Dealing with air compressor condensation

[redsox1]

I've got a 30 gallon air compressor tank and am wondering how everyone deals w/ the issue of removing condensation from their tanks between use. I only use mine occassionally so it seems wasteful to fill the tank to start a small job and then drain it completely at the end of the day. Instead, what I've been doing is leave it charged all the time (with the switch off) between uses and then every once in a while (weekly) I'll open up the drain for a couple of seconds to remove what water has accumulated. It's usually less than a teaspoon full of water. My shop is in an insulated basement so heat/humidty is low. My thought is that whatever water accumulates will be in the bottom of the tank anyway so what good does it do to drain entirely vs a quick blast to drain once in a awhile. Thoughts?? I'd like my compressor to last a long time without rusting out.

 

[Redneck in training]

That is how it is normally done. Get rid of the water and close the drain. There are also automatic drain valves.

Air Compressor Automatic Drain Valve

 

[Bird]

I have a vertical 30 gallon compressor, so I removed the drain valve from the middle of the bottom of the tank and installed an elbow with a 6" piece of pipe out to the edge of the tank and a ball valve. The lever type valve makes it quick and easy to open for a second.

I, too, never drain the air pressure because I use the compressed air so often, but I quickly open and close that drain valve every time the compressor is run and sometimes in between. So the amount of moisture is no more than what would be in that 6" pipe.

 

[JerryK]

I have a vertical 30 gallon compressor, so I removed the drain valve from the middle of the bottom of the tank and installed an elbow with a 6" piece of pipe out to the edge of the tank and a ball valve. The lever type valve makes it quick and easy to open for a second.

I, too, never drain the air pressure because I use the compressed air so often, but I quickly open and close that drain valve every time the compressor is run and sometimes in between. So the amount of moisture is no more than what would be in that 6" pipe.

I do about the same thing. I mount my air compressor up on the barn wall and tap it from the bottom drain plug. Put a BIG drip leg downstream...just before my reelcord and female quick connects...and drain it as often as I think about it. I have a ball valve on the bottom of the drip leg and just crack it open real quick.

 

[redsox1]

Thanks for the feedback, sounds like I'm on the right track. I also put an extension w/ ball valve off the bottom drain to make it easier to reach and empty. Just wasn't sure if it was neccessary to completely empty the tank once in awhile to really dry it out. I guess with the small amount of water I'm removing now I should be alright.

 

[Bird]

My current compressor is only 6 years old, and I drained all the air out of it once. And the only reason I did it that one time was curiosity to see how long it would take it to build up to its shut off pressure of 155 psi.:laughing:

 

[redsox1]

Seems like a lot of noise and wear and tear for nothing then. I'll stick w/ what I'm doing, thanks again. Any other opinions out there?

 

[viceprincipal]

Seems like a lot of noise and wear and tear for nothing then. I'll stick w/ what I'm doing, thanks again. Any other opinions out there?

I haven't seen anyone disagree with you? Or was there a post that got deleted?

 

[redsox1]

No disagreements, I just meant no use in draining the tank if there is no clear benefit. This has to be one of the few threads I've seen that everyone agrees on one plan of action.

 

[grsthegreat]

I thought about adding an auto drain on my tank,. but the compressor shop talked me out of it. Told me there really designed for industrial units that are constantly running, not ones just full of air. If i understand this correctly, the moisture is mostly created when the motor becomes hot from continuous use, and the air coming in is real cold. So a tank just sitting with air in it doesnt have the same issues.

At any rate, i try to drain mine about once a month, and i hardly ever get any moisture showing up. My refrigerated dryer gets any that does survive.

 

[Tenn_Blue]

That was my understanding as well - that the moisture comes when the hot air pulled into the compressor "cools down" in the tank and the moisture condenses out of it.

By keeping the tank "full" most of the time, you minimize the amount of water you dump in the tank, as opposed to filling the tank every time you wanty to do something.

Unless I am painting, I usually only drain the tank once a month. Since the paint process uses a lot of air (both in prep AND in painting), I drain the tank (and the water/trash filter in my paint booth line) before every operation when doing paint work.

As an aside, air dryers usually quickly heat then cool the incoming air to percipitate the water vapor out of it before leaving the dryer....

 

[Redneck in training]

The truth is that the amount of water is proportional to volume of the air pumped at given ambient humidity. The water gets knocked out when the air enters the tank and cools down. In example in very cold winter day the air is virtually dry. At hot and muggy summer day it contains significant amount of water vapor.

