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Thread: First gas forge build please help me across the line

  1. #21
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    What happened to this thread? Forge builder I would like to hear your response to this, as a user of a gas forge I would like to know if there is a safety issue I should be aware of that I am perhaps not.

  2. #22
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    Quote Originally Posted by Forgeron View Post
    What happened to this thread? Forge builder I would like to hear your response to this, as a user of a gas forge I would like to know if there is a safety issue I should be aware of that I am perhaps not.
    I think Corin already answered this question few times, eg here:
    Quote Originally Posted by niroc View Post

    The limits of flammability of LP Gas are approximately 2.4% - 9.6% gas to air. If we have too much air, or too much gas ignition and sustained combustion cannot occur. These are extremely narrow limits of flammability in the world of fuel gasses. Acetylene for example has upper and lower explosive limits of around 2% - 98% gas to air. It is suffice to say. That in a gas cylinder, hose and regulator, we will always have over 9.6% gas to air. It is physically impossible for a flashback to occur. If we are mixing with oxygen however and oxygen inadvertently goes back up the fuel gas line, or visa versa then yes, bad things can and do happen.

    The risk of a leak from the extra joints that you have when a flashback arrestor is used, and the risk of fitting breakage due to added leverage, is far greater than a flashback, which is not even possible.



    None of these standards even slightly suggest that flashback arrestors should be used.

    Gas forges are NOT in the scope of any welding standard, and nor is there such a thing as a standard for Furnaces, unless you are talking about the American version of the word that relates to central heating appliances.

    I trust this clears things up and explains my grumpy and tired response to the assertions made above. I am 100% open to questions and am happy to assist with anything I am competent to assist with.

  3. #23
    Registered Member Gof's Avatar
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    niroc

    let me see if i have this right as being a newbe and trying to get my head around some of the details takes me a lot long than i would like.
    So with this gas and air, a flash back arrestor would only be needed if the oxygen was in a bottle store under pressure and not when the oxygen is at normal atmospher pressure or do i have it wrong

    thanks
    gof
    grumpy old fart

  4. #24
    Dealer Corin Urquhart's Avatar
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    Quote Originally Posted by Gof View Post
    niroc

    let me see if i have this right as being a newbe and trying to get my head around some of the details takes me a lot long than i would like.
    So with this gas and air, a flash back arrestor would only be needed if the oxygen was in a bottle store under pressure and not when the oxygen is at normal atmospher pressure or do i have it wrong

    thanks
    gof
    grumpy old fart
    I think I understand the question but forgive me if not.

    Flashback can occur in any system where gas is mixed with air, subject to the mixture and flame speed. In an atmospheric burner this can (and sometimes does) occur in the burner tube, after the air has been mixed with the gas, IF the mixture has too much oxygen AND the pressure is very low (hence gas velocity is slower than flame speed). It makes no difference in such a system other than making a lot of noise in the form of loud combustion, and only if it is a very irregular occurrence.

    In a system where we introduce oxygen and mix with gas under pressure, gas or oxygen can conceivably flow into the pipe lines, flashback can occur and even steel will burn in the presence of oxygen. Bad things will happen i these circumstances.
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  5. #25
    Dealer Corin Urquhart's Avatar
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    Incidentally I am sorry that Forge Builder has disappeared.
    Was it something I said?
    I was very much looking forward to seeing the stack of information that was to be provided. Manners do maketh the man and if I offended with my "grumpy as" response to the implied accusation that my equipment was not safe or to standard, I am terribly sorry.

    I sometimes feel being able to say "I was wrong" maketh the man but that is just a feeling I get sometimes.

    Anyhow, carry on.
    Gameco's Knifemaking and Blacksmithing supplies has a new Web Store!
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    Registered Member Nemo's Avatar
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    As quoted "The limits of flammability of LP Gas are approximately 2.4% - 9.6% gas to air.", and knowing this full well, I provide the following example. On a recent camping trip we used a gas burner to heat water. One of those little fellas that screw directly to the top of the cylinder. Well, after some use, I found I could smell gas. Deciding to check it by smelling I wasn't able to pin point it and so, I took to it using my trusty cig lighter. as I suspected, ignition was found at the O'ring seal that lay between bottle and cylinder. I then put my face to it and blew it out (second shot mind you). As the cylinder was under pressure and the leak moderate, I had no issue doing this. Others in the camp literally bolted. I know this is not recommended practice by any stretch but when in the bush we do what we can... P.S. I was confident in my actions but would never condone anybody to do the same....Just my 2c.

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    Registered Member arpie12008's Avatar
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    I can also remember many years ago when a clever person decided to change an lpg bottle while it was on and a flame burning nearby. As soon as he loosened the connection a reasonable sized flame appeared at the bottle connection. He took one look at this and set off running. GREAT!! I ended up with some minor burns on the wrist from turning the valve off but certainly nothing exploded.

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