Best approach for drying air from air compressor

[Ronald Blue]

We use this exclusively on our equipment. They are a little higher than most in cost but the desiccant cartridge will last a long time because it self cleans. These are high duty cycle in our applications because the air system on some equipment is cycling continuously in brake application every machine cycle. The only thing that fouls them is when the engine driven compressor begins to put oil into the air system. These are made by SKF.

[Alan Lightstone]

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. :^)

True. I don't know the answer to that.

Will the compressed air push the water out of the lowest tubing and into the filter/desiccant cartridge?

[Alan Lightstone]

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.
Attachment 448021
(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

Nice setup, John. Very instructive. I'm assuming that the air comes into that system from behind the pressure valve, with the drip leg below it, then through the filters / desiccator and then to the manifold which dictates where it then goes?

[John K Jordan]

Nice setup, John. Very instructive. I'm assuming that the air comes into that system from behind the pressure valve, with the drip leg below it, then through the filters / desiccator and then to the manifold which dictates where it then goes?

Thanks - I put a lot of thought into it and designed it along with designing the shop building.

Yes, the air compressor is behind the wall in a sound-insulated closet with the dust collector. I wanted everything, including the motor disconnect, accessible from the main shop without having to go into the next room and into the closet. (I wired the dust collector controls the same way)

The drip, water separator, desiccator, regulator, and manifold are next. Behind the wall (in the closet) are lines to three RapidAir lines plumbed through the walls and ceiling to three zones, each with it's own cutoff valve in case one line were to develop a leak. I have compressed air outlets throughout the wood, welding, and little machine shop areas and one outside. This works very well down on the farm!

The accessible motor cutoff lets me easily cut power to the compressor when I'm leaving the shop. Once, in the daytime, fortunately, the pressure switch on the 5hp compressor stuck and the compressor ran continuously for a little while before I walked by the shop and heard it. I know a guy whose shop burned to the ground when his compressor ran continuously like that when he was not home. Ack!

JKJ

[Alex Zeller]

If it was me I would put a set up like John pictured on the wall. Instead of the pipe going through the wall I would just put a short hose with a disconnect on it that can be connected to your air compressor. Make it out of brass so it'll be colder than the air coming in and help condense the water. Where the air comes out you want that to be going up and then back down. You could even put a drip leg there although by that point the water should have been removed. When in use I would check to see what temperature the brass inlet pipe is. If it's room temp you are fine, which it most likely will be, but if it's warm then adding a radiator of some sort before the drip leg would be worthwhile.

[John K Jordan]

If it was me I would put a set up like John pictured on the wall. Instead of the pipe going through the wall I would just put a short hose with a disconnect on it that can be connected to your air compressor. Make it out of brass so it'll be colder than the air coming in and help condense the water. Where the air comes out you want that to be going up and then back down. You could even put a drip leg there although by that point the water should have been removed. When in use I would check to see what temperature the brass inlet pipe is. If it's room temp you are fine, which it most likely will be, but if it's warm then adding a radiator of some sort before the drip leg would be worthwhile.

Air people recommend about 20' of pipe before the dryers and such to give the air time to cool and the water vapor condense. Copper pipe is probably best, a long one would make a decent radiator. I've seen it recommended to slope this pipe upwards from the compressor so moisture runs back down away from the outlet and collect liquid before it reaches the compressor. I suspect if the copper line was too small diameter a high air flow might carry condensed water with it.

[Ronald Blue]

As I recall when I was involved in the locomotive rebuild there was 50 feet of line between the compressor and the reservoir for cooling purposes. There was also an after cooler at the compressor. The reservoir was equipped with a type of automatic drain valve that was constantly spitting roughly once per second. It was said to be more efficient than the type that blows air for several seconds every time the compressor unloaded. No other moisture removal device was used. Dry air is critical in a brake system and in cold weather operations. Cooling the air down helps with moisture removal. Air being discharged is at an elevated temperature and warm air more easily carries moisture. That's the benefit of cooling the air down.

[Charles Lent]

A friend of mine had mounted two 100 lb repurposed propane tanks upside down on the outside back wall of his shop, with the compressor installed inside the shop. Under the tanks he installed a large 3 way solenoid valve that was electrically connected to the compressor power source. When he turned on the air compressor, this valve closed and the air from the compressor filled both of the tanks. When he was done using the compressed air for the day and turned the power switch off, the 3 way valve switched off, dumping the compressed air from both tanks, along with any condensation that had built up in them. You didn't want to ever be anywhere in close proximity to this dumping cycle when it happened. The sudden roar when the 3 way valve opened to atmosphere, dumping the air in the tanks, would drop you to your knees, but he had no condensate build-up issues in the tanks.

Charley

[Alex Zeller]

A friend of mine had mounted two 100 lb repurposed propane tanks upside down on the outside back wall of his shop, with the compressor installed inside the shop. Under the tanks he installed a large 3 way solenoid valve that was electrically connected to the compressor power source. When he turned on the air compressor, this valve closed and the air from the compressor filled both of the tanks. When he was done using the compressed air for the day and turned the power switch off, the 3 way valve switched off, dumping the compressed air from both tanks, along with any condensation that had built up in them. You didn't want to ever be anywhere in close proximity to this dumping cycle when it happened. The sudden roar when the 3 way valve opened to atmosphere, dumping the air in the tanks, would drop you to your knees, but he had no condensate build-up issues in the tanks.

Charley

Reminds me of my bridge painting days. We used steel grit to remove the old paint. The 'pot' for the sand blaster was about 12' tall and on two semi trailer axles. It held something like 40 tons. We used two 2000 CFM air compressors connected to it. If I had to guess I would say it was easily 2000 gallons. At the end of the day I would manually open up the vent, a 2" steel pipe, and let it blow. By the time it vented the pipe was covered in ice.

