When to replace air compressor tank.....

[kevin.decelles]

I have a 60gal air tank bought ~2006 from House of tools. Recently the ball valve started to leak (the lines pressurize over time with the valve 'closed'). I replace this yesterday.

While I had it off, I stuck my finger in the tank and fished around. It was 'damp' and had a rust residue -- which I anticipated given the time. I have one of those auto-moisture solenoids on this unit so it is bleeding water automatically.

The question: When would it be prudent to replace the tank? I've seen people replace it because of insufficient CFM, burned up motors.......

Assuming that the filter(s) upstream capture any particulate/moisture, is there concern? Or is the concern more corrosion/tank-failure (has anyone ever heard of a tank failing?)

 

[cuslog]

I have a 60gal air tank bought ~2006 from House of tools. (has anyone ever heard of a tank failing?)

I believe there's several youtube videos - mostly tire explosions but I seem to remember seeing a couple of compressor tank explosions - look quite violent.
When is the right time to replace, I really have no comment - just because I'm as guilty as anyone of putting off replacement for $ reasons (and forgetting to drain for long periods of time).
I've been nursing along an old 2hp Craftsman for several years now - its probably from the '70's. I've never had one blow up and I think that in the Western (relatively dry) climate and with draining once in awhile, you're probably OK.
The old Craftsman is getting rather loud though and I have been looking at the new "quiet ones" - but then there's always something else I'd rather spend the money on.

 

[historicalarms]

Yes air tanks can become very unstable, even the thicker air brake equipped transport trucks have been known to rust completely through in time. They are particularly susceptible to condensation build up, air from the engine mounted compressors is very hot and the air is deposited into tanks that are open to the weather changes of travel. They all have daily drain petcocks but i have worked with guys that go weeks without draining....they think of it when the tank volume for air supply drops to an "almost no breaks" situation.
Small shop compressors in a controlled environment will create less condensation but the tank itself is usually a much weaker holding tank.

One thing my old man discovered years ago...when his brother in law tells him not to use an old hot water tank for a makeshift much larger air tool holding tank (60 gal tank)....don't do it. That tank worked for a couple of years with us working around it's position in the shop a lot ....but one day, luckily we were both outside, that tank spit with a full charge...shook the 40x48 building a bunch and the blast of air escaping through the door cleaned the shop floor quite nicely. If you've ever blew up a bicycle tire when you were a kid, multiply that by a multitude of ten or so.

 

[Brent H]

Hey @kevin.decelles - a 2006 tank holding about 150 psi?

if you are concerned you can get the tank hydrostatically tested to 25% above working pressure and see if you have any leaks - or do it yourself- I would think, however, that if you are auto draining and have just a bit of moisture/rust you will be fine for many more years.

You could also scope the tank and look for any visible deep pitting.

 

[CalgaryPT]

I think these are one of those threads where most of us have a hunch, but none of us are true experts. We all look at it through the lens of our own experience. I too have seen the videos of catastrophic failures. However, these are not the norm. When I worked out at the old NOVA Service Centre in the 1980s the guys there told me they discarded tanks at any sign of failure. They said they tend to develop pinhole leaks first and that complete failure along the weld seams that split the tank were rare.

I knew a guy once who flushed his tank every few years with CLR to clean the inside walls. I'm not sure if he is (was?) a Darwin Award candidate. I would think in the same way that rust provides some degree of protection to unpainted light standards, the same may be true of tank walls. Also, I always wondered if horizontal tanks rust faster because of the increased surface area contacting water, but I'm not sure. Additionally, I recall reading a thread somewhere where a guy swore up and down that a constantly pressurized tank lasted longer than one left empty and charged up and down throughout its lifecycle. Can't recall if he was some sort of expert, or just another guy talking out his bum. I guess the logic would be similar to the forensic engineering findings about the original Comet airplane where they discovered that the pressurization cycles were causing cracks in the plane itself. I dunno.

