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Air Compressor Tank Blow Up - Leg Amputated

Kevin Horton

Kevin Horton

Well Known Member
A local area car rebuilder had his air compressor tank explode recently. One of his legs was mangled enough that they had to amputate it below the knee. Supposedly the tank was old, and a bit rusty.

Keep the water drained from your tanks guys! If the tank is getting on in years, maybe you should think about taking the tank out of service and replacing it with a new one.
 
tank safety.....how???

This is NOT how you want to end your building/flying days, is it?

Makes me think...I have a little 40-year old compressor, the outside paint is pristine, but I'll bet the inside is like a 1972 dodge dart.....nearly toast!
perhaps we should all borescope our tanks asap!...the only real way of knowing the inside condition.
I've seen new, premium brand tanks that advertise they are epoxy coated inside, but most of us by the regular (cheapest) ones we can find. the trend toward upright compressors might make this problem even worse; easier to drain, but more surface area, with the moisture concentrated at one spot!
 
Do a google image search for "compressor tank explode" and you will find some gnarly images...on the same level as dudes who got hit with a hellfire or detonated a suicide vest. He was lucky it was just a leg. Let's be careful out there.
 
When I bought my AC, I thought of pouring a quart of preservative oil into it, letting it sit a week, and then draining it well. I didn't do that. I suppose a quart of primer would have done as well or even better.

Since then, I've never drained more than about a cup of water from it, so that quantity of rust-preventive would have been enough. How effective it would have been, I can't say. I remember I was concerned about the oil contaminating the air -- primer would have been better, I think.

My AC has a 60 gallon vertical tank.

Dave
 
We had a locomotive main reservoir tank explode in Melbourne a couple of years ago. Designed for an operating pressure of around 800kpa, they somehow managed to pump well over 1500kpa into it before it let go, here's some photos of the aftermath...

Just because it is "air", we cannot let our guard down. There's more than enough stored energy in most any sort of compressor receiver to do a lot of damage if it lets go.

Be careful.
 
It used to be that all tanks > 30 gal were required to meet ASME pressure vessel standards in the USA. They are thicker, have inspection ports, and have a metal identification plate welded to the tank.

BTW, DO NOT PUT OIL in your tank to preserve it, and be sure any preservative you might consider would not explode under pressure!
 
I did this to mine...
Remove the drain valve that comes with the tank. It is typically buried well under the tank, hard to reach, covered in cobwebs, and commonly difficult to open/close. In place of the factory drain valve, insert a brass elbow. Connect the elbow to a short brass pipe out from under the tank where it is easily accessible. Put a good valve on the end of the pipe; one that is easy to open/close. Doing this will make draining the tank easier, thus will likely be drained more frequently. Also, doing this will take the water out of the steel tank into the brass pipe.
 
This came up before and I posted how years ago I had an old compressor in my garage that overfilled due to a faulty pressure switch combined with a faulty pressure relief valve. I was in the garage working when it blew up. The compressor was under the workbench against the wall. It blew the back wall of the garage out and the workbench apart sending debris over 100' behind the garage. The compressor motor and pump separated from the tank and went flying out the front. Luckily I was not injured. It is mandatory to drain your tank at least once per week AND check the PRV!
 
Automatic Drain Valve

I installed an automatic drain valve on my 80gal tank. Opens for a few seconds before the low pressure switch cranks up the compressor to blow out any water.

John Salak
RV-12 120116
 
Very sad story, but a good thread - I've often wondered what the life of the tank should be. Seems like even with draining, the inside would be constantly moist (1cc vs 10 cc of water, what's the difference?). I think I'll send my little boroscope camera in for a look.
 
Standard practice at my workplace was to use 10-30 PSI of air to move latex between large tanks. The tanks have an agitator, and the latex uses limestone dust as a filler, so the interior of the tanks wears over time. Somehow, the NTD guys missed the fact that one of the tanks had worn to paper thin after years of use.

And, then one day, boom!! The entire bottom of one tank blew out, launching the cargo van sized tank into the roof of the facility. No injuries, but latex everywhere, spooked employees, and very concerned management. We were probably saved by the fact that the tank was almost full of latex, so there was a relatively low amount of energy stored in he small volume of compressed air in the tank.

We have since switched to pumping filled latex.
 
I don't think I would recommend priming the inside of the tank. When the primer starts peeling off, pieces may get in your airlines and fittings and cause you a lot of grief.
 
12vaitor said:
I installed an automatic drain valve on my 80gal tank. Opens for a few seconds before the low pressure switch cranks up the compressor to blow out any water.

John Salak
RV-12 120116
Click to expand...

Same here, I just build a small timer circuit to hold open a solenoid valve at the bottom of the tank for 1 second on each startup, feed that through a 1/16" orifice and it's just a small little puff of water followed by air on each startup, no problems.

