Small compressor - more moisture? (California Air Tools 2010A)

[Guy Dotan]

I replaced my (broken) 6 Gallon Bostitch with a California Air Tools 2010A. The CAT is smaller but the CFM rating at 90PSI is similar (2.2 vs 2.6 for the Bostitch.) I noticed that there a LOT more moisture in the compressed air with my new CAT. I empty the tank after each use. It's just after I use it for a while (with an air gun to clean stuff) I get a very wet stream of air. Any clue why? Is it the smaller size?

I can still return the CAT. Any advice would be greatly appreciated.

[James Gunning]

It sounds like the water that was normally condensing and running down to the bottom in your older, larger, tank may be getting picked up in the airstream with the new tank. With my compressor, if I run a blow gun a long time, the air will tend to pick up more moisture. Maybe time to put a drier on that air line. Living in Florida, air in the tank is a given. Lots at this time of year.

[glenn bradley]

The moisture quantity comes from the air. The compressor doesn't generate more or less moisture. Anything taken in through the intake gets compressed including the humidity. Warmer air often holds more moisture than colder air (unless you live in the desert basin like I do) :). You've probably seen 'zig-zags' or 'switchbacks' of copper pipe with a drip-leg or moisture trap post-tank that are used to cool the air before it gets to the tool. Post-tank coolers and drawing cooler air initially can help but, this is not really practical in a mobile unit.

[Guy Dotan]

Might be the humid garage and the current heat wave + the smaller size of the tank. Makes sense, (I think.)

[Bill Orbine]

I wonder if the fact that the tank being aluminum could be a contributing factor for higher moisture content?

[Charles Lent]

The moisture gets in there from the air drawn in and compressed. When you compress air to 90 psi or more a lot of the moisture that was in the air has to condense and fall out. Cool this compressed air and even more moisture will condense out. The more compressed air that you use from the air compressor, the more humid air will be drawn in and compressed, leaving more water in the tank. It's worse on humid days and less on dry days. The air is like a sponge. It will hold a certain amount of water. Compress it to 50% of it's size and it will have to give up zbout half of the water that it originally held. Squeeze it into 1/4 of it's original size and it will give up even more water. This is what you are doing when you compress the air from the room and put it into the compressor tank. All that water doesn't fit in the air any more, so it ends up in the compressor tank.


If you lived in the desert with 3 % RH you would find very little, if any, moisture condensing in the tank. Move to New Orleans and that compressor may condense out almost as much moisture that it makes compressed air (I'm exzagerating here). It's all relative, depending on the environment, how high the pressure that you compress the air to, and how much air is drawn into the air compressor and squeezed into a smaller space than it occupied when free in the room.


Charley

[David Kumm]

I may be repeating but a faster running piston compressor may heat the air as it compresses it more than a slow running one due to heat in the head. The tank then either cools the air and the water drops into the tank, or if small, allows heated air out where it cools in the hose and spits out the tools. Dave- oversimpliying

[Scott T Smith]

Guy, I've found that moisture is more of a problem when my compressors cycle on and off frequently and the air does not have enough time to cool inside the tank; allowing the moisture to condense out inside the tank instead of in your tools.

As others have stated, warm air will retain more moisture. When you cool air rapidly, it gives up the moisture. Air typically heats up when compressed and cools when decompressed (such as when using a blow gun), which is why you notice it more when using a blow gun or other high air consumption tool.

if you still have your broken Bostich tank you can plumb it inline to your CAT compressor for more air storage, which will allow fewer cycles of your compressor and more time for the air to cool in the tank. I use a Rolair Air Keg to augment storage on my portable CAT compressor, and some portable air tanks to augment the PC Pancake compressors on one of my mobile shop trailers on the farm. In both instances, I added an air coupler on the tank side of the manifold (high pressures side) and simply use a standard air hose to plumb in the auxiliary tank. Tool air hoses are connected to the normal location on the compressor so that they are fed by regulated air pressure instead of the higher tank pressure.