Compressor Drain

[Michael Gabbay]

Well after reading the post the other day about a blown compressor, I made it a number one priority to run to HD and pick up a 1/4" street ell, 1/4" x 4" brass pipe and a 1/4" ball valve. This afternoon when I got home from work I installed it. It was about 15 minutes worth or time and OH WHAT A DIFFERENCE! :)

Now draining the tank is just a quick turn of the valve for about 10 seconds or so. This is a MUST do for all compressors.

I'll post a pic as soon as I can.

Mike

[Ernie Hobbs]

Yeah, after that post, I went out and drained my 10-year-old Devilbiss compressor for the first time. The sludge that came out was very nasty. Any advice about how to clean the tank out really good?

[Michael Gabbay]

Here's the pic.

[Don Baer]

Every time I read one of these posts I say to my self "Self, you REALY REALY need to o that next time you are in the shop", Then I forget. Going to make sure it gets drained tonight.

:rolleyes:

[Steve Clardy]

Yep. MInes been that way for several years now. I have a hose on it too, directing the water under the rollup door. I TRY to remember to drain it daily, as it runs a lot.

[Mike Stanton]

:D I open my drain every night and drain water ultil it stops then close it. I don't thinkit is nessary to drain all the air. Then next time it is easyer to fill it. Mike

[Dale Thompson]

Michael,
You have started an excellent thread in terms of the safety of compressor tanks and pressure tanks in general. There are a number of federal (CFR)codes on the testing and retesting of pressure vessels. These can be quite cumbersome and expensive. :(

On the other hand, there are ways of performing very simple and "free" tests on your tank to get a general idea of its condition. Perhaps the best and easiest of these is referred to as the "ring" test. Simply tap your tank with a small metal hammer. If you get a "ringing" sound, the tank should be OK. On the other hand, if you get a "dull thud", the interior of the tank is seriously corroded and you will place "life and limb" in jeopardy by applying pressure to that tank. :eek: Even draining your tank on a regular basis is not necessarily a guarantee that your tank will maintain its structural integrity. Corrosion will attack a "corrosion point" in the tank and the water vapor left, even after a "drain", will not curtail that attack. A "salt water" environment can quickly accelerate this problem. :eek:

The CFR (Code of Federal Regulations) normally requires a hydrostatic test at 5/3 of the intended MAXIMUM operating pressure of a tank. Obvious external corrosive "pitting" and failing the "ring test" disqualify the tank from being rehydrostatically tested. :(

My point is, be careful with ANY pressure vessel. They are all potential rockets or bombs. ;) :)

Dale T.

[Dale Thompson]

A tank that is frequently pressurized and depressurized is much more likely to fail than a tank that is under pressure on a constant basis. It's called "metal fatigue". I would suggest that the former is quite common with a home or small shop compressor. ;) :eek:

EGADS!! Now I know why I use a bicycle pump to run my framing nailer and other pneumatic tools! :eek: :D ;) :) YEAH RIGHT!! :cool:

Dale T.

[Randy Meijer]

Seems to me that no matter how often you drain your compressor that there will always be some moisture left in the tank. Do compressor manufacturers coat the insides of the tanks with rust reisitant coatings or do we just have to expect that our tanks will rust out sooner or later?? I'ved seen posts about folks who have had compressors for 20 years.......how much of a problem is a rusty tank. In the real world can we expect the compressor to fail before the tank rusts out?? Is there something that could be put in the tank to reduce the rust problem??

[Bill Lewis]

Randy,

Being one that had to replace a tank on a compressor (bought it used) I can tell you that It is very doubtful that the manufacturers are doing anything to the inside of the tanks. The replacement tank I bought (www.mscdirect.com (http://www.mscdirect.com/)) was primed on the outside, and bare metal on the inside. I suspect that this is the same condition that the manufacturers receive them too.

I considered coating the inside, but I couldn't decide if that was a good thing to do or not. It could lead to the coating flaking off over time, and getting in to the lines, or the drain.

BTW, I found out later that my compressor was built in 1967, and yet it had an ASME standard tank which was a direct replacement and a perfect fit. You gotta love standardization! Oh, and yes I really need to remember to drain my tank this weekend, thanks for the reminder!

[Bruce Overholt]

Interesting thread. Right now I own a PC Pancake Compressor. I bought it because of the free finish nailers that came as a kit with the compressor.
However, I have come to find that I really use my compressor a lot for blowing saw dust off tools and out of my garage. I will eventually would like to to get a larger stationary unit.
I realize the the pain in draining a large tank daily. I often wonder at what point or tank capacity that one might stop thinking about draining the tank daily?
Just a thought...

