Slightly OT: Draining Portable Air Compressors - Are We Just Kiddng Ourselves?

[DerbyDad03]

I have a pancake style PC air compressor. The drain valve is partly up the side so that the unit has to be tipped - and balanced on one leg - in order to drain it.

There is no way that all of the water is draining out. Maybe if it was left tilted for hours it might drain completely, but the location of the valve, being so close to one leg, makes it impossible to leave it tilted.

If the valve was centered between 2 legs you could easily prop the unit in the tilted position, but the way they designed the valve location makes that nearly impossible.

So, we drain what we reasonably can, then set the unit upright and some water is going to run back to the bottom of the tank. Even if the valve is left open, I doubt there is enough air circulation for the remaining water to evaporate before the next daily use.

It seems to me that the bottom of the tank is always going to be wet and therefore subject to rusting. Sure, less water means less surface area to rust, but if the very bottom of the tank is "under water" 100% of the time,

1/16" or 1/2" isn't going to make much difference at the very bottom, is it?

*If* the tank is going to explode due to rust, which is more dangerous:

Having a small area (the very bottom) that rusts out and blows or letting a larger area rust, spreading the release point over a larger area? Sure, it will probably still be a single point of failure, but if the area around the failure point is already weakened by rust, wouldn't the explosion be less violent?

[Markem]

Well you have some experimenting to do then! ;>

[OFWW]

There shouldn't be any explosion. If it rusts through it will at the first just bleed out air. Maybe air and water. If your pressure relief valve isn't working then replace it.

Oil less compressors are more subject to the rust problem because their is no oil vapors in the compressed air to coat the tank.

Depending on how often your compressor is in operation should control how often you drain it. If in continuous use I'd say about once a week, once a month if used frequently.

Most of those systems will have compressor failure before a rust failure.

[Leon]

Bleed the tank with the valve just partly opened and with full pressure but turned off and let the air drain completely. While depressuring tilt the tank back and forth until you no longer get water.

You will never get all moisture out, it begins filling again every time the unit runs and the heat generated compounds the problem.

On these small units you drain the water mostly to keep water out of the lines and going to your tools.

[nailshooter41]

That's really the gist of it. You sling your little compressor into the bac k of you vehicle to go to the next job and that rusty, nasty condensation r olls all over the tank while riding around. Including the aperture that le ts out the air, which goes right into your air lines, then into the guns or other equipment.

I learned at a coatings spraying seminar that the pulsing on/off action fro m shooting your nailers or spraying with your guns actually pushes the cond ensate down the air lines due to the direction of the air flow.

BTW, that's why automatic gun oilers work, and why inline filters on compre ssors are needed.

Robert

[Ed Pawlowski]

Right they "should" not, but these people seem to disagree with you

[DerbyDad03]

Do I want to rely on "shouldn't" in this situation. ;-)

Depending on who you listen to, some say leak, some say explode. Discretion, valor, and all that. I know which way I lean. ;-)

How does one test that? I can pull the ring all day to empty the air, but how do I know that it will blow automatically when the situation calls for it?

I equate that with testing a GFCI. All the button tells me is that it worked when I pressed it. It doesn't tell me that it will work when it actually needs to. Sure, if the test fails, I'll know that it *wouldn't* have worked when needed, but a passing test doesn't tell me that it *will* work in the future. That last button push may have killed it.

I've been using mine for a few minutes maybe twice a week for the last month. For example, I shot about 20 nails yesterday, another 20 last week sometime.

I don't drain it every day, but when I do, I certainly get some water out of it. But the frequency of draining doesn't really address my question. I could drain it every day or even every hour. There is still no way that all of the water is going to come out based on the location of the drain, unless the unit was left balanced on one leg, perfectly positioned so the drain is at it's lowest point. It's a terrible design and almost assures that there will always be water in the tank.

"Most". That's kind of like "shouldn't explode" isn't it? ;-)

[nailshooter41]

Wow... I am now looking at my compressors completely different. Ticking time bombs? I dunno. After reading this thread I am thinking that I need to ditch all four of them before I am killed or at least seriously injured.

Except for the compressor I use to paint, I just drain them once in a while, mostly when I think about it or before they go to storage. After reading this, it sounds like I might be playing the construction worker's version of "compressor roulette"!

Robert

[DerbyDad03]

I assume (hope) you are joking.

As I'm sure you know, if they really were that dangerous, they wouldn't let just any shumlp walk into a Walmart and buy one, toss the instructions away and never drain it. Then when it's half filled with water, they are allowed to sell it on Craigslist with no background check or psychological evaluation on the buyer. ;-)

Besides, that's what life insurance is for.

[OFWW]

Agreed.

Well, after looking at the Photo's in the repost linked to, I'd have to say I changed my opinion. Basically because the tanks are slightly thicker than heavy gauge sheet metal, that and an oil less compressor shouted short life time to me.

I am so used to working with the commercial stuff I never considered these inexpensive things, and I have several here.

I was also used to inspection dates for tanks, in commercial use.

