[Mr Anonymous]

i'm considering chaining mine to the barn post next to it

[hgerhardt]

Originally Posted by F ROCK

Air compressor explosion videos were popping up on my feed.
Wow. I drain my tank but not every time........ [snip]


Here's another that shows some aftermath of a different explosion.
https://www.youtube.com/watch?v=sm_FJ6Pat4I&t=60s

That 2nd video almost qualifies for a Darwin Award. What were they thinking re-welding that bung on the bottom??

I replaced the manual tank drain valves with solenoid valves on both of my compressors set up with a push button to energize. I purge them every time I turn them on and after I'm done for the day. Make sure you get one rated for the max pressure of the tank.

https://www.mcmaster.com/4738K138/

[KEN CROCIE]

Had a neighbor explode his horizontal tank. The end cap blew of, shot 50' into a telephone pole like a sharp edged discus.

[dataway]

That is a super trick drain valve .... might have to get me one of those.

[stuta]

WOW....I'm going to rethink my setup in the garage! I have to reach over mine to throw the wall switch off....yikes. My old girl is about 50 years old too.
30 gal. horizontal unit I got as a B-day gift as a kid. I normally drained the tank after each use, but I didn't the last two times cause my back was hurting : (
Excuse me while I walk out there now to open the valve...wish me luck

[dataway]

Was just looking through some of the data. Appears a high proportion of the explosions were small horizontal units, about 80% of the time the cause attributed to lack of maintenance (draining). I'd guess the horizontal tanks have the water lying in a larger area in the bottom that leads to more rust than you would get with a vertical tank. Some tanks exploded because people plugged the drain valves (because they were leaking). Some are not ASME certified.

Saw a LOT of no-name, cheap compressors in the pictures.

Just looked around ... not many of the small horizontal units are ASME certified, and the ones that are, are priced accordingly. Was thinking about replacing my old 5 gallon portable air tank with an ASME unit ... can't find one so far.

If I'm not mistaken any compressed air tank used in a commercial environment in the US has to have ASME certification.

[darbikrash]

Sort of a timely thread for me. I've been using a DeWalt 2 HP vertical that I bought new- it lasted about 4 months and the electric motor failed a couple of weeks ago. This shut down my 5 axis mill for about 2 weeks to get a replacement compressor. No more Home Depot compressors for me so I upgraded to a 7.5 HP Kaeser. It's interesting that the better made compressors go to great lengths to try and manage water in the tank, this one is a "dry tank" which means the dryer and refrigeration occur before the air gets into the tank- not after. Also, an automatic tank drain as well as a dryer condensate drain.

The day after the install, I was running my mill and listening intently to the cutter, and I thought I heard my front office heater kick on. Nope it was the compressor. I could barely hear it. Worth every penny right there.

One last thing, the better compressors epoxy coat the tank insides, which seems like a pretty good idea to me.

[stuta]

Originally Posted by darbikrash

Sort of a timely thread for me. I've been using a DeWalt 2 HP vertical that I bought new- it lasted about 4 months and the electric motor failed a couple of weeks ago. This shut down my 5 axis mill for about 2 weeks to get a replacement compressor. No more Home Depot compressors for me so I upgraded to a 7.5 HP Kaeser. It's interesting that the better made compressors go to great lengths to try and manage water in the tank, this one is a "dry tank" which means the dryer and refrigeration occur before the air gets into the tank- not after. Also, an automatic tank drain as well as a dryer condensate drain.

The day after the install, I was running my mill and listening intently to the cutter, and I thought I heard my front office heater kick on. Nope it was the compressor. I could barely hear it. Worth every penny right there.

One last thing, the better compressors epoxy coat the tank insides, which seems like a pretty good idea to me.

That's an awesome setup!
Definitely a case of "you get what you pay for"....at least in this case : )

[dataway]

Yep, the only way to go is dry the air before the tank. My whole setup is based on that principle ... and more separators and filters after the tank too. Haven't gotten a drop out of the tank vent since I made these modifications to a new IR compressor.

