Air Compressor Tank Explosion Danger

[roger55]

I have heard that when a compressor tank fails, it usually just starts leaking though a pinhole that develops. But, although rare, sometimes they will explode and do a tremendous amount of damage.

I have a Sanborn 5HP compressor that I bought new in 1989 or 1990.
So, it's darn near 20 years old. It's an 80 gallon tank and the performance numbers are 18 scfm @ 100 psi and 16 scfm @ 175 psi.
Just last month, I put a new electric motor and belts on it and it is working perfectly. I have drained the water on it fairly often and after hard use.

Should I be thinking about investing in a new compressor?

Should I be concerned enough to warrant having this compressor hydro tested? Doing this sounds like kind of a hassle. I don't know if there would be anyone in San Angelo that does this. If I had to take it to Dallas or Houston, I think I would just rather invest in a new compressor.

Or, should I not worry about it and keep using it until a breakdown and then consider a new one?

 

[Junkman]

Using a ball peen hammer tap around the bottom of the tank, and if it dents easily, then that is an indication that the tank is going bad. If you like the compressor, then just buy a replacement tank from a compressor company, or you might be able to take yours to them, and they will do the conversion for you. Why buy new when the old one just needs a new tank???

 

[nissan_crawler]

Personally, I wouldn't worry about it.

 

[Nealcrenshaw]

I wouldn't worry about it either,just replace it when it fails.I never heard anything about a tank exploding, the only thing that would happen is the air would leak out as the tank eroded.

Just curious, do you have any vents installed in that closet for air flow over the compressor when running it with the door close, or do you just keep the door open? if not, have you had any problems with it overheating? Seems like airflow would be hampered with the door close.

 

[Bolster]

My shop teacher filled my head with "explosion" stories too. First I saw some rust coming out when I vented the water I was distraught and figured I'd ruined the compressor. Sounds like this is a little overkill.

Are there any methods to cut down on rust in the tank, besides venting it regularly?

 

[bugdust]

Could smaller tanks be sealed inside with something like masterseries? It would be pretty hard to do with a larger tank I think.

 

[roger55]

Just curious, do you have any vents installed in that closet for air flow over the compressor when running it with the door close, or do you just keep the door open? if not, have you had any problems with it overheating? Seems like airflow would be hampered with the door close.

There is a window in the room on the right that you cannot see.
So, I can keep the door closed and open the window if I am going to be using a lot of air. Keeping the door closed keeps the noise and heat out of my shop.

 

[eschoendorff]

Personally, I wouldn't worry about it.

There are plenty of old compressors in auto shops that are in worse condition than yours - and keep on working.

Then again, you need to do what makes you comfortable.

 

[kartracer55]

Ill be honest, when Im around old compressors I do definitely get nervous, especially old portable air tanks that can not be drained. I know my husky portable air tank says discard by **-**-20XX, so I'd imagine there is some expected life span of them.

AS for replacing, tough call. Grainger sells a replacement tank for $716

 

[CatfishXpress]

I think you should get rid of that death trap and get a new one, I'll give you $50 bucks for the old one.

On a more serious note, I wouldn't worry about the compressor, but I would move the paint away from the water heater on the top shelf.

 

[Kevin54]

My cousin fixed his with JB Weld and has been working for years. I'm not going to swear by it, but I think the tanks exploding are a myth. If you develop a leak or pinhole, it will leak air. Take a tank past it's bursting point and it will explode. It can't explode if it's leaking, unless you pump is building it up at a really tremendous fast amount.

 

[383astro]

On a more serious note, I wouldn't worry about the compressor, but I would move the paint away from the water heater on the top shelf.

I second that

and what is that sticking out of the wall by the doorway just above the baseboard? drain for?

 

[Cobra4B]

How often do you guys drain the tanks? I've had my large craftsman compressor for 3 years now and usually do it 2x a year.

My father has an old craftsman on that's still going strong that he never drains... he's had it over 20 years.

 

[roger55]

How often do you guys drain the tanks? I've had my large craftsman compressor for 3 years now and usually do it 2x a year.

My father has an old craftsman on that's still going strong that he never drains... he's had it over 20 years.

Your dad might want to read this thread.
And the one I posted over in Hotrodders.com:

http://www.hotrodders.com/forum/compressor-motor-just-burned-out-today-150077.html

He might be in worse shape than I am in if never drains it.
When I worked at a shop as a teenager and went to drain their compressor, it was at least half full of water.
I don't think I've ever had more than a gallon drain out of my compressor.

