nitrogen rather than helium on the cart we use for =20= > fills. Amazingly, we seemed to have not observed any ill effects =20 > from this. I thought about it and decided that if you really did =20 > your fills correctly, you could get away with this, because none of =20= > the gas should enter the transfer line, and if the line is =20 > sufficiently above the bottom of the storage dewar, any condensed =20 > nitrogen would not be pushed into the transfer line. At any rate, =20 > we did later de-energize a couple of the solenoids to move them to a =20= > new building. There was no problem whatsoever with putting in the =20 > charging rods, so if there was icing from the nitrogen, it was not =20 > substantial. (Of course, it is possible that the tank had just been =20= > put on the cart when I noticed it and was never used, but I always =20 > presumed it had been used.) > > This leads me to another question. I once had a mass spec =20 > service person tell us that we should use ultra-high purity helium =20 > (UHP, 99.999%) for the liquid helium transfer into an FT-MS =20 > solenoid. I thought he was crazy, but I supppose it is possible =20 > that it would be better for that particular magnet. Do any of you =20 > use UHP helium gas for transfers? We certainly do not. > > Jane Strouse > > > > > Message received: > = __________________________________________________________________________= _____ > Dear Spinners, > > First of all, happy holiday season!!! > > I have been a passive observer and certainly taking advantages of =20 > the fruitful discussions at AMMRL. Here is a story that I feel I =20 > can use to contribute to the community. I am very much embarrassed =20= > in making such mistake, as you can see I am even hiding my name, but =20= > I still want to post it, so everyone could learn something from it. > > I have been filling liquid helium to my 400 MHz magnet by myself and =20= > for the past two years I thought that I have been using helium gas =20 > to pressurize the tank (well, read the label before using it). Just =20= > a few days ago, I found that it had been argon gas all along. =20 > Before using this gas cylinder, there had been no problem doing it =20 > and after switching to the tank, I started experiencing technical =20 > problems and I blamed the liquid helium supplier and moisture in the =20= > air. Here were the problems: (1) the liquid helium inlet (on the =20 > magnet side) seemed to be =93ice=94 blocked, (2) it took from one to = two =20 > hours to fill it, and (3) at the end of the filling process, it was =20= > extremely difficult to pull out the transfer tube (somehow the tube =20= > got stuck somewhere in the system on the magnet side and especially =20= > on the liquid helium tank side - I even destroyed one of my transfer =20= > tubes to pull it out). Of course the root of the problems is that =20 > the argon gas solidified in the system. Just last week, I found the =20= > mistake and switched to helium gas; everything goes back to normal =20 > now. > > So, what can we benefit from such odd experience? Although some =20 > might think that there are other factors to consider, from the =20 > experience I believe that we don=92t need ultra high purity helium gas = =20 > at all for the refilling. A regular grade helium gas will do the =20 > job just fine. The gas I used is almost 100% purity argon and it =20 > has been two years. If it doesn=92t hurt the magnet this way (in =20 > terms of building up alarming level of solids in the magnet or =20 > clogging the system permanently), why we need to use ultra high =20 > purity helium gas? By the way, the boiling point of argon is about =20= > -186 C, oxygen is about -183, and nitrogen is about -195 C. > > Anyone cares to shed some more opinions? > > =46rom someone too embarrassed to show his/her name. > > = __________________________________________________________________________= _____ > > > > > > ---------------------------------------------------------------------- > Dr. Jane Strouse > Director, UCLA Molecular Instrumentation Center > 1410 Molecular Sciences Building > Los Angeles, CA 90095-1569 > (310)-825-9841 - voice > (310)-825-2280 - fax > strousej@chem.ucla.edu > http://www.mic.ucla.edu > ---------------------------------------------------------------------- > --Apple-Mail-20--112230430 Content-Type: text/html; charset=WINDOWS-1252 Content-Transfer-Encoding: quoted-printable Hi everyone and Happy New = Year,Because = we use our own dewars which are never warmed up we always use UHP helium = to avoid any buildup of contaminants in the helium dewar.Deryck = Webb---------------------------------------------------------------= ---------------------
