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user notification Pump - hammer analysis

Hello,
I am working on hammer analysis for water distribution project which consists of pumps, rising mains, ground tanks.
I am working on two scenarios for the same network

1.       Without surge protection: in this scenario no user notification error and network is working fine with high negative pressure.

2.       With surge protection: In this scenario I have add surge tank near the pump station and validated the network it’s showing a user notification "Combined pump and motor efficiency should be between 30% and 95% inclusive. Check your pump definition."

Pump Definition:
Head tab:  
Pump Definition type: Design point 1
Efficiency tab:  
Pump Efficiency: Best Efficiency point
Motor tab:  
Motor Efficiency: 75%
Transient tab:  
Motor and pump Inertia: has been calculated using the pump calculator
Speed (full): 1500 rpm
Reverse spin allowed is: deselected.
  Please kindly help me to resolve this problem
Thanks,
Digvij Puli
  • Hi Digvij,

    The efficiency is different depending on the operating point of the pump. In the properties of the pump in question, look at the pump head and flow for the timestep you're using for your initial conditions, then compare that operating point with the graph at the bottom of the pump definition dialog to see what the pump efficiency is. Then, multiply that efficiency times the motor efficiency to get the overall efficiency.

    Because the four-quadrant characteristic curves (based on the selection of Specific Speed) used during the transient simulation are developed for pumps at their ‘rated’ values, it is important for the pump to be operating near its best efficiency point for the initial conditions.

    If you need further help, please send the model to technical support.


    Regards,

    Jesse Dringoli
    Technical Support Manager, OpenFlows
    Bentley Communities Site Administrator
    Bentley Systems, Inc.