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Gas orifice design

ChrisJ
ChrisJ Member Posts: 16,963
edited December 2017 in THE MAIN WALL
Hi all.

I would ask @Tim McElwain but I think he's got more important things to deal with at the moment.

Gas orifice drill sizes are readily available but what I can't find is the length of the orifice. As in fine I need a #31 drill size but how deep should it be at that dimension before going larger?


We made this where I work to convert an outdoor lpg hurricane burner to NG.

Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.

Comments

  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 18,819
    I would think you would drill it all the way through. Are you concerned with the orifice being long that the #31 will be too restrictive at that length??

    most orifice's are about the size of an 1/8 pipe plug so I guess if it's a long orifice drill it oversize and leave a 1/4" drilled at #31.

    Just guessing. Anyway to clock the meter after drilling to check it out?
  • ChrisJ
    ChrisJ Member Posts: 16,963
    > @EBEBRATT-Ed said:
    > I would think you would drill it all the way through. Are you concerned with the orifice being long that the #31 will be too restrictive at that length??
    >
    > most orifice's are about the size of an 1/8 pipe plug so I guess if it's a long orifice drill it oversize and leave a 1/4" drilled at #31.
    >
    > Just guessing. Anyway to clock the meter after drilling to check it out?

    Yeah that's what I'm concerned about. I'm hoping there's engineering data out there for it.

    I'm hoping to fire it up this weekend to see how it works.

    Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.

  • Bob Harper
    Bob Harper Member Posts: 1,134
    There are charts in NFPA 54' showing BTU flow rates for a given orifice at a given pressure for a given gas.
  • ChrisJ
    ChrisJ Member Posts: 16,963
    Bob Harper said:

    There are charts in NFPA 54' showing BTU flow rates for a given orifice at a given pressure for a given gas.

    Yes.
    And none of them specify how long the orifice is, only it's diameter.

    Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.

  • ChrisJ
    ChrisJ Member Posts: 16,963
    @captainco Any thoughts on the length of an orifice? Is there a design spec for it?

    Like I said I need a #31 orifice diameter but how long? It's got to have an effect to an extent unless anything 1/2" to 1/16 is considered fine

    Single pipe 392sqft system with an EG-40 rated for 325sqft and it's silent and balanced at all times.

  • ratio
    ratio Member Posts: 4,149
    It looks like as thin as possible yet able to withstand the forces applied: see http://www.springer.com/cda/content/document/cda_downloaddocument/9783319168791-c2.pdf?SGWID=0-0-45-1505283-p177306192

    See § 2.5.5 in particular.

    Until you end up with what's basically as piece of pipe, I doubt that it matters much for our application.

    ChrisJ

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