Wet air supply

By Staff
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– I just started sandblasting a bunch of parts, and my air supply is way too wet. I have two cyclone air separators in the line between my air compressor and my blast cabinet, but it’s still too wet. Now what do I do? How can I get very dry air without spending an arm and a leg? – Joseph

– Could the location of the separators have anything to do with it? I have a bank of four separators located right off my compressor, and I have never had that happen. I don’t know if the quantity of separators or their location might make a difference. It’s just a thought. – Allen

– Try this: With a full tank of air, drain the tank of any water. Let the tank sit at rest for 30 minutes and then drain again. Clean and dry both water separators. Don’t forget, you’ll still have water in the air hose. Dry it as best you can. Preferably, hang the hose and let the water drain out and dry. If you can, add another water separator at the blast cabinet.
Let us know what happens. By the way, do you live in a very humid area? – Jim

– As said previously, make sure your receiver is thoroughly blown down (drained) and ditto for your moisture traps.

Typically, one moisture trap is located close to the compressor/ receiver, but one is also needed at the far end of any hose run as more water will condense in the long hose run. I like to have only a short length of hose from the last moisture trap to the blaster. Make sure that you start out with a dry system and hoses. If your receiver has a slug of water in it or your hoses have pockets of water in them, you may not get the water reduced to an acceptable amount at your tool.

Moisture traps that are close together don’t add much drying as the moisture doesn’t condense in I the short distance between them. Long hose or pipe runs condense additional water. Low spots in the hoses or pipes form pockets of water that may overwhelm the moisture traps as your work time accumulates. Have your final trap close to your work. This may help. – Kid

– I had the same problem when I got my cabinet. I ended up running 150 feet of 3/4-inch copper air line from the compressor to the cabinet. Then, I bought a DeVilbiss three-stage air drier system that’s used in body shops. It has a pre-filter then charcoal and then desiccant. I have no water in my air. Another thing is that you need a large air compressor. I have a 7 HP two-stage. If it’s too small, it will run constantly and heat up the air and create a lot of water.

Before I did all this, I could only blast for half an hour until my cast parts would turn rusty. Now I can blast all day if I want. The desiccant lasts about one year with moderate use. – Rudy

– Joseph, I ran into the same problem using a 55-cfm pump at 120 pounds for blasting. I had a filter and water trap at the compressor and also at the blaster. I ended up adding 50 feet of hose between them to allow the water to settle a little, and it helped.

That compressor creates a lot of heat, and the water couldn’t separate quick enough. The ideal cure would be an after cooler to speed up the process. Perhaps by using a coil of copper tubing in a bucket with cold water flowing into it? Just a thought. – Randy

– I run my air through 1-inch black pipe with traps at the beginning and end like that shown in the ‘tip’ book. I don’t usually have any problems unless the humidity is high for days, and I do a lot of blasting. – Paul

– The coil of copper in a cold bucket works amazingly well. It’s slightly more complicated than just coiling the tubing in the bucket. I built one in a 55-gallon drum, and I can sandblast in extremely humid weather. If anyone is interested, I can draw a sketch of mine.- Roger

I live in central Pennsylvania, and I have never thought it was overly hot or humid here. Then again, I’m a boiler operator in a power plant so what do I know about hot or humid – everywhere other than work feels air-conditioned to me. But, the compressor is upstairs in my shop, and I do think it might be a little warm for it up there.

– I’m toying with the idea of running some copper coils through a window air-conditioning unit, so it seems like a win-win situation to me – dry air and AC in the shop. – Joseph

– I’ve been reading about refrigerated air driers, and I think it’ll work. A coil in front of the cold output side, a separator, then a pass in front of the condenser or hot output side to warm the air up will make it so it doesn’t sweat in the lines, then another separator, and one near the cabinet.

I’m also going to bring the compressor downstairs, which will make it easier to service anyway. I have always hated changing the oil on the ledge that it’s currently sitting on. When I decided to put it up there it seemed like a great way to save floor space, but it has become an enormous hassle to work on. – Joseph

– I have used an old 80-gallon tank in line just ahead of the blast cabinet. This allows the air to cool before it goes into the water separator, which is just before the sandblaster. Most of the water stays in the compressor tank – or the auxiliary tank – and the last bit stays in the water trap. I empty all of the drains frequently. This works even on humid days, and it’s cheap.

The extra air tank also allows a longer duration of blasting before the compressor can’t keep up. We have used the coil-in-water idea for cooling the breathing air for the sandblasting helmet on big outdoor jobs. We had 50 feet of 3/8-inch copper coiled in a cooler with disconnects on both ends. Fill it with 5 gallons of water and a bag of ice, and it’s like air conditioning, you never want to take the helmet off. Good luck! – Al

– Most of these posts have touched on the problem: Hot air holds more water than cold air. The harder you work your compressor, the hotter the air.

Four water traps at your compressor won’t help much because they only begin to work as the air cools. The fix: Use an adequate compressor, pipe air lines in black pipe (safer than PVC, and it doesn’t sag). Incline the pipe slightly (4 inches in 50 feet is okay) to drain water away from compressor. Set the water trap at least 50 feet away from the compressor. When you tee off your lines, tee up and elbow down to the water trap so the water in the line passes to the drain leg at the end of the system.

Desiccant and refrigerated driers are great, but expensive. I’ve seen some good systems in body shops where they ran a coil through an old refrigerator. – Dick

– Many valid points have been made, and this thread hit close to home since I have a DeVilbiss 6-1/2 HP, 17-cfm, two-stage compressor on an 80-gallon tank. I used iron pipe to run a sloped air line across the ceiling of my shop to the bead blast cabinet. At the bottom end of the line as it comes down the wall, I placed a drain valve. Above that, there is a T, which goes into a dryer and then the regulator. After the regulator, another T runs through the wall to a valve and spigot outside for sandblasting. Off that same T, a line goes into the bead blast cabinet via the foot valve. It works in Florida! You can’t get much more humid than that. – Harry

SmokStak (www.enginads.com/ smokstak.cgi) is an engine conversation bulletin board with over 50,000 messages on file, and is part of the Old Engine series of Web sites that started in 1995 as ‘Harry’s Old Engine.’ Harry Matthews is a retired electronic engineer and gas engine collector from Owego, N.Y., now residing in Sarasota, Fla.

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