Compressed air contains enormous energy and demands respect - I have "played" with it for about 20 years now at pressures up to 25,000 psi and if you pay attention to what you're doing you'll be fine - if you get complacent you'll get hurt in a hurry.

Here is a shot of a SCUBA bottle I intentionally pressured to failure back in 2007, basically just because I was challenged with the age-old "Betcha can't", so I proceeded to demonstrate that I could. This was air, not water - the 3000 psi rated tank unzipped itself rather dramatically at about 7200 psi, and these two pieces were all that we found. These two parts were 250 yards and 400 yards from the blast point, we never found the missing 1/3 of the tank.

lezu.jpg
 
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I would think draining the tank regularly, while a good idea, is NOT going to prevent the tank from rusting. The inside of the tank is saturated with moisture, regardless if there is a little puddle of water sitting on the bottom. I actually used a borescope on my compressor tank a couple years ago, it was unbelievably rusty inside.
 
So what's the real answer then? Are we supposed to replace the compressor / tank when it's getting rusty? or just sometime before it fails? and how would one know that? Seems like maybe there needs to be a defined service interval where the tank is replaced.

Mine puts out a batch of bright orange sludge and crud each time I open the valve to clear it.
 
airguy said:
Same here, I just build a small timer circuit to hold open a solenoid valve at the bottom of the tank for 1 second on each startup, feed that through a 1/16" orifice and it's just a small little puff of water followed by air on each startup, no problems.

Compressed air contains enormous energy and demands respect - I have "played" with it for about 20 years now at pressures up to 25,000 psi and if you pay attention to what you're doing you'll be fine - if you get complacent you'll get hurt in a hurry.

Here is a shot of a SCUBA bottle I intentionally pressured to failure back in 2007, basically just because I was challenged with the age-old "Betcha can't", so I proceeded to demonstrate that I could. This was air, not water - the 3000 psi rated tank unzipped itself rather dramatically at about 7200 psi, and these two pieces were all that we found. These two parts were 250 yards and 400 yards from the blast point, we never found the missing 1/3 of the tank.

lezu.jpg
Click to expand...


not that it matters much, but are you sure it was rated at 3k psi? That looks like a steel tank which would have been rated at 2200 or 2700 I think, depending on vintage and the number of bomb tests it had been through.
 
walkman said:
not that it matters much, but are you sure it was rated at 3k psi? That looks like a steel tank which would have been rated at 2200 or 2700 I think, depending on vintage and the number of bomb tests it had been through.
Click to expand...

Quite sure, we blew up several during the course of that week. I had 3 of the steel 80 cubic foot 3000psi tanks that we sacrificed, and a few aluminum ones as well, they all gave their life for our enjoyment. A few handles of Crown made the sacrifice as well, it was a good week. The aluminum tanks tended to bulge and rip, but not separate into fragments like the steel did, the steel tanks definitely gave the better show.

*disclaimer* - you should probably NOT try this at home... :D
Closed course, professional driver, do not attempt.
 
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Musings

akarmy said:
So what's the real answer then? Are we supposed to replace the compressor / tank when it's getting rusty? or just sometime before it fails? and how would one know that? Seems like maybe there needs to be a defined service interval where the tank is replaced.

Mine puts out a batch of bright orange sludge and crud each time I open the valve to clear it.
Click to expand...

I used a 25 gal with brazed end caps at 125psi and it was 50 yrs old. I used a 30 gal ASME tank for 20 yrs @ 125 psi, and now have used an IR 60 gal, ASME @175 psi for 20 years. Kinda scary not knowing the design parameters, but IR (purchased new) did not recommend any testing or time limit.

I searched for a while for OSHA requirements for pressure vessels and could not find a good reference. ASME codes cost money to get, but a reference I found did say to test the vessel yearly at 1.5 times max working pressure to ensure compliance. I assume that was in a commercial environment. IR website says they test their air receivers at 1.3 X working pressure. A hydrostatic test would do that. Remove all devices, plug then outlets, fill to the highest point with water, use a pressure gage with the right range, and pressurize with a pump (pressure washer) or a hand pump like a grease gun. The pressure should hold for 10 minutes. Then drain and be happy. I have an old 60 gal tank that I have been uncomfortable about using, so this is something I can do (when it gets warm).

When testing with water, if a fracture occurs, the pressure energy is so low that it would just leak a cup or two then stop. No explosion. Personally, I would check to ensure that the water had less than 100 ppm TDS, and then rinse with less than 10 ppm TDS to ensure the inside was clean and the extra minerals would not promote faster corrosion internally.
 
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From Boyd Butler....

emailed to me....