It's probably best to drain the tank every day if used every day. But, I bet most people don't do that.
For a hobbyist, I would say once a week to once a month would be good.
However, if you are painting a car, I would drain it every day.

 

[Charles (in GA)]

A family friend many years ago ran a Hertz rental car franchise in our home town. In his shop he had a large old shop compressor, and one day, after a number of years, he realized that it ran frequently. Finally he realized he had never drained the tank, and it was nearly full of water.

Compressor tanks do occasionally explode violently. Its not the norm, but it does happen. A guy on another forum I visit said his did it one day when he was not at home, and only a short time after it had been discussed on that forum. He came home and found a hole in the roof where the compressor had blasted all the way up to it. Entire bottom weld gave way apparently. Compressed is very powerful, lots of stored energy, that is why you should not use PVC pipe for air plumbing, if it gives, there is lots of energy behind it to spread the pieces all over the place and injure someone. Think what happens when the valve on a 3000 psi cylinder gets knocked off, it goes off like a rocket. Air compressors, while not containing that kind of stored energy, have enough to do serious damage or injury.

That being said, I'm not going to go around worrying about it. If the compressor is old and hasn't been kept drained, you might consider pulling the large access plug that is in most of them (after releasing all of the pressure) and using a bright light to examine what you can see of the inside. That will give you some clue to condition. Its a shame that they don't slosh them with some kind of epoxy when they manufacture the tanks.

Charles

 

[tdkkart]

Any pressure vessel will fail if enough pressure is applied to it, the results of these failures are impressive and VERY dangerous, especially if the contents of the vessel are compressed. Compressed gases expand when they are released causing very large displacement of the gases. It's exactly like a bomb going off.

So yes, a compressor tank exploding will cause a BIG problem.

There used to be a tool vendor that visited farms in my father's area, came around one year showing off pictures of a compressor that someone had decided to modify for higher pressure. The compressor was something like a 20 or 30 gallon portable tank, originally had a single stage 125ish psi pump. The owner decided to put on a bigger motor and tank and then bump up the pressure. The first thing that happened of course was that it started popping the relief valve, so he removed the relief and plugged the hole with a pipe plug. 2nd thing that happened was that the pressure switch apparently failed to shut off the pump. The explosion was impressive, took a 8x8 ft chunk out of the corner of a pole building, all the way from the ground to the roof. Broke off the 6x6 corner post flush with the ground. Blew a 2ft deep crater in the gravel floor. The remains of the compressor were found nearly 200ft away, split open like an oyster shell. Amazingly enough, the tank was not rusty inside.

However, unless you somehow over-pressurize your tank far beyond it's designed capacity it is very unlikely to catastrophicaly fail. As has been said, the standard failure mode for a compressor tank is to corrode from the inside, which will eventually result in a pinhole leak.

I wouldn't worry too much about a compressor blowing up except for being overpressurized.

Water pressurizing is the safest way to pressure check a tank because water does not compress so the failure of the tank will be much less impressive.

Google "steam explosion" and you'll find some pretty impressive reports.

 

[rinny_tin_tin]

Any pressure vessel will fail if enough pressure is applied to it, the results of these failures are impressive and VERY dangerous, especially if the contents of the vessel are compressed. Compressed gases expand when they are released causing very large displacement of the gases. It's exactly like a bomb going off.

So yes, a compressor tank exploding will cause a BIG problem.

There used to be a tool vendor that visited farms in my father's area, came around one year showing off pictures of a compressor that someone had decided to modify for higher pressure. The compressor was something like a 20 or 30 gallon portable tank, originally had a single stage 125ish psi pump. The owner decided to put on a bigger motor and tank and then bump up the pressure. The first thing that happened of course was that it started popping the relief valve, so he removed the relief and plugged the hole with a pipe plug. 2nd thing that happened was that the pressure switch apparently failed to shut off the pump. The explosion was impressive, took a 8x8 ft chunk out of the corner of a pole building, all the way from the ground to the roof. Broke off the 6x6 corner post flush with the ground. Blew a 2ft deep crater in the gravel floor. The remains of the compressor were found nearly 200ft away, split open like an oyster shell. Amazingly enough, the tank was not rusty inside.

However, unless you somehow over-pressurize your tank far beyond it's designed capacity it is very unlikely to catastrophicaly fail. As has been said, the standard failure mode for a compressor tank is to corrode from the inside, which will eventually result in a pinhole leak.

I wouldn't worry too much about a compressor blowing up except for being overpressurized.

Water pressurizing is the safest way to pressure check a tank because water does not compress so the failure of the tank will be much less impressive.