My experience more recently is with a Campbell Hausfeld 60 Gal Single Stage. It's the largest I've owned in my life. I got it in 2012 I believe (judging by my first oil change noted on the maintenance tag in 2013). I change the oil every year, and replace the pressure relief valve every 3 yrs. or so. I tried at least three different automated drains, including a fancy one I controlled with an Arduino circuit I built. None worked reliably past a few months. Eventually I replaced the cheap stock petcock with a right angle brass elbow, about a foot of pipe, and a good ball valve. This makes it easy to drain regularly (so you'd think I'd do this right?). I can even rotate it with my foot instead of getting down on all fours. This is especially nice as my knees have bone chips in them from the days when a Big Mac was a hamburger instead of a sandwich, BMO was called Bank of Montreal, and the nearby KFC franchise was called Barney's Kentucky Fried Chicken. So...yeah, a long time ago.

@kevin.decelles ' post reminded me to do some maintenance, so I just drained mine. (Thanks Kevin.) For a 10+ year old tank the water still looks not bad, although a few years ago I recall some really nasty stuff coming out. I drain mine several times a year, usually spring and late fall, and clean the air filter. I plan to use this compressor until it shows signs of failure. But for now it seems to be just fine. I can't see myself going through the trouble to have it tested. If it makes it to 20 years, I may just replace it with a new one instead.

 

[Tom Kitta]

Tank explosions are very, very, very rare. Usually it just starts leaking 99.99% of the time, then you need to replace it.

Proof (by contradiction):

Imagine that most of the time when tank is old it explodes, say even 50% of the time. Since compressors are very common in North America we can assume that there are at least 30 million compressors that are at least 20g. That would be less then 1:10 vs. pp. And at least 10 million 60g tanks (again less then 1:30).

With so many compressors around you can safely say that for 60g units about 500k reach 20 year mark every year. With 50% explosion ratio that would mean... 250k of them would go off! and that is just the larger ones.

Certainly with 100s of thousands of compressors exploding there would be 100s if not 1000s people hurt or dead! Every year! in just US!

With such a huge danger to health compressor tanks would not only be "regulated" they would certainly have "explosives" sticker on them and stern warnings. It probably would be illegal to even have a compressor tank more then 10 years old. There would be stern regulations regarding testing, possible certifications every 5 years etc.

-------

A lot of things have to go wrong for the tank to split open in explosive way - usually a large area is rusted through and very, very weak, thus as leak happens it is strong enough to tear remaining metal apart and do a split.

This is why instead of 1000s of tanks exploding all the time we get few videos of this happening.

 

[cuslog]

"With such a huge danger to health compressor tanks would not only be "regulated" they would certainly have "explosives" sticker on them and stern warnings. It probably would be illegal to even have a compressor tank more then 10 years old. There would be stern regulations regarding testing, possible certifications every 5 years etc."
SSSShhhhhh !! Jeez, don't give them ideas, then we'd have to take a course, get licensed, have them re-certified every few years.

 

[RobinHood]

Hydro test the tank if you have concerns - the only sure (& safe) way to know. Just my 2c.

 

[cuslog]

Just wondering: Do any / all of the industrial / high grade compressor tanks have a liner or epoxy coated interior, or stainless tanks ?
I would have thought that some kind of epoxy coating of the interior wouldn't be that expensive to do ?

 

[Brent H]

We do on the ship - hydro test every 10 years, annual visual and safety valve check. Can be worse for higher pressure tanks. Our tanks are used for both service air and engine starting -
The engine starting being the regulation requirement. Tanks are blown down every watch by the Oilers/engineers do at least 2x a day. The tanks are built - overbuilt - compared to a “shop” type air compressor tank. It take a long time (like 60 plus years) to see anything abnormal provided the tank is maintained (like internal epoxy coated for corrosion resistance).

Our tanks on the ship are running 450 PSI - that is lots. Typically it is only in the 150 range for most ships. The engines need 19 bar (285 psi) minimum to turn over and we have 4 - some voodoo math for CFM and we need at least 27 bar in the 2 cylinders we have.

anyway gone off on a tangent -

Unless the tank is showing visual signs of corrosion on the exterior- paint blisters, pitting, rust etc. It should be A-OK. If you have knowledge of the tank sustaining damage, witnessed impact or there is dents etc in the tank, corroded fittings etc You should be fine - remember there is also a safety valve in the tanks to keep pressures well below the “boom” limit

 

[Janger]

Tank explosions are very, very, very rare. Usually it just starts leaking 99.99% of the time, then you need to replace it.

