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  1. #1
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    Default Degassing Old Gas Bottles

    Any tips on Degassing Old Gas Bottles so they are safe to cut into?


    I have an old 9kg gas bottle, I took the valve out and let it sit, filled it with water, drained it sat it upside down for a few days, sat it up the right way for a few weeks. Still has a gas odor so I'm reluctant to cut into it with the grinder.

    Would blowing into it with the compressor do anything??
    …..Live a Quiet Life & Work with your Hands

  2. #2
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    I wonder if the local Fire Brigade would have any answers.

    Ross

  3. #3
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    Default

    I think Vinegar gets rid of that Mercaptan residual smell.

    You know your going to blow your self up, and take half the neighborhood with you.

    Now that's been said.

    A squirt of exhaust gas from a hot engine will put Co2 in it.

    A squirt from a Co2 extinguisher does the same.

    You've seen that LPG tank fire pit thing I have. I cut that mostly still filled with water.

    Regards Phil.

  4. #4
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    Neighbor of mine turned up with one of them big LPG gas storage tanks. About three odd feet wide by about six long. Asked if he could borrow me plasma to chop it up. LA la la...

    Neighbour then produced a gas sensing electronic device with a probe that he put into the tank to show no residual LPG. Still, I let him do it and stood well clear... Well clear...

  5. #5
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    I'm not worried about the smell in terms of smell, just if it indicates any residual gas.

    So I should start the car put a hose in the window and take the gas bottle inside the car with me??? That should filler with CO2



    Hadn't thought about cutting it still filled with water, how does that go on the angle grinder…….


    Hmm if it doesn't blow up, or gas me, maybe I can electrocute myself! So many ways to die trying to build a gas forge!!
    …..Live a Quiet Life & Work with your Hands

  6. #6
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    Wonder where I could borrow a gas sensing probe?
    …..Live a Quiet Life & Work with your Hands

  7. #7
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    Quote Originally Posted by DSEL74 View Post
    Wonder where I could borrow a gas sensing probe?
    No need to borrow, just drop into yer local gas fitter and get them to check it for you.

  8. #8
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    Quote Originally Posted by Machtool View Post

    A squirt of exhaust gas from a hot engine will put Co2 in it.

    A squirt from a Co2 extinguisher does the same.

    On a serious note, what does the CO2 do? Is it inert gas, and or replace the LPG?
    …..Live a Quiet Life & Work with your Hands

  9. #9
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    Quote Originally Posted by DSEL74 View Post
    On a serious note, what does the CO2 do? Is it inert gas, and or replace the LPG?
    What does CO2 do? ...if you listen to the greenies it is a planet destroying gas

    Me-thinks its just good plant food

  10. #10
    BobL is offline Member: Blue and white apron brigade
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    Quote Originally Posted by DSEL74 View Post
    On a serious note, what does the CO2 do? Is it inert gas, and or replace the LPG?
    Both

  11. #11
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    Quote Originally Posted by DSEL74 View Post
    On a serious note, what does the CO2 do? Is it inert gas, and or replace the LPG?
    Hi,
    First up.There are double hazards present flammable/explosive and chemical/ toxic.

    Co2 is not an inert gas but does perform a similar way to an inert gas, in that it will not support the ignition of the LPG necessary for fire or explosion.

    Anybody who wants to cut into a LPG cylinder should be absolutely certain about the potential explosive state of the cylinder contents.

    The gas is heavier than air. I empty those I cut, by standing them upside with an open valve for 2 weeks,then remove the valve.

    The odor likely then remaining is residual mercaptan, soaked into (not the exact word I am trying to think of, but you have the idea) pores of metal.It is very concentrated and a lil bit goes a long way

    Google the MSDS of this stuff yourself as it not nice stuff. It is toxic poisonous stuff and can be explosive - at 300C. With due respect to the other posters answering your query, do this yourself as you are the one who will get hurt or killed if it it all goes bad.

    If you are the slightest bit unsure about this Do Not cut or weld on the cylinder until you are positive it is safe.

