Repairing Air Compressor Tanks

DelMN

Member
I just picked up a Rol-Air compressor with gas engine and twin tanks. The tanks leak at the bottom. Is it a good idea to repair, if so, what's the best way? Use a welded patch and/or just weld the holes? I will have a professional welder do it. Don't know if he has repaired air tanks but a good welder. Just want your feedback. Thanks in advance.
 
(quoted from post at 19:09:33 04/06/17) I just picked up a Rol-Air compressor with gas engine and twin tanks. The tanks leak at the bottom. Is it a good idea to repair, .

NO, NO, NO. :shock:
 
Do you like to gamble? How much of a risk taker are you? Can you find a welder that has nothing to lose when it comes to liability claims?
 
An air compressor tank is a nice bomb. When they leak, the metal in the area of the leak has corroded (inside) if you weld it, you radically change the metallurgy of the heat affected zone at the weld. If it blows you may be dead. if it blows with someone else in the building your widow will have nothing. Jim
 
Pretty good chance the entire bottom is thin from rust. Most likely the welder will be chasing holes for awhile. As he closes one hole another will appear. Use the motor for another project and scrap the tanks.
 
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The only time I've ever welded on an air compressor tank was one with a defect weld toward the top, not rusting out at the bottom. The only fix for one rusting out is a new tank.
 
I have seen it done but they replaced the whole bottom of the tank. A patch 4 inches by 30 inches. It was still fine 7 or 8 years latter. Now I Also saw the aftermath of an air explosion on a Mennonite farm. Lots of those guys use diesel engines and air tools. They hook an air compressor to the diesel engine while they are milking the cows at the same time. They use really really big air tanks for storage. How about a couple of 500 gallon tanks in the basement of your house just down from the barn?? What happens when something lets go? Picked up the whole house and moved it slightly to the side 5 or 6 inches. They jacked the house back up a few days latter and put it back where it belonged. Simple answer is $400.oo for a new tank is very cheep.
 
Contact Samuel Pressure Vessel Group. They sell good tanks at reasonable prices. If you value your life or those around you DO NOT weld on a rusted old tank
 
Use at your own risk. Like stated, welding isn't kosher, it might increase the danger of blowing. Soldering tiny holes with an iron might give you a couple years. An iron shouldn't even blue the steel. Use at your own risk.
 
I have repaired air tanks. I cut the entire bottom out and basically made a new tank. I also pressure tested it full of water and then applied 250 PSI to it with a Porta power. With it not full of a compressed gas if it failed while pressure testing it does not explode.

I would NEVER just weld a patch on the hole only. I cut them out until I have good metal all the way around. I then do GOOD welds with a wire feed welder. If you weld it with a rod welder you more than likely will have leaks where you stop and start.

If you count your time and materials you can buy a good tank cheaper.
 
It still concerns me about welding an air tank even if replacing the entire bottom. Reason is, welded areas like to rust even faster, plus the metal now has different properties as it has had very intense heat applied. If a "repaired" tank explodes, results would most likely be far worse than a non-repaired tank.
 
This is one of those perennial subjects that comes up every few months. And the responses are always the same, split between "are you nuts?" and "I've done it plenty of times and haven't had one blow up (yet)".

Consider the fact that when you repair an air tank, you put not only yourself at risk, but anyone who happens to come near the repaired pressure vessel. If you are fine with the possibility the tank might rupture and take your head off, that's one thing. But do you really have the right to put your family, friends and employees at risk?
 
I would put a want ad on craigslist for an air compressor tank. I sold a tank there because the cheap oil less compressor took a dump.

Or I would sell it and buy a new air compressor.

No way would I attempt to weld a tank. I bet if you cut the tank apart, it would look like the 17 year old rim I took off tractor that was full of mud and water. Massive amounts of rust and deep pits.

There would be no way to weld a rust pit. You would blow a bigger hole in tank with welder.

Replace only, not repair.
 
Wonderful, let's go buy some tank of unknown origin and condition from a complete stranger... It's sure to be better than the rusted out one I have now!

Even better, let's sell my rusted out old air compressor to some unsuspecting schlub!
 
The main reason for an air tank to rust out is from water laying in the bottom of it. The water comes from condensation from the atmosphere - especially during humid weather.
The metal used in air tanks is generally a relatively mild steel. I worked for several years in a shop that made pressure vessels. Some of those vessels held pressures of over 10,000psi. I was one of the mechanics that hydro tested these vessels.
Welding itself is not much of a problem. Imperfections in the weld will cause leaks. More important is the condition of the rest of the tank. Hydro testing after the repair at twice the working pressure will determine the integrity of the tank.

A caution, though. Once a tank has rusted through from the inside, it should be assumed that the rest of the tank is weakened. The proper way to test a tank is using water, not air. The reason being that water is nearly incompressible, so that if a vessel fails, it won't make a big boom. Compressed air, on the other hand, contains a lot of energy, and will make a significant boom.
 