Google "steam explosion" and you'll find some pretty impressive reports.

You would think that a working overpressure relief valve would prevent explosion. Also, a visual inspection with a light should indicate interior condition. Don't they hydro these like they scuba tanks, etc.

 

[tdkkart]

You would think that a working overpressure relief valve would prevent explosion. Also, a visual inspection with a light should indicate interior condition. Don't they hydro these like they scuba tanks, etc.

Theoretically a relief valve will prevent an explosion, IF it's sized right.
Look at the relief valve on your compressor, it's probably got 2-3 1/8" holes in it, and a smaller one on the stem inside. Do you suppose happens when this valve is on a 25cfm compressor?? If the compressor can over run the air leak the pressure will contimue to go up till something else gives up. Hopefully the motor will overheat and trip the breaker before the tank explodes.

I'd imagine a new tank design is hydro tested, and possibly some samples later, but I doubt that all are pressure tested when they are manufactured, especially the Harbor Fright specials.
Kinda spendy to test each one.

 

[rinny_tin_tin]

Theoretically a relief valve will prevent an explosion, IF it's sized right.
Look at the relief valve on your compressor, it's probably got 2-3 1/8" holes in it, and a smaller one on the stem inside. Do you suppose happens when this valve is on a 25cfm compressor?? If the compressor can over run the air leak the pressure will contimue to go up till something else gives up. Hopefully the motor will overheat and trip the breaker before the tank explodes.

I'd imagine a new tank design is hydro tested, and possibly some samples later, but I doubt that all are pressure tested when they are manufactured, especially the Harbor Fright specials.
Kinda spendy to test each one.

Gotcha ....given that these are low pressure receivers in relatively benign environments, maybe they don;t need periodic hydro. But now...don't these receivers come with a fixed blowout plug of some type in addition to the overpressure relief valve and set above the trip pressure of the relief valve?

Mine has a fixture set right on the receiver that I understood to be a blowout plug of some type.

 

[Cobra4B]

Well I just went out to drain my compressor after reading this. there's a warning on it about rusted tanks failing and to drain after every use.

The drain valve was a PITA to turn so I start turning it w/ vice grips... nothing.... so I take it all the way out... bad idea.... boom... hisss.... lots of air. I let the pressure down to 60psi before doing this. I think the water in the bottom of the tank is frozen... I left the vent screw out and will let it drain out.

I'm going to start draining it ever couple of weeks now.

 

[russlaferrera]

Cobra, In all this time you and your father never had water coming out of your air tools?

Now that you drained the tank , why don't you make an easier system to do this the easy way?

 

[Bolster]

How often do you guys drain the tanks? I've had my large craftsman compressor for 3 years now and usually do it 2x a year.

My father has an old craftsman on that's still going strong that he never drains... he's had it over 20 years.

Good grief! I drain my 20 year old 30 gal at the end of each day ... forgot ONCE and still feel bad about it...and yes, I get a little rust out of it now, even with my "faithful" draining.

 

[Cobra4B]

Cobra, In all this time you and your father never had water coming out of your air tools?

Now that you drained the tank , why don't you make an easier system to do this the easy way?

He never uses air tools... just uses it to fill up things w/ air and use the air hose etc. See my other post about my crappy Craftsman air tools not being able to break the lugs off of my vehicles.... thus I hardly use air tools either. I use it for the air supply and filling up tires etc. I do all of my wrench turning by hadn and w/ my kickass lithium battery powered drill. What's an "easier system" Is there something out there... I'm clueless.

 

[Uncle Buck]

As suggested drain daily, and I would replace the pressure popoff valve if I really did not trust the compressor. The popoff is your safety device to guard against the big BOOM, so take care of it.

 

[nissan_crawler]

As suggested drain daily, and I would replace the pressure popoff valve if I really did not trust the compressor. The popoff is your safety device to guard against the big BOOM, so take care of it.

I'll add to this, especially with the compressors some of us have on here...Be sure the popoff is rated for the cfm of your pump!!! I run two of them, because even with one popped, the pump would still pressurize the tank (according to the specs for the popoff).

 

[janarvae]

I drain my little 30 gallon C-Man almost after every use. Sometimes I'll let it sit overnight if I'm going to be using it the next day also. If you're having trouble twisting the drain valve, try some antisieze on it....

 

[J.A.F.E.]

Cobra, In all this time you and your father never had water coming out of your air tools?

Now that you drained the tank , why don't you make an easier system to do this the easy way?

I replaced the drain taps on my two little compressors with 1/4 turn ball valves. I needed a 90* elbow to clear the floor as the legs are pretty short on both tanks. But that also brings the valve out to where it's easy access.

