Nitrox Transfills

[Ghetto Diver]

Need help in calculating what the end O2 content will be when transfilling between Nitrox and Air tanks.
I have the other scenarios down i.e. what the tank will equalize at etc.
This will be a mix of AL80's and AL100's

I am sure it's prolly easy and I am overlooking the answer...

 

[OBXDIVEGUY]

V-Planner and Multi-Deco apps both have built in calculators for exactly this.

 

[tbone1004]

or buy an O2 analyzer.... That said it's not rocket science, basic algebra because it's fractions.

1000psi of 21%+1000psi of 32%=26.5% at 2000 psi. Tank volumes don't matter, only pressures

 

[packrat12]

tbone1004,

That is only true if you are holding the volume the same. OP indicates an AL80 and a AL100 tank. Would need to know original % and PSI in each to figure this out. Or as you said, use an O2 analyzer.

 

[geoff w]

Calculate the actual volume of gas in the cylinders (add up all the full or partial volumes based on pressure relative to max rated pressure), figure out the total cubic feet of oxygen in each tank and add those up, and do the division (total volume oxygen divided by total volume of gas). Should work if you have two or more tanks once everything equalizes in terms of pressure. Or as recommended, use an O2 analyzerAre you trying to get a specific final mix in all your tanks, or just want to know what the end result will be?

 

[nimoh]

tbone1004,

That is only true if you are holding the volume the same. OP indicates an AL80 and a AL100 tank. Would need to know original % and PSI in each to figure this out. Or as you said, use an O2 analyzer.

What do you mean by "holding the volume the same"? If you are transfilling, you are going to change the volume of gas in both tanks

If you have an AL100 with 1000psi of air and you raise it to 2000psi by transfilling from an AL80 that contains 32%, you will have an AL100 with 26.5% filled to 2000psi. No need to know volume, and no need to know the pressure in the AL80. It it turns out the 80 didn't have enough pressure to get the AL100 up to 2000psi and only got it up to 1500psi, then you would have 23.75%....still no need to know the volume or the pressure of the source cylinder.

 

[tbone1004]

tbone1004,

That is only true if you are holding the volume the same. OP indicates an AL80 and a AL100 tank. Would need to know original % and PSI in each to figure this out. Or as you said, use an O2 analyzer.

You obviously need original psi of the tank you want, and o2% in each, but the real answer is just buy an O2 analyzer, they're not that expensive. Transfilling isn't rocket science, it's the same math as PP filling tanks
https://www.divenavstore.com/analyzers

 

[nimoh]

Calculate the actual volume of gas in the cylinders (add up all the full or partial volumes based on pressure relative to max rated pressure), figure out the total cubic feet of oxygen in each tank and add those up, and do the division (total volume oxygen divided by total volume of gas). Should work if you have two or more tanks once everything equalizes in terms of pressure. Or as recommended, use an O2 analyzerAre you trying to get a specific final mix in all your tanks, or just want to know what the end result will be?

total volume of oxygen divided by total volume of gas? You do realize you are going to end up with different mixes in each tank right?

The tank pressures will equalize with gas from the higher pressure tank moving to the lower pressure tank, but the partial pressures will not fully equalize through a transfill hose.

 

[rhwestfall]

the he!! with theory, or math mistakes, just get and use an analyzer. Follows the rule of: If you don't know the gas, test it.....

 

[nimoh]

the he!! with theory, or math mistakes, just get and use an analyzer. Follows the rule of: If you don't know the gas, test it.....

I agree. I would do some rough calculations to estimate what I'll end up with, but would never dive it without analyzing it and being sure.