thanks for the reply, 3 goes into 80 26 times is what I was thinking, why would I only get one refill in a 3 cf tank from an 80 cf tank?
heh.... you can't do math with pressure that way.
think of it this way. each time you breath on a tank, the pressure goes down over time as you breath. that's because each time you remove a small amount (say .5cf).
have you had the Open Water course yet?
couldn't I at least get ten refills or so before the big tank's pressure drops below 3000 psi,
the big tank (AL80) will drop below 3000psi on the FIRST FILL. Sorry, but that's just the laws of Physics.
Go google Boyles Law, Ideal gas law, and other pressure laws.
at which point the smaller tank wouldn't get full refills any longer...we were guessing about 10 full/complete refills, tell me if you agree to that guess. The techs at spare air business said I would get several refills from a standard diving tank, but I didn't know enough about the pressure specifics to quiz them I just assumed they weren't lying.
yeah you might get several, but not 26 that you came up with in the first above sentence.... (several is 3 or 4 ).
When you buy the spare air kit you get a refilling adapter meant to hook up to a standard diving tank, I was assuming this would be all I would need to refill off a standard rented tank, when would I need to use that bank system you are talking about?
forget I mentioned the bank system.....
![Shake Head :shakehead: :shakehead:](/community/styles/scubaboard/smilies/shakehead.gif)
that would be if you were filling direct at a shop off their compressor/bank system. (and not using the tank transfer adapter).
So if you want to see how many fills you get, here ya go...
Someone else can check my math and see if I made a mistake. (I duplicated my formula for the rest of the dives, so if there's a mistake it will duplicate itself)
This is for 15 fills.
Let's assume you use an 3000psi AL80, which is really 77 cubic feet, to start with and an empty 3.0cf Spare Air rated for 3000psi.
seeing that you're adding volume to your starting base pressure of 3000psi, you're never going to get 3000psi in that Spare Air by doing a transfer fill.
Anyway, here is what I came up with. (I think it's right.) I'd attach it via Excel spreadsheet, but the attachment feature of SB has been broken for some folks for over a year
Fill #
|
AL80 start PSI
|
AL80 CF
|
Total capacity (of both)
|
resulting PSI
|
Spare Air final volume CF
1| 3000 |77 | 80.00| 2888| 2.89
2| 2888| 74.11| 77.00| 2779| 2.78
3| 2779 |71.33| 74.11| 2675 |2.67
4| 2675 |68.66| 71.33| 2575| 2.57
5| 2575 |66.08| 68.66| 2478| 2.48
6| 2478 |63.61| 66.08| 2385| 2.39
7| 2385 |61.22| 63.61| 2296| 2.30
8| 2296|58.92| 61.22| 2210| 2.21
9| 2210|56.71| 58.92| 2127| 2.13
10| 2127|54.59| 56.71| 2047| 2.05
11| 2047 |52.54| 54.59| 1970| 1.97
12| 1970 |50.57| 52.54| 1896| 1.90
13| 1896 |48.67| 50.57| 1825| 1.83
14| 1825 |46.85| 48.67| 1757| 1.76
15| 1757|45.09| 46.85| 1691| 1.69