Bruce

[Kirk (KC) Constable]

I have the 60 gallon PC. I drained it for the first time in a long time a couple weeks ago, and got an alarming amount of water out of it (coffee can full). I checked it yesterday and got nothing. It stays full of air and seldom cycles, so I suspect that will limit the amount of water. I'm gonna try to remember to open the valve every week or two in the future.

KC

[Jack Wood]

I have an old old old compressor and after reading this thread I went out and drained it and yuck! There was what appeared to be oil mixed with the water, that can't be a good thing can it?:rolleyes: I guess that the pump is failing and letting in oil to the tank? Oh well, I'll show this to the wife and tell her I just gotta replace this death machine before someone gets hurt:D Any suggestions on a repalcement? I don't spray paint, I just use it to run a brad nailer and blow dust out.

[Aaron Montgomery]

I did this back in '03. I can tell you that the compressor gets drained a whole lot more than it used to. (never) I've got a clear plastic drain hose (from the furnace humidifier project) that goes into a Gatorade bottle. Makes it real easy to see what comes out of the compressor.

http://home.insightbb.com/~apmonte/Graphics/WoodShop_27.jpg

[Michael Gabbay]

Hey I'm gald I'm helping to bring the compressor safety issue to light. I also have wondered why manufacturers don't coat the inside with a corrosion resistant membrane. I doubt the cost would be all that much.


My next modifcation is to build a cabinet around the tank so in case there is a failure, it will help reduce the impact to those around the unit. I keep my compressor in the garage and have an air line running into my basement shop.

Mike

[Bryan Somers]

Michael

You did the very thing I would all but beg the install team at my last job to do. I had to go in behind them and service the stuff, makes it much more convenient.

[Dale Thompson]

Do compressor manufacturers coat the insides of the tanks with rust reisitant coatings or do we just have to expect that our tanks will rust out sooner or later?? ?

Randy,
The latter is probably and hopefully true. For example, why don't we see any more of those shops that will "rustproof" your new car and why did all the manufacturers "void" your "rust" warranty if you had your car "rustproofed"? :confused:

The reason is that corrosion will "focus" on any unprotected area - even if it is the size of a pinhead. This focus will penetrate the base metal far faster than if the entire tank or car parts were left unprotected. :eek:

In most cases, you are better off with a tank that has not been "rustproofed" than you would be with a "rustproofer" who was having a "bad hair day", if you know what I mean. ;)

Relax, Randy, your tank will last longer than the compressor motor but don't forget to give it an ocassional "ring" test! :)

Dale T.

[Dev Emch]

Couple of points.

1). I did run accross a metal-head who had a large 80 gal compressor explode in his shop. He was at work when this happened and you could see all the studs showing through the dry wall! The walls looked like the wings off a world war one fighter plane or the wright bros plane! The garage door was totaled. A number of folks speculate that had he been in the shop during this event, he may have been killed.

2). A bunch of us are sworn supporters of quincy pressure lube pumps. All of us bought ours used at auctions and this pump will outlast a few tanks. As you begin to utilize older, well made american pumps such as quincy, devilbliss, denver-gardner, worrthington, etc., you will find that these things were built to last and frequenly will outlive the reciever tanks. Newer pumps as found on compressors at home depot, etc. will not. But these are cheap enough to just toss when you wear one out.

3). Here is a question for all you tank experts. Most vertical tanks have drains on the bottom. My horizontal 120 gallon tanks does not. Does anyone have any ideas on how to install a bottom drain on a tank like this?

[Steve Ash]

Randy Meijer's post about lining the insides of a tank got me to thinking what the scuba tank industry did. When I first started diving (1973) the tanks were all made of steel... and we were required to get them hydro tested frequently. Then they came out with a plastic liner to fit the inside of the tank kinda like a baby bottle liner. This didn't last too long, however they came out with aluminum tanks and that is what they are all now made of....we still need to get them hydro tested and visually inspected, but since aluminum scuba tanks can withstand high pressures what would be wrong with aluminum air compressor tanks? Just a thought.

[Jim Knauss]

What I do for my compresser is leave the drain vale open just a smedgeon, ( thats a little :) ), and it self drains. The air all leaks out eventually, but I figure it will be stale by the time I use it again anyway. :)

Works for me,
Jim Knauss

[Dale Thompson]

[QUOTE=Dev Emch]Couple of points.

1). I did run accross a metal-head who had a large 80 gal compressor explode in his shop. He was at work when this happened and you could see all the studs showing through the dry wall! The walls looked like the wings off a world war one fighter plane or the wright bros plane! The garage door was totaled. A number of folks speculate that had he been in the shop during this event, he may have been killed.

