Question (WOODWEB Member) :
We are spraying water-borne clear topcoats on mostly maple veneer plywood. We are experiencing some contamination that is resulting in what look like small fisheyes. Cleaning the gun did not help. So we looked at our air supply. We have a 5 micron inline filter on the tank output. It does catch some water. Since the air can be hot at this location, and carry more water vapor, we also have two filters just before the last 25 feet of hose line leading to the gun. The first of these two is another 5 micron filter. It does catch a fair amount of water depending on the weather. Immediately after this we have a 0.01 micron coalescing filter. Its job is to collect any remaining water and oil vapors. It does catch some water.
We have depended on the red/green indicator on the top of this last filter to determine if it needs servicing. It is still green. We decided today to internally inspect the filter cartridge for no obvious reason other than we still have contamination. What we found surprised us. There was a heavy build-up (up to 1/2" thick in places) of what appears to be calcium on both sides of the filter cartridge. At least it looks like calcium. However, we are used to seeing calcium build-up from the local water supply on and around faucets. The air compressor is not connected to the water supply, so this is puzzling.
We have ordered a new filter cartridge for the coalescing filter. We have cleaned out the filter housing. It is not perfect, but the heavy build-up is gone. We have flushed out and brass-brushed the housing quite well. We are also replacing that last 25 feet of hose line leading to the gun. We don't think there really is a good way to clean it. For less than $40, it is less expensive to simply replace the hose instead of risking a recurring problem. My questions are: has anyone had any experience like this? Or, does anyone have some ideas on what that residue was? Or, why it was on both sides of the filter cartridge? We do not have anything scheduled for the finishing department for the next few days. The replacement filter cartridge and new hose line should arrive before we do. Hopefully, by early next week, we will know if this resolved the contamination issue. We are still curious on how this happened. By the way, we have noticed that the drain on our vertical compressor tank is not draining much, if anything, for the last month or two. The tank dates back to 2006 and is located indoors. If there is an accumulation of this same white stuff inside the tank, how would we clean it?
Forum Responses
(Finishing Forum)
From contributor T:
First thing is clean your tank and drain daily.
If the tank isn't draining like it should:
- Purge air from system
- Remove drain valve or pet cock
- Depending on drain style open manual drain on bottom of tank.
- If you have a bucket level drain then there is a hose leading from that going down into the bottom of the tank. These clog constantly.
I would bypass this system by putting a valve and garden hose on the bottom of your tank so you can easily drain the tank daily. This is the first thing you need to address and the most important thing. If your tank is full of water you will always have issues. I had the same problems in the past and found this to be the main culprit.
My new system uses in this order an after cooler, oil separator, 150cfm fridge air dryer, water separator, in line dryer and final filter at both booths. Even with all this equipment we still get some moisture is we don't drain the main tanks daily. If you get your tank cleaned an running properly and have your new filters installed and still have issues then pick up some inline desiccant filter that you can place right at your gun as a last line of defense. The ones I used in the past were an orange color and I got them at a local auto body store. Before setting up my new system I had them on the inlets of my kremlin and gracos and on the gun air inlet as well. They change colors when they go bad.
