This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

System Head Curves

I am developing system head curves for high service pumps.  I am generating a few curves to cover various flow ranges.  I have noticed that the system curve starting point is lower than the head required to pump to the desired hydraulic grade line.

For instance, in one system curve I am using a suction side hgl of 957 feet and a discharge side hgl of 1067 feet and my flow requirement is 7 mgd.  This would mean that at least the pump would need to produce 110 feet of lift to meet the discharge side hgl.  However, the curve I generated in watergems starts out at 0 mgd and the head is calcuated at 98 feet.

I guess my question is why would the system curve ever dip down below the minimum static head?

Respectfully,

Aqueduct

Parents
  • Hello,

    This could happen if the downstream boundary is supplying demands. Consider the below example network:

     

    You might expect the "static" head (point on the system head curve at zero flow) to be 150 - 100 = 50, but when the pump is off (flow = 0) the difference between the suction and discharge HGL is only 48 feet. The reason is because when the pump is off, the tank supplies the demand at J-2. The flow from the tank induces head losses in the pipe between the tank and J-1, reducing the HGL on the suction side of the pump.

    If this doesn't help, I would suggest submitting your model to technical support or explaining a bit more about how your network is set up.


    Regards,

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

Reply
  • Hello,

    This could happen if the downstream boundary is supplying demands. Consider the below example network:

     

    You might expect the "static" head (point on the system head curve at zero flow) to be 150 - 100 = 50, but when the pump is off (flow = 0) the difference between the suction and discharge HGL is only 48 feet. The reason is because when the pump is off, the tank supplies the demand at J-2. The flow from the tank induces head losses in the pipe between the tank and J-1, reducing the HGL on the suction side of the pump.

    If this doesn't help, I would suggest submitting your model to technical support or explaining a bit more about how your network is set up.


    Regards,

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

Children