Jump to content

AER_2263

Water coming through airline when spraying

Recommended Posts

Hi,

 

I wonder if anyone can offer any advice.

 

My compressor, an RDG Tools Model 18-2, is carrying water/moisture (it has no smell so can't be a solvent) through to my airbrushes when I spray without paint. It mixes water with enamel paint too when spraying, which is not a good thing. The compressor does have a moisture trap, this has some condensation on it (a problem in itself?) but no actual water. You can empty this moisture trap by pressing the valve in, this does not seem to have any effect though - the water/moisture is still sprayed. However after spraying for a few minutes water will carry through. I've tried different airbrushes and hoses, and it happens with both - pointing at the compressor. Some water is sprayed with the air but some if forced out of the airbrush head. I just can't see where this water is coming from if the moisture trap is empty.

 

Do you think it is worth stripping down the compressor to find a source of moisture? Or just scrapping this one and buying new?

 

Cheers

Share this post


Link to post
Share on other sites

Does it have a tank?

Share this post


Link to post
Share on other sites

Does it have a tank?

 

Nope. Its a very basic compressor, I've copied the spec below. I have noticed the max pressure produced not being as high as when I first got it.

 

 

MINI AIR COMPRESSOR PERFECT FOR AIRBRUSHES

Ref: 65456R

 

POWER 1/8 HP

AIR SUPPLY 23 L/MIN

AIR PRESSURE 30-35 PSI

SPEED 1450 RPM

AIR EXHAUST : 1/8" BSP/NPT

WEIGHT ONLY 3.7 KG

COMES COMPLETE WITH AIR REGULATOR AND WATER TRAP

Share this post


Link to post
Share on other sites

It may be the moisture trap is not working or a single one in the airline is not enough, but another moisture trap can be plumbed in to the line.

 

The fixtures threads vary a bit, but any home mechanic should be able to sort it out, and several suppliers offer conversion and coupling adaptors. You may find the makers offer extra traps, Ebay may be a source of the moisture traps as well.

 

The moisture comes from the air, as simple as that, maybe the air it is drawing in is naturally damp, and moving to a new position may help. Make sure any foam air filter fitted, is both there, and in good clean condition.

 

In the extreme a large external air tank can be added, made from a gas cylinder, but it will need engineering skills to add it. The moisture condenses as the pressurised air expands, and the tank gathers the water, and little would be carried over.

 

hope this helps,

 

Stephen.

Share this post


Link to post
Share on other sites

post-6750-127853902356.jpg This type?... then strip and clean the trap, and it should work. Try using it well off the floor, in case it is picking up damp cold air.

 

Is it being used in a shed or indoors?

 

It would be feasable to feed to an airtank, and then take off the line to the airbrush, this would drop the moisture. Any gas tank of say about a foot high and four inch dameter would do, or an old fire pressure extinguisher body, with plumbed on air connectors. The output overall would be the same as the compressor puts into the tank. It would need draining every so often.

 

Stephen.

Share this post


Link to post
Share on other sites

Hi,

 

I wonder if anyone can offer any advice.

 

My compressor, an RDG Tools Model 18-2, is carrying water/moisture (it has no smell so can't be a solvent) through to my airbrushes when I spray without paint. It mixes water with enamel paint too when spraying, which is not a good thing. The compressor does have a moisture trap, this has some condensation on it (a problem in itself?) but no actual water. You can empty this moisture trap by pressing the valve in, this does not seem to have any effect though - the water/moisture is still sprayed. However after spraying for a few minutes water will carry through. I've tried different airbrushes and hoses, and it happens with both - pointing at the compressor. Some water is sprayed with the air but some if forced out of the airbrush head. I just can't see where this water is coming from if the moisture trap is empty.

 

Do you think it is worth stripping down the compressor to find a source of moisture? Or just scrapping this one and buying new?

 

Cheers

Hi, ;)

The problem is not with the compressor but with the humidity in the atmosphere at the time of airbrushing. Even the most expensive compressors with moisture traps are still capable of producing moisture. If your moisture trap can be dismantled then dry the inside with kitchen towel - and do so before each spraying session! Keep a small hair dryer handy - ready plugged in! and at the first sign of moisture - blow directly on to the moisture - works a treat!

Hope this helps.

Bill.

Share this post


Link to post
Share on other sites

The water is in the air naturaly (normally called moisture) and settles out when the pressure rises in the tank, in effect it is "squeezed out" of the incoming air during the compression.

 

You have probably been spraying in a damp atmosphere recently and it has just built up over a period of time before you noticed it.

 

The immediate solution is simple, unscrew the fitting in the tank where the hose/regulator/connection fits and turn the tank on it's end, the water wil drain out.

 

We get it all the time with commercial compressors, if you think you have problems just imagine the trouble this can cause to someone who is respraying vehicles profesionaly.

 

Wally

Share this post


Link to post
Share on other sites

As another suggestion, RDG do a small moisture trap which screws directly onto the air input of the airbrush. I use one of these, & it's proved a useful & effective last line of defence. You can see condensation building up within it, & it's easy to clear every so often whilst spraying....

