Android - PastoBlend
had another, can't locate it - was a real simple GUI....
had another, can't locate it - was a real simple GUI....
Are there formulas for Blending Nitrox and how to achieve a certain percentages?
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As others have said, the math is not that complex and there are several programs out there that do the job if you wish to blend your own nitrox. But the question becomes, why bother?
20 years ago, because none of the local shops offered nitrox or O2 fills, I used to keep several T cylinders of O2 and Helium in my garage. Because I didn't have a haskel, blending nitrox usually involved dumping tanks down to a level where I could then put O2 on top of them, and then I had to drive over to a dive shop that would let me blow air on top of my tanks. I had to keep track of the O2 banks (I used to keep 3 cylinders to get the highest pressure possible), and once or twice a month I had to make a special trip to the welding supply company to swap cylinders out.
The time commitment to fill tanks for a weekend dive and maintaining the Oxygen banks was pretty high. And as I recall the cost of the O2 was around $0.05 per cubic foot once I figured out rent for the cylinders, etc.
These days, I can just drive up to the local shop and have them blow 32% on top of my tanks. It costs me $0.08 per cubic foot, and takes a fraction of the time. Remember, in 1995 after I blew O2 into the tanks I had to go to the shop to have them blow air on top of my tanks, now I skip the whole pre-mixing dance routine.
I don't know about you, but my time is worth more than the $0.03 per cubic foot price delta between a 1995 home brewed nitrox fill and a 2015 store bought nitrox fill.
20 years ago, because none of the local shops offered nitrox or O2 fills, I used to keep several T cylinders of O2 and Helium in my garage. Because I didn't have a haskel, blending nitrox usually involved dumping tanks down to a level where I could then put O2 on top of them, and then I had to drive over to a dive shop that would let me blow air on top of my tanks. I had to keep track of the O2 banks (I used to keep 3 cylinders to get the highest pressure possible), and once or twice a month I had to make a special trip to the welding supply company to swap cylinders out.
The time commitment to fill tanks for a weekend dive and maintaining the Oxygen banks was pretty high. And as I recall the cost of the O2 was around $0.05 per cubic foot once I figured out rent for the cylinders, etc.
These days, I can just drive up to the local shop and have them blow 32% on top of my tanks. It costs me $0.08 per cubic foot, and takes a fraction of the time. Remember, in 1995 after I blew O2 into the tanks I had to go to the shop to have them blow air on top of my tanks, now I skip the whole pre-mixing dance routine.
I don't know about you, but my time is worth more than the $0.03 per cubic foot price delta between a 1995 home brewed nitrox fill and a 2015 store bought nitrox fill.
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Quite possibly not, John.
But it does speak directly to the OP.
But it does speak directly to the OP.
I looked at the plans for a DIY blending stick and did not quite have the guts to go through with it. I'm the kind of guy who, if my car breaks down, opens the hood to make sure the engine is still there. If it is, I'm lost.
It still would not help. There is just not enough local diving in my area that calls for nitrox or trimix to make it in any fashion that could be called cheap. The deepest truly local diving maxes out at about 34 feet. Believe it or not, I stick with air in that situation. To get down to the depths in which nitrox or trimix is justified, I have to drive 6-7 hours and spend nights in a motel. I do that a fair number of times a year, but it sure isn't even once a month. I won't use a full oxygen supply bottle on a trip my any means, and the rental cost of that oxygen supply bottle (and/or helium) for the rest of the month or two alone will take me out of the cheap range.
I have a transfill whip that I can use when I need trimix or nitrox, and I have a trimix analyzer, but those are some really expensive fills, believe me.
---------- Post added February 13th, 2015 at 03:40 PM ----------
You are describing my situation, except that I cannot even begin to afford having that many bottles on hand. I also figure that the cost of O2 right now for me is about .25 per cubic foot, depending upon how much I keep the bottles on hand and the resulting rental cost.
Gas Blender Download - Softpedia
more of a solution to get what you want rather than what you get....
more of a solution to get what you want rather than what you get....
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Different mindsets, John.
On occasion, I'll notice that the moon is nearly full and thus the tides must be good for a "zero dark thirty" dive. Need to clear my head of the noise. OMG, what do I have? Mix and match, now just need a ticket on the NJ turnpike.
Life is back to good...
On occasion, I'll notice that the moon is nearly full and thus the tides must be good for a "zero dark thirty" dive. Need to clear my head of the noise. OMG, what do I have? Mix and match, now just need a ticket on the NJ turnpike.
Life is back to good...
Kevrumbo
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Easy Gas Blending Recipes in Metric System:
Gas Blending in Metric is a lot more intuitive as well. . .
Starting from an empty tank or set of tanks -For example, an AL40 deco cylinder (5.5L/bar tank rating in metric); and AL80 twinset backgas Cylinders (two 11L/bar tanks for a total rating of 22L/bar):
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.
