Compressor Newb

[Sub100]

What is meant by "Cascade" - want to make sure I am getting this 100%.

It sounds like a bank is not the way go - certainly no one here is jumping up and down saying banks are great go for it.

Banks sound like an interesting solution to a problem I may not have. An issue I do have is sending a dive team diving for a week and I dont really want to give them a compressor to go on the trip and trying to carry that many filled dive bottles is difficult.. But then again, would I trust them with an air bank (as in not to kill themselves or someone around them because of operator error)_? probably not.

 

[rob.mwpropane]

I fill my bank one tank at a time so I allow my compressor to vary it's pressure rather than running at high pressure for hours. Also the point of having a bank is to run it as a cascade to maximize efficiency. I wouldn't give up my cascade for love or money. I can fill almost a dozen tanks before cranking up the compressor.

How many tanks do you have in your bank? Just curious.

Not trying to jack the thread....

 

[Miyaru]

What is meant by "Cascade" - want to make sure I am getting this 100%.

Let's say you have 3 tanks of 50 liters in your bank, each at 250bar.
You connect a 10 liter tank which has 50 bar.

Open the first bank-tank and let the pressure equalize: (50x250 + 10x50) / 60 = 216.67bar end pressure.
Then you open the second bank-tank and let the pressure equalize: (50x250 + 10x216.67) / 60 = 244.44bar end pressure.
Finally you open the third bank-tank and let the pressure equalize: (50x250 + 10x244.44) / 60 = 249.07bar end pressure.

Then you do tank number 2 (also 10 liter) which has a :

Open the first bank-tank and let the pressure equalize: (50x216.67 + 10x50) / 60 = 188.89bar end pressure.
Then you open the second bank-tank and let the pressure equalize: (50x244.44 + 10x188.89) / 60 = 235.18bar end pressure.
Finally you open the third bank-tank and let the pressure equalize: (50x249.07 + 10x235.18) / 60 = 246.76bar end pressure.

This is purely theoretical. Steel tanks should be filled to 232bar, alu tanks should be filled to 207bar. In the calculation above, the volumes are not corrected by air compressibility factors.
The important part is understanding how the bank-tank-pressures after a fill are used to calculate the next fill. By filling this way, you use the bank more effectively than having all tanks in one bank open and filling dive tanks in one go.

 

[RayfromTX]

How many tanks do you have in your bank? Just curious.

Not trying to jack the thread....

4@444 cu ft. @ 4,500 psi
1st and maybe second donees are just off the first donor depending on starting and ending pressure of the donee tanks.
3rd taps into the 2nd donor tank.
4th or 5th may tap into the 3rd donor tank.
6th 7th or 8th will require using the 4th donor tank.
Somewhere around the 7th, 8th or 9th tank, getting a full 3442 psi fill is no longer possible from the cascade depending on how low starting pressures were.
I'm currently at 5 fills and I have just started to tap the 3rd tank but some were not used down very far and some were aluminum and only filled to 3,000 and one was an al19. This is from memory.
Current pressures are: tank 1=1,700 tank 2=2,600 tank 3=4,200 tank 4=4,500

 

[rob.mwpropane]

4@444 cu ft. @ 4,500 psi
1st and maybe second donees are just off the first donor depending on starting and ending pressure of the donee tanks.
3rd taps into the 2nd donor tank.
4th or 5th may tap into the 3rd donor tank.
6th 7th or 8th will require using the 4th donor tank.
Somewhere around the 7th, 8th or 9th tank, getting a full 3442 psi fill is no longer possible from the cascade depending on how low starting pressures were.
I'm currently at 5 fills and I have just started to tap the 3rd tank but some were not used down very far and some were aluminum and only filled to 3,000 and one was an al19. This is from memory.
Current pressures are: tank 1=1,700 tank 2=2,600 tank 3=4,200 tank 4=4,500

Thanks!! Some great insight!

 

[rjack321]

I fill my bank one tank at a time so I allow my compressor to vary it's pressure rather than running at high pressure for hours. Also the point of having a bank is to run it as a cascade to maximize efficiency. I wouldn't give up my cascade for love or money. I can fill almost a dozen tanks before cranking up the compressor.

oh Ray I know exactly what will make you question why you spent so much time, money and space on a cascade

A rebreather lol

 

[RayfromTX]

I can't do it. I dive with and for my wife. She is not someone that you would want to train on a rebreather. It's never going to happen.

I didn't spend a lot of time, money or space on the cascade. It's relative I suppose. Taking them in to be bead blasted was the biggest part of the effort I have expended and that has been paid off many times over in convenience of always having 32% on tap with the turn of a knob. It's like that tool that you didn't think you really needed until you had it and then never want to be without it again.

I do love rebreathers though. The previous owner of my setup got a rebreather. That's why he sold the setup I have for less than half what he had in it. All I had to do was inspect and assemble. I hope he maintains his rebreather better than he did those cylinders.

 

[rjack321]

I can't do it. I dive with and for my wife. She is not someone that you would want to train on a rebreather. It's never going to happen.

I didn't spend a lot of time, money or space on the cascade. It's relative I suppose. Taking them in to be bead blasted was the biggest part of the effort I have expended and that has been paid off many times over in convenience of always having 32% on tap with the turn of a knob. It's like that tool that you didn't think you really needed until you had it and then never want to be without it again.

I do love rebreathers though. The previous owner of my setup got a rebreather. That's why he sold the setup I have for less than half what he had in it. All I had to do was inspect and assemble. I hope he maintains his rebreather better than he did those cylinders.

I was just teasing you.

Yeah I have 2x 4500psi, 2x 3600psi and 3x 2200psi of 32% on tap. Most of the time it just sits there but it's nice to fill stuff quickly without even starting the compressor sometimes.