[Ronald Blue]

Reminds me of my bridge painting days. We used steel grit to remove the old paint. The 'pot' for the sand blaster was about 12' tall and on two semi trailer axles. It held something like 40 tons. We used two 2000 CFM air compressors connected to it. If I had to guess I would say it was easily 2000 gallons. At the end of the day I would manually open up the vent, a 2" steel pipe, and let it blow. By the time it vented the pipe was covered in ice.

That reminds of a friend who used to have a welding shop. He routinely bid on work for one of the kind items and he got a contract to build some tanks for a cooking oil recycling business. These were large tanks that were several thousand gallons liquid capacity. I don't recall the length or diameter. One of the requirements was they had to be pressure tested. Not high pressure but 10 or 15 psi for a predetermined length of time. At the bottom there was a pipe nipple welded in. I think it was 6" in diameter. He had done the pressure test and his shop compressor had ran steady for hours and hours to finally build up the required pressure. So then it was time to release the pressure. Now this guy always has lived hard and fast as a little set up for the rest of the story. He backed his pickup up to the tank to stand on the bed while he removed the cap. Because after all there wasn't a lot of pressure in the tank. I don't recall how he removed the cap because I wasn't there. But when it let go it was not what he anticipated. He claimed it moved his truck several feet. The cap was blown out into a field and never recovered. Just one of his experiences he has had. He would do anything for you. But you don't always want him to.

[John K Jordan]

That reminds of a friend who used to have a welding shop. He routinely bid on work for one of the kind items and he got a contract to build some tanks for a cooking oil recycling business. These were large tanks that were several thousand gallons liquid capacity. I don't recall the length or diameter. One of the requirements was they had to be pressure tested. Not high pressure but 10 or 15 psi for a predetermined length of time. At the bottom there was a pipe nipple welded in. I think it was 6" in diameter. He had done the pressure test and his shop compressor had ran steady for hours and hours to finally build up the required pressure. So then it was time to release the pressure. Now this guy always has lived hard and fast as a little set up for the rest of the story. He backed his pickup up to the tank to stand on the bed while he removed the cap. Because after all there wasn't a lot of pressure in the tank. I don't recall how he removed the cap because I wasn't there. But when it let go it was not what he anticipated. He claimed it moved his truck several feet. The cap was blown out into a field and never recovered. Just one of his experiences he has had. He would do anything for you. But you don't always want him to.

I worked in a laboratory once where we tested pressure vessels. One thing we NEVER did above ground was test with air pressure - too much chance of catastrophic failure and explosive rupture of a weld since compressed gas contains so so much energy. Tests were done one of several ways - one was test for leaks with trace amounts of gas at very low pressure and check outside with a sensitive halon gas detector. Another method was to hydro test - fill with water then pressurize that - if the tank failed the release of even a tiny amount of water from a weld instantly dropped the high pressure in the entire tank to nothing and prevented an explosive rupture. To pressure test with air we used a crane to lower the tank into a large underground bunker built into the middle of the building.

The danger is the reason they hydro test gas cylinders.

[Ole Anderson]

An air drier would have come in handy yesterday. Working in the driveway on my 4 place snowmobile trailer trying to find a broken wire in my electric brakes. Had to remove the wheels. As the temperature dropped below freezing, my impact gun began to quit working. Traced it to moisture freezing in the quick connect at the gun. Sudden change in pressure as it entered the gun caused water to freeze in the connector and the gun to quit working. Good thing I had my 24" HF breaker bar. Salt on open threads for 8 years really causes problems. Had to chase threads on both the nuts and studs. All 20 of them. Turns out (at the last wheel removed of course) that the suspension at some point had bottomed out and crushed the brake wires, breaking three of them. All is now good.

Snowmobiling this year is going to be problematic as we generally are out long enough that we need to stop at a bar or restaurant for breakfast, lunch or dinner. No indoor dining this year in Michigan. Carry out just doesn't work when snowmobiling.

[John K Jordan]

....Traced it to moisture freezing in the quick connect at the gun. Sudden change in pressure as it entered the gun caused water to freeze in the connector and the gun to quit working. Good thing I had my 24" HF breaker bar....

Snowmobiling this year is going to be problematic as we generally are out long enough that we need to stop at a bar or restaurant for breakfast, lunch or dinner. ...

Huge temperature drop when gas expands. You can make dry ice that way.

But yikes, consider moving south! I grew up in Pennsylvania, a good place to be FROM. Been in TN for pert near 40 years now.
For extended playing in the cold I think I'd pack a lunch in an insulated bundle with a hot pack.

[Rob Sack]

What about using a heater core with a fan blowing across it? O'Reilly's had a copper unit with 5/8" hose inlet and outlet for around $60.00. By using a trans cooler or ac cooler, does the 5/16" or 3/8" inlet and outlet affect to air flow and/or volume?

[Charles Lent]

I don't think a heater core will stand up to the pressure, but an air conditioning condenser coil or a transmission oil cooler coil can handle it. Automotive air conditioner condenser coils typically see 350 psi pressures on hot days. Your air compressor won't have working pressures that high. Transmission oil pressures can run higher than that. Most of these coils have 5/8" or larger fitting sizes and the inlet usually feeds into 3 sections of the finned coils in A/C condenser coils, coming back together at the outlet fitting, so 3 sections of finned tubes all connected in parallel inside. The 5/8" fitting becomes the restriction or the pipes feeding or exiting it, in this case. You should be looking for a high pressure coil with inlet and outlet fittings at least as large as the lines on the compressor that will connect to it. Mount it so the compressor fan pulls air through it or add an electric fan that runs when the compressor runs. An automotive engine radiator or heater coil never sees more than about 30 psi, so it will not do for this application.

Charley