Home fill station for dummies?

[rjack321]

My divesoft analyzer will show Argon. I bought a used drysuit bottle once that had an Argon label on it. Hooked it up and sure enough it showed something like 20% Argon. So they got Argon once, used it, topped with air. But more important, the Divesoft did show it as Argon.

Hard to know how accurate that is as its not really meant to analyze gases other than O2, N2, and He. The good news is that is registered something different at all. So if the mix is off you might investigate further.

I guess the real test would be, does it read 100% helium in a 100% argon environment? Or some other wacky number due to the speed of sound in argon being something unexpected

 

[broncobowsher]

I have no idea what it would do with a He Ar mix. I have the feeling it would not be a valid number. That speed of sound in a mix, no idea how that cancels, blends, smears, or maybe even double delay/echo. I took some physics classes in college, but nothing that advanced.

I don't have any pure Ar around to see if it reads 100% either.

 

[taimen]

My divesoft analyzer will show Argon. I bought a used drysuit bottle once that had an Argon label on it. Hooked it up and sure enough it showed something like 20% Argon. So they got Argon once, used it, topped with air. But more important, the Divesoft did show it as Argon.

Interesting... According to manuals, it doesn't display "Argon" It should display "Foul air" if the result doesn't fit a mixture of oxygen, helium and air. This is enough to pick up serious argon contamination and warn about unexpected result, but it does not detect argon. AFAIK measured parameters are pO2 and the speed of sound in the mixture. If that combination does not fit into a mixture of O2/He/air it dispalys foul.

Analyzer Manuals - divesoft.com

— Foul Air, for instance Foul Air (10 % O2 ), is foul or vitiated air with a reduced oxygen content. It cannot be mixed with gases designed for preparation of breathing mixes commonly available to the diver (air, oxygen, helium); therefore, its presence indicates a problem. This may include ongoing corrosion inside the bottle or contamination of the mix with argon, carbon dioxide or another gas. Such air cannot be used for breathing under any circumstances.

 

[stuartv]

I just looked at the specs on my shop compressor.

2HP
26 gallon
5.5CFM at 90psi

Is 5.5CFM enough to drive a booster?

I may have started with a bad assumption - that my shop compressor is beefy enough to drive a booster. Hmmm...

 

[Jack Hammer]

I just looked at the specs on my shop compressor.

2HP
26 gallon
5.5CFM at 90psi

Is 5.5CFM enough to drive a booster?

I may have started with a bad assumption - that my shop compressor is beefy enough to drive a booster. Hmmm...

That can work. Overall how much cfm you need
depends on the booster, what you're pumping, and the tank size mostly. I drive my Haskel mini with a Dewalt .75cfm compressor. It pumps super slow and I can get a 3L up to around 2500psi, it will go higher but takes way to long. The advantage for me is I got that for free then I can use a few hundred psi out of a steel 72 to top off.

 

[tbone1004]

I just looked at the specs on my shop compressor.

2HP
26 gallon
5.5CFM at 90psi

Is 5.5CFM enough to drive a booster?

I may have started with a bad assumption - that my shop compressor is beefy enough to drive a booster. Hmmm...

Alright, misconceptions.
NO compressor is "too small" to run a booster. It may just take a million hours to fill, but as long as it is capable of exceeding the stall pressure that you need, it will run.
Where does this rumor come from? These boosters are THIRSTY! They want a TON of gas, like a metric **** ton of gas to use the proper engineering term. The Haskels are rated to cycle at 1 cycle/second. In order to run at their rated speed, they can consume well over 70cfm of drive gas which is why they have 1/2" NPT drive gas inlets. A good rule of thumb for "real" compressors is 4:1 for cfm:hp. Some of the real nice ones are a bit better. We have 500HP behemoth compressors that are 2200cfm @110psi at work for example that run the main central air for the plant. The "normal" ones we have for supplemental air or high pressure units are 15hp and just shy of 30cfm @90psi.
To run the Haskel at rated speed, you would need a 15-20hp compressor to drive a pump big enough to have 70cfm at 90psi. The ones you can get at Home Depot etc. which are really not industrial rated pumps are typically around 2.5-3:1 which is what you said you have.
So the root of the rumor that a pump isn't big enough stems from the duty cycle of most compressors. If you have a compressor that is "over" the consumption then it will cycle and most compressors are rated for 50% duty cycle with 20-30min cycles. The big oil filled ones are usually OK for continuous duty but you may want to put an electric fan to help with air flow.

Your pump will be more than sufficient for CCR bottles and topping off of doubles and what not, but I would try to abide by any duty cycles in the manual if you are transfilling large quantities of gas, especially as the boost ratios get higher and the pump starts working harder. Down around 60psi/2000psi outlet on boost gas, I wouldn't worry about it, but as soon as you get up to 100psi/3000psi outlet I would start paying attention.

 

[Jeremy Williams]

I just looked at the specs on my shop compressor.

2HP
26 gallon
5.5CFM at 90psi

Is 5.5CFM enough to drive a booster?

I may have started with a bad assumption - that my shop compressor is beefy enough to drive a booster. Hmmm...

So some quick back-of-the-napkin using eyeball measurements and my mini-sport uses like... .145 ft3 per cycle worst case? That's really rough, based on the diagram of the mini-sport, so that one value could be off by a lot and shift all of the rest of these numbers... But this is the internet so we can just guess and run with it! I try to cycle it about once per second... So 9 CFM or so? Assuming that's correct, your compressor would be running a significant deficit, I think.

 

[rsingler]

So toward the end of the fill, the booster will run a few strokes, the reservoir will drop below stall input pressure for 30:1, and the compressor will start running until the reservoir exceeds stall and you get another stroke. But since you're continually on the edge, the little compressor is now running continuously, and maybe exceeding the duty cycle @tbone1004 referred to above?

@tbone1004, can he get away with this for one 3l bottle by getting "almost there", and then turning the compressor off to cool 60% of the time toward the end?

 

[stuartv]

My compressor has a big label on it that says 100% duty cycle.

 

[tbone1004]

@Jeremy Williams what pressure are you using for that per cycle case? Either way the napkin math is nearly impossible without knowing the displacement of the piston and since it is 100% reliant on the outlet pressure of the boost gas, it's going to be infinitely variable for gas consumption.

@rsingler from the post above, @stuartv has a 100% duty cycle compressor so it will be fine for any of the boosters, they'll just go really slow when they get to higher outlet pressures which is fine. The biggest nuisance I have found is the lack of pressure maintaining valves. If the compressor is not able to keep up with the booster, i.e. running 100%, then the system cycles to essentially 0psi once the booster cycles and the filters stop doing anything productive. If I can find a reasonably priced PMV for this stuff, I'll let everyone know...