Two bottle cascade vs direct filling

[BackwoodsGA]

I have a 3 cfm compressor and three 4500 bottles in a cascade system at 4,500 p.s.i.

You can't fill very many cylinders from a cascade system that small before the pressure drops way off. It would be even more limited with only two bottles in the cascade.

I have found that the only time I really use my cascade is late in the evening when I want to refill a few cylinders without waking the neighbors with the compressor.

Closest neighbor is a half a mile away so noise is not problem. Love the country life!! Then again closest air fills are an hour away hence the compressor.

 

[divingtactics]

I would like to add a little on the small compressors. I don't know about any other brands, but the small Bauer Jr II, Oceanus and Coltri MCH6 compressors are not rated for continuous duty. In order to keep the weight and price down, they economize on the crank shaft and bearings so they are not really meant to pump up bulk bottles.

The Oceanus is supposed to be rated for continuous duty Ray. It has an oil pump too and can run up to two banks:OCEANUS-E3Y/NOAA | BAUER Compressors

I have four bank bottles on mine, 1 at 4750 PSI, 2 at 3300 PSI and another separate 1 at 3300 PSI to drive the Haskel. So far, so good and if it ends up breaking down, I'll either fix it or buy a bigger one.

You are right about heat, as she spins fast and generates a fair bit of heat. I've ended up replacing all the o-rings in the heads and valves with Viton as it handles the higher temps.

 

[rcontrera]

The Oceanus is supposed to be rated for continuous duty Ray.

Yeah ... Bauer kind of says two things at once. It is continuous duty but only if you have up to two bank bottles. To me continuous duty is running at rated pressure 24/7.

But Oceanus IS a good little compressor. Over the years I have sold a lot more of them than the Junior.

 

[clownfishsydney]

I cannot understand why you need/want to have a cascade. Just fill direct off compressor, preferably with twin whips as this slows filling and creates virtually no heat. Partial pressure filling? I do not understand how this relates to what you have written. If you want Nitrox, then why not make an oxygen stik and do it this way. This is how we do it, works great.

 

[p1p]

I originally was going cascade, and dropped it. By the time you figure 2 bottles, all the plumbing, regulator, 1 way valves, etc it was not economically feasible.

yes, it would be nice to silent fill and/or topoff,but not at the cost.

 

[divingtactics]

Cascade is good for two things:

1. Late night fills
2. Cold gas

 

[BackwoodsGA]

I am banging my head trying to decide if I am going shoot for "E" air or OCA air. In the past I have partial pressure blended at my dive shop. Well is is closing, that was the big reason for the compressor. I plan to continuous blend and both the shops I fill at when off from home have nitrox banked. All of my steels, nine of them are O2 clean for now. Thoughts?

 

[Graeme Tolton]

Do you plan on ever requiring deco gas? If yes, most certainly you will need oca. If you never plan to need to partial pressure blend, you will be ok with grd e.
Imo better off with more filtration than less.

 

[divingtactics]

The more you start to research, the more you will realize that more filtration is almost a must. There are so many dependents on achieving even Grade E air;

PMV setting
System holding pressure beyond shutdown
Temperature and humidity of intake air, which has a huge bearing on lifespan of your cartridges
Temperature of your compressor
Compressor condition - rings, internal cleanliness etc
Type of oil you use - synthetic of mineral - only synthetic for cont blending

It goes on and on. Lawrence Factor have an excellent library with a number of good articles: Lawrence Factor - Document Library

As does Scuba Engineer: Filter System Design

After many hours, discussions and dollars, I ended up fitting a 33-inch tower to my little Oceanus with dual moisture indicators - one after the P21(P0) and one after the LF tower. Of course there are additional check valves, PMV, bleed valves etc. I also have a third filter, which contains Hopcalite only even though I take my intake from outside beside a park and my Oceanus is run by 240-volts, you can never be too safe. Greame Tolton hit it on the head with "Imo better off with more filtration than less."

 

[RSALVAREZ]

I don`t read when this tread starts, i am not a tech diver, but i have an stewart warner 3.5 cfm and i use it to fill my AL80, it take`s 25 minutes on each tank, after read the filter design article, and the articles, i found that have a cascade will help me to fill the cascade on nights when the ambient air is more clean,less humidity and less CO as i live in a residential area, i will rent 2 compresed air cylinders from the local airgas company, if i am right i can fill the cascade to 3500 psi on the night and fill my tanks to 2500 psi at a low rate, then if i need the 3000 psi, i can use the compressor on the dive site to top the tank`s in less time, also if i want mix oxigen, the cascade will supply the air at the same temperature, i am right? just quote the fittings and valves, for me, i think that have your cascade will be a good option , i will do for my own use,