[Jewelry making - Article 00567] - Re: [Orchid] Acetylene prestolite torch safety

[Ed Howard]

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    I would not characterize acetylene as "safest for use inside your
    home" for a few reasons. Though acetylene will not pool in low areas
    like propane or other liquified gases, it does have the widest range
    of combustibility of any gas and takes the coolest spark to ignite. 

    Leaked acetylene will combust in any mixture in air from 2% to 80%
    and a spark from static electricity (635F) is enough to ignite it. If
    you smell leaked acetylene your next thought should be whether if you
    touch something you are going to throw a static electricity spark and
    start a fire! 

    By comparison propane and natural gas have a range of combustibility
    of about 5%-15% and require a much hotter spark to ignite; propane
    needs a 920F spark and natural gas needs a 1,163F spark. Natural gas
    also has the advantage of being much lighter than air (specific
    gravity of.6 compared to acetylene at.9 and propane at 1.5) so it too
    rapidly dissipates. 

    The other danger is simply having a cylinder of fuel gas in your
    home. Cylinders store a lot of energy in a small place. Consider that
    a "B" tank of acetylene has 40 cf of gas or 58,800 BTUs of energy
    while a 5 lb propane tank has 108,000 BTUs. To get a feel for this,
    one BTU equals the energy from lighting one wooden kitchen match.
    Think about that acetylene tank as having 58,800 matches or the
    propane tank as having 108,000 matches and they danger that would
    present if they were all lit at once. 

    In London, UK there is a safety campaign focused on acetylene
    cylinders, which you can link to here:
    http://www.london-fire.gov.uk/news/cylinders.asp#safe_cylinder 

    The website notes that from January - June, 2007 there were 17 major
    acetylene incidents in the city that caused roads and buildings to
    be shut down. The website notes: 

    "Acetylene presents a unique risk in comparison to all other bottled
    gases due to its instability. Heating or mechanical shock can cause
    spontaneous internal heating. The risk of explosion remains for 24
    hours unlike all other gases which are safe once the initial fire has
    been extinguished. In the past whole cylinders and fragments have
    travelled for 175 metres." 

    Heating can result from a torch flashback and "mechnical shock" can
    be as simple as a cylinder falling over or being dropped. If this
    happens it would be like lighting all 58,800 matches at once. 

    My company manufactures natural gas pressure boosters, systems that
    eliminate gas cylinders from jewelers' studios. Our customers
    include jewelers in shopping malls, where gas cylinders are normally
    prohibited and our systems are permitted in the downtown Los Angeles
    Jewelry District where all gas cylinders are also prohibited. When a
    Fire Marshal in Boulder, CO came upon one of our systems being used
    by a glass lampworking artist his comment was, "This is a fireman's
    dream!" 

    I would argue that gas-to-gas natural gas is far safer than
    acetylene, and using a torch booster as the gas supply is safer than
    any gas in a cylinder. 

Ed Howard
G-TEC Natural Gas Systems
www.safe-t-gas.com
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