What equipment do I need (and how do I) put the helium from a 12?
diameter balloon back into a helium cylinder?

Background:
I need to fill a 12? diameter balloon with 900 cubic feet of helium. 
To do this, I plan to purchase four cylinders (55?x9.25?) that each
hold 290 cubic feet of helium that is pressurized at approximately
2600 PSI.  I would like to return the helium to the cylinders upon
completion for future use.  I am assuming that this could be done with
some type of compressor or vacuum or something (but I am totally
clueless).

Question:
What equipment would I need to accomplish this and where can I
purchase it?  A big bonus in the answer would be any information on
the process of how this could be accomplished.

Thank you.

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Request for Question Clarification by hedgie-ga on 19 Apr 2004 11:22 PDT

They fill them somehow, right?

But commenter leoj is probably confusim HE with liquid Nitrogen.
To liquify He is possible but hard, But cooling it is the way.

It is not something to tey at home. Here is a quote:

Workplace Hazardous Materials Information System
 
Compressed gas cylinders shall not be refilled without the express
written permission of the owner. Shipment
of a compressed gas cylinder which has not been filled by the owner or
with his/her (written) consent is a
violation of transportation regulations

www.boc.com/gases/pdf/msds/G005.pdf

here is more:
. preventative maintenance on the helium liquefaction system, the
cryogenics gas filling station, helium compressors, high pressure
dewars, cylinders and vacuum ...
www.hr.arizona.edu/06_jcl/jobdesc/50924.htm?5092

is this an answer?

Sounds easy enough.

Just connect a suitable compressor between the pipe from the cylinder
to the balloon.

Or am I missing something?

My problem is that I can only find compressors that have low psi (like
100-200).  Additionally, they only have an intake for air.  This would
need a hose on the end in order to draw directly from the balloon and
it would also need to be able to create an extremely high pressure
(2600 psi or so).  I can't find the product that will do it.  I'm
thinking that it may be called a vacuum or something other than a
compressor.  Any help would be greatly appreciated.

Perhaps you need a High Vacuum Pump?

http://vacuum-pumps.globalspec.com/LearnMore/Manufacturing_Process_Equipment/Vacuum_Equipment/Vacuum_Pumps/High_Vacuum_Pumps

I can assure you that just refilling the tanks as needed will be much,
much cheaper than pumping it back in to the tank.

If you intend to use the helium through many refillings, perhaps you
want to get helium in liquid form instead.  Liquid helium is used
often for scientific experiments, and provided in dewers.  The
pressure is lower, but you still wouldn't want to attempt to refill
the tank yourself.  Of course, the downside to using liquid helium
dewers as your source is that over time it will boil off (there are
relief valves) and you lose your investment and need to resupply.

Hope that helps.

You're probably looking for something like they use for refilling
SCUBA diving tanks.  Search google for "helium scuba compressor"
and/or "helium compressor"

Hi all,

Hedgie - I appreciate the effort, but I think that you may be going in
the wrong direction on the answer.  I'm really looking for a place
that sells a machine capable of accomplishing my need.

Leoj - Liquid helium is too scary/difficult.  I just want to transfer the gas.

Sleepingsquirrel - Thank you!  I'm finding a bunch of scuba
compressors that go to 5000 psi and that are reasonably priced. 
That's the solution.  Thank you so much!

The cost of the equipment to do what you want would cost orders of
magnitude more than the helium.  Unless you intend to fill thousands
of balloons you are far better of releasing the helium and buying
more.  Even then recompressing may not be cost-effective.  If you are
going to do very large numbers of fills I suggest that you contact
several gas suppliers and explain your needs to them.  Tell them that
the gas could be recovered, but don't make doing so a requirement. 
Ask them propose helium supply systems, and pick the best proposal. 
Hire an engineer to help you with this.

By the way, have you considered using hydrogen?  It might not meet
your requirements, but it is cheap and not as dangerous as most think.

Forget about putting the geni back in the bottle, equipment to do that
is about $50,000. buying more bottled gas is cheaper, not only do you
need to cool the bottle and gas but the pressure you need to get it in
there is very high and again very expensive for the equipment. Trust
me