Two bottle cascade vs direct filling

[BackwoodsGA]

What advantage/disadvantage would small 3cfm compressor on a two bottle cascade system have a on a larger 5-6 cfm direct filling? I plan to partial pressure or continuous blend nitrox depending on the setup. Trying to get a good direction before I start spending money. I have read Oxyhacker's book front to back, just looking for opinions from someone who has been there done that. I will be filling eight to ten takes every two weeks or so.

 

[Graeme Tolton]

What type of bottles are you filling? What cascades are you looking to buy? Will the 8-10 all be filled at the same time? Are you buying new or used? Electric or engine driven?

 

[BackwoodsGA]

What type of bottles are you filling? What cascades are you looking to buy? Will the 8-10 all be filled at the same time? Are you buying new or used? Electric or engine driven?

Filling 108's to 3300, cascade is 900 cu'ft with two cylinders. I just need to refill them between dive trips, just eight over two weeks. All equipment is used and single phase electric.

Thanks!

 

[Graeme Tolton]

Sounds like 4500 psi cascades. Will the compressors you are looking at go to 4500? If there is no rush to fill and you dont plan on filling for others, why not go with the small one without the cascades? Are you using doubles? If you are, you can just use transfill whips between sets and fill them all in one shot.

A cascade is great if you dont want to use the compressor for every fill, but i see no advantage of pumping 4500 psi when all you ever need is 3300 and are never in a hurry for it. To achieve efficiency with a cascade system, you need both high and low pressure bottles.

 

[BackwoodsGA]

Sounds like 4500 psi cascades. Will the compressors you are looking at go to 4500? If there is no rush to fill and you dont plan on filling for others, why not go with the small one without the cascades? Are you using doubles? If you are, you can just use transfill whips between sets and fill them all in one shot.

A cascade is great if you dont want to use the compressor for every fill, but i see no advantage of pumping 4500 psi when all you ever need is 3300 and are never in a hurry for it. To achieve efficiency with a cascade system, you need both high and low pressure bottles.

Thanks, kind of what I was thinking, if I could fill two 108's at a time I think my fill rates will be ok with even a 6 cfm compressor. My only question is partial pressure filling direct from compressor even with a hyper filter or continuous mix filling and I am sure that's another can of worms...

 

[Graeme Tolton]

If you had one hp cascade, you could regulate your fill rates easily. When my compressor is running, i use the banks to help control fill rates. My compressor is 15 cfm, so filling the tank and one cascade gives me a good fill rate. But more often, i just fill right from the cascades and fill them when they get low.

 

[BackwoodsGA]

Yea the small compressor was only a 3500 psi comp with cascade cylinders, don't make allot of since. Seems the bigger compressor for now and then cylinders in the future may be the better option.

 

[Graeme Tolton]

The value of lp cascades cannot be understated. They are also cheaper. If you had fewer tanks and dove throughout the week, a small cascade would make a great deal of sense. Best to start small and expand. 3 or 4 cascades and you would only need to run the compressor every other time.

This is what mine turned into ( so far).

 

[DA Aquamaster]

It also depends what 3 cfm compressor you have. A Stewart Warner compressor for example will handle continuous running, while most other smaller portable 3-4 cfm compressors will not. They are intended to only fill 1 or 2 AL 80s at a time, then sit for awhile. Filling a set double 108s to 3500-3600 psi with a 1/3rd left in them is pushing right up to that limit (about the same as two AL 80s from 500 to 3000 psi in cubic, feet, with a little more stress due to the higher fill pressures). However, filling the top half of couple cascade bottles would be far harder on it.

And if the plan were to only run the small compressor 30-40 minutes at a time to fill the cascade system, then you just as well be filling a set of 108s at a time and skip the cascade system.

 

[BackwoodsGA]

Yea I am trying to make sure I start out in the right direction. I know compressor and filter it number one and I will add after that. I have a refrigerated truck body I plan on putting it in with the intake outside. I can cool it down to 40 with no problems so I can keep it cool.

---------- Post Merged at 08:42 PM ---------- Previous Post was at 08:34 PM ----------

It also depends what 3 cfm compressor you have. A Stewart Warner compressor for example will handle continuous running, while most other smaller portable 3-4 cfm compressors will not. They are intended to only fill 1 or 2 AL 80s at a time, then sit for awhile. Filling a set double 108s to 3500-3600 psi with a 1/3rd left in them is pushing right up to that limit (about the same as two AL 80s from 500 to 3000 psi in cubic, feet, with a little more stress due to the higher fill pressures). However, filling the top half of couple cascade bottles would be far harder on it.



And if the plan were to only run the small compressor 30-40 minutes at a time to fill the cascade system, then you just as well be filling a set of 108s at a time and skip the cascade system.

I am going to probably go with a 5-6 for now. Didn't you used to do allot of old Scubapro regulator overhauls? I have one I need serviced for a pony setup.