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  1. #1
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    Default Vertical tank for compressed air

    I need a steel tank with mounting legs and drain hole at bottom, suitable for receiving compressed air.
    Height up to 1.8 meters.
    Diameter up to about 500mm.
    Maybe there's a dead compressor somewhere, with a tank that's still OK?
    I can pick up between Sydney and Canberra.

  2. #2
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    I have it on good advice that 45kg LPG bottles make good receivers.
    Turn them upside down and they have a fill/drain hole, and you can easily make up a stand using a couple of rings made from flat bar with legs attached to avoid welding to the tank itself if that concerns you.

    Automotive LPG tanks are similar but have more fitting holes in them.

    Be wary of used compressor tanks and air receivers from an internal rust perspective. All will have rust to a varying degree, and they get scrapped from businesses if they fail internal inspection. From memory there's a certain volume above which they become a registered pressure vessel and subject to periodic inspection.
    In comparison the couple of LPG bottles I've opened up had an almost oily coating on the inside and zero rust.

    Steve

  3. #3
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    Quote Originally Posted by OxxAndBert View Post
    I have it on good advice that 45kg LPG bottles make good receivers.
    Turn them upside down and they have a fill/drain hole, and you can easily make up a stand using a couple of rings made from flat bar with legs attached to avoid welding to the tank itself if that concerns you.
    Steve
    Thanks for the info, Steve.
    I think I'd need at least one other threaded hole than the bottom drain, for filling. Another one for a valve and pressure gauge would be useful.
    Another consideration is that I want the air to come out with no odour. That might be difficult if it's been used with LPG?

  4. #4
    BobL is online now Member: Blue and white apron brigade
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    Quote Originally Posted by nadroj View Post
    Thanks for the info, Steve.
    I think I'd need at least one other threaded hole than the bottom drain, for filling. Another one for a valve and pressure gauge would be useful.
    Another consideration is that I want the air to come out with no odour. That might be difficult if it's been used with LPG?
    I have tried several methods of getting rid of the mercaptan from LPG tanks.
    Starting with an empty tank and the valve removed.

    On the first one I just repeatedly filled it with and released the air - This did very little to remove the mercaptan.
    I could still clearly smell it after some dozens of refills
    I then tried filling it with plain water and leaving it in the sun - also near useless,

    Then I filled it with warm soapy water, rolled the tank around on the lawn and let it sit in the hot sun for a day before emptying the water and repeated that 7 times.
    This definitely had an effect at removing some of the mercaptan. This tanks has now been refilled with compressed air maybe 50 x and the smell is just barely detectable.
    This tanks has become my small portable air reservoir.

    I have heard that something more caustic like dishwashing powder is more effective than plain detergent helps but then it needs really good rinsing.
    I've also heard that strongly heating the tank full of water containing detergent , and using an organic solvent may help, ie put a litre of meths into the tank and rolling the tank around

  5. #5
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    Default

    That mercaptan smell sounds like a lot of work to be rid of.
    I think I'd have to give it a miss anyway, even though I have an old 45kg LPG tank here.
    The lack of enough threaded bosses limits its suitability as a usable air reservoir.

  6. #6
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    Quote Originally Posted by nadroj View Post
    The lack of enough threaded bosses limits its suitability as a usable air reservoir.
    Threaded boss can be purchased or made, holesaw to suit and weld it in. Simples!

    As for the mercaptan smell fill it with water and a heavy borax mix. Make a rich solution ,roll it around over a few days. and flush.
    Rinse and repeat a few times.

    Grahame

  7. #7
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    Even if you were concerned about welding in a new boss, the single hole isn't a show stopper.
    From memory the welded in boss in a 45kg bottle is approx 75mm diameter, and about 20mm thick. Plenty of meat there to either tap a new hole for a gauge, or even substantially enlarge the existing hole for a larger fitting.
    Fabricate some form of threaded manifold to go into it with as many bosses as you need. Loop it back up a bit and put your drain at the bottom.

    No drama's if you just can't be bothered messing around with it - I completely get that too

    Steve

  8. #8
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    Quote Originally Posted by Grahame Collins View Post
    Threaded boss can be purchased or made, holesaw to suit and weld it in. Simples!

    As for the mercaptan smell fill it with water and a heavy borax mix. Make a rich solution ,roll it around over a few days. and flush.
    Rinse and repeat a few times.

    Grahame

    Wouldn't that be a bit of a safety issue, considering it would be used as a pressure vessel which as far as I am aware would need a ticketed welder to complete that job and then go through the inspection process.

    Nothing is ever simple! haha

  9. #9
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    Quote Originally Posted by OxxAndBert View Post
    Even if you were concerned about welding in a new boss, the single hole isn't a show stopper.
    From memory the welded in boss in a 45kg bottle is approx 75mm diameter, and about 20mm thick. Plenty of meat there to either tap a new hole for a gauge, or even substantially enlarge the existing hole for a larger fitting.
    Fabricate some form of threaded manifold to go into it with as many bosses as you need. Loop it back up a bit and put your drain at the bottom.

    No drama's if you just can't be bothered messing around with it - I completely get that too

    Steve

    Do you know what thread they use? If they are common BSP or NPT threads I would look into using an adapter to go from the 75mm diameter to a more common 25mm and fit a galvanised T piece in the bottom which will allow for your drain via a ball valve and then connect your pressure to the other side.

  10. #10
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    Try 5/8" BSP Left Hand x 14 TPI for thread.

    That's what mine appears to be .

    Its a bit hard to measure while it is connected.

    140 psi or thereabouts.It is 2.5 mm thick sheet,

    It is well within the domain of a competent welder who can weld a bead around the socket without undercut or inclusions.

  11. #11
    BobL is online now Member: Blue and white apron brigade
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    Plenty of connections on my 2 tanks.

    Is there something special about these?
    Propanetank.JPG

  12. #12
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    Quote Originally Posted by BobL View Post
    Plenty of connections on my 2 tanks.

    Is there something special about these?
    Propanetank.JPG
    that is a forklift gas bottle.

  13. #13
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    Quote Originally Posted by Grahame Collins View Post
    Threaded boss can be purchased or made, holesaw to suit and weld it in. Simples!

    As for the mercaptan smell fill it with water and a heavy borax mix. Make a rich solution ,roll it around over a few days. and flush.
    Rinse and repeat a few times.

    Grahame
    I would strongly recommend nobody attempt this unless they have experience welding pressure vessels.

  14. #14
    BobL is online now Member: Blue and white apron brigade
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    Quote Originally Posted by snapatap View Post
    that is a forklift gas bottle.
    Thanks for the info, The only one boss I can clearly identify is the "overflow for the fill" . The square threaded connect and what's under the yellow cap looks like a quick fit connect?? what so many?

  15. #15
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    Quote Originally Posted by snapatap View Post
    I would strongly recommend nobody attempt this unless they have experience welding pressure vessels.
    Seeing this forum is the wrong place for this type of discussion .I''ll start a new thread in the welding Forum.
    In that forum I'll discuss the procedure.

    Snapatap,

    We can discuss it there OK?

    Grahame

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