Share this post


Link to post
Share on other sites

Many good theories here ;), It is actually so that the so called "water-trap" is just that, it is made to separate very small water drops in the compressed air.

The problem occurs when the compressor gets warm (as it does, touch it if you dare...),

then there is no more water drops, instead you have vapor! (a result from damp air being heated and compressed).

And that is something that the water-trap can´t handle.

You need to let the vapor condensate before reaching the water-trap.

The remedy is to remove the water-trap from the compressor and install a air-hose,

at least 3 meters long, and then install the water trap on the end of it.

A good thing about that is that if you mount it at the bench you can adjust the air pressure where you sit.

The more expensive solution is to buy a "Desiccant", it dries the air but isn´t really for the hobbyist...

Share this post


Link to post
Share on other sites

I used to get this problem when using one of those "Diaphram" compressors. For whatever reason, moisture forms in the airline itself; no water trap is going to catch it.

The simplest solution is to take the airbrush off the airline every 10 mins or so, and then start the compressor. Run it until you actually see the moisture being blown out of the airline. It only takes a few seconds. Re-attach airbrush and carry on for another 10 mins or so...

Share this post


Link to post
Share on other sites

Thanks to everyone for their replies, some very useful stuff.

 

Bertiedog - yes that's the compressor.

 

The regulator and moisture trap unscrew from the main assembly, but there is no way to get into the moisture trap. So, using the hair-dryer I managed to remove all the condensation from the moisture trap.

 

I spray just outside my back door, with the compressor inside. I moved the position of the compressor (to outside), no water at all this time. Some did arrive, but not as much as before - I unscrewed the airbrush and let the compressor work a couple of mins - this cleared it. The water IS related to the heat of the compressor, when it gets very hot that is when the water is produced. Apologies for the non scientific terminology here!

 

I don't think this compressor is a right-off just yet, I'm just going to make sure the moisture trap is completely clear before spraying and vary the position of the compressor.

 

Cheers.

Share this post


Link to post
Share on other sites

It all has to do with the moisture in the air, as other people have posted.

 

You are compressing air, and moisture. When you compress air, you reduce the amount of moisture that it can hold in saturation. You are also heating the air (by-product, unwanted). This heating allows more moisture to be held in the air. If you cool the air (via a longer length of line, or a tank), then the moisture will percipitate (rain) out in the tank, until you reach the new saturation level at that temperature. Now, there are 3 ways effectively to reduce the moisture beyond that point: Dessicant, cooling, or pressure drop. Any one of them _will_ cause moisture to drop out of the air. What you are after is a dew point in the air before the air brush of less than the ambient conditions, otherwise, the pressure drop at the air brush will cause droplets of moisture to appear in your spray.

 

I'm used to heatless dessicant driers, but then we're talking a 7 hp oil less compressor running 24/7/365 here :). The easiest answer in modeling use is to spray under conditions that are less likely to cause the dew point to exceed that of the ambient air, so pick dryer, hotter days to do your spraying on, and put the compressor in the warm & dry air not in the basement.

 

James Powell

Share this post


Link to post
Share on other sites
I spray just outside my back door, with the compressor inside. I moved the position of the compressor (to outside), no water at all this time. Some did arrive, but not as much as before - I unscrewed the airbrush and let the compressor work a couple of mins - this cleared it. The water IS related to the heat of the compressor, when it gets very hot that is when the water is produced. Apologies for the non scientific terminology here!

 

I don't think this compressor is a right-off just yet, I'm just going to make sure the moisture trap is completely clear before spraying and vary the position of the compressor.

 

Cheers.

 

I am wondering whether the temperature gradient between 'inside' and 'outside' is what is causing this. I assume that 'inside' might be the kitchen? If so this room and the bathroom represent the maximum humidity If you take warm humid air, compress it so it can carry loads of water and then rapidly cool it (my air brush spray is freezing), the water is rapidly condensed into visible droplets.

 

One other solution is to use acrylics.

Share this post


Link to post
Share on other sites

I am wondering whether the temperature gradient between 'inside' and 'outside' is what is causing this. I assume that 'inside' might be the kitchen? If so this room and the bathroom represent the maximum humidity If you take warm humid air, compress it so it can carry loads of water and then rapidly cool it (my air brush spray is freezing), the water is rapidly condensed into visible droplets.

 

One other solution is to use acrylics.

 

It doesn´t really matter where you keep your compressor this time of the year as the relative humidity is so high.

As I said earlier, the only remedy is to make a "condenser-hose" between the compressor and the water trap (or buy a desiccant...).

And BTW, it doesn´t matter if you use acrylics or enamels. Water splatters over the smooth wet paint is never good!

Share this post


Link to post
Share on other sites

but there is no way to get into the moisture trap.

 

 

 

 

 

 

The glass bowls on water traps normaly unscrew from the body to allow for cleaning.

 

 

OzzyO.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.