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Adjust full scale in an orifice flowmeter

  1. May 20, 2009 #1
    Hi everybody!
    I hope somebody can help me...

    We are using a plate orifice to measure water feed to a reboiler; the pipeline size is 1" and the orifice was initially designed for 0-1800 kg/h of water, with a maximum pressure drop of 1000 mm water. As water feed doubles may I simply change pressure drop - by doubling the higher value of scale - to obtain water flow?

    Thank you ( ang forgive for my bad english...)
  2. jcsd
  3. May 20, 2009 #2
    Considering that water has virtually no viscosity and the changes in rheology due to pressure and temperature are negligible, I'd say you could assume a linear relationship between pressure drop and volumetric flow.

    This is not the case for other fluids: oil-based and gases (water vapor included).

    EDIT: I'm not sure what a "reboiler" is: I'm assuming that a single-phase fluid (clean liquid water) is flowing through your orifice meter. If you're dealing with more than one phase (suspended solids, gases), you won't get a reliable measurement using an orifice plate meter.
    Last edited: May 20, 2009
  4. May 20, 2009 #3


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    Ummm...the flow rate through an orifice is a function of the square root of the delta P. You might want to rethink that aspect. You will, most likely, introduce a bot more error by keeping the flow coefficient constant, but it shouldn't be a very large amount.

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