Proof (by contradiction):

Imagine that most of the time when tank is old it explodes, say even 50% of the time. Since compressors are very common in North America we can assume that there are at least 30 million compressors that are at least 20g. That would be less then 1:10 vs. pp. And at least 10 million 60g tanks (again less then 1:30).

With so many compressors around you can safely say that for 60g units about 500k reach 20 year mark every year. With 50% explosion ratio that would mean... 250k of them would go off! and that is just the larger ones.

Certainly with 100s of thousands of compressors exploding there would be 100s if not 1000s people hurt or dead! Every year! in just US!

With such a huge danger to health compressor tanks would not only be "regulated" they would certainly have "explosives" sticker on them and stern warnings. It probably would be illegal to even have a compressor tank more then 10 years old. There would be stern regulations regarding testing, possible certifications every 5 years etc.

-------

A lot of things have to go wrong for the tank to split open in explosive way - usually a large area is rusted through and very, very weak, thus as leak happens it is strong enough to tear remaining metal apart and do a split.

This is why instead of 1000s of tanks exploding all the time we get few videos of this happening.

I like your counter example 'proof' Tom. So question to members - has anybody had a tank blow up? Does anyone know someone whose tank has blown up (I mean you've seen the wreckage yourself in person)?

 

[phaxtris]

I have fixed a few compressor tanks as favors, they don't explode, just develop rust pin holes around the drain, then leak air...I would say it's time to replace once it has an actual hole you can't seal up with a few tacks

 

[CalgaryPT]

I like your counter example 'proof' Tom. So question to members - has anybody had a tank blow up? Does anyone know someone whose tank has blown up (I mean you've seen the wreckage yourself in person)?

Not me, nor do I know anyone who has had one blow up. I've probably owned 10 compressors in my life. Only one pin hole near a drain, as @phaxtris says. That was years ago...quick weld and no more problems.

 

[CalgaryPT]

We do on the ship - hydro test every 10 years, annual visual and safety valve check. Can be worse for higher pressure tanks. Our tanks are used for both service air and engine starting....

When Brent gets me a job on his ship one of my tasks will be to drain the tanks daily.

 

[Tom Kitta]

Also note that 450 PSI is around triple most shop compressor rated PSI of 150. Thus different rules will apply to these tanks.

Same as tanks for welding gases - which are to be tested every 10 years.

 

[RobinHood]

We had a pneumatic manure pump on the farm. There was a 240 gal tank and compressor (150 psi system). The tank lasted about 10-15 years in the very corrosive environment. They all developed pin hole leaks. We ran them until the leak rate was too large so the pump could not fill the tank in a reasonable time. They all corroded from the inside out. The compressor & tank were inside the barn and used the “dairy air”, not fresh air from outside. That for sure accelerated the internal corrosion. The tanks never blew up.

Mr Pete 222 “tubalcaine“ looks at a used compressor tank here:

And he has other videos where he examines the subject

 

[kevin.decelles]

Thx, you have echoed my thoughts. I bought several tanks at auction a few years back (60 gal) and cut one open. Rusty for sure but nothing that would give me pause


Sent from my iPad using Tapatalk

 

[Alexander]

Just wondering: Do any / all of the industrial / high grade compressor tanks have a liner or epoxy coated interior, or stainless tanks ?
I would have thought that some kind of epoxy coating of the interior wouldn't be that expensive to do ?

Some air tanks in manufacturing are rated for wet service. All of the wet service tanks I have seen were made of stainless steel.

 

[Perry]

This post reminds me of this youtube video.

He follows up with these two....

 

[Tom Kitta]

A tank should not fail on the weld. Welds should not fail - if they do it means the welding had a problem.

As you can see from a video of Tublecain his compressor tank lasted 40 years before pinhole leak.