How do I calc' the per-tank psi on my doubles?

[In10se]

nvm

 

[Joanna.Cordry]

There's a pretty easy way to do the math in your head. I was taught something called a "tank factor", which is the volume of gas in cubic feet that corresponds to 100 psi in your tank or tanks. For an Al80, the TF is 2.5; for doubles, it's 5. So, if you have 900 psi in double Al80s, it's 9 x 5 = 45 cu ft. If, for whatever reason, you want to know how much gas is in EACH tank, it's half of that.

You can also use this to do gas matching before the dive if you are diving with someone who has different size tanks. Once you figure out what volume each diver has, you can calculate turn pressure in your head more easily.

 

[paul19may]

Or do everything in the metric system and then it all becomes a breeze at any depth/ pressure!

Of course, if you are diving with imperial everything then naturally your spg will not be in bar but in psi and your depth meter will be in ft and not metres, so then you will need a ready reckoner to convert psi-to-bar and ft-to-metres at depth (not so hard, surely) plus work out your tanks internal volume and then convert that to litres- easy, really once you get the hang of it!

Past performance is no guarantee of future performance.
May contain nuts.

 

[miketsp]

After reading this all I can say is; "Thank God for metric simplicity".

 

[Charlie99]

, so then you will need a ready reckoner to convert psi-to-bar and ft-to-metres at depth (not so hard, surely)

70 bar per 1000psi is a pretty easy psi to bar conversion.

3m per 10' is a pretty easy feet to meters conversion. Or use the equivalent alternative of multiplying feet by 3, then dividing by 10. (Example: 50' x 3 = 150, move the decimal to get 15m.)

It's not that I really care about depth in meters that much, but that it is an easy way to get atm or ata. 50' * 3 /10 / 10 = 1.5 atm or 2.5ata.

 

[texdiveguy]

Or do everything in the metric system and then it all becomes a breeze at any depth/ pressure!

Of course, if you are diving with imperial everything then naturally your spg will not be in bar but in psi and your depth meter will be in ft and not metres, so then you will need a ready reckoner to convert psi-to-bar and ft-to-metres at depth (not so hard, surely) plus work out your tanks internal volume and then convert that to litres- easy, really once you get the hang of it!

Past performance is no guarantee of future performance.
May contain nuts.

Gee Paul I am just now catching onto the feet vs meter conversion....now this!!!