Really Slow Compressors?

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OTF

Coney Island Whitefish Biologist
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I don't know much about breathing gas compressors so I'm expecting to learn that this is a dumb thought. But here's my question:

Are there any little compressors designed to fill tanks to high pressure REALLY REALLY slowly? Like, I don't care if I have to wait 2-3 days for it to finish filling big doubles for use on the weekend.

Theoretically such a slow (or under-driven) oil-less compressor could run at very low electrical draw, extremely quietly, without building up much heat, little risk of CO generation, and perhaps even be small and inexpensive. I see a lot of potential advantages if fill speed isn't a factor. I own plenty of tanks and don't need quick fills.

I'm not talking about the sketchy chinese mini compressors. Though maybe under-driving one is an option?

Does anything like this exist? Any reasons such a thing would be a terrible (or good) idea? Thanks.
 
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I have a medical o2 compressor that couples to a oxygen concentrator...
For filling small o2 tanks at home....
I have used it to fill oxy acetylene torch tanks.....
Its 3 stage turns very slow and is cooled by a fan...
Specs out at 2.2lpm or .078 cu ft min
Not sure what pressure... but will do 3000 psi for certain medical tanks.

Input from the concentrater is 20psi.
If you had a shop compressor. Use a regulator and set it to 40ish psi it should double the output...
Put a big PVC pipe with silica between it and the air should be plenty dry...
First compressor will take out most of the water... but be sure to drain it... and a cheap oilless compressor is best.

also remembered to know what air the compressor is getting.. like garage door is open and a vehicle is running out side..

I also would use a carbon filter on the output.
 

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I don't know much about breathing gas compressors so I'm expecting to learn that this is a dumb thought. But here's my question:

Are there any little compressors designed to fill tanks to high pressure REALLY REALLY slowly? Like, I don't care if I have to wait 2-3 days for it to finish filling big doubles for use on the weekend.

Theoretically such a slow (or under-driven) oil-less compressor could run at very low electrical draw, extremely quietly, without building up much heat, little risk of CO generation, and perhaps even be small and inexpensive. I see a lot of potential advantages if fill speed isn't a factor. I own plenty of tanks and don't need quick fills.

I'm not talking about the sketchy chinese mini compressors. Though maybe under-driving one is an option?

Does anything like this exist? Any reasons such a thing would be a terrible (or good) idea? Thanks.

Inexpensive doesn't exist because you still need the filters which aren't cheap, moisture separators, all the precision parts etc etc.

The compressor @Rol diy linked to would still need a $1500+filter setup and is similar to the Invacare compressor that I have which is 3 stage and fan cooled but only pumps to 2200ish psi. I wouldn't go any higher than that due to heat.

You could slow a Rix down to barely nothing and do it with a used SA3 or SA6. I did it with SA6, but the SA3 is smaller. If you are going to do it, I would get a Rix SA6 for a couple grand and put a 3-phase motor in it with a VFD so you can control the fill speed, and buy a filter setup with auto drains, but to do that would cost you about $6k. You would have variable fill rates from about 0.5cfm up to 6cfm if you put a 5hp motor in it, or if you wanted to run it off of a normal 110v you could get about 0.1cfm up to about 2cfm.
 
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A pressure vessel and granular carbon is not that expensive... check out oxygen hackers... and surplus center
 
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Thank you all for the info.

All it needs is a water wheel!

I have a medical o2 compressor that couples to a oxygen concentrator...
For filling small o2 tanks at home....
I have used it to fill oxy acetylene torch tanks.....
Its 3 stage turns very slow and is cooled by a fan...
Specs out at 2.2lpm or .078 cu ft min
Not sure what pressure... but will do 3000 psi for certain medical tanks.

Input from the concentrater is 20psi.
If you had a shop compressor. Use a regulator and set it to 40ish psi it should double the output...
Put a big PVC pipe with silica between it and the air should be plenty dry...
First compressor will take out most of the water... but be sure to drain it... and a cheap oilless compressor is best.

also remembered to know what air the compressor is getting.. like garage door is open and a vehicle is running out side..

I also would use a carbon filter on the output.
Neat! An O2 concentrator sure would be nice!

Inexpensive doesn't exist because you still need the filters which aren't cheap, moisture separators, all the precision parts etc etc.

The compressor @Rol diy linked to would still need a $1500+filter setup and is similar to the Invacare compressor that I have which is 3 stage and fan cooled but only pumps to 2200ish psi. I wouldn't go any higher than that due to heat.

You could slow a Rix down to barely nothing and do it with a used SA3 or SA6. I did it with SA6, but the SA3 is smaller. If you are going to do it, I would get a Rix SA6 for a couple grand and put a 3-phase motor in it with a VFD so you can control the fill speed, and buy a filter setup with auto drains, but to do that would cost you about $6k. You would have variable fill rates from about 0.5cfm up to 6cfm if you put a 5hp motor in it, or if you wanted to run it off of a normal 110v you could get about 0.1cfm up to about 2cfm.


Of course if I did this I would have a seriously good filter stack. Hard getting around that.

You said you wouldn't run a medical compressor like that to high pressure because of heat - but wouldn't that be less of a factor if you ran it as slow as I'm talking about? Although I'm not keen to push any compressor far past its rated output pressure.

A pressure vessel and granular carbon is not that expensive... check out oxygen hackers... and surplus center
Yeah, I have some reading to do.

I really do like the idea of running something like a Rix3 super slow, cool, and quiet on a tiny 110v motor.
 
@OTF those are little baby compressors and not designed for that. It's one thing if they were rated for it, but their compression ratios are much lower and it takes about 2 days to fill an AL80 to 2200. On top of that you need to fill it from a compressed gas source. You could convert a medical concentrator and compressor, but by the time you do that a Rix SA3 is a much better compressor and will do what you want.
 
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For what its worth.
My o2 compressor is rated for 3000 psi. The normal o2 tanks are like 2200psi. But the higher pressure tanks have a magnet at the fill port. That triggers a hall effect sensors... then the control board allows 3000psi before it shuts off. If I was moding it for air I would remove all the electronics/ o2 verification etc. And just use a pressure sw...

If you like tinkering, somewhat hydraulic savee and found a cheap unit and are mechanically inclined,
it might be a cheaper way to go, but slow.
I do not know your skill set.. if it's not very high buy something pre made.. you will be cheaper...

But I do like rix compressors. But never had one... but seems like you need to stay on top of the seals...
The vdf idea is a good one I have done it myself... but be careful on oil compressors... enough oil needs to be thrown around inside for splash lube....
Easier to get a 220 3 phase. And vdf.
Steal 220v from 2 different 120v plugs to make 220v if you don't have a welder plug...
I have an adapter made for doing that...
 
@Rol diy when doing small VFD motors from a normal wall plug they are usually 230vac 3-phase motors and the VFD takes care of not only phase conversion, but also the voltage boosting. My Rixes have 115vac 1p into the VFD and output 230vac 3p.

You are correct with splash lube, can only go down to about 90% of the rated speed for the oil to work so can't slow them to a crawl. The Rix doesn't care if it's going 1500revs per day/1rpm or 1500rpm, couldn't be bothered.
 
https://www.shearwater.com/products/perdix-ai/

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