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Old 16th August 2007, 14:27   #2 (permalink)
wedivebc
Dave Tomblin

 
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Current Rebreather/s:
Megalodon
Other CCR

Other Rebreather/s:
Not Bought Yet
Inspiration Classic
Sport Kiss
Other CCR
 
Join Date: Feb 2005
Location: Vancouver Island BC Canada
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Re: heliair vs trimix

Quote: (Originally Posted by gallathan) View Original Post
just thinking about blending heliar diluents vs blending trimix. Think blending trimix in dil cylinders at home may be error prone, so tempted to think about heliair, but have a dilema.

Seems you can go 2 routes, 1) Keep the PO2 of the heliair the same as my trimix dils i.e. 1.0. As heliair has a fixed N2 to O2 ratio (79.1:20.9) that results in high END's ~ 37/38M. I know the oxygen added by Rebreather to go from PO2 1.0 to PO2 1.3 will dilute the diluent a little, thus reducing the END, but not a lot.

2) Go with a dil with a PO2 of 0.836 instead of the 1.0 I normally use for Tx diluents. This is perhaps not the most optimal diluent for loop flushing, BUT does result in an end of 30M, like my timix bailouts, but concerned this will result in Rebreather having to add more O2 to the loop - reducing O2 duration and/or leading to more buoyancy issues.
Whats the normal practice for choosing a helair diluent, how do these factors get balanced?
I choose to use heliar because 1 it is easier to blend , 2 I don't own a helium analyzer so I can always predict my He based on my O2 content and 3 it gives me a mix that has a very acceptable END if you consider the planned O2 content I run is .2 below my setpoint so for 90m dive a 10/50 dil gives me an END of ~40m which is quite acceptable to me.
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Dave....

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