" I am not a member but read your forum. About the air compressor tank failure, could you please add this to it. Why it failed could have been the problem. A friend of mine had his fail, much larger than the one they lost. It was on a very cold day in December, it was located in a separate building which was destroyed by the blast. The problem was two fold, one the shut off failed due to the fact it had frozen water in the line, two the safety valve was also frozen shut. It had nothing to do with the age or quality of the tank. The tank was an ASME stamped tank, more than likely 1/2" steel, mine at home is a 100 gallon ASME tank which has bungs in it so you can inspect the inside. Also usually if one is getting bad from rust, its in the bottom, they start to leak long before they will fail. Let me add one more tank not to use, a water pressure tank as my neighbor had one blow up in his shop, from the blast some windows imploded inside and some went outside. It was due to a stuck shut off switch.
Please post this along with another fact, using old propane tanks or Freon bottles is asking for disaster as they are not made to have air in them as they do not have any rust protection. My qualifications are, I am a retired heavy duty mechanic along with having my A&P license. I also started a build way back when the kits were made beside Vans house in an old chicken coop it was before the RV4 was produced. An RV3 that when I got the fuse started sat in a finished one and didn't fit. Thanks for your time, Boyd Butler Chiloquin Oregon. "
 
I have a 45 minute timer that purges water out for one second, scares the poop out of folks walking by the garag when it purges
 
Two things occur to me:

This seems a bit like the reporting of aviation accidents; conclusions that are drawn in the press may not be valid.

The second references the email Doug posted about the failure mode having to do with frozen water causing a failure of two different safety systems. This accident happened in Quebec in the winter...REALLY COLD.

I confess that I don't drain the tank as often as I think I should...maybe once or twice a year.

I also wonder as to the effect of completely draining and refilling the tank often, which equals a much larger pressure cylcling, ( O psi to 135psi) vs. letting it refill at the automatic level, 75 or so psi to 135. I am not qualified to have an informed opinion on this, but my gut (always a bad engineering instrument!) tells me that full cycling will reduce the life. Or is it that, because it's steel and not filled to its structural limit, there's no limit to the number of times it is cycled?

Please educate me:)
 
KRviator said:
We had a locomotive main reservoir tank explode in Melbourne a couple of years ago (...) Here's some photos of the aftermath...
Click to expand...

airguy said:
Here is a shot of a SCUBA bottle I intentionally pressured to failure back in 2007...
Click to expand...

Ok, here's one we had to deal with at work:

QantasExt1_gallery__533x400-600x400.jpg


Here's the PDF of the full accident report. The tank blew up in the belly, making a huge hole in the skin. It rocketed up right through the cabin floor, nearly swung an exit door handle all the way to "open" (the door would not have opened, but still), hit the cabin ceiling, fell back through the hole it had made on the floor, and fell out the huge hole it had made on the belly skin :eek:
 
AirShowFan said:
Ok, here's one we had to deal with at work:

QantasExt1_gallery__533x400-600x400.jpg


Here's the PDF of the full accident report. The tank blew up in the belly, making a huge hole in the skin. It rocketed up right through the cabin floor, nearly swung an exit door handle all the way to "open" (the door would not have opened, but still), hit the cabin ceiling, fell back through the hole it had made on the floor, and fell out the huge hole it had made on the belly skin :eek:
Click to expand...

Blimey!

Did that happen in flight?
 
It may, or may not, help, but my big compressor is chained to the concrete block wall nearby. And it's in a normally vacant part of my shop.

Obviously, you can't chain down a portable compressor... or can you!? Maybe you should!

Many manufacturers recommend bolting these things down.

YMMV!
 
Lot's of good information here.
My 80 gallon 220V compressor is at present sitting in below zero temps. I just tripped the circuit breakers to it and took its pressure down to 70psi from the usual 120. The unit will not be re powered until it warms up.
 
walkman said:
Blimey!

Did that happen in flight?
Click to expand...
Yep, FL290 over Asia. They never found the #4 tank, it fell into the ocean.

Incidentally, the linked report is only the preliminary report, HERE is the final report, at 15MB in *.PDF format it is a bit of light reading before bed!
 
I have always felt nervous standing near air compressor tanks, and now I know why. I kind of thought I was being a bit paranoid thinking about all the force that the tank was holding back, but after reading this post, I now realize that I wasn't really being that unreasonable...:eek:
 
We have a nearly 1000 cubic foot nitrogen tank at work currently rated at 9600 psi. I get a little nervous around it, but it IS better inspected and maintained than your average air tank.;)
 
Automatic Drain

Despite the seemingly mediocre reviews, I have had one of these on my compressor for a few years and have been very happy with it:

http://www.harborfreight.com/automatic-compressor-drain-kit-68244.html

I serviced the valve itself once when it briefly stopped working.

A friend and I just installed one on his compressor as well, and it's working great.

Every time the compressor motor turns on or shuts off, this device emits a short burst of air (and whatever moisture has collected) from the tank drain. The long term effect is that moisture never really has a chance to build up inside the tank to an appreciable degree. A bit of a pain to plumb (will likely require a trip to the hardware store for fittings) but if you can build an RV it'll be a piece of cake.
 
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