Help With Wet Air, Please

[Pete]

I like pneumatic power tools and use them almost exclusively when working on the boat. It is summer in New Bern, with hot temperatures and high humidity; did I mention HIGH HUMIDITY. I am having trouble with water in the air lines and going through the tools. For spraying paint, I use a separate filter, separator, regulator in the last length of hose so I do OK with lower volumes of air, and a down stream filter. But, with high volume air tools and no down stream separator, I get lots of water.

The air compressor has a new 60 CFM Wilkinson filter/separator at its output. I do get some condensate in this unit and the air tank.

My theory of what is happening is: The air in the tank is hot as you would expect. Hot air holds more moisture than cool air. The Wilkinson unit is also pretty warm as you would expect, being right at the tank output. The output of the separator is high humidity air, but no condensate. As the air travels down the hoses, maybe 100 feet, the air cools and condensate starts to drop out in the hose. As a the amount of condensate increases in the hose, the cooling effect of the water in the hose increases, causing a ever increasing cooling of the air and increased condensate drop out. In actual use you see very little condensate getting to the tools in the beginning of daily use, but once you start to see a little condensate make it to the tool air outlet, the longer you continue to use the tool the worst it gets.

Another separator close to the end of the hose run would probably help, but I hate to have to drag it around with the hose all the time. Any thoughts and ideas on solving this problem would be appreciated.

Pete

 

[Bill Allen]

At the flow only a dryer will help seperators only catch liquid. When the pressured air comes out the dew point is lowered and ya get water. You can get around it by either spending money for a refrigerated dryer or dump your air line (metals best) in a bucket of cold water (or your beer mister) add seprerator after it and the problem will be gone. Need to lower the air temp to condense the vapor then dump it. If you want to know more let me know as it's my business, service, repair and parts for industrial air equipment. Bill

 

[krush]

Make sure you drain your tank. You can also put a time activated purge on the bottom of the tank. We can talk theory all day, but that won't get very far. Another idea as to why you get more condensate later on is that as you use the compressor longer, the tank gets hotter and thus air inside it. This doesn't allow the moisture to drop out in the tank--or another way of saying it is the tank is cold when you first start.

Pressure drop through expansion at the air tool (it's how it works) also causes cooling which can drop out the water if the temp drops below the dew point.

Your dryer may be oversized and not very effective. I think some units operate via velocity and if you are oversized the velocity won't be very high. You could just use the stuff and not worry about it (it's what I do LOL). Oil the tools when you are done if it's a huge concern.

Make sure the tank is drained is a good first step though.

 

[Bill Allen]

Good comment, need to get the water out first, although with separators on his stuff that should help quite a bit as far as raw water goes. In my personal shop I have a small after cooler with a fan on it right after the compressor tank. I have it higher then the tank so the water that condenses drains back into the tank and I drain it there. In the N.E. I don't have quite the problem as you would have. Although we run air tools and even do some painting with it. The enemy is the discharge temps, lower them and that would help. Water since it doesn't compress is always a problem and as the pressure rises becomes more of an issue. You didn't mention if you have a single stage or two stage compressor, they'll be a little less of an issue with the two stage as you get a little cooling between stages. First thing is an aftercooler to bring down the temps of the discharge air. Cheap and easy start, if you have a beer box near it might even want to consider running some tubbing inside. Dryers in design try to get a 35 degree air temp, elimanting almost all the water. For painting you can go with a point of use desicant unit which will eliminate all the water and almost any oil. Flow will be a problem for the smaller point of use and since the desicant is a throw away (some people have had sucess baking it in an oven after it becomes wet) it can become a little expensive for air tools. Bill