I'm just guessing that have weakened (rusted out) from the inside out to the point are leaking, the cost of finding good used replacements at a flea market or garage sale for cheaper are much safer. If they are already leaking, the damage is done and you can't see the extent of the damage that could be deadly. Speaking of that, I just heard a news blurb yesterday about a boiler explosion somewhere yesterday and ended up killing one - three people next door at some other business applying for jobs. Rust causes bad things to happen especially under pressure, so just be careful.

Mark
 
I feel sorry that you picked up the compressor, I would have assumed it was in working order, no way I would expect a used tank to be any better than the one you have.
 
Video not funny and hope the guy was ok, but I sort of feel that way every time I use my chinese Harbor Freight compressor ... not sure if it will blow skyhigh. :shock:
 
JD,

Welding up a pressure tank like that without an ASME R stamp is just inviting a lawsuit to financially ruin you.
 
Best to replace the whole tank. Not sure how big yours are , but I did a small one by using an air tank sold at semi truck dealers for trailers. They are not that expensive. Many people use Propane tanks for air storage tanks too.
 
If "I" were going to repair a leaking/rusted-out air tank, I would release all pressure and drain any moisture from the tank, treat the tank with rust treatment, coat the inside to protect the remaining tank, then add about 1/4" thickness of fiberglass to the entire outside of tank.

In other words, I'd buy a new tank.

Geo - That was an AWESOME reference you made between an air tank and a 17-yr-old tractor rim!! Keep in mind, though, that air compressors that are regularly used will normally see MUCH more moisture than the inside of a tractor rim.
 
Replace it. If you repair it it will need to be ASME certified again and that will cost more than a new tank. I suspect that no insurance company in the world would pay for any damages or injuries caused by an un-certified repair to a pressure vessel.
 
> I suspect that no insurance company in the world would pay for any damages or injuries caused by an un-certified repair to a pressure vessel.

Insurers pay all the time for the boneheaded actions of insured parties. That's pretty much the definition of "negligence".
 
I was going to put a large metal patch over the entire tank once but , then I thought better of it. Due to the oil I would have treated it as welding a gas /fuel tank. But like I said I ended up throwing away the compressor. Tank would be uncertified , could be dangerous etc etc. It would be a series of pinholes you would be chasing and still have a shot tank.
 
Best not to repair it with over patches or trying to weld the holes. I made several accumulator air tanks out of 10 inch pipe and welding the ends with 1/4" plate steel. If I was to repair a bottom rusted air tank I would cut all the bottom out and make sure the fabricated new bottom was welded to the non rusted upper. A proper weld is stronger than the metal your welding. Weld beads that look like bird dropping are not considered proper welds.
 
You can blow a brand new certified tank when a relief valve fails when the pressure switch fails at the same time with a large enough motor and a tight enough belt. Silly to compare those pictures with the side ripped out with a hole rusted in the bottom. It takes extreme pressure to blow the side off.
 
I doubt you will find a professional welder to attempt such a repair.

Typically once pin holes appear, the entire bottom surface is all thin ready to wear through Swiss cheese, and will keep breaking through. I know many back yard mechanics will brazze or even weld, but it's a 'here hold my beer' sort of deal..... Could have real bad results. Lot of us started with old 100lb compressors, now we got a 125 or 150# compressor and try to put all that extra in the same tank.... It gets frightening, really......

There are lots of YouTube videos on this. Those tanks can rupture and then zip open like they had a zipper, quite amazing.

Here is one. It's only 3 minutes to view.....

Paul
Air tank boom
 
When I was young I was a photographer for a newspaper. One assignment I had was to go out to a diesel garage where they had a large commercial upright compressor they had been repairing. The bottom of it finally gave out and the compressor took off like a rocket and went through the tin roof of the building landing in a field next to the shop.
 
(quoted from post at 19:09:33 04/06/17) I just picked up a Rol-Air compressor with gas engine and twin tanks. The tanks leak at the bottom. Is it a good idea to repair, if so, what's the best way? Use a welded patch and/or just weld the holes? I will have a professional welder do it. Don't know if he has repaired air tanks but a good welder. Just want your feedback. Thanks in advance.

Cost vs benefit ratio is upside down.
 
Another thing to add. Have you ever seen one of these used in a tire shop? Fill with 125lbs. air and stick the nozzle between the tire bead and the rim. Pop the ball valve handle quickly. FWOSSSH! Tire seats itself. Then just air up the tire. Guy poped on a truck tire out in the yard like you and I would eat a donut.
a156750.jpg
 
Yeah, I haven't had the chance to see this done often enough. Could probably sit and spend a whole day watching tires get "blasted" onto rims. *lol* So far I've only seen this with auto tires.
 

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