Problem welding air compressore tank

  1. Capt New Member

    Messages:
    12
    Location:
    Italy
    hello guys
    This days I'm facing a problem welding a gpl bottle
    Want to use it as a compressore tank
    I want to weld a threded tube (plumbing) in the the hole of the bottle
    But after I weld it leak air alot
    I don't know if it possible ! or it require other type of welding machine
    NB : I'm not a professional welder this is my first time using an odl arc welding machine of 2002 I guess
     
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  2. Capt New Member

    Messages:
    12
    Location:
    Italy
    I use E6030 rod
     
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  3. voipio Member

    Messages:
    1,001
    Cambridge, UK
    The pictures show that parts of the weld have no weld penetration, so will leak, plus the cracks in the metal plate on top are concerning. They shouldn't be there. Also, is the threaded pipe galvanised? If so, all of the zinc should be removed in the weld area. The weld fumes coming from zinc are bad for the lungs!
     
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  4. Capt New Member

    Messages:
    12
    Location:
    Italy
    Thank you for your replay
    I'll upload the fotos of the pipe
    On the website of the sellers said ita a zinger steel(iron) ....
    So how to take off the zinc?
     
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  5. mtt.tr

    mtt.tr Member

    Messages:
    4,012
    Essex England
    I strongly advice against this, compressed air holds alot of energy this is an accident waiting to happen
     
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  6. tom2207 Member

    Messages:
    2,496
    Location:
    uk northern ireland
    To tackle small radius pipe welds even for a good stick welder is a chore ,,, bung some one local with a mig a tenner , or a packet of buns and they will have it done in five mins ,, everyones happy and safe , then practice welding on something thats not important , till you get the hang of it all.
     
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  7. brightspark

    brightspark Member

    Messages:
    31,667
    Location:
    yarm stockton on tees
    clean all the galv of it and weld of it a try again new one on there doesn't look to be enough penetration there as said above not the best of things to be practicing on
     
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  8. barking mat

    barking mat Barking at Pigeons

    Messages:
    4,602
    Location:
    Brittany, The Arz Valley.
    Why not cut off that attempt, and drill and tap it?
     
  9. brightspark

    brightspark Member

    Messages:
    31,667
    Location:
    yarm stockton on tees
    its half inch bsp .getting the rite drill and a tap will be hard work
     
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  10. Capt New Member

    Messages:
    12
    Location:
    Italy
    Well I'm afraid to penetrant another then it will make a hole in the pipe
    I use a 2mm rod and amper around 60amp
    When I weld on stell plate it show that the weld are fine
    But with pipe there is some stuff black hard to pull
     
  11. Capt New Member

    Messages:
    12
    Location:
    Italy
    How sorry
    I didnt understand
     
  12. Capt New Member

    Messages:
    12
    Location:
    Italy
    How sorry?
    Yes its plumbing 1/2
     
  13. Memmeddu

    Memmeddu Member

    Messages:
    2,943
    Location:
    Italia Sardegna
    I'd like to avoid to weld this kind of stuff TBH.
    Expecially without tools suitable for the task.
    Working with compressed gases is really dangerous ,few people do that even professional welders many times refuse to do things like that .
    In this case welding would even be not necessary .
    Using 6013 for most of application is an Hazzard ,and critical stuff like a pressure vessel could even translate in suicide to my eyes .
    Personally I should have to do something similar but I'm able to get rid of most of the issues of the case + test the weld safely .
    I'm pretty confident that you would not be able to work safely or obtain a good weld with your actual equipment and materials .
    I would like to make you aware of the hazards involved in what you're trying to do .
    1st despite the fact many people use propane tanks as air tanks , it's not the better idea , but you didn't blow up so you managed to clean it up from the LPG residue .
    Contamination of the base metal would make difficult to weld on it
    At least in Italy those tanks are rated for 30Bar ,more than enough for the purpose .
    2nd it should have a 3/4" NPT female thread , left or right hand depends on the manufacturer.
    So wouldn't be necessary to weld a piece of pipe on it because there are correct size nipples available .
    3rd weld on one of this tanks expecially nearby where the valve is fitted could cause to melt safety pressure release caps , and could be dangerous once pressurised
    4th a piece of galvanized pipe (zinc coated) gives problems ,causes porosity , contaminations ,slag inclusions and others frustrating situations .
    5th the electrode you can't weld critical stuff with 6013 , you need correct stored and baked 7018 , good metal preparation , correct manipulation etc
    6th last but not least , you have to test the tank after welded , once it's cooled down to ambient temperature , you must fill the tank with water and use a pump to take the pressure up to 1.5 times the working pressure and leave it in pressure for 24-48 hours and then check if the pressure went down .
    NEVER NEVER PRESSURISE A VESSEL WITH AIR FOR TESTING ,IT COULD BLOW UP INJURING PEOPLE OR KILLING THEM

