Nitrox Blending

[andydiver06]

Hi I plan to do DSAT Gas Blend course but problem is that I have to travel to Thailand for doing it. Anyway I'm trying to understand the concept of PP blending. If I'm wrong please correct. (I have no intention of filling Nitrox without Gas Blender's certification).

Required Nitrox 36%
Final pressure in S080 luxfer O2 Clean Nitrox makrked 11.15 lit tank -210 bar gauge
Residual O2 in Gas - 32%
Residual Pressure in tank - 50 Bar gauge

pO2 residual - (50+1)*32/100 = 16.32
pN2 residual - (50+1)*(100-32)/100 = 34.68

pO2 required - (210+1) * 36/100 = 75.96
pN2 required - (210+1) * (100-36)/100 = 135.04

Diff pO2 = 75.96-16.32 = 59.64
Diiff PN2 = 135.04-34.68 = 100.36
Pair - 100.36/0.79 = 127.038
PO2 fill req = 59.64-(127.038*.21) = 32.962

So for filling top up the tank with Pure O2 with a O2 whip upto 50+33 = 83 bar gauge
from 50 bar gauge ( very slowly to avoid friction )
Then fill compressed EANX21 / Safe Air upto 210 barg

The allow the tank to settle for 2 hours or roll the tank for 5 minutes and test the mix

 

[kidspot]

an excellent resource (and just plain fun read) is the Oxy Hackers book from http://www.airspeedpress.com

 

[andydiver06]

Thanks Kidspot. I have read your earlier topics about making your own Oxy analyzer and heard about the book. Its USD 35 + 35 USd shiiping from US to India. Quite a lot for me. Just tell me whether my calc is ok .

 

[LSDeep]

looks about right (actually to a point behind the comma i wouldnt bother with). in completely acceptable tolerances you top with 32.9 bar o2 and 127.1 air. gives you a mod of about 30m on 1.4 or 35 m on 1.6pp (actually a little less i think, but within the 1m range). let it settle or roll is recommended and i would do it, in real live its often taken straight on the boat to be dived. i guess the roll gets replaced by carrying / boatmovement action . anyway it is not as subtle as trimix so i guess it would be ok. i would avoid the direct use if poss.
here are some links if youre interested to more software (but be careful - its evil if you dont know the formulas by heart ), spreadsheets etc. http://www.cisatlantic.com/trimix/tools.htm
use at your own risk and send me a signed liability release before visiting the site