    Grahame
    The Safety Nanny

  12. #12
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    Quote Originally Posted by Grahame Collins View Post
    ...The odor likely then remaining is residual mercaptan, soaked into (not the exact word I am trying to think of, but you have the idea) pores of metal.It is very concentrated and a lil bit goes a long way

    Google the MSDS of this stuff yourself as it not nice stuff. It is toxic poisonous stuff and can be explosive - at 300C. With due respect to the other posters answering your query, do this yourself as you are the one who will get hurt or killed if it it all goes bad.

    If you are the slightest bit unsure about this Do Not cut or weld on the cylinder until you are positive it is safe.

    Grahame
    The Safety Nanny
    Grahame, do you know if that mercaptan will show up on them gas testing devices ?

  13. #13
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    Quote Originally Posted by YBAF View Post
    Grahame, do you know if that mercaptan will show up on them gas testing devices ?
    Sorry, no.

    I suspect the residual amounts to be so small as to not be explosive, but unaware about the toxic nature of mercaptan, until I explored on line.

    Having opened in excess of half a dozen of the things I hope I haven't done myself any harm. I have more searching to do before I'll think about doing any more.

  14. #14
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    Cool

    Hi there,

    Now I don't claim to be an expert on the subject but I have cut open about 4 LPG cylinders. Mostly in an effort to build the "perfect" camp coonara. The last one I did about 3 weeks ago. I have had no issues with the method I use. However, do it at your own risk!

    Firstly, if there is any residual gas inside, I use it in the usual method..... lots of BBQ's etc. or if you're dodgy like me then you will decant into another lpg cylinder. If there is only a very small amount then I may be inclined to vent it into the open but only if there is a very small amount as venting large amounts of LPG is likely to find an ignition source next door and come back to bite you!

    Once the LPG cylinder is "empty" as in the contents are at the same pressure as atmospheric pressure, I carefully remove the valve and fill with water. Let it sit for a week. Then empty and cut it open. The residual gas smell is as others have said is Methyl Mercaptan. Our noses are so sensitive to that stuff that when it's mixed with the gas, our noses can detect gas (LPG or Natural) long before it even registers on a gas detector.

    Filling with CO or CO2 or leaving it filled with water when making the first cuts would further reduce any risk of flashing.

    I always use an angle grinder (lots of sparks) and never had an issue.

    I have another LPG cylinder waiting to be cut up. It still has a fair amount of LPG in it and so have been using it for BBQ. If anyone is interested, I can do a little experiment. I'll empty it, remove the valve, fill with water and then take it to work and do some testing with our gas detector. The gas detector will measure how close the gas mix is to the flammable range as a % of the LEL. The lower explosive limit (LEL) of propane is roughly 2% and the Upper Explosive limit (UEL) is about 10% by volume. Outside of these ranges and it's either too lean or too rich to burn. By using the above methods of emptying, we would be aiming to get the % volume of LPG way, way below that 2% LEL.


    Our gas detectors are programmed to go into alarm at 5% LEL. A fart will send it into full alarm....... apparently.

    WRT the toxicity of Methyl Mercaptan, I suspect that our noses are so so sensitive to the stuff that we would smell it long before we gave ourselves a harmful dose, long before reaching any PLV (peak limitation valve) STEL or TWA value. Our gas detectors at work also have a PID (photo ionisation detector) which measures volatile organic compounds (VOC) in PPM. The same experiment would also pick up any residual levels of the Methyl Mercaptan. I'd be happy to report those figures too.

    Cheers,

    Simon
    Girl, I don't wanna know about your mild-mannered alter ego or anything like that." I mean, you tell me you're, uh, super-mega-ultra-lightning babe? That's all right with me. I'm good. I'm good.

  15. #15
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    Quote Originally Posted by simonl View Post
    Mostly in an effort to build the "perfect" camp coonara.
    Seems every one that wants to cut one open, wants to turn it into something that will hold a fire.

    That would be the other method, empty it, pull the valve so it has a gaping big hole in it that wont allow pressure to build up, let it vent for considerable time, and toss it on a camp fire, and let it burn out.

    Surely there's not an issue with burning Mercaptan? Or are gas fired barbecues about to be out-lawed, due to the toxicity its putting into my snags.

    Regards Phil.

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