Just finished my first practical exam for my gas blending course. I had to mix 6 bottles of 50%, 3 with O2 and air and 3 with O2 and 32% in 30 minutes.
Nailed every single one with less than .5% variance!
Feeling pretty happy right now. Next week we do trimix.
(Remote Expedition Partial Pressure Gas Blending in the field using Metric is a lot more intuitive as well. . .)
Starting from an empty tank or set of O2 clean tanks (5.5L or AL40 deco cylinder; and 11L or AL80 twinset backgas Cylinders for example):
Nitrox 50 (add 37% O2):
For every 100 bar of Eanx50 deco mix, you need 37 bar of pure O2 and top off the remainder with [hyper-filtered clean] Air;
Nitrox 32 (add 14% O2):
For every 100 bar of Eanx32 mix, you need 14 bar of pure O2 and top off the remainder with Air;
20/20 Trimix (add 4% O2 & 20% Helium):
For every 100 bar of 20/20 Trimix, you need 4 bar of pure O2, 20 bar of He and top off remainder with Air;
25/25 Triox (add 12% O2 & 25% Helium):
For every 100 bar of 25/25 Triox, you need 12 bar of pure O2, 25 bar of He and top off remainder with Air;
30/30 Triox (add 19% O2 & 30% Helium):
For every 100 bar of 30/30 Triox, you need 19 bar of pure O2, 30 bar of He and top off remainder with Air;
21/35 Trimix (add 9% O2 & 35% Helium):
For every 100 bar of 21/35 Trimix, you need 9 bar of pure O2, 35 bar of He and top off remainder with Air;
18/45 Trimix (add 8% O2 & 45% Helium):
For every 100 bar of 18/45 Trimix, you need 8 bar of pure O2, 45 bar of He and top off remainder with Air;
15/55 Trimix (add 7% O2 & 55% Helium):
For every 100 bar of 15/55 Trimix, you need 7 bar of pure O2, 55 bar of He and top off remainder with Air;
12/60 Trimix (add 5% O2 & 60% Helium):
For every 100 bar of 12/60 Trimix, you need 5 bar of pure O2, 60 bar of He and top off remainder with Air;
10/70 Trimix (add 4.5% O2 & 70% Helium):
For every 100 bar of 10/70 Trimix, you need 4.5 bar of pure O2, 70 bar of He and top off remainder with Air.
Using a 11L (AL80) cylinder, or set of twin 11L doubles (double AL80's) for a total of 22L,
a full tank or set of tanks is 200 bar:
-->Therefore, all you need is 2 times the amount in bar for O2 (& He for Trimix) from above recipes for a particular mixture.
Example)
21/35 Trimix requires blending 9% Oxygen and and 35% Helium; Therefore a full 11L (Al80) cylinder(s) at 200 bar total pressure needs 18 bar of O2 (2 times 9 bar equals 18 bar), and 70 bar of Helium (2 times 35 bar equals 70 bar); and top off remainder to 200 bar with [hyper-filtered clean] Air.
