Best approach for drying air from air compressor

[Robert Engel]

Alan,

I also live in FL so I know exactly what you're dealing with.

IMO you don't need an expensive dryer unless you're spraying a lot. I elected to buy a turbine sprayer rather than worry about moisture in compressed air.

I use an inline water separator, and with the Rapid Air piping system, each outlet block has a drain (which I've never used).

Also, the longer the runs are, the less issues you'll have.

[Brian Holcombe]

My compressor has a cooler and desiccant type dryer system, in addition to that it has a valve which automatically drains the tank multiple times through each cycle. On the line I have a filter/regulator/oiler at each tool. The air is clean, cool and dry.

[Alan Lightstone]

Multiple drip legs, so to speak. I hesitated to respond to this, because the OP seems to be seeking a mobile solution. The easiest solution, and the only one I know of, is to have a passive piping system of some length, with repeated drops (and vertical takeoffs to the next leg.) That’s cheap and effective, but not mobile. Dessicants are useless when they’re saturated, FWIW.

Actually, not looking for a mobile system. But also really didn't want to hard pipe, as all the DC and electrical piping go below the raised access floor in the workshop. The runs to the wide belt sander and two individual drops for tools are rubber tubing (or whatever that stuff is made of), not metal.

So there's really no vertical drop outside of perhaps the initial 2 feet from the compressor outlets to the floor. In fact, the run goes upwards at the end about 2-3 feet to the wide belt and outlets.

[Alan Lightstone]

Alan,

I also live in FL so I know exactly what you're dealing with.

IMO you don't need an expensive dryer unless you're spraying a lot. I elected to buy a turbine sprayer rather than worry about moisture in compressed air.

I use an inline water separator, and with the Rapid Air piping system, each outlet block has a drain (which I've never used).

Also, the longer the runs are, the less issues you'll have.

I use a turbine for spraying, so thankfully that isn't an issue, Robert. The runs are about 25-30 feet.

But blowing sawdust off a piece of wood just before I'm about to spray it, and have it spit water on it, is not what I expected/was looking for. And I worry if the water vapor might be ruining the mechanism in my wide belt sander (this may be a non-issue, but I've thought of it).

I had thought that the automatic drain valve on the tank would take care of this, but it clearly doesn't.

[Charles Lent]

What pressure is an AC condenser coil good for? I've been contemplating putting in some kind of heat exchanger between the compressor and tank.

Automotive air conditioners have as high as 350 psi working pressures on their condenser coils when the automotive air conditioners are running on very hot days. I've never seen a max pressure rating for one of these coils specified, but my air compressor systems never run over about 150 psi, so I decided that I'm safe to use one of these refrigeration condenser coils in my air compressor system. You might also want to consider using a large transmission oil cooler as an alternate to the refrigeration coil. The air conditioner coil that I have on my 2 hp 20 gallon unit has been in use for this purpose for almost 15 years. I have no idea how old it actually is. It has been trouble free, except for occasional leaks in my soft copper flare connections to and from it. These leaks are caused by the significant vibration that the unit has when it's operating. I'll likely be putting Blue Locktite on the flare fitting threads the next time I have to fix a leak, to see if that will help.

Charley

[Jim Becker]

What pressure is an AC condenser coil good for? I've been contemplating putting in some kind of heat exchanger between the compressor and tank.

Not sure about that, but the tubing might be too small in diameter for the application, even if it's up to the pressure task.

[Michael W. Clark]

Alan, I wonder if you are not getting the water out if your lines go down under the floor and back up to point of use?

If lines drop down from above, a drip leg will help separate free water simply using momentum and gravity of the water droplets.

I’m in TN and get a lot of humidity too, a lot more water in the summer.

[Tom Bender]

The A/C radiator is a good idea. It would be better to mount it independent from the vibrating monster.

