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Will flame flow backwards

  1. Jun 16, 2013 #1
    Consider this case.

    An LPG cylinder is used to provide LPG to a rubber pipe (3/8" diameter).
    If a regulator is attached to the cylinder, and the rubber pipe is just left open on the other side to let gas out, and a match is kept at the open end.
    Will the flame that is created at the open end of rubber pipe move all the way inside the rubber pipe and reached inside the cylinder? Or will the gas flowing at high velocity just not let the flame move back inside?
    The pressure regulator is set at 1.2 bar gage pressure, however the pressure gauge after the valve shows 0 reading, since the pipe is just left open to the atmosphere.

    The rubber pipe is about 2m long.

    A gate valve is used to let the gas out in somewhat controlled quantities.

    Schematic attached - i primarily wanted to know if the flame will move backwards and reach the cylinder or not (to know the safety issues)

    Attached Files:

  2. jcsd
  3. Jun 16, 2013 #2


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    As far as I know, it's the lack of oxygen in the tank and hose that prevents flame propagation. Don't take my word for it, though.
  4. Jun 16, 2013 #3


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    It will not travel back inside the rubber hose. However, it could burn the rubber hose off and continue to make it shorter and shorter....
  5. Jun 17, 2013 #4
    oh thats okay :P....

    all i didnt want is the flame going back towards the gas cylinder and blasting the cylinder!
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