~Steve

 

[Cobra4B]

When you guys drain them do you let the air out first or let it down to a specific pressure? Do you just let it hiss air until the water stops comming out or do you drain it fully each time? Just curious.

 

[nissan_crawler]

I just crack it open until water stops. I've never let the air out.

 

[dxdexter]

Do you just let it hiss air until the water stops coming out or do you drain it fully each time?

You should drain off the moisture daily (I do it when I remember). With a pressurized tank open the drain valve until the water stops flowing and air spurts out.

I only fully drained (intentionally) my compressor three times in the last 20 years. Once each to replace the drain ****,to replace the pressure switch and to replace the copper inlet line. Completely draining the air out of the tank on a daily basis is a waste of electricity and puts extra wear and tear on the pump.

 

[Bolster]

When you guys drain them do you let the air out first or let it down to a specific pressure? Do you just let it hiss air until the water stops comming out or do you drain it fully each time? Just curious.

My Devilbiss' instructions said to drain the H2O daily and to drain all the air out of the tank daily, too. So for years I did this (well, 95% of the time). But it really is a waste to let out all that compressed air, and build it back up the next morning.

So now, I drain all the air out only when I know I won't be using the compressor for a couple of days.

If I AM going to use the compressor again the next day, while draining the water, I let the pressure run down from 110 to 80 or 70, just so it isn't sitting under full pressure. More out of superstition, than any rational reason.

 

[shocksystems]

Explosions definitely happen. But I would agree with others, it is rare.

Someone posted a link like the following one here some time ago:

http://www.cdc.gov/NIOSH/FACE/stateface/ca/05ca010.html

What a terrible way to die.

You notice in the investigation they theorized it was the type of oil used in the compressor and not related to corrosion in the tank.

There are numerous other stories though. Here is a link to a google news search on the topic:

http://news.google.com/archivesearch?q=air+compressor+explosion&btnG=Search&hl=en&um=1

I think about this risk every time I look at my compressor. I am amazed that people sell Air Compressors on Craigslist regularly that they advertise as having a leak. I have seen them suggest "it just needs to be welded". That would scare the hell out of me. This scared me away from buying a used one.

Proper care of your compressor (draining the tank regularly and only using OEM standard oil) is probably your best protection. I have also heard that one of the reasons why compressor manufacturers insist on compressors being bolted to the floor is to reduce the chance of it flying in the event of a sudden air leak.

Jim

 

[Cobra4B]

Thanks for the education guys... I'll start draining the water out of mine after each time I use it and bi-weekley when not regularly in use.

 

[roger55]

I second that

and what is that sticking out of the wall by the doorway just above the baseboard? drain for?

The paint is moved. I just had it there temporarily. It's an electric w/h anyway.

That is a vacuum fitting for my bead blaster. I keep the vacuum on the other side of the wall so I don't have the noise in my ear.

 

[andrew86mcallister@gm]

How often do you guys drain the tanks? I've had my large craftsman compressor for 3 years now and usually do it 2x a year.

My father has an old craftsman on that's still going strong that he never drains... he's had it over 20 years.

I know this is super old, but you should drain it weekly at the very least. I do it daily and I don't keep it pressurized when I'm not using it.

I got an old craftsman compressor from an estate sale. It seemed awfully heavy, and took almost no time to fill, it was 40 gallons I believe. I noticed a tremendous amount of water coming out of my tools. SO I decided I should drain the tank. IT WAS HALF FULL OF WATER. I almost **** myself.

 

[seber]

If you do a search for catastrophically failed tanks you will find it is always the cheap sheet metal type. Stationary tanks are heavier wall and will develop small leaks rather than blow out. You can tap around with a ball pien hammer if it bothers you, but I wouldn't worry about it until it fails. Probably many decades from now.

 

[zendriver]

Not an engineer, but I'd think a tank would rupture by being over-pressured, more so than developing a leak.

 

[PCustoms]

Not an engineer, but I'd think a tank would rupture by being over-pressured, more so than developing a leak.

Well when the rust and pitting has reduced the wall to 25% and pinholes are starting, 50psi can be "overpressure"

 

[zendriver]

Well when the rust and pitting has reduced the wall to 25% and pinholes are starting, 50psi can be "overpressure"

I'm sure it's exactly the same.

Better relace the tank.

 

[tarbellb]

Best Fix for this -

1) Take the extra drops from your PVC air lines
2) melt them down to a slurry
3) fill the bottom of the tank

Boom, good for another 50yrs!