 

[The Haymaker]

The truth is that the amount of water is proportional to volume of the air pumped at given ambient humidity. The water gets knocked out when the air enters the tank and cools down. In example in very cold winter day the air is virtually dry. At hot and muggy summer day it contains significant amount of water vapor.

This.

I run a pretty hefty air cannon with my 60 gallon unit, along with the usual, home shop, air tools. Hot and muggy Maine summers definitely create more moisture in the tank.

 

[grsthegreat]

This.

I run a pretty hefty air cannon with my 60 gallon unit, along with the usual, home shop, air tools. Hot and muggy Maine summers definitely create more moisture in the tank.

do you shoot pumpkins :laughing:

 

[Tractor Seabee]

Here is the fly in the ointment, especially when you live in a humid climate lke here in W WA. The water in the bottom of the tank is what is in the air you bring into the compressor. That air is heated from compression which actually seems to be drier (psycrometrics), still the same moisture but humidity goes down. The air cools in the tank due to the radiating surface of the tank, the water drops out and collects in the bottom of the tank. When a tank fails (leaks) it is 99% rusting out from the inside. Remember rust is oxidation. You keep adding more oxygen as the compressor runs. Even a little bit left in starts the rust process, then the rust collects and holds moisture against the steel. A quick blow is not enough, leave the valve open till you get no more drip or vapor. Do this on a cold day and it will really sink in as you will see the vapor.

So blow down often, do not let the water accumulate. I know a guy who said Ah, I do not need to do that. I went to his tank (50 GL) opened the drain, it was plugged. Blew off all the air, removed the drain valve and, got a gallon of rusty water plus a lot of rust. Told him he is a failure waiting to happen. He is now a believer. The pressure on the tank has no relevancy to the moisture, it is the cfm of thru-put. The more you use it the more water you get. The guy piping from the bottom is only assuring the piping system also stays wet inside. Threaded pipe rusts out twice as fast as you are cutting away half the wall thickness to make the thread. If you have a large system like the painter and have an air dryer, put the drier between the compressor and the tank; that is the way large industrial systems are piped. Keeps the water out of the tank and downstream piping. Remember also not all the moisture drops out in the tank, again the pyscrometrics which is way more technical than appropriate for this forum.

Ron

 

[boggen]

have a portable setup.
inital start up = drain open.
then once done for the day = drain open

i generally allow air compressor to get near 60 psi. before opening drain valve.

to high of a psi. and anything near the drain port ends up being a projectile weapon. and if i go less. tends to be some moisture / water that does not make it out.

if i had a stationary setup. i might opt for a eletronic valve. so when ever air compressor motor started up. the valve would open for a couple seconds. or some such. it would be either that, or a nice easy 1/4 turn ball valve. and pipe leading to a floor drain or like.

 

[ultrarunner]

I've put in several auto drain valves and they work great... most are akin to an automatic ball valve that opens and closes on a predetermined frequency that is adjustable.

I also put one in the senses the compressor start stop cycle and has a short blow every cycle... the air has to be dry because it is part of a pneumatic control system.

For the paint compressor, I also have a refrigerator/dryer that chills the air and drains the condensate... this is entirely separate from the compressor.

For insurance... at each point of use is a high quality filter and water never collects unless something is amiss... like the refrigerator/dryer being turned off...

The State inspector comes out every 5 years to inspect and the first thing he does is look for moisture...

 

[The Haymaker]

do you shoot pumpkins :laughing:

AT them maybe.... Haven't gotten to the large scale version.

Newtons Law pneumatic cannon - YouTube

 

[jake98]

I think they're gonna rust, one way or the other. There's always moisture in there, and I don't think it takes much to get rust going.

 

[JerryK]

Here is my current set-up.... PLEASE keep the snickering down to a minimum... Unit started out as a 2hp Craftsman compresser in 1973, with a 20 gallon tank. It now has a cheap-O 10 gallon on it and I have replaced the pressure switch. The box on the bottom allows it to run 10 minutes at a time unless you turn on a lighted bypass selector switch. So when a hose breaks you don't find that your compressor has been running for hours with a thick oil mist in the air.... don't ask me how I know about this. The second picture is where I drain the moister. I also use an inline water filter if I am painting. Just keep all my air tools oiled up good the rest of the time. I also added a large air filter on the intake years ago. Anywhilst, it may be ugly but it works....