Trans-fill an AL30 from AL80 or HP133

[chuck34gboro]

I'm trying to figure out which would be better to use to fill a pony.

Lets assume the AL80 is at 3000psi (77cf), the HP133 is at 3442psi (133cf), and the AL30 is at 0psi (0cf).

Basically i wanna know if I equalize a full al80 or full hp133 with an empty al30, what would be the final presure for both processes?

I took honors Physics in High School but that was 15 years ago. I know there is a formula and i've tried searching but everything I read online makes me feel like Penny talking to Sheldon. If you are the kinda nerd that knows formulas, you probably know who Penny and Sheldon are.

 

[Reef_Haven]

Divide the actual volume you have (77cf) by the capacity of the two tanks (107cf); This is the percent of volume you will have in each tank. (77 X 72%) 55.4 (30 X 72%) 21.6 ; Pressure for each tank (3000 X 72%) = 2160

I'll have to think a bit harder about the second scenario.

 

[aquaregia]

Or more from first principles:

Pressure * volume = constant (at constant temperature). Specifically, it's nRT, so it sort of describes the net molecule-energy in each tank. Sort of.

So, you can determine the PV product in each tank and know that each will be present in the final product.

So the AL80 has (3000psi*77.4cuft)=232,200 psi*cuft
The AL30 has 0 psi*cuft, therefore the tanks together (and thus the final system) must also have 232,200 psi*cuft.

The final system has 107.4cuft total, so (following units) it must finish at (232,200psi*cuft / 107.4cuft) = 2162psi.

 

[JBRES1]

You could use the HP133 to fill the pony to about 2800 , and you would still have close to 104 cu ft of gas in the 133.
Or you could full the pony off of the 80, then top off with the 130 . You would end up with a short fill on the 80, close to 55 cu ft.
So my vote would be to fill off of the 130.

Jim breslin

 

[Indian Valley Scuba]

Great responses guys!

 

[iztok]

See next one.

 

[iztok]

What is your goal?

If you want the most filled AL30 then you should first equalize it with AL80 then with HP130.

107cft total volume with 77cft gas in it - 77/107 72% - 2160 PSI - 21.6 cft in AL30

Then it gets bit more complicated as they are different pressure tanks. For calculation you can calculate AL30 to 3442 PSI.

30 - 3000
x - 3442

x = 34.4

34.4+130 = 164.4 cft total volume with 130+21.6 = 151.6cft - 92% (of 3442 PSI) - 3167 PSI

So now you have AL30 and HP130 at 3167PSI and AL80 at 2160 PSI.

Enjoy

Now I just saw you said HP133. Oh well... too lazy to recalculate but you saw the thought process.

 

[Indian Valley Scuba]

Iztok, shouldn't you be checking in someplace?

 

[iztok]

LOL! I should be packing at the least. But baby is now finally asleep in the same room where my suitcase and gear is so I will have to postpone packing until 3am when I hope to transfer her to another room (she usually wakes up then for a bottle).

 

[chuck34gboro]

Thanks for the responses. These are the formulas I was looking for.

I'll probably end up filling the pony at the FD or LDS when its empty but now I know how to figure out what the final pressure will be if I top off from another tank.

Thanks again.