CU air lines for home shop - what diameter?

The longer the time air stays in the tank or lines the more water will come out of it.

One place I worked didn't have that bad of water problem unless the sand blaster was in operation. Without the blaster air stayed in the tank long enough for most water to condense. With the blaster air didn't stay in the tank long at all so condensation occurred in the lines. (should be noted the blaster had it's own supply line).

Opportunity for the air to cool as it occupies the second tank is, I think, the major factor. Before this tank was given to me, I had a 7 gal tank inside an old fridge. Seat of the pants data says the results are fairly equal. Just don't have to pay the electric to run the fridge now.

mj

It's a dynamic system, you're creating a pressure drop at the air outlet, the pressure is coming from the smaller tank at the air compressor, so it will expand into the second tank which is closer to the outlet and at a lower pressure. If you are using a very minimal amount of air the pressure would be nearly uniform, but the larger tank would still allow the air to cool and shed moisture.

A holding tank is one hell of an idea.

I have a 2 stage and 60 gallon tank that runs through a flex line to a stationary regulator then to a DeVilbiss filter/ separator. Both the regulator and separator are rated at 200 cfm. I figured the regulator turned back to 100 psi (separators rated at 150) would drop temperature enough to get water out. I get no water from the separator. However if I put a 50 foot hose on the separators outlet the tool dribbles.

At first I was surprised (for a few seconds) but realize the air doesn't have time in the tank to lose enough temp for the water to condense. It doesn't lose enough temp till it's in the hose which is acting like a condenser. (Let's all say Duh)

Plan is to use 3 or 4 inch black pipe (I have to check ratings, black pipe may not be suitable) vertically on the wall. From bottom to top I would screw together a cap with drain, a 1' nipple, a 'T' for air entry, then a 3 ~ 6 foot pipe topped with a reducer cap that would go through a union then to 3/4 inch line on the ceiling. I would also like to make a slide in baffle. All this to give the air someplace to cool and water to condense in a pipe where the air velocity would be slow enough so water could drop to the bottom.

Even with this contraption I know water will still come out of the air in the ceiling pipe.

I would like to carry this post on but Wife just called and said theres an estate sale with a bunch of metal and wood tools.

Later.

On Wed, 17 Dec 2003 22:52:35 -0500, aribert wrote something ......and in reply I say!:

I do not know the figures for pipe size vs length vs flow, as I do not have a plumbed system, but only a portable and some hose.

I do know that some tools use a lot of air for short periods, using the Comp tank to provide the "pulse" requirements, even though the Comp cannot keep up with max demand of the tool (rattle gun, for instance). So the peak need, not the compressor supply capability, is the controlling factor.

**************************************************** sorry remove ns from my header address to reply via email

I was frightened by the idea of a conspiracy that was causing it all. But then I was terrified that maybe there was no plan, really. Is this unpleasant mess all a mistake?

If you can get copper pipe rated for the pressurem you'll get better cooling - thinner wall and higher thermal conductivity.

Ted

When I plumbed my studio for air, I went with 3/4" copper for a few reasons:

1. PVC is dangerous if it breaks... it explodes shrapnal.
2. PVC and vinyl air hose insulates the air and doesn't allow it to cool, meaning the moisture stays in it... VERY bad for painting and sandblasting (you may not do it now, but what about in 2 or 3 years or for a friend?)
3. Copper is easy to install. (I had NEVER sweated copper before my shop and I now have zero air leakage in over 80' of pipe.

One suggestion... If you're going to install a moisture separator (one of those canisters which traps the water) put in a minimum of 30' of line BEFORE the separator to allow the air to cool. Also put in a drain and valve before the separator to catch most of the cooled water before it gets to the separator.

These guys who put in a moisture separator out the outlet of the compressor are wasting their time and money since the hot air holds the moisture and allows it to speed right though the separator.

I just have a zig-zag of copper on the wall after it leaves the compressor... the 3/4" more than compensates for the loss of flow with the extra cornering the air does.

James, Seattle

SOunds like a radiator fin set is needed on the output before the water separator.

