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Thread: Can You Weld on a ASME Tank?

  1. #1
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    Default Can You Weld on a ASME Tank?

    I found a Craftsman air compressor on the curb. It has a good GE compressor motor and a good ASME tank and regulator. It unfortunately has a crappy oil less compressor, which you can no longer get parts. I would like to convert it to a compressor with a normal oil bath lubrication, but to do that, I'll have to weld on new brackets for both the motor and the compressor.

    Are there any guidelines for welding on an ASME tank? The tank is certified to 150 psi and I plan on obtaining only a single stage compressor.

  2. #2
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    Sure, you can do it but the tank will no longer be ASME when you are done. Unless you carry your own certification as a welder with an "R" stamp and have a third party inspect it. I used to build tanks like that for a living among other things. They are rarely more than 1/8 inch thick unless it's a large industrial unit. ASME manufacturers favor MIG welding for that kind of work. Make sure your pieces are scrupulously clean, have good fit up with no gaps first. Below 1/4 inch thick usually doesn't require bevelling

  3. #3
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    If you own it you can do anything to it you want.
    The question is, should you weld on it.
    That depends on your welding skills.
    Can you weld some new brackets to the old ones and stay away from the tank itself?
    Seastar
    I cut it off twice and it's still too short!

  4. #4
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    Can you yes, should you No.

    Compressor tanks are registered pressure vessels and to do it "legally" you have to jump through many hoops and procedures. Welding tickets, welding procedures, paper work up the ying yang, hydro-static testing afterwards and maybe x-rays to boot plus government inspection and certification. All that if it is done at a licensed welding shop, you have to provide that if you do it yourself, if you want to remain legal AND the gov'ment says OK, which they probably won't. If you don't care about being legal then forget all that but remember those tanks are bombs waiting to go off and welding on them will alter them, possibly not for the best.

    That being said I brazed up a rust out on the bottom of my tank about 15 years ago and it is still going strong, but not a good idea.
    Last edited by loose nut; 08-13-2019 at 09:51 AM.
    The shortest distance between two points is a circle of infinite diameter.

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  5. #5

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    I would. I'd also statically pressure test with a pressure washer

  6. #6
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    How about a couple steel straps around the tank to hold your pump and motor bracket in place?

  7. #7
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    Quote Originally Posted by The Metal Butcher View Post
    I would. I'd also statically pressure test with a pressure washer
    I have welded onto an ASME tank in the past and hdro-tested it by completely filling the vessel with water. Then I attached a T to one of the fittings, a gauge at one side and a grease gun at the other. Once the vessel is completely full it only takes a very minute amount of additional volume to increase pressure rapidly. I went to 450 psi and called it good for the intended purpose which only operates at a maximum of 110 psi.


    Quote Originally Posted by strokersix View Post
    How about a couple steel straps around the tank to hold your pump and motor bracket in place?
    This would be my first choice if there was any concern of my welding abilities or the ability to properly test it after.
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories

  8. #8
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    Referring to my previous post, and also what Loose Nut said: if you are using the compressor in a business then you need to be ASME to be legal. If its just a homeowner job then you can do whatever, but you should be aware that the insurance company *will* nail you if anything happens.

    I've had my welds tested to hydraulic pressures in addition to ultrasound, BUT that was on the company's time and money. They have an interest in the certification and it is not portable -- I cannot use it for my own work. Doing code work also requires carrying a minimum of one million dollars in liability insurance in my state. You will not get that insurance without having the relevant cert.

  9. #9
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    Why not just bolt some adapter plates to the old mounts and bolt the new motor & compressor to the new plates?

  10. #10
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    Quote Originally Posted by The Metal Butcher View Post
    ...I'd also statically pressure test with a pressure washer...
    Probably not a good idea. Even a (relatively) low pressure washer will exceed the burst rating of most tanks by
    a significant amount. Hydro testing a small tank like you describe doesn't need more than 300 PSI or so.

    Over the years we've modified and repaired many small air tanks--added brackets and repaired cracks and rust
    spots. Small tanks like you describe tend to rust out on the bottom due to un-drained moisture--they're surprisingly
    thin. As long as you can get to clean, full thickness material and you know how to weld well it's not too much of
    an issue.

    And of course it depends on the use. Most of our work was on small, portable compressors. We didn't have any
    certification so we'd never weld on larger stationary compressors. That said, I've seen some compressors with
    horrible looking weld repairs that held air just fine...
    Keith
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