Gas topping off spreadsheet or website?

[Ulfhedinn]

I was looking for a website or spreadsheet to be able figure out topping off of mixes. Is there anything like this out there?

example...

Steel 130 filled to 2200PSI with 32% o2
Topped off to 3400PSI with 21% o2

What is the 02 mix in the Steel 130 now?

 

[eponym]

Add the oxygen pressure in remaining original gas to the oxygen pressure in the fill gas. Then divide by final pressure.

Example:

Steel 130 filled to 2200PSI with 32% o2
Topped off to 3400PSI with 21% o2

( .32 x 2200 + (3400-2200) x .21 ) / 3400
( 704 + 252 ) / 3400
.281
which means 28.1%

Just working this quickly as an example, math night be off.

-Bryan


PS. If you work a range of examples for a given pair of original and new gases (3000 remaining, 2600, 2200, etc) and make a small reference card you can do this without calculation and be within a fraction of a percent. I did this for our shop when we started banking 32%.

PPS. You can leave off the decimals in the first line of the computation if you like, then your answer is already in percent (28.1).

 

[tomfcrist]

Answer to your example is 28%.

Not sure of any website or spreadsheet, but there is an iphone app called Nitrox tools.....there is also one for trimix.

---------- Post added April 26th, 2012 at 01:23 PM ----------

and the pressure is the only concern...the capacity of the tank has no bearing on the mix.

 

[Ulfhedinn]

Add oxygen pressure in remaining original mix to oxygen pressure in the fill mix. Then divide by final pressure.

Example:

Example: ?

 

[tomfcrist]

refer to your other post

 

[N2DeepInAz]

I'd suggest purchasing V-Planner if you're going to do top off and be mixing your own gasses. It's deco planning software but has some really great tools included in it for gas mixing.

Quick running of the numbers would put your final mix at 28.1%, YRMV.

Always make sure to analyze your final mix and plan the dive accordingly.

 

[T. Bix]

I had the same problem so I wrote one. It was pretty easy and if you're familiar with the "Have, Want, Need" table it's in that sort of format. it's a bit tricky to get the formulas to work and display correctly but with a little tweaking you'll get it and learn something along the way!! Good Luck, Keep us informed on your progress.

 

[waterpirate]

+1 for vplanner.
I have been mixing trimix with Ross software for 4 years and could not be happier. I use the old mix top off for new mixes, after I drain my tanks.
Eric

 

[Randy g]

V-Planner!

 

[DevonDiver]

PADI (ahem!) actually do a nice little bit of software, for windows, called the Gas Mix Calculator.

Allows you to plan initial fills, or top-offs, for air, nitrox and trimix. Metric and/or Imperial. Gives MOD (1.4/1.6) whilst you're at it.

It normally comes with the 'Gas Blender' course manual.