Is that Kaeser a rotary?

[SRR]

https://www.youtube.com/watch?v=x-hL_s0-KR4

[flyingn]

always drain my steel ones and have an aluminum tire filling tank so i dont worry so much about that one

[Greg Reid]

Well, that's scary..I have that exact compressor and it's at least 20 years old. It has already developed a pinhole in the bottom from rust. It stopped itself back up which suggests to me that there's a significant amount of rusty sludge down there.
I need to find a good tank for it...but where can you purchase just a tank?

[242177P]

Originally Posted by F ROCK

...

Here's another that shows some aftermath of a different explosion.
https://www.youtube.com/watch?v=sm_FJ6Pat4I&t=60s

[dataway]

Places like Northern Tool sell ASME rated tanks .... probably $5-600 for a 60 gallon. If you have a good compressor head it's worth replacing the tank. If you have a old rebranded compressor probably makes more sense to just replace the whole thing.

Most of the store brand stuff is all made by the same companies with slightly different options and different paint. When you get up to around $1600 (5hp, 60gal) you start seeing a better quality compressor, but still typically India made compressor head, US ASME tank. Around $2000 you start getting into some US made compressors, same tanks as the $1600 compressors ... but better compressor head, maybe even US made. Names like Quincy etc.

I've been real happy with my IR. It's one step above store brand, and rated as a "commercial" compressor, but certainly not the quality of the old US names, has the typical India produced cast iron pump.

[Ben M.]

Originally Posted by darbikrash

This shut down my 5 axis mill for about 2 weeks to get a replacement compressor. No more Home Depot compressors for me so I upgraded to a 7.5 HP Kaeser.

We used Kaesers at work for a variety of applications, they are on a completely different level than the Homey Depot Chinesium stuff you buy for $300-500. Lots of engineering went into them, they also will service them for you on the regular according to schedule if you use them often enough (as we did running a cryo-plant). It 100% is a case of getting what you pay for. You're more likely to have problems with the controls hardware than the motor or pneumatics on one of them.

[mgarblik]

Title of thread is drain and inspect compressor tank. I think the drain part has been pretty well covered and I appreciate the ideas for auto drains and drying the air. How about inspecting the tank before it explodes? Obviously, perforation on the outside or a rough surface or a tiny leak is a ticking time bomb. Any other suggestions for a more routine inspection of the tank? When I drain my tank, rusty water always comes out, but if the tank is un-painted, untreated, that probably doesn't mean much.

[dataway]

Not much you can do except pull a plug and use a remote inspection camera.

Not sure what kind of drain setup you have, I use a full 1/2" NPT with a ball valve ... the ball valve is key ... you can whip the valve wide open and see if it carries particles of rust out with the water mist .... might want to run the pressure down low before doing this.

If you see flakes of rust coming out you are probably in the danger zone.

[mgarblik]

My compressor is old. But a 80 gallon ASME tank, 2 stage, sold by Grainger. Dayton brand, manufactured by Campbell Hausfeld. The drain is a ball valve, but only 1/4" NPT. Too small to get my camera into. Plus you would be going up through the bottom and probably not be able to see the real rust area. Possibly I could put a camera through the outlet of the tank and look down toward the bottom. The outlet is 3/4" NPT.

[Sirrotica]

This is taken from the site, Practical Machinist, and is the opinion on older air receiver tanks from a mechanical engineer. This is the link to the whole discussion, which is quite lengthy. It covers air tank failures on all types of equipment, including the air cannons used in the Punkin Chunkin competitions:

https://www.practicalmachinist.com/v...eplace-384769/

We've had quite a few threads on this 'Board discussing used/old air tanks. As a mechanical engineer who has spent a portion of his career dealing with pressure vessels including old/historic steam locomotive boilers, my professional opinion is: do NOT take a chance on an antique air receiver. Scrap it. Make a planter or water trough out of it, but do NOT use it as an air receiver.