Not Auto size, there are smaller or home made heat sinks.

Martin

We have an aftercooler device on the main air line at work that is a jacketed tube (i.e., a tube within a tube), that has water flowing through it to a drain anytime the compressor is running. This water is controlled by a solenoid. The aftercooler sits vertically on a wall with a float type water seperator at the lower end of it. As the unwanted water in the air condenses, the float bowl fills with water, and as the float rises, the water in the bowl is expelled. Float settles back down to seal off after draining, then repeats. The drier air continues on through the system. One consideration on this system in a home shop would be the possibility of the water freezing in winter. A closed loop antifreeze system could be used to prevent this.

RJ

I have a different type of shop air supply system then most. My shop is located in my out building that is 150 feet from my house. My air compressor is located in the basement of my house. I did this for a number of reasons, but the key reason is much dryer air then out in the shop to start with. In the winter the basement is heated and central air keeps it dry in the summer months. I have a 3/4" black poly-pipe buried four feet deep running from the basement out to the shop. In the shop I have the regulator that takes the pressure from

125 psi max to 80 psi. The entire shop is plumbed with the same 3/4" black poly-pipe. The poly-pipe is the same type used for lawn sprinkler systems except it is rated at 220psi @ 70°F I believe its call Gold-Line. My system has over four years on it and has worked great. I have mosture traps installed in the shop, however, I have no moisture in the air or the traps. The hose from the house to the shop works like a chiller, I think. It's cheep and will not shatter like PCV. I purchased a 300 foot roll from Lowes for around $23.

Eric D

I can see a big advantage to having the pipe buried for any length. Would pull allot of heat out of it, do lots of condensing.

One of my concerns with using any polymer pipe is compressor oil. The Devilbiss site states " Certain solvents, paints and chemicals may attack plastic bowl and can cause bowl failure. Do not use near these materials." I remember reading in the Devilbiss site where they specifically mention to avoid certain types of compressor oils. Damned if I can find it now.

I wouldn't use plastic pipe, not fond of copper either though I've seen it in commercial settings that have passed OSHA inspections. OTOH copper would have better heat transfer and no rust.

About shop plumbing and sizing I was going to try writing about how to make the drops but it's easier to post a link .

Sure enough, tis a waste of time to put the separator near tank. I found that out. The PO of my separator had it screwed straight into the compressor tank and it was collecting water but it was a single stage baby compressor on a 60 gallon tank, not a decent sized 2 stage heat making pump.

This is the same link I posted earlier in this thread:

Note the way the taps come off the main line, first they go up then down. Was going to write this but it's easier to post a link, and I know how many like references. Helps keep the water in the main line in the main line. When I hard plumb the shop I'm going to mount my separator on a stand so it can be moved to where it's being used.

Here's a kick in the ass.

I went to an auction where there was a new looking I-R air drier the size of a mid sized chest freezer. I don't remember what it went for but I do remember it made me cry, the bid wasn't much for what it was.

I should put a timer on my compressor, it does seem to pump up quicker in the cold. I think it has to do with the fan blowing cold air across the finned tube going between the stages.

Cold air is denser, so it should help any system.

It's an advantage only if the condensed water has someplace to go. If it just accumulates in the pipe, it's going to get blown out sooner or later. Bob

This is VERY true. I used to have to carry extra bowls for certain Festo and Watts regulators and dryers, as they would degrade and blow out at the bottom, generally near the manual drain plug. Ive installed zinc bowls and the simple little float drain kits in the bowls and the problems in those particular shops went away.

Gunner

'If you own a gun and have a swimming pool in the yard, the swimming pool is almost 100 times more likely to kill a child than the gun is.'" Steven Levitt, UOC prof.

I'm not sure what type of compressor oil you are using and maybe it would eat the poly-pipe. In my compressor is straight SAE 30 wt oil. The type that comes in poly-type plastic bottles. In my case this is the only oil that might come in contact with the pipe. I can see your concern if you use solvents, certain paints and other chemicals in your system or around it. My air system is for running air tools.

Eric D