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>
>How about a conversion chart for US/RestOfWorld Tanks sizes and
>pressures? I'm from the UK where we have metric sizes, eg. 12.2 litres,
>232 bar and currently, I'm in the US and an getting confused with tanks
>sizes. Whats a 80 cu.ft. tank in real numbers, and how can an 80
>cu.ft. tank be "pressurised" to 100 feet ??
>
>I'm sure it's easy to do - someone give me the formulas and a set of
>standard (US) tank sizes and pressures and I'll do it ...
>
Disclaimer: the following equations and calculations were evaluated at
approximately midnight, so they may or may not be correct. I
think they are. ;)
Well, after about 10 minutes of looking up constants and solving the
equations, I have come up with the following conversion formulae.
To convert litres to cubic feet:
1) x litres * 0.035316 cubic feet/litre == y cubic feet
To convert psi to bar:
2) x psi * 0.068930 bar/psi == y bar
This gives a tank at 3000 psi to be a 206.8 bar tank. Rember that the size
of the tank in litres is the internal "empty" volume. this will require
another calculation.
To convert the "rated" size of the tank to the internal volume (in ft^3),
you can use the following formula.
3) x ft^3 * 0.004876 == y ft^3 internal volume
This gives an 80 ft^3 ft tank to be about 11 litres.
The combined formula to convert an x cubic foot tank to y litres is:
4) x ft^t * 0.138071 ft^3/Litre == y litres
Obviously, these equations can be manipulated to provide the reverse
conversions.
>
> ... how can an 80 cu.ft. tank be "pressurised" to 100 feet ??
>
If you mean, How can an 80 ft^3 tank be pressurized to about 3.07 bar, then
the answer is to pressurize it to about 44.6 psig. At a depth of 100 feet,
you pressure guage will read empty while there is really 59.25 psi absolute
still in your tank. As you ascend, you will still have this pressure, so
your guage will register more air as you come up. This increase is about
14.7 psi per 33 fsw (1.013 bar per 33 fsw or 10 msw). At the surface, your
pressure guage, then, will read 44.6 psi IF you use no air from 100 ft to
the surface.
If that wasn't your question, I hope this info helps you to find the answer
to what you meant to ask.
NOTE: The constants I used for these formulae came from the Diver's
Handbook of Underwater Calculations by Wayne C. Tucker. It is available
through Best Publishing Co. ISBN # 0-87033-254-6. Since it's midnight my
time, there may be an error in my math. Admittedly, I forgot that the size
in litres was the "empty" size at first. You can check my math if you want,
but I think it's correct.
Carl W. Meilahn
NAUI # 14470
cmeilahn@cc*.cc*.ut*.ed*
cmeilahn@cs*.ut*.ed*
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