In evaluating boilers or large industrial air receiver tanks, the matter is a different story. The boiler or industrial air receiver is large enough to be entered in most cases. Ultrasonic thickness gauging (UT) will tell a part of the story of a tank's condition. UT is applied to finite points on a tank shell. It may miss a localized thinned or pitted area. Similarly, a hydrostatic test may not tell the whole story. Tanks or pressure vessels are normally designed with a factor of safety used in the design calculations. Over the years, this factor of safety (at least in ASME pressure vessel and boiler codes) has climbed upwards. It is by virtue of this factor of safety that a tank with thinned areas in its shell can still hold pressure and pass a hydro test. However, some tanks or boilers have locally thinned areas that are 'right on the ragged edge' of failure. In other words, there is just enough metal remaining to contain the pressure of working pressure or hydro testing. No factor of safety remaining. Should any further loss of material due to corrosion occur, or should a pressure spike occur (such as a safety valve not properly set or not functioning), the result can be a catastrophic rupture of an air tank. There is nothing benign about an air tank. Air, being a compressible gas, will 'unzip' a tank and blast it into shrapnel.

Each year, when I worked at a hydroelectric powerplant, we'd get a visit from a 'risk assessment' team from the insurance underwriters. This team was made up of mechanical and electrical engineers with a wealth of practical experience. Each year, they'd have some new case history of an air receiver explostion. This was due to corrosion from within combined with a lack of regular internal inspections, lack of UT, and lack of maintenance (such as having drains checked to be sure they were clear of scale and blowing down freely).

As for welding on a pressure vessel: if it has an ASME code stamp, the short answer is "don't". You invalidate the code stamp and unless you use a boiler shop with an "R" (repair) stamp for "U" (unfired) pressure vessels, should the tank let go, you are liable (if you are still around to answer suits brought against you by anyone injured or property damaged from the failure of the tank).

If the tank has no ASME code stamp, unless you are prepared to run a set of engineering calculations on the tank, and prepared to design the alteration to the tank to provide a drain connection, DON'T. Assuming you are able to handle the engineering end of it, unless you have a qualified welding procedure and are a welder qualified to that procedure (according to ASME), DON'T get any ideas of welding on the tank. Poking a hole into a tank shell with a drill or hole saw, let alone with a torch or plasma cutter and then welding on the tank using a MIG welder is a recipe for a tank failure.

I can appreciate your wanting to keep the historic old tank for its appearance, particularly if is a riveted tank. However, practicalities and safety outweigh aesthetics and historic appearance. Member John Ruth put it succinctly on this 'board some years ago: "Boiler codes are written in blood". By extension, any pressure vessel containing a compressible substance has the potential to rupture catastrophically and blast shrapnel with enough force to be lethal.

By way of example: my buddy has an auto repair garage. The next door neighbor has a house in close proximity to the garage. One day, my buddy hear a hell of a bang from the neighbor's place and ran out to see what happened. The neighbor had bought an el-cheapo air compressor at a yard sale. When he fired it up, there was a small pinhole leak in the air receiver. The compressor could keep up with the leak, so the neighbor started using the compressor with the leak in the air receiver. One fine day, he had the compressor in his yard and was using it. The air receiver let go, and the result was the bang my buddy heard. The air receiver unzipped itself, luckily did not blast any shrapnel, and the blast propelled it upwards. Whatever goes up must come down, and the compressor and what was left of the receiver landed on the roof of the neighbor's house.

I know common wisdom is to say: "they don't build 'em like the used to". This is true of the compressor, and with proper maintenance or repair, the actual compressor can outlast a few generations of owners. The receiver is another matter. It may well have been designed to a lower factor of safety than what we use in current design practice. It has had an unknown service life, and may well have significant 'wastage' (loss of material) from corrosion. Smaller air receivers were often built with a lap-riveted long seam and end heads brazed in before welded construction took hold. Too many unknowns and the potential for that old air tank to become a bomb to justify using it.

There is a ton of information, if you read the whole thread.

[Formulajones]

I just read the first sentence and it told me pretty much everything


"We've had quite a few threads on this 'Board discussing used/old air tanks."

That's the problem right there LOL