View Full Version : Air Assist Moisture

Garrick David
06-01-2010, 7:42 PM
Hello All,

I have some issues with my air assist building up so much moisture that it sometimes comes out the nozzle.

It has a moisture capture on it.

Has anyone else had this problem, and what did you do to fix it?



Dan Hintz
06-01-2010, 7:55 PM
What kind of moisture trap do you have? If you have just the upside down bottle type trap, that only captures moisture that has condensed into droplets by the time it gets to the trap (make sure the trap is one of the last things on your line just before it enters the laser). If your air is that moisture-ridden, there are a few things you can do.

You can use a desiccant, but with high moisture content it will need to be replaced/recharged often. You can use a dehumidifier in the shop, but it will need to run for a few days on high to make a difference, and if surrounding atmo moisture content is always high, the machine will be working overtime with little effect. You can run extra-long hoses before the trap, give the air a chance to cool down and the moisture to condense.

George Brown
06-01-2010, 10:14 PM
I use an oilless compressor and keep the room humidity to about 60%. Air from the compressor goes to a standard compressor particle filter/moisture trap. From that, it goes to a 2 foot 2 inch pvc pipe filled with silica gel with blue indicator. From that, a final particle filter (mostly there to make sure no silica gel beads get into the laser air supply). I have no problems with moisture at all with this setup.

Dan Hintz
06-02-2010, 6:10 AM
60%? That's pretty high... I would drop that back to 40% or so...

Mark Winlund
06-02-2010, 10:00 AM
I haven't heard one solution mentioned here, and that is a refrigerated air dryer. These are industrial units designed specifically to remove moisture from compressed air. The smallest ones go for around $500. I have used one on my laser equipment since it was new and have had zero problems with it. The Pacific Northwest is not noted for it's dry conditions, either!

Grainger has them. If you don't have the cash for the commercial one, a pretty good one can be made from an old refrigerator and a roll of copper tubing rolled around a form.

The commercial ones use a "tube within a tube" method, which is very efficient.


Bill W. White
06-02-2010, 9:22 PM
Being a sandblaster and airbrush artist in S. Florida we really deal with humidity and believe me water in the pressure pot is a major problem. Solution is to cool the air down to room temp. before trying to trap water. Air comes out of a compressor at around 150 degrees and will hold lots of water then as it cools down the water condenses and the problems start.
Several ways to attack the problem as was mentioned earlier a ref. unit is
a great answer but expensive. Another solution is to run 50 feet of steel or copper pipe from the compresser then get a good water seperator this will allow the air coming out of the compressor to cool down to room temp. then go thru the water trap and should solve your problem. Don't forget to drain the compressor tank ofter . This system works so well I rarely turn on the Ref. unit unless I am using both big compressors and blasting something really big. Hope this helps

Bill white

John Noell
06-03-2010, 12:55 AM
To solve a minor problem with water in the air line to the laser, I use plastic tubing that has enough extra length (about 18" extra) to immerse a couple of coils in a jar of water. The extra cooling it gives the compressor air means my in-line filter regulator (about 12" from the laser) does not have to work so hard to do a better job of keeping any water from getting to the laser.

Cherie Irwin
06-29-2011, 2:29 PM
John, I just wanted to let you know that I tried your method of running the tubing for air assist through a container of water, and it WORKED. I live in St. Louis, and we have very humid summers. I had problems from the very beginning with water coming through the air assist. I was looking for the least expensive solution possible, and it turns out that yours works like a charm. No water in the line at all, and I am working in my garage without air conditioning.

Thank you.

Rodne Gold
06-29-2011, 3:00 PM
The easiest solution is to route the air assist outside of the lens box , if it is directed at the cut , the lens wont get dirty as the fumes/debris blows away before it has a chance to get to the lens , I hate pressurised lens boxes and have converted all my lasers that have used thst system to external nozzles , no moisture problems and no constant lens cleaning.

Bill Cunningham
06-30-2011, 9:21 PM
Silicagel is not a particularly long lasting medium, usually when you see it it's white or clear, which means it's dead,(like the little packages marked 'Don't Eat') and needs to be reactivated. Cookie sheet in the oven will do it.. When it turns slightly blue it's ready to go again, providing you didn't get any oil on it.. A pressure tube full of marbles also works well to gather moisture & most oil. The marbles provide a huge amount of condensation surface.. For low pressure life support operations, Activated Alumina is usually used, and reactivated by back flushing warm air. The best material to remove humidity is Molecular sieves 13x.. It will also remove some Co2.. Molsieve can be reactivated the same way as silicagel.. It's much more expensive but would give us a dewpoint of more than -100 @3000 psi without much effort.. A lot of the desiccant cartridges you see are full of molsieve 13x, it looks like white petrified mouse poop.. A couple of loops of copper tube in a container of water, then into a tube of marbles w/drain on the bottom, then into a tube of activated alumina (this stuff is cheap). with felt pad/screen inserts at the top and bottom to keep any alumina dust from leaving, then out to what ever your using it for. It will be dry. Working molsieves are inert, and when put on your tongue will feel hot. If they don't, put them in a metal bucket, and in the oven for an hour or so..

Robert Farrell
06-30-2011, 11:07 PM
Garrick I had that issue and i now have three harbour freight inline traps on my compressor no more moisture problem. Most of the moisture is in the second trap which i drain periodically.

Michael Simpson Virgina
07-01-2011, 2:01 PM
Inline trap is the way to go. Just be sure to check it every now and then. I have to empty mine once or twice a year.

John Noell
07-01-2011, 3:13 PM
My inline trap will have an inch of water in it after a few hours! Even with the AC on in the shop 24 hours a day, the tropical humidity makes removing enough moisture from the air assist "interesting."

Greg Bednar
07-02-2011, 11:26 AM
Has anyone tried a peltier plate attached to the top of the moisture trap? My trap has an aluminum top where the polycarbonate bowl screws into. I have no moisture problem per se, but I did attach a clear section of hose from the trap to the back of the engraver so see if there was any moisture accumulating after the filter. To my chagrin, there was - but very little since my humidity is around 40% year round.

Still, I don't mean to hijack the thread, but my question is: could the peltier plate assist in the moisture problem by cooling the aluminum top of the trap, or would this exacerbate the problem? Here is what my trap looks like:

Dan Hintz
07-02-2011, 9:17 PM
Still, I don't mean to hijack the thread, but my question is: could the peltier plate assist in the moisture problem by cooling the aluminum top of the trap, or would this exacerbate the problem? Here is what my trap looks like:
It's not going to help... the problem is the amount of cooling possible by a peltier device is insignificant compared to the CFM of the airflow, so no appreciable cooling will occur.

Greg Bednar
07-02-2011, 11:47 PM
no appreciable cooling will occur.

What a Bummer,eh? Time for more research on the desiccants.