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On 11/8/14, 5:20 PM, David Rieben wrote:
Hi Jim,
At the risk of drifting OT, I must jump in here and ask how you are
able obtain 180 L of LN2 for ~$70 when I was locally quoted around
~$4.75/L a couple of years ago! I happen to own a 111 L cryogenic
container (not a pressurized dewar, just a bio-specimen preserving
cryo storage tank, with the non-sealing styrofoam lid -- retails new
for ~$3500 -- eBay special ~$200, including S&H) and I was trying to
locate a local supplier of LN2 (just to have a little cryogenic fun)
and received this "shocking" price quote from a local welding supply
jobber! Maybe I should've "shopped around" a bit more, but I found
that most industrial cryogenic liquid suppliers in my locale were
geared toward tanker truck quantity purchases of the cold stuff, and
were only set up to dispense it into a sealed, pressure dewar tank.
Bingo.. $70-80/fill is into a 180L/45 gallon dewar (e.g. a GP45) with
all the fittings, and under pressure. The pricing is basically set to
be roughly the same as GN2 in a pressure bottle.
Dispensing into a open container (e.g. a wide mouth specimen jar) is
something most places are not set up to do, and they lose a lot due to
vaporization in the process of bringing it down to atmospheric pressure:
it fizzes like soda water. If you think about it, it's the same with gas
nitrogen: you can't show up at AirGas and say, here's a big balloon,
fill it with 300 cubic feet of N2.
You have to have the liquid line from your bulk tank (or your handy 45
gallon dewar) run through a cryogenic line to a phase separator (which
is basically a sintered metal plug) that expands the pressurized LN2 to
ambient, and separates the liquid from the gas boiloff.
I have a small narrow neck dewar that holds about 3-4 gallons, and it is
a pain to fill. I used to fill 5 gallon insulated water containers (you
know, the kind you see on the back of a work truck) from a low pressure
bulk dewar, and that was a lot easier.
BTW, if you're filling a unpressurized container from a 230 psi high
pressure bulk tank it's a lot harder.
The only supplier that could accommodate my non-pressurized storage
dewar to dispense LN2 by the liter was the welding supply that was
asking nearly $5/L! Needless to say, I quickly abandoned the idea of
purchasing 50-100 L (@ ~$5/L) of LN2 just to "have fun with", but I
still have that 111 L storage dewar sitting around ;^/
Yep..
You might start asking around for medical and metal fabrication places..
Someone who gets large amounts of LN2 in big tanks might be willing to
fill your open mouth dewar if they're familiar with the process (metal
fab uses it for rapid quenching, for instance).