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Turning on VSP based on Condition in WaterCAD

Parsa Pezeshk
Offline

I am modeling a pump station (set as VSPs in parallel, lets name them Pump Set 1) that is fed from an above-ground storage tank by gravity and pumps to a distribution system. I put the pump controls on the pump station discharge pressure and it is working as expected. 

My above ground storage tank is fed by another set of VSPs (lets name them Pump Set 2) (different location) that pump from a chlorine contact basin (with control set on HGL on the chlorine contact basin, to maintain) and that is working as expected also.

Depending on the flows in and out of the storage tank, the storage tank can become full. In this case, I would like to set up controls that would turn off the chlorine contact basin pumps and activate another set of VSPs in parallel (Pump Set 3) (not the two sets already mentioned) to pump directly from chlorine contact basin to injection wells. 

How can I do this? 

WaterCAD does not seem to like it when I set Pump Set 3 pumps (VSPs with control on chlorine contact basin) to OFF at time zero of my EPS since there are two different pump sets with the same control nodes even though the Pump Set 3 is OFF initially. I would like the two pump sets to alternate based on my condition (if storage tank is full, Pump Set 3 to take over, if storage tank is not full, Pump Set 2 to pump to storage tank).

  • 0 Offline

    Hello Parsa, 

    What error messages do you receive after you set controls for Pump Set 3? OR is it unable to solve hydraulic calculations kind of error? More details about it would be helpful. 

    Does the below situation describes your case as well, please go through it and let us know.

    Modeling multiple VSPs where only one turns on at a time  

    If not then please elaborate the issue, if required you may upload model files as well. 

    Regards,

    Sushma Choure

    Bentley Technical Suppport

  • 0 Offline in reply to Sushma Choure

    Thank you Sushma. I will upload the model files along with more information. I had some ideas that wanted to test first to see if it would resolve the issure. 

  • 0 Offline in reply to Sushma Choure

    Hi Sushma. I uploaded the model. I get a "Network Unbalanced" message and my controls are not working.

    Here is a schematic of my system:

    Here is the system description and what I would like to achieve:

    PMP BW34, PMP BW35, PMP BW36 are set as VSPs set to maintain the HGL in CCB
    (to pump out whatever flow comes into CCB) and Pump to Above-ground Storage Tank 
    ---------------------------------------------------------------------------------------------------------------------
    AST feeds PMP3, PMP4, PMP5 by gravity.
    PMP3, PMP4, PMP5 are set as VSPs to maintain a set pressures at node D
    ---------------------------------------------------------------------------------------------------------------------
    The HGL in the AST varies based on inflow from PMP6 and PMP7 and outflow to PMP3, PMP4, PMP5
    ---------------------------------------------------------------------------------------------------------------------
    During the EPS, if the AST becomes full:
    Turn OFF PMP BW34, PMP BW35, and PMP BW 36
    Turn ON PMP1 and PMP2 as VSPs with control on CCB HGL (meaning, PMP1 and PMP2 would maintain the level in CCB  instead of PMP BW 34, PMP BW35, and PMP BW36)
    ----------------------------------------------------------------------------------------------------------------------
    Once the HGL in AST decreases to a set value:
    Turn OFF PMP1 and PMP2
    Turn back ON PMP BW34, PMP7 BW35, PMP BW36 with VSP control on HGL in the CCB

    Here is how I wrote the controls:

    If HGL in the AST goes above 129 and there is a flow in pipe P-BWPMPS-Discharge (meaning AST feed pumps are on), then turn PMP