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Master Diver
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Cascade tank volumes

Fri Feb 10, 2017 2:48 pm

Des anyone know whee I can find a chart or teach me AGAIN how to calculate the cubic feet of air in some of my cascades? I want to find our at 2250 psi how many cubic feet each tank holds. Thanks in advance. Robohips
First dives? 1967 and I never lost the fever.

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Master Diver
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Re: Cascade tank volumes

Sat Feb 11, 2017 12:23 am

Pardon my lazy cut and paste of a post I made on that other board for a similar question. The numbers/tanks are different, but the math is the same. There are other methods discussed, so the thread may be worth a peek. ... ks.411223/

OK I was hoping someone with better math skills than me (Awap) will give you a simpler method; but the rascals have abandoned us; so here's one way. Transfer a known volume into the PST tank. Divide that volume by the pressure now in the tank to give you a constant. Next, multiply the constant by the working pressure to give you the volume at working pressure.

For instance, let's say you rent/borrow/buy/steal an AL 80 which actually holds 77 cu ft. at 3000psi

77 divided by 3000 gives you the constant (0.0256 cu ft per psi) for the 80

Transfer a known amount out of the 80 and into the PST (let's say take it down to 2000)
1000 x 0.0256 = 25.6 cu ft out of the 80 and into the PST

So now, we measure the psi in the PST tank and we have say 900 lbs
25.6/900 = 0.0284 our constant for the PST tank.
0.0284 X the working pressure 3000 give us the full volume 85.2 cu ft.
A sincere THANK YOU to all at VDH who make this wonderful resource available and to all the thoughtful contributors.

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Re: Cascade tank volumes

Sat Feb 11, 2017 9:22 pm

This is the kinda stuff Luis loves.....Snow must have cut off his net connection.

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Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB

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Re: Cascade tank volumes

Fri Feb 17, 2017 8:15 pm

Here is some data on a couple of typical cascade cylinders.

A rough estimate of capacity for this size cylinders (diam. = 9.25” to 9.3”, height about 51 inches) is that you get a bit over 100 cu ft per 1000 psi.


The picture below show my four cascade cylinders. The two on the left are 3AA- 3600, and the two on the right are E 9421-4500.


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