AMMRL: Summary- bladder for He fills
KLMoran@ashland.com
Thu, 29 Nov 2007 10:58:42 -0500
Dear AMMRLers,
Thank you to Tim, Jags, Jerry, Susan, Chris, Robert, Kevin, David, Ana,
Deane, Jerry, and Rainer for responding to my question about where to
obtain a bladder for pressuring He tanks during magnet fills. We need an
alternative to bottled He gas, which is now under strict allocation -- at
least in our area of the US.
People who use the method responded. Oxford sells bladders for this
purpose, although any ball bladder will do. At least two people responded
that a latex glove can be used if necessary. The technique is simple:
secure the bladder to the dewar vent, open the vent to inflate the bladder
(not too full!), close the vent, allow the bladder to warm up, then open
the vent and squeeze the warm gas back into the dewar. Continued manual
'pumping' eventually builds up enough pressure to transfer the liquid.
Others responded that they use liquid helium dewars with internal heaters
to build up pressure. Others use a vacuum pump. A helium recovery
system was also recommended, which seems the best, most obvious and
unfortunately most expensive solution.
The complete responses are below.
Cheers,
Kelly
-----------------------------
We still use this method as standard for all our systems. Last time we
looked Oxford Instruments were selling the bladders. Our system is very
simple- we just connect a length of rubber tubing to the He gas port
(sliding it on to the outlet is good enough if it is a tight fit) and then
join this to the bladder with a plastic connecting tube. Purge with gas
from the dewar and it is set to go. I would imagine any rubber bladder
would suffice- we have used both soccer and rugby bladders.
------------------------------
We regularly use this method. Any football bladder of good quality,
connected to one of the inlets (side) of the container, would do the job.
I feel that this method is more economical and efficient.
--------------------------------
I have seen it done before with a simple rubber latex glove. Just slip
the glove over the outlet and tie it in place with a rubber band. Then as
the tank builds subtle pressure the glove will expand like a ballon.
During the fill you can massage the pressurized glove to continue
generating enough agitation to maintain positive pressure.
------------------------------
since a long time I am using a vacuum pump (a SV16, of course used in
opposite direction), to pressurize our liquid helium cans. I take the
necessary
gaseous helium from the recovery line.
I am very happy with this method. If you don't have a recovery line, maybe
you can collect evaporating helium using a balloon.
---------------------------
I have never used the bladder method to pressurize a dewer, but for
many years
we have used an alternative method that does not require He gas.
We buy our liq He from Praxair in 250 L dewers, and they almost
always come
with a internal electrical heater that can be switched on as required to
pressurize the dewer. Of course one has to keep an eye on the
pressure when
doing this, but have never had a problem with this method. See if
your vendor
can supply dewers with a built in heater.
-----------------------------------
Talk to your GC colleagues. They probably have a finite monthly
allocation.
[my response-- my GC colleagues are switching to H2!!]
------------------------------------------------
There are some LHe dewars that have built in pressurizing systems that
with the use of an extension cord, plug into a
standerd wall outlet. However these are usually regulated @ 4 and 8 psi
(for MRI systems), Usually NMR fills are done
@1.5 to 2 psi.
I guess you could talk to the supplier or your engineering dept. to see if
they can come up with a fix. Somthing that is
regulated @ 1 to 2 psi.
-----------------------------
The recovery system is something that would be good if you shared the
costs with other users. If you can’t get budget to make one maybe you can
justify budget to visit one (or some) to study? It brings our costs from
$6-8 /LHe down to $2.50/LHe.
The system uses basic plumbing available at most hardware supplies. The
gas at 2-4 inches water pressure finds its way to a Bladder room at a
higher floor level. From there it is pressurized into a storage tank
whereby it can be liquefied, in our case about a mile away. You or by
your supplier can Liquefy if they are willing to come get the gas. The
major expense is the liquefier. If your supplier has one half your
solution maybe your status would change from user to partner.
We recover at all times even during fills. We use inexpensive positive
displacement gas meters used in the natural gas industry one on each room
but that is only for enterprise wide accounting and a good amount of CYA.
They are networked and the Cryo-guys call us when they see odd flows. This
has prevented quenches at least 3 times from out of the blue failures that
cause high boil-offs. Our delivery dewars have custom built computerized
meters too; also networked so Cryo always knows where the He liquid is or
is not (if someone swiped it).
Let me know what you come up with for a pumping bladder because I too am
drawn to the simplicity and am always scared there might be a steel tank
mishap one day and for safety sake alone would like a better solution.
We need to conserve the Helium. Whole industries depend upon it. It
will only get more scarce.
Like I said before if you can ditch the liquefier and compress to big
tank … that will save a ton of money. You can gas purge simply cooling
the line slow at first. Here’s some of our solution in Pic’s: I think one
time in an emergency I used gloves and Teflon tape to pump warm gas in at
the end. A royal pain … open valve to glove… let it balloon … close the
valve while it warms … open valve and squeeze gas in … close valve and
wait a moment … repeat.
Anyway I have more info if you need it.
------------------------
Bruker includes a bladder with some of their magnets. It is used to
maintain helium gas pressure during magnet cooling, but could likely be
adapted for your purpose. Bruker Center can likely identify it for you.
-----------------------
>From Bruker:
We don't sell bladders. We do sell a helium fill regulator, which is used
for
pressurizing the helium dewars.
Part #91588 REGULATOR HELIUM GAS FILL $250.00 In stock
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I never heard of the method, but am very interested in knowing more.
i signed a one year contract with Air products to secure my He needs,
under pressure from them.
Please let me know what good suggestions you get to save the gas!
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