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Finding if the correct pump is installed

  1. Nov 1, 2007 #1
    I am having problems with a pump installed.

    I am trying to determine if it is to large for the application because there is alot of cavitation during the process. I have the pump information 60GPM with a 5Hp Motor. RPM is 1725. How can i calculate lbs/hr of the fluid flowing?
  2. jcsd
  3. Nov 1, 2007 #2

    jim mcnamara

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    For water @8.33lbs/gal:
    Code (Text):
    60(gallons per minute)  * 60(minute in an hour) * 8.33
    if the pump never cavitates.... this would be the max possible flow.
    If the pump cavitates, you'll have to measure the actual outflow rate for one minute which is arguably the best solution. Get a forty gallon container, direct the output into the container for one minute. Substitute that value into the equation above.

    If that is physically impossible you will have to estimate your flow. Can you restrict outflow? If so keep restricting outflow until no cavitation occurs. Then estimate what the reduced flow is as a function of the restriction diameter vs the output diameter.
    There will be slop in there, because as head pressure goes up, the pump has to not only lift water, but also push it out through the restriction. Remember Bernoulli.

    Sorry if this is excessivley trivial, but I can't tell what your situation is.
  4. Nov 1, 2007 #3


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    If the pump is cavitating, I would look at the NPSH you have in your system. It sounds like you are trying to pull to much on the inlet.
  5. Nov 1, 2007 #4


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    Can you tell us a little more about your specific system layout?
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