Dev,
I've seen the inside of a pickup truck where a very small high-pressure vessel (about 2" by 12") exploded due to the heat buildup. :eek: The small cylinder looked, as you say, like a warped airplane propellor. The upholstery, dashboard, and all other fabrics were shredded like they had been through a meat grinder. The amazing part was that there were no broken windows in the cab. The owner was not in the truck at the time or he would have been ground Chuck - even if his name had been Bill! :eek: :) Am I sick, or what? :confused: :cool:

Dale T.

[Chris Padilla]

3). Here is a question for all you tank experts. Most vertical tanks have drains on the bottom. My horizontal 120 gallon tanks does not. Does anyone have any ideas on how to install a bottom drain on a tank like this?

Dev,

Seems to me you could simply drill a hole in the tank and tap it with a pipe thread so that you could screw in a brass nipple (1/4" is probably a good size). Now, of course, I do not know how thick the wall of your tank is.... Take a close look at the drain on a vertical tank compressor and see if that gives you some ideas.

[Dev Emch]

Chris...
My biggest fear is that you need to weld on an extra section of steel to hold the threaded hole. Look at all the threaded ports on the current steel tanks. They are all like that. I think if I go that route, I will be paying someone to hydro this tank. But you really do need to have a drain in the bottom of the tank. I just dont understand why this large tank has no nipple ports on the bottom. Plenty on the sides and on the top, just none on the bottom. Its also set to run at 175 PSI. I certainly do not wish to have a 120 gallon tank with no drain and a 175 PSI operating pressure in the same building in which I am working!!!!!

On another similar topic. Did you guys see the Power Tool Nationals on TV a while back? One guy who was trying to win the super modified category came up with the following entry. It was a large oxy cylinder mounted on a sled with wheels. The idea is to gas it up to full capacity and then when the green like blinks, take a 20 pound sledge hammer and whack the nipple valve with extreme prejudice. Cetainly he would have had the best time; however, in the end, the judges decided not to let him enter. Something about safety...

[Bruce Page]

Dev, It’s probably not a good idea to drill & tap straight into the tank like that. I would be surprised if the tank head wall thickness is any more than 1/8” thick – if that. A standard ¼-18 NPT would only give you a hair over 2 threads to screw into. You would be much better off finding someone that could weld a steel nipple that has been drilled & tapped onto the tank. A good 1/8" fillet weld would be plenty strong.

[Randy Meijer]

....Relax, Randy, your tank will last longer than the compressor motor but don't forget to give it an ocassional "ring" test! :)

I'm not overly concerned; but do want to take all "REASONABLE" precautions. As a SCUBA diver of many years experience, I have seen what a failed high pressure vessel can do and would like to avoid such an occurrence in my shop!!

Stopped off at H/D tonight and picked up the hardware to install a "ball valve" on my little compressor.....cost right at $10. The valve was the big item at $6.50.

As to putting a drain in that 120 gal tank, first thing I would do is contact the manufacturer. Maybe one of those side ports has a tube that runs to the "bottom" of the tank and will drain it without the need for a tap on the bottom?? Other area of concern is that adding a new port would almost certainly void any manufacturer's warranty. And finally, I would probably want to find a welder who is certified to weld pressure vessels.....this is not the kind of job I would farm out to my neighbor and his Sears welder!!!

[Christian Aufreiter]

Hey I'm gald I'm helping to bring the compressor safety issue to light. I also have wondered why manufacturers don't coat the inside with a corrosion resistant membrane. I doubt the cost would be all that much.


I'm not familiar with the compressor offered in the USA. But here, in Europe, some brands (for example Kaeser, Schneider etc.) coat the inside of their compressor tanks.

Regards,

Christian

[Jimmy Walker]

[QUOTE=....we still need to get them hydro tested and visually inspected, but since aluminum scuba tanks can withstand high pressures what would be wrong with aluminum air compressor tanks? Just a thought.

Steve I think the very reason they don't is what you said. Ya gotta have 'em checked and re-certified ever so often. Aluminum does have a few issues.
I think being knocked around in the shop would be one. Aluminum IMHO has a better chance of stress type wear that steel.
I think cost is more than likely the biggest reason. Most tanks I'm sure are made overseas and steel is just cheaper.
As far as draining the tank, I have always drained mine every time I'm through with it. Back in the '70s when I twisted wrenches for a living it was SOP to drain the compressor when we left for the night.
I have 2, a pancke and a 20 gal upright. I only "keep" air in a portable tank. Where I live it's the life of the tank to drain it.

[Dale Thompson]

Dev, You would be much better off finding someone that could weld a steel nipple that has been drilled & tapped onto the tank. A good 1/8" fillet weld would be plenty strong.