[Tom Bender]

Charles, your analysis is good and precooling before the tank is a good solution. There is a second part to the condensation story. When the air goes back to atmospheric pressure at the spray gun or blowoff nozzle it gets cold, often below dew point and condensation from the room air can be generated. This is where it helps to get the compressed air to a much lower dew point.

[Ronald Blue]

If you were concerned the AC condenser might not have enough flow you could always mount two in parallel. You want a tube and fin style as well. The ones used in a lot of vehicles today are microchannel or more accurately a lot of tiny tubes close together. They can't be flushed out in the event of a ac system failure like a compressor grenading. While that shouldn't be an issue in a compressed air system they aren't what I would recommend. I service mobile hvac systems in my job.

[Brian Holcombe]

I ran heavy wall copper line for my system, it helps in this regard since the tube will dissipate heat. Whatever you decide, if you end up with a DIY solution make certain that you are within the industry recommended margin of safety for pressure and that it is approved for use with air (as opposed to fluids).

[Alan Lightstone]

Alan, I wonder if you are not getting the water out if your lines go down under the floor and back up to point of use?

If lines drop down from above, a drip leg will help separate free water simply using momentum and gravity of the water droplets.

I’m in TN and get a lot of humidity too, a lot more water in the summer.

Having the lines go down then back up is unchangeable in my workshop.

I just received the PneumaticPlus 3-stage air drying system, and a larger desiccant container. Not sure where to place it in the system, but thinking just before the wide belt sander and one of the air drops I use for tools and blowing off stuff.

Can't really think of a place to put a drip loop, considering the majority of the tubing is flexible tubing that runs under the floor, then comes up to the outlets.

[Doug Dawson]

Having the lines go down then back up is unchangeable in my workshop.

I just received the PneumaticPlus 3-stage air drying system, and a larger desiccant container. Not sure where to place it in the system, but thinking just before the wide belt sander and one of the air drops I use for tools and blowing off stuff.

Can't really think of a place to put a drip loop, considering the majority of the tubing is flexible tubing that runs under the floor, then comes up to the outlets.

The lines appear to be the lowest component in your system. What are you going to do when they fill up with water? How do you plan to drain them? This appears to be a deep structural problem. :^)

[John K Jordan]

Alan,

I use a home-made gravity trap before a water separator just in front of a desiccant dryer, this one: https://www.amazon.com/gp/product/B002PR8ZXK

This is in the main shop on the outside of my dust collector/air compressor closet.
air_comp_ctrls_IMG_20150124.jpg
(Don't have a straight-on photo since it's in a narrow hallway.)

Never get water in the air line. Any water vapor that gets past these can still mess with plasma cutting so I use an inline desiccant dryer right at the input to the plasma cutter for extra protection.

BTW, the desiccant dryer is not designed to replace the desiccant - they want you to buy a new cartridge. Instead, I bought a spare cartridge (in case I broke it), pried it open, and replaced the desiccant beads with indicator desiccant. I do this every time now. Lots cheaper than a new cartridge. I "recharge" the desiccant in a toaster oven.

JKJ

[Michael J Evans]

Alan,

I use a home-made gravity trap before a water separator just in front of a desiccant dryer, this one: https://www.amazon.com/gp/product/B002PR8ZXK

This is in the main shop on the outside of my dust collector/air compressor closet.
air_comp_ctrls_IMG_20150124.jpg
(Don't have a straight-on photo since it's in a narrow hallway.)

Never get water in the air line. Any water vapor that gets past these can still mess with plasma cutting so I use an inline desiccant dryer right at the input to the plasma cutter for extra protection.

BTW, the desiccant dryer is not designed to replace the desiccant - they want you to buy a new cartridge. Instead, I bought a spare cartridge (in case I broke it), pried it open, and replaced the desiccant beads with indicator desiccant. I do this every time now. Lots cheaper than a new cartridge. I "recharge" the desiccant in a toaster oven.

JKJ

I sell filters, lubricators, regulators, etc. There are dessicant dryers where you can buy just replacement beads.