The more it is prematurely released, like with the ring, the weaker the pop off setting, so that can be a good thin.

That was my thinking when you first posted that. Today I realized that more than likely when your tank is setting normal that your bleed valve probably has a tube That arcs to the bottom of the tank. So it would drain the water, in any in that position, it you tilt it then you'd get air, and very little water. Check your manual if you can still find it, to verify it. If it is removable, then remove it and verify it, but mark the position of the valve before you remove it, so that you can set it back properly if it has a pickup tube attached.

There are automatic drain valves available so that are electronic so that you can set the drain cycle and length. Most A/C supply houses stock them as does Grainger's etc.

My small ones I drain after a days use, the large one monthly.

True enough. Point taken. :)

[OFWW]

But it doesn't keep you alive. ;)

[OFWW]

Made me think a little different with these inexpensive things, Thanks.

[Ed Pawlowski]

We used to have our industrial tanks inspected according to law in MA. They use an ultrasonic test and check multiple points on the bottom section of the tank. Of course, they are much thicker than the typical home compressor.

I would think you can find most problems just by tapping around with a metal rod and listening.

[DerbyDad03]

No need for the manual, the instructions are right on the tank.

And yes, you have to tilt it forward and balance it on that nearby leg to get the water out. Only air comes out if it not tilted. The valve has to be at the lowest point to drain, basically pointing straight down.

I don't see how an "arcing tube" would work anyway. How would the water overcome gravity and climb the tube to the drain? As far as I recall, gravity sucks.

[nailshooter41]

Yessir.

The compressor is probably the least dangerous tool I have on my job sites. Several different types of saws, nail guns, trim guns, drills, drivers, h ammer drills, portable table saws, heavy duty grinders, cutting torches, ch ain saws, portable metal bandsaws, etc., etc., etc. are of great concern. The air compressor, not so much.

Probably had about 50 of them over the last 40 years, and they are probably the ONLY tools on the job that haven't hurt someone (or me). The only fai lures of my compressors have been motors, compressor heads, regulators and only one tank failure. The tank failed because it was heavily dented, then when the inside crease of the dent rusted and had a slow leak after a few more months it was done.

It may be another of my many shortcomings, but I just don't see a compresso r as a source of a catastrophic failure. I work around them all day long, s ometimes with two or three working at the same time. I think I am the only one that drains their tanks regularly, and certainly the only one that chec ks the oil on the oil splasher regularly. Still... no dramatic failures.

Until this thread I never thought about the compressors as more then routin e maintenance items, tools that occasionally wear out.

Robert

[OFWW]

Although it might be wise to do this with an empty tank.

[OFWW]

I see what you mean.

On mine the air pressure forces it out. The tube ends right near the bottom of the tank, below the water line, so to speak. I have seen several commercial systems that way also. Horizontal tanks with the drain screwed in the center of the Bell end. Although normally the come out of the bottom of the tank like you would expect.

I checked some other models and they were all basically like yours, My guess is that it is to maintain as low a profile as they could.

[DerbyDad03]

s. Several different types of saws, nail guns, trim guns, drills, drivers, hammer drills, portable table saws, heavy duty grinders, cutting torches, chain saws, portable metal bandsaws, etc., etc., etc. are of great concern. The air compressor, not so much.

ly the ONLY tools on the job that haven't hurt someone (or me). The only f ailures of my compressors have been motors, compressor heads, regulators an d only one tank failure. The tank failed because it was heavily dented, th en when the inside crease of the dent rusted and had a slow leak after a fe w more months it was done.

sor as a source of a catastrophic failure. I work around them all day long, sometimes with two or three working at the same time. I think I am the onl y one that drains their tanks regularly, and certainly the only one that ch ecks the oil on the oil splasher regularly. Still... no dramatic failures.

ine maintenance items, tools that occasionally wear out.

Thus my subject line. I think there is a lot less to this "better drain the m every time or we're all going to die" warning than one would be led to believe by reading the label s. If it really were a given that they are going to rust and kill people, they wouldn't be allowed to design them like my PC unit that can't really be drained completely by using their suggested "tilt" process.

I'm sure not going to lose any sleep over this.

[Jack]

I'm with you on this. I have had only one compressor over the last 40+ years and I got it used, but I rarely to almost never drain it. It's a

30 gal, not portable one and I have a filter for water/oil/dirt. The filter never has water in it, and when I drain it after years it had a some water, not all that much.

Also, I never saw or even heard of a compressor exploding, or even popping a hole, and I've been around them my entire life. Also, I know that draining out the water will not dry out the tank, and damp mixed with air rusts. Under water doesn't rust near as much as damp does, because water doesn't hold much air, so I wonder about all this draining, at least in non-portable tanks.

And, even if I'm all wet and just lucky, I agree with the derby dude that if they were all that dangerous, Big Brother would require a license to sell, buy or use them, and people like me would be blowing ourselves up on a daily basis.

[Leon]

Again, it is about helping to prevent water from entering the hoses and tools.