    I'm pretty sure that your welder wouldn't run 7018 ,the tank is already compromised .
    Cut it and make a barbecue .

    Now I will tell you how I would proceed .
    CO2 fire extinguisher bottle
    Once emptied remove the valve body it should have an M30 thread .
    Go to the local machinist and ask him to make you an adapter .
    If too expensive you may consider to buy a steel fitting ,chamfer the bottle neck put the fitting inside and weld It with vacuum sealed 7018 H4 R .
    Pressurise the bottle using water and a manual test pump if it doesn't blow open (it will not blast because you're using water and not air) after reaching 30 bar it should be able to contain 10 bar of compressed air
     
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  14. Memmeddu

    Memmeddu Member

    Messages:
    2,943
    Location:
    Italia Sardegna
    Are you Italian?
     
  15. premmington

    premmington Member

    Messages:
    2,014
    Location:
    Norfolk
    30+ years ago I once did some weekend work for a haulage company fitting on trucks in their workshop.

    All the compressor tanks were contained behind a concrete blast wall with a roof - with a staggered entrance like a bomb dump with a locked gate. To gain access to the area - there was signage to let the pressure out of tanks before entry. There were valves and pressure gauges on the outside of the blast wall - so you could do it before entry.

    Curiosity got the better of me - and I asked "why all the fuss with the compressors". Answer I got from the owner was "we had a tank explode 20 years ago and a fragment of it went thru my sons heart and killed him" - this reply left me speechless - looking for a hole to crawl into. Then he smiled at me and said "if you go into the compressor room while there is pressure in the tanks - it is instant dismissal - then I will ring your Mother to tell her why you have been sacked".
     
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  16. More Amps Member

    Messages:
    187
    Location:
    Scottish borders
    Si! ((His profile says he's in Italy)
     
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  17. brightspark

    brightspark Member

    Messages:
    31,667
    Location:
    yarm stockton on tees
    he might have emigrated and ethnic :laughing:
     
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  18. Memmeddu

    Memmeddu Member

    Messages:
    2,943
    Location:
    Italia Sardegna
    Scary story but makes think about
     
  19. mike os

    mike os just a little insane.....

    Messages:
    6,960
    Location:
    North Wales
    Get a qualified welder to do this for you, its a pressure vessel and if it goes wrong the consequences can be serious or even fatal.

    Once welded it should be hydraulically tested to at least 1.5x operating pressure


    There is no shame in not doing it yourself, I wouldn't weld a pressure vessel myself
     
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  20. metalmelt Member

    Messages:
    589
    Location:
    UK
    The stark reality is that you can die if you get it wrong, also, other people can die if it is under pressure and explodes and Beirut is a recent example of an explosion where it went wrong.

    When they manufacture these tanks they put then in water for a reason, when they are produced they have to be tested and on many tanks it is 3X MWP to allow some margin, they are also predominantly machine welded for consistent welds and the only things hand welded are the rings on the joints on tanks made in two halves and welded together and these are only located and heavily tacked in, when the two halves are bought together the top slides over the ring and they weld to a penetration depth of 150% or one and a half the depth if the tank thickness to ensure heavy welds.

    They are screwed onto a rig which drops them into a large water tank and fills them to 3 X there MWP and they are held there for a specific time, often the tank is suddenly discharged (depending upon safety requirements) and repressurised; if they go bang (and they do, specifically on destruction tests) the worst you get is a drowning and skin is waterproof, it isn't yet bullet or shrapnel proof and that is why bulletproof vests were invented.
     
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