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Thread: minimum acetylene pressure in tank?

  1. #1
    Join Date
    Mar 2010
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    Default minimum acetylene pressure in tank?

    I know to keep the acetylene pressure at the regulator below 15 psi, and to avoid rapidly depleting an acetylene cylinder.

    My question is there a minimum pressure that needs to be maintained in a cylinder for safety reasons - especially focused on large capacity cylinder. I am currently depleting a 350 cu ft TW or #5 cylinder. Since I have only done a minimal amount of brazing, silver soldering and aluminum (gas) welding and no cutting or general heating this past year, the cylinder has been below 30 psi for the past year (currently looks to be 10 to 15 psi). On smaller cylinders (70 to 140 cu ft) I have run them until they would not support a flame - can I safely do the same with a larger cylinder? Is it safe to fully deplete even a smaller cyl?

  2. #2
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    May 2018
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    SE MI USA
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    My LWS says I can use my 75 cu-ft acetylene tank until it doesn't work any more, as long as it's upright and I'm not drawing too fast. If I bring one in for exchange and mention that there is still any bit left in it, I get chewed out (in a friendly way) for wasting money. I don't know why it would be different with a larger tank.

    When in doubt, call the place that exchanges/fills your tanks. They will certainly tell you if there's a problem with running the tanks dry.

  3. #3
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    Quote Originally Posted by DrMike View Post
    ...My LWS says I can use my 75 cu-ft acetylene tank until it doesn't work any more, as long as it's upright and I'm not drawing too fast...
    With any cylinder you should leave a tiny bit of residual pressure in the tank when you return it. If you allow the tank
    to drain down till it's completely empty the gas supplier will have to purge it before it can be refilled. A tank that is
    drained too far and not properly purged will be "skunky" for the next user--it doesn't take much air in a tank for this to
    happen. On average we probably see one or two skunky bottles a year...
    Keith
    __________________________
    Just one project too many--that's what finally got him...

  4. #4
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    Default

    Recommended cylinder minimum is 25psi to be sure not to draw any of the acetone from the cylinder.

  5. #5
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    Mar 2010
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    Default

    Thanks for the replys. I left a small (but less than 25 psi) amount in the tank. Now I need to get rid of the cylinder. I bought it at auction (a bunch of welding related items, including this large cylinder) for $100 plus auction premium and sales tax. Auctioneer assured my that is was a customer owned cylinder. I'll have to drive cross town to get to the welding supplier whose name is on the cylinder tag. Hopefully it will end up being customer owned and the welding supplier will allow me to exchange it for a much smaller cylinder like a 140 cu ft in place of the 350 cu ft cylinder that I have a real hard time handling.

  6. #6
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    Quote Originally Posted by aribert View Post
    ...I'll have to drive cross town to get to the welding supplier whose name is on the cylinder tag. Hopefully it will end up being customer owned and the welding supplier will allow me to exchange it for a much smaller cylinder like a 140 cu ft in place of the 350 cu ft cylinder that I have a real hard time handling...
    I would call first and try to ascertain if it is or is not a customer owned cylinder. If you walk in to the store with a
    cylinder that is in fact not customer owned they may seize it on the spot. In my experience a cylinder that has the
    company name cast into the cylinder head flange is not a customer owned one and still (always has) belongs to the
    company. This happens more than you think. Some unknowing person buys a cylinder at an auction or on Craigslist
    and the first time they try to have it filled they discover that they do not actually own it. Bingo! Gone! Around here
    the local companies usually co-operate with each other so even if you take the cylinder to a place other than the one
    whose name is on it the LWS will grab it and return it to its rightful owner...
    Keith
    __________________________
    Just one project too many--that's what finally got him...

  7. #7
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    Dec 2016
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    Not sure how the welding supply would be able to tell if it is privately owned or not. I own my tanks and kept the receipt but when I refill them they just give me full tanks in exchange. Some have the suppliers name and some do not. If someone took one of my tanks in without the receipt they would have no way to trace it. Not sure how they would handle that, assume it is leased or furnish a receipt to prove otherwise. I would not buy any tank without a receipt from the supply company showing it is privately owned.

  8. #8
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    Quote Originally Posted by BobinOK View Post
    ...Not sure how the welding supply would be able to tell if it is privately owned or not...
    Up here in the Great White North if a tank has a name embossed on the ring it belongs to a gas
    company. If it has no ring it's a privately owned cylinder. There may be exceptions and there are
    a couple LWS shops that will get cylinders filled but they have to send the cylinders to the States
    so not a simple process. Another thing that Canadians have to watch out for is the markings on the
    cylinder. Virtually all cylinders will have US DOT markings but to be used in Canada a cylinder must
    also have a Transport Canada number stamped as well...
    Keith
    __________________________
    Just one project too many--that's what finally got him...

  9. #9
    Join Date
    Jul 2015
    Location
    S.E. MI, Metro Detroit
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    Aribert,
    If you are near Lincoln Park, check with Baker's Gas. The only requirement
    they have is to transport cylinders secured upright in a truck or trailer, no car trunks.
    Larry

  10. #10
    Join Date
    Mar 2010
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    Metro Detroit
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    [QUOTE=LKeithR;1212947]I would call first and try to ascertain if it is or is not a customer owned cylinder. If you walk in to the store with a
    cylinder that is in fact not customer owned they may seize it on the spot....


    Keith:

    I did experience that (bought a used set of leased cylinders) when I first bought a welding set - when I was a teenager my father got a small portable oxy/acet kit with about 40 or 60 cu ft cylinders and they were customer owned - I did not realize that companies LEASED their cylinders.

    In this case I don't mind if the cylinder is taken away with out compensation, I want to be rid of this overly large size cylinder that I can't handle by myself very well. In the rare chance that it is customer owned, I'll ask to downsize to a 140 cu ft WS/SW/#4 size cylinder.

    I more than got my moneys worth on the welding equipment & supplies that were part of this auction lot back in 2003 or '04, the 350 cu ft of acetylene in the cylinder was a bonus.

    BobinOK:

    I too have received cylinders with company name on the ring. My experience has been that private cylinders are typ 140 cu ft or smaller (for acetylene) and leased cylinders are larger - regardless of the name on the ring.


    metalfixer:

    Thanks for the info. As I am in Macomb County and I want to unload this cylinder, I might as well go to Plymouth/Wayne Welding in Garden City (their sticker is on the cyl). This cyl. does not have a "ring" on the neck but under sticker is stamped "Royal Oak Gas Products, Detroit. So in the last 67 years, the cyl has not traveled far from home.

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