Question How many times can I fill a steel 72 off a pair of 130s?

[Cthippo]

I just took my daily diver in for a vis and a fill and realized it costs me as much in fuel as it does for the fill. My thought is that it's only a little more expensive to fill my 130s than my the 72, and so if I got them all filled, how maby times could I refill the 72 off the 130s before I had to take thr whole mess back in? The 72 is 2216 psi and the 130s are 3000 psi.

 

[broncobowsher]

It would depend on how low you ran the 72s down to as well. Need that number to fill in the math.

 

[iointerrupt]

Basically 1 or 2 times.

Assuming the 2 HP130s filled to 3000psi, and an 11 liter LP72 run down to 1000psi:

After first transfill:

<LP72: 2682psi (70cf)>
<HP130 1: 2203psi (87cf)>
<HP130 2: 2682psi (106cf)>

After running the LP72 down again, and another transfill:

<LP72: 2300psi (60cf)>
<HP130 1: 1723psi (69cf)>
<HP130 2: 2300psi (91cf)>

Picture only gets worse if you run it down to 500psi.

 

[rx7diver]

Fill all three. Then dive the 72. Then use the two HP130's as a mini cascade system to refill the 72. Is this what you're thinking to do?

ETA: Are you certain that the 130's are 3,000 psig (rather than 3,442 or 3,500)? And are you able to get the 130's "cave-filled"?

rx7diver

 

[johndiver999]

Basically 1 or 2 times.

Assuming the 2 HP130s filled to 3000psi, and an 11 liter LP72 run down to 1000psi:

After first transfill:

<LP72: 2682psi (70cf)>
<HP130 1: 2203psi (87cf)>
<HP130 2: 2682psi (106cf)>

After running the LP72 down again, and another transfill:

<LP72: 2300psi (60cf)>
<HP130 1: 1723psi (69cf)>
<HP130 2: 2300psi (91cf)>

Picture only gets worse if you run it down to 500psi.

the little steel holds about 67 cuft at 2250

 

[davehicks]

This is why you use a booster. I do this to to fill 14 and 40cf CCR cylinders with air and O2 at home.

 

[Cthippo]

Fill all three. Then dive the 72. Then use the two HP130's as a mini cascade system to refill the 72. Is this what you're thinking to do?

ETA: Are you certain that the 130's are 3,000 psig (rather than 3,442 or 3,500)? And are you able to get the 130's "cave-filled"?

rx7diver

Yeah, that's what I am thinking. I will double check in the morning, but I believe the 130s are 3000.

 

[rhwestfall]

Search this board. There is a discussion that links to a program (can't remember the name or if it is an app or a PC program),,

 

[rhwestfall]

Flaska-Tank & gas calculation app

Android is coming, it's in review with Google since yesterday. I haven't been able to test on any actual Android device so who knows, it might work. The rock bottom section at the top shows what goes into the rock bottom gas volume. You can configure your SAC rate (of course) and the times...

scubaboard.com

 

[rhwestfall]

That might be it or there might be another...