So if you want to make trimix really easy 

!!!Warning those of you not trained in mixing don't do this at home!!! 

Bank up EAN 36 

You can do this with a variety of tools 

1 - atm entrainment with an oil free compressor 

2 - a denitrogenation membrane separation system 

3. The NS Research ANX Supreme automatic partial pressure mixing system

once you have a stable 36% EAN -- just blow HE on top to the final pressure. 

the proportion is 50/50 --- 50% EAN36 50% HE and you have an 18/50/32 trimix 

for a 3500 psi fill you put in 1750 of EAN 36 and 1750 of HE 

If you are banked up on the 36 you can cascade your HE --
run the booster on the EAN its easier and uses less drive gas that way. 

Top ups are easy too. The proportions are always the same If you have a set
left over with 2,000 psi  add 750 of HE and 750 and you will have 3500 psi
of 18/50/32 


As to the temperature of your gas while mixing --- the temperature rise
occurs during the initial opening of the filling valve. If you use a needle
valve (Whitey) and you have not slammed any gas into any other portion of
the system -- opening this valve a 1/4 turn for 30 seconds then another 2
full turns over the next minute your gas will stay nice and cool --
remember when gas expands from a storage cylinder it will get cold -- when
it trans fills it should not heat up if your valve and plumbing is clean
and without restrictions. The biggest single mistake a filler makes is
opening the needle valve first and then the Sherwood Fill Valve or the
scuba valve. The full system must be open and then you open the needle
valve and let the gas temp ramp up to the fill rate. 

If you use a Haskel booster the AGT 15/30 two stage is an inter cooled
system and there it uses the drive exhaust to cool down the gas, anyone who
has ever used a haskel booster knows how much ice will form on the exhaust
system when run for a while.  

Helium mixtures may take a few hours to stabilize but if mixed slowly they
will usually analyze up properly -- its important to use a flow meter on
the analyzer to get an accurate analysis. Waving that thing in the air to
calibrate to air is just silly.  If you mix a lot of trimix with oxygen
content lower than 21%  it may behove you to order up some calibration gas
from your gas house in a small flask, a good mix is 16 % oxygen 84%
nitrogen - calibrate your meter to that each time and your trimix analysis
will be top-dead-center accurate. 

Mix it up ........

Joel Silverstein
http://www.nitroxdiver.com
http://www.gasblending.com 




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