[Jewelry making - Article 00244] - [Orchid] Natural Gas - Actual Numbers

[Dan]

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    There seems to be much confusion on the list about natural gas
    torches. 

    Residential natural gas is supplied to the house at a fixed pressure
    typically no more than 11" WC (water column) this is about 1/2 psi.
    If they can't tell correct you information about the torches they
    sell without having more information, Tech support should be given
    guidelines as to what questions to ask and where to go to get the
    answers. Too much ignorance about the issues from even the Sales
    people (so called tech support) at the OEM. 

    I think 3/4 " pipe equipped with a back flow prevention device in
    the piping or on the torch will work for most anything except high
    heat requirements like casting. The oxygen will be adjusted at it's
    regulator. No adjustment for the Natural Gas except the hand valve.
    And bigger tips (orifices) used than for LP or Acetylene. Cooler
    flame, less heat, slower heating time etc. 

    To amplify: The regulator at the house meter supplies no more than
    1/2 psi. More can damage the gas valves used on furnaces, water
    heaters etc. (It's printed right on the side of the valves. approx 14
    in w.c. to 1/2 psi) When all appliances are shut off the pressure
    rises to a "lock up" pressure from the meter regulator so setting at
    11 in wc keeps it below 1/2 psi. The gas valves at the furnace etc.
    drop the pressure to approx 3.5 inches of water column to feed the
    burner orifices. Natural Gas has less heat content per cubic foot than
    LP (propane) the standard is 1 therm; 1000 BTU's per Cubic Foot for
    Natural Gas. If I convert a furnace from Natural gas to LP the
    regulator in the gas valve at the furnace is removed and the
    regulation is provided by the LP regulator at the house. The standard
    is 10.5 to 11 in wc pressure for LP. The orifices are changed to ones
    with a much smaller hole. Altitude enters into the picture somewhere
    also. 

    Given:
       altitude 0-2000 feet
       standard heat content of gas (LP or Natural)
       pressure at orifice
       size of orifice
       the heat output should be able to be figured

    Anyone can measure inches of water column by using a glass and
    hooking a tube to the gas. The tube is inserted into the glass with
    the other end connected to the gas source. As the tube is raised or
    lowered into the glass bubbles form from the end. At the point that
    the bubble forms but doesn't push out you measure the depth of
    insertion into the water. That is Inches of Water column! 

    All of the talk about pounds of pressure for a natural gas is for
    large systems like glass kilns, factories, or long piping systems. My
    suggestion is to see if the torch tech support can or will, supply
    heat output ranges (BTU's) for given size tips. Then a regulator
    supplier of natural gas regulators should be able to tell you if it
    is possible with standard available gas pressures and what size line
    is needed. 

Dan Wellman


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