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WaterCAD - PRV and PSV

Hi,

The model I'm working on is divided in two primary sections.

Section 1 is fed by a reservoir pumped into a PSV and a PRV in serie. The goal of the PSV in this case is to limit the maximum pumped value to 2300 lpm with a 92 meters of head and the PRV limits my head to 92 also to avoid pressures being too high on downstream nodes.

A single line leads to the Section 2 of the distribution network. I have a pump in this section that allows the reservoir in the first section to fill a tank at higher altitude.

Once the tank is at a certain level, the pump in Section 2 is closed, a pipe is opened to allow reverse flow at the pump location and the pump at my reservoir is closed to allow the whole system to be fed by the water tank. Once a certain level is reached, the pumps are started again and the pipe is closed to allow the refill of the water tank.

The system works fine as long as I keep the PSV inactive. Once I activate it, the PRV cannot supply pressure and the system becomes unbalanced. Considering that the sum of my demands is under 700 lpm, I'm not sure what could cause this issue.

Note: I'm working on an EPANET model that was converted to WaterCAD

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  • The PRV and PSV are two distinct valves in the system I'm working on. The setting should be fixed for both of them.
  • Please provide your model and let me know which PRV and PSV you are referring to.

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    Regards,

    Craig Calvin

    Bentley Technical Support

  • Here are some things you may want to consider:

    • The tank initial hgl needs to be between the control range (ex 324.00m).
    • One pump starts on and the other one starts off. Change the initial status of “PUITS” to off to be consistent.
    • It may be simpler to control PRV-3 directly instead of opening and closing the adjacent pipe. To open the PRV, have the control action set the setting (42 m) and to close it, have the control change the status to closed.
    • Whenever pump PUITS turns on, it seems to always add enough head to bring the HGL above the PSV setting. You could try removing PSV-4 and pump PUITS, then set the reservoir elevation to the PSV's hydraulic grade setting (292.85m).

    After making the above changes, all time steps balance with much less trials. I sent you a PM with a link to download a modified version of your model.

     

    Regards,

    Craig Calvin

    Bentley Technical Support