Bruce,
I agree 100% with your design concept. May I add that the welded tank should ALWAYS be hydrostatically tested after any welding. As you know, the heat of welding anneals (softens) the surrounding metal and any tank failure should occur between 1/2" and 1" of the weld. According to UL and the DOT, any failure at the weld or significantly remote from the weld are categorized as either weld failures or material failures. Neither are acceptable on a production basis. :eek: Just a thought!

Dale T.

[Bruce Page]

Bruce,
I agree 100% with your design concept. May I add that the welded tank should ALWAYS be hydrostatically tested after any welding. As you know, the heat of welding anneals (softens) the surrounding metal and any tank failure should occur between 1/2" and 1" of the weld. According to UL and the DOT, any failure at the weld or significantly remote from the weld are categorized as either weld failures or material failures. Neither are acceptable on a production basis. :eek: Just a thought!

Dale T.Dale, I agree with you that the tank should be tested hydrostatically, particularly if it is an older tank that could have substantial internal rust and pitting. I also think that finding a welder that is ASME Pressure Vessel Certified is overkill.
If it were me, I think I would find a replacement tank from Grainger, MSC, McMaster-Carr etc.
JMHO

[John Cavanaugh]

Just in case anyone is looking for a kit for doing this.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=46960

I just bought one the other day but havent had a chance to install it yet. For $16 I figure its a pretty cheap investment for not having a tank blow up.

--
John Cavanaugh

[Chris Padilla]

John,

I don't get it...how is it automatic? They don't give much info on the site....

[John Cavanaugh]

John,

I don't get it...how is it automatic? They don't give much info on the site....
Chris,

I believe what this does is.

- At some interval (I think its something like a 10psi drop) it automatically squirts some stuff out of the drain.
- Apparently this keeps water/sludge from collecting at the bottm.
- Im not fully clear, but this *may* allow you to not have to fully empty/drain your compressor daily

--
John Cavanaugh

[Chad Pater]

Just in case anyone is looking for a kit for doing this.

http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?itemnumber=46960

I just bought one the other day but havent had a chance to install it yet. For $16 I figure its a pretty cheap investment for not having a tank blow up.

--
John Cavanaugh

MY question is always...for 16 dollars why isn't this come standard with all new models??? If they charge us 16 they could put it on for 5-10 dollars?
Chad

[Jerry Bittner]

Harbor Freight has a relatively inexpensive automatic drain. It operates off the unloader line of your compressor. Cost is around $15 and installation is relatively simple.

Another easier solution is to visit the orange box and get a "soft seal" drain valve. It replaces the existing drain valve and you no longer need the pliers to open it.

[Bill Lewis]

Dev,

You don't have to modify your tank to add a drain. However if you were, you would have to weld a bung to the tank to accept the thread.

The solution is really pretty simple. Use a dip tube. Using an existing fitting on the side of the tank, use the proper reducer busings. Add a brass fitting that has a compression fitting and use small diameter (1/8"), soft copper tubing to extend inside the tank and bend it down to the bottom. Angle cut the end of the tubing to keep it from sucking itself to the bottom of the tank. Lastly, make sure that the tank has some slope to the end with the dip tube.

[Dev Emch]

Thanks to all who considered my dilema on the tank drain. What I found was the ASME tag indicating that my tank was made in 1971. Boy that tank has seen some service. Good thing we dont have very humid air out here.

But in examining the tank more, I found that there is a very tiny 1/4 or 1/2 inch bung on the bottom of the tank just to the right of the right leg assembly. And there is a tiny cock valve. Rather cute little thing actually.

So my tank does have a drain. I was just not looking in the right place.

Now I need to find out if the tank is still valid or if it needs to be replaced. I checked out the cost of a new 120 gallon horizontal tank. Looks like $650 bucks. OUCH!

[Keith Outten]

A 20 gallon air tank can totally destroy a two car garage.

ASME vessels are built to very strict standards, the welds are generally Nondestructively Tested and the vessel is always hydro tested by the manufacturer. Draining your air tank regularly is an absolute necessity to keep any liquid from degrading the bottom of the tank.

What many people don't know is that many tanks rupture when the welds that attach the compressor base plate to the tank fail. The cyclic vibration from the motor and compressor can cause the fillet welds to crack. When this happens the crack probagates into the tank and it explodes. When you service your air compressor take a very close look at all the welds that connect the mounting plate to the tank. If you have any doubts use paint remover to remove the paint so you can see the bare weld, you can paint the welds again after inspection.

When in doubt call someone to check your tank or take it to a professional.

While we are on the subject don't forget to replace the relief valve on your home hot water heater every few years. This is particularly important for those of you who have boilers that heat your home and provide domestic hot water.