Deryck Webb - NMR = Technologist
NANUC - = Canada's National High Field NMR Centre
Room 103 = Email: deryck@nanuc.ca
NANUC Bldg. = = Phone: (780) = 707-0857
University of = Alberta = Fax: (780) 492-9174
Edmonton, Alberta = Cell: (780) 707-0857
Canada T6G 2E1 = AIM: derycknmr
=On Dec 26, 2007, at 1:43 PM, Jane Strouse = wrote:I indirectly = received the message below from someone who was pretty embarrassed about = having used the wrong gas to pressurize the storage dewar for helium = fills. I thought I would relate my experience with this sort of = thing. Quite a number of years ago, I found that the people = working for me had been using nitrogen gas. I have no idea how = long this had been going on or how it happened that we ended up with = nitrogen rather than helium on the cart we use for fills. = Amazingly, we seemed to have not observed any ill effects from = this. I thought about it and decided that if you really did your = fills correctly, you could get away with this, because none of the gas = should enter the transfer line, and if the line is sufficiently above = the bottom of the storage dewar, any condensed nitrogen would not be = pushed into the transfer line. At any rate, we did later = de-energize a couple of the solenoids to move them to a new = building. There was no problem whatsoever with putting in the = charging rods, so if there was icing from the nitrogen, it was not = substantial. (Of course, it is possible that the tank had just = been put on the cart when I noticed it and was never used, but I always = presumed it had been used.)= This leads me to another question. I once had a mass spec service = person tell us that we should use ultra-high purity helium (UHP, = 99.999%) for the liquid helium transfer into an FT-MS solenoid. I = thought he was crazy, but I supppose it is possible that it would be = better for that particular magnet. Do any of you use UHP helium = gas for transfers? We certainly do not.
Jane = Strouse
Message = received:
Dear = Spinners,First of all, happy holiday = season!!!
I have been a passive observer = and certainly taking advantages of the fruitful discussions at AMMRL. = Here is a story that I feel I can use to contribute to the = community. I am very much embarrassed in making such mistake, as = you can see I am even hiding my name, but I still want to post it, so = everyone could learn something from it.
I have been filling liquid helium to my 400 = MHz magnet by myself and for the past two years I thought that I have = been using helium gas to pressurize the tank (well, read the label = before using it). Just a few days ago, I found that it had been = argon gas all along. Before using this gas cylinder, there had = been no problem doing it and after switching to the tank, I started = experiencing technical problems and I blamed the liquid helium supplier = and moisture in the air. Here were the problems: (1) the liquid = helium inlet (on the magnet side) seemed to be =93ice=94 blocked, (2) it = took from one to two hours to fill it, and (3) at the end of the filling = process, it was extremely difficult to pull out the transfer tube = (somehow the tube got stuck somewhere in the system on the magnet side = and especially on the liquid helium tank side - I even destroyed one of = my transfer tubes to pull it out). Of course the root of the = problems is that the argon gas solidified in the system. Just last = week, I found the mistake and switched to helium gas; everything goes = back to normal now.
So, what can we benefit from such odd = experience? Although some might think that there are other factors = to consider, from the experience I believe that we don=92t need ultra = high purity helium gas at all for the refilling. A regular grade = helium gas will do the job just fine. The gas I used is almost = 100% purity argon and it has been two years. If it doesn=92t hurt = the magnet this way (in terms of building up alarming level of solids in = the magnet or clogging the system permanently), why we need to use ultra = high purity helium gas? By the way, the boiling point of argon is = about -186 C, oxygen is about -183, and nitrogen is about -195 = C.Anyone cares to shed some more = opinions?
=46rom someone too embarrassed = to show his/her name.
Dr. Jane = StrouseDirector, UCLA Molecular = Instrumentation CenterLos Angeles, CA = 90095-1569Jerry Hirschinger "Re: AMMRL: The big OOPS"Previous message: "Re: AMMRL: MRI Console Needed, MRI Magnet Trade-in"