# 8 to1 ratio of compressing

by Dennis
(Denver,Co)

I have read some where maybe here that if you took a volume Say one quart at 14.7 psi it would take 8 of those quarts squeezed into each other to get 100 psi?? Is that true??

Thank You
Dennis Daily
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Dennis let's look at it a different way.

The free air around you is at approximately 14.7 PSI, depending on a couple of variables.

If you want that air to be at 100 PSI, you would have to take a volume of that air (let's just assume that we are talking about a cubic foot of free air) that is at 14.7 PSI and put 6.8 of them into that same cubic foot to have the air pressure in there reach 100 PSI.

Does that help?

Bill

## How to explain the difference between CFM and PSI

by Shane Hoeckel
(Baltimore MD)

I regularly argue with my father on the difference between PSI and CFM. We have a 20gal craftsman compressor on wheels. When using a 1/2 inch air gun, it struggles and usually won't budge whatever bolt we are trying to loosen. I have since bought an 80 gallon 5HP compressor that is in our garage.

No matter what my father thinks there is no difference between using his 20gal compressor at 100psi, or my 80gal compressor at 100psi. I know that when using the same 1/2inch gun on my 80gal compressor, it has more power and ability to loosen bolts.

How can I explain to my father why this is? I need factual evidence to show him that his smaller compressor lacks the CFM to properly supply the 1/2inch air gun.

Thank you
Shane Hoeckel
410-790-5882
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Hello Shane...

You are correct. 100 PSI is 100 lbs. per square inch of applied force.

What you are applying the 100 lbs. of force to does not recognize that it came from a 1 HP air compressor or 50 HP air compressor.

Force is force.

Where the force breaks down is in the air demand.

An air tool may need 20 CFM of compressed air at 100 PSI to run properly.

If your compressor can only deliver 5 CFM at 100 PSI, then the air tool cannot run properly. It must have both force and flow.

A too small air compressor can generate the same 100 PSI of force that a big air compressor can, but it cannot deliver a consistent 100 PSI when the air tool demands more air than it can produce.

A small air compressor running a big demand air tool cannot supply enough air consistently to run the tool.

See the pages on this site under CFM on the sitemap for more info.

Cheers,

Bill

## Reduced flow through air line

by Aaron

I have a compressor with a 20 gallon tank and a 2 HP electric motor. My problem is that when I plug my air tools into the outlet on the compressor, they operate as they should. When I hook up a hose to the compressor and then to the tool, they are lacking power. I have tried different size hoses and nothing seems to change the outcome. Any help would be appreciated.
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Aaron, you don't indicate what tools you are using, but your complaint is not unusual for a 2 HP compressor. They just don't produce a lot of air.

When you plug the air tools into the discharge port of the compressor, I suspect that it seems that they work well, but how do you know, for sure, since you cannot do work. In order to do work with the tools, you need to be able to move them, and that means a hose.

You also don't indicate what size hose you have tried, but regardless, I suspect your compressor problem is that the air tools you are attempting to use quickly exceed the capacity of the compressor, the pressure drops (even more through a hose) and the tool doesn't work right.

Bill

## Air Volume under water

by Brian
(Texas)

What would the volume of 1 cu.ft. of air at sea level be 10ft below sea level (under 10ft of water)?
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I guess if you knew how many atmospheres the water pressure would exert at that depth, you could extrapolate.

Since I'm not a diver and have no experience with water pressure at depth, I hope someone out there reading this can offer advice.

Cheers,

Bill

### Comments for Air Volume under water

 Aug 12, 2013 The tower of Piza by: Anonymous As I recall 30" of mercury is one atmos, and 34 ft of water is one atmos. So 10 feet under water, would be about 1.3 atmospheric pressure.Taking 4 years of physics sometimes helps, but it doesn't get parts of discontinued Sears compressors. (grin)_____________Thanks... (grin)B.