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Thread: pump shutoff head

  1. #1
    Member
    Join Date
    Dec 2016
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    56

    pump shutoff head

    I have a pump with a shutoff head 76 m
    However, when I run the simulation I get a head gain of 96 m
    The pump is pumping from reservoir with 5 m head.

    Why do I get a head gain of 96m (shutoff head is 76m)? IS it possible to set up the pump to automatically get closed when the head is 76m or higher?
    How can I set up the pump to turn on at specific time and shut off at other specific time?
    Is it possible to set up the pump to turn on and to turn off at specific times depending on the flow or pressure?

    Pump1.JPG
    Last edited by Vladyman; July 11, 2018 at 10:30 PM. Reason: added more questions

  2. #2
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    Innovyze Employee



    Join Date
    May 2015
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    386
    Vladimir,

    It looks like at one point you used a curve for this pump and or a constant power pump option. Are you by chance looking at results that are from either another scenario or from a previous run? It is difficult to know exactly what is going on without seeing your model, but it should not be not physically possible for a pump to have a shut off head of 76 M and pump at 98 M so our best guess is that you may have been changing the pump characteristics and pump type (based on the Curve being specified and the constant power values filled in) and are potentially looking at results from either a different scenario or a previous run.

    Please look in your model explorer and see what is the current active output. It should show as "*Active*:Standard" if it is the last model run for this scenario. If a run crashed or failed it may show a previous scenario named run in the area to the right of the "Run Manager" button (aka the running man) in the model explorer.
    (click if need a larger image)
    Active Standard.png

    The only other thing I could think may have occurred is if you are using a very high accuracy (above 0.01) in your simulation options may cause inaccurate results or if the scenario reached max trials the results may also be inaccurate.

    As for your other questions:
    Why do I get a head gain of 96m (shutoff head is 76m)? IS it possible to set up the pump to automatically get closed when the head is 76m or higher?

    Innovyze Response: This should not be possible and most likely represent results from a different model run. Look in your Output Results for the pump and find the "Type" field. Does it show as Exponential Curve Pump or something else? If it is not showing as "Exponential Curve Pump" you are definitely not looking at the results associated with this pump input shown. Try plotting the output pump curve for this pump by using the "Pump Curve" output option listed under Graphical Output. This will place a dark point on the pump curve used. If the curve does notreflect the input data shown, you are not looking at current output associated with this input. Try running the model again and do you get a green light or a red or yellow light? Yellow indicates one or more warning messages were issued while red means the model would not converge to a solution. You can use the full status report to review warning messages.

    Output pump curve (you will have to select the pump element when you hit "Open")
    (click if need larger image)

    output pump curve.png

    A pump operates where the system curve and the pump curve intersect and if the head gain for a pump exceeds the shutoff head the pump cannot physically operate. See this Blog post on system curves for more information: Introduction to System Curves – Basic Hydraulic Considerations

    How can I set up the pump to turn on at specific time and shut off at other specific time?
    ​Innovyze Response: As understanding controls is a fundamental aspect of hydraulic modeling, we suggest you review the help sections under Content List: Using InfoWater -> Controls regarding simple and rule based controls to understand how these controls work. This will give a detailed explanationof the two major types of controls within the model software. I would review both the methodology and Dialog box help sections for simple and rule based controls:

    (click if need larger image)
    Simple and Rule based Control methodology.png


    Controls can most certainly be created to operate on "clock time" or simulation elapsed time as desired.


    Is it possible to set up the pump to turn on and to turn off at specific times depending on the flow or pressure? Innovyze Response: If after you review the help sections noted above you should have a much better understanding of how controls work and it will show you can easily control a pump based on discharge pressure or flow. However, It is not recommended if your pump turns on and off by system pressure to use a simple control to turn the pump on by low pressure, but to consider using a rule based control to turn the pump off by low flow as this is often more stable. If you use rule based controls make sure to adjust the rule timestep (and WQ timestep as a matter of practice) in the time settings to be 1/10th the hydraulic timestep for best results (EPANET recommendation) and have the "Enable Rule Control" in the General tab of the simulation options checked for rule based controls to work properly.

    The modeler can easily set up controls based on pressure at a junction, flow in a pipe or level in a tank as things controlling pump operation.


    Patrick Moore

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