Gas Blending in Metric (cont.):
Starting from an empty tank or set of tanks -For example, an AL40 deco cylinder (5.5L/bar tank rating in metric); and AL80 twinset backgas Cylinders (two 11L/bar tanks for a total rating of 22L/bar):
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.
Gas Blending in Metric (cont.):
Now how did we get the "cookbook recipes" for blending the particular mixtures above? And why for instance with Nitrox 50, can't we use 50 bar of Oxygen and 50 bar of Nitrogen for every 100 bar of Eanx50 to blend a seemingly real intuitive "half & half" mixture?
The answer is YES! You can blend 50 bar of O2 and 50 bar of N2 -->If you are mixing pure O2 AND PURE N2 TOGETHER!!!
But for practical means, why do you need pure N2 when you can just use Air with its natural constituent contribution of 21% Oxygen & 79% Nitrogen?
Using Air this time, let's blend 100 bar of deco mix Nitrox 50:
We know empirically that for every 100 bar of Eanx50, 50 bar must be O2 and 50 bar must be N2;
Quantitatively then, how much Air do we need to add in order to give us a N2 amount of 50 bar?
Algebraically and by Dalton's Law, you divide 50 bar N2 by 79% (the %age of Nitrogen in Air), and this yields approximately 63 bar of Air needed. And of this 63 bar of Air, 21% of it (the %age of Oxygen in Air) contributes to the amount needed for O2: approx 13 bar of Oxygen.
Therefore, instead of initially mixing in a full 50 bar of O2, and since we're using Air instead of pure N2, you only need 50 bar minus the 13 bar Oxygen contribution from Air, which equals 37 bar. So hence the cookbook recipe of for every 100 bar of Nitrox 50, add 37 bar of pure O2, and fill the remainder with Air to 100 bar (100 bar total minus 37 bar of O2 equals 63 bar --the amount of Air needed for N2 which we calculated above).
Now to fill an empty 5.5L/bar deco tank (same as an AL40) with Nitrox 50, we need 200 bar of the above recipe (i.e. "For every 100 bar of Eanx50, add 37 bar of pure O2, and then fill the remainder with Air"). Therefore just multiply 37 bar by 2 which equals 74 bar of O2 needed, and then fill the remainder with Air to the total fill pressure of 200 bar.
Similarly, it all applies also to the Trimix recipes --the only difference is accounting for the exact percentage and amount in bar of the Helium constituent in the total mixture . . .
The answer is YES! You can blend 50 bar of O2 and 50 bar of N2 -->If you are mixing pure O2 AND PURE N2 TOGETHER!!!
But for practical means, why do you need pure N2 when you can just use Air with its natural constituent contribution of 21% Oxygen & 79% Nitrogen?
Using Air this time, let's blend 100 bar of deco mix Nitrox 50:
We know empirically that for every 100 bar of Eanx50, 50 bar must be O2 and 50 bar must be N2;
Quantitatively then, how much Air do we need to add in order to give us a N2 amount of 50 bar?
Algebraically and by Dalton's Law, you divide 50 bar N2 by 79% (the %age of Nitrogen in Air), and this yields approximately 63 bar of Air needed. And of this 63 bar of Air, 21% of it (the %age of Oxygen in Air) contributes to the amount needed for O2: approx 13 bar of Oxygen.
Therefore, instead of initially mixing in a full 50 bar of O2, and since we're using Air instead of pure N2, you only need 50 bar minus the 13 bar Oxygen contribution from Air, which equals 37 bar. So hence the cookbook recipe of for every 100 bar of Nitrox 50, add 37 bar of pure O2, and fill the remainder with Air to 100 bar (100 bar total minus 37 bar of O2 equals 63 bar --the amount of Air needed for N2 which we calculated above).
Now to fill an empty 5.5L/bar deco tank (same as an AL40) with Nitrox 50, we need 200 bar of the above recipe (i.e. "For every 100 bar of Eanx50, add 37 bar of pure O2, and then fill the remainder with Air"). Therefore just multiply 37 bar by 2 which equals 74 bar of O2 needed, and then fill the remainder with Air to the total fill pressure of 200 bar.
Similarly, it all applies also to the Trimix recipes --the only difference is accounting for the exact percentage and amount in bar of the Helium constituent in the total mixture . . .
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runsongas
Contributor
baue has a handy z factor table available if you want to calculate it out by hand. i imagine the software packages already compensate for it automatically though.
BAUE Z Factor Table
BAUE Z Factor Table
There are plenty of free/cheap deco apps that also include blending calculators. Plug in the existing %, existing pressure, the % being added, and the ending pressure... and it gives you the ending %. Similarly you can plug in everything including the desired % and it will tell you how much air and how much O2 to add. For typical recreational mixes, using one of these apps is marginally faster than doing the math on a napkin... but more likely to be correct every time.
It also doesn't take much recreational nitrox diving for you to be able to estimate "If I have 1000psi of 32% and have the shop top off to 3000psi at 21% I'll end up with about 25%" off the top of your head.
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