What size compressor ?

[a878bob]

I have 2 small boosters to fill my 3l cylinders. I wondering what the ideal cfm of a new compressor should be.

The boosters are single stage, single action. The bore and stroke is about 6” x 6”. So im figuring about 0.1cf per stroke. Say 30 cycles a minute. And 3cfm.

Any input would be helpful. The specs i have for the boosters are not really specific.

 

[Dsix36]

I think your 3cfm would be extremely light for a booster. I began with a small direct drive oilless one with 6cfm and it was way to small to keep the booster going for any duration. I now have a 12cfm and it is working fine. My booster has a similar size drive size as yours.

 

[a878bob]

I figured as much, and it's academic for sure, but how does the math work out. It seems the way I figured it, the math is correct.

 

[tbone1004]

@a878bob assuming those volumes are correct, then yes it's 3cfm at ambient pressure, and 30 cycles/min is slower than most of the boosters are rated for, but if that's the speed you want to run, then the 3cfm is correct.
What you haven't factored in is pressure though. so the chamber needs 3cfm to cycle at 0psi back pressure, but if it can't cycle until 15psi, then it's ~6cfm, 30psi=~9cfm, 120psi=~27cfm. Those pressure ratings for the booster to cycle is going to be based on the boost ratio and the outlet pressure. If you have a Haskel, or have something that is really close to a Haskel, you can look in their literature and see the drive gas consumption curves that they have published.

 

[a878bob]

Nice tbone, I hadn't thought of it that way. Suppose the compressor is rated at 3cfm at 120 Psi.

I have all the haskel curves, I'll look, I have to admit they are hard to decipher for me.

 

[a878bob]

 

[a878bob]

So this seems to be the closest to what I have. Ag30. For example: I'm just gonna pick a spot on the curve, outlet pressure 2000psi, gas supply pressure 700, gas output of 5,
We need a drive air quantity of about 46cfm, I'm I reading it correctly.

 

[BRT]

So this seems to be the closest to what I have. Ag30. For example: I'm just gonna pick a spot on the curve, outlet pressure 2000psi, gas supply pressure 700, gas output of 5,
We need a drive air quantity of about 46cfm, I'm I reading it correctly.

So 30 or 40 hp

 

[a878bob]

I'm just trying to make sure I'm reading the curves correctly. The graph needs to go out to the right farther to meaning full to me.

 

[tbone1004]

@a878bob remember that that is cycling once per second as that is the rate they are designed for. Also, the point of me pointing you to those is to show that it's basically impossible to have a big enough compressor at home.
The AG30 is capable of consuming something stupid like 70cfm, which would require a ~15-20hp compressor, which is about 15kw and would require 70a service, just for the compressor. You're not going to have that at your house. It will just run slow.

@BRT low pressure air compressors rule of thumb is 4:1 for cfm:hp. the 1:1 ratio is generally applicable for high pressure pumps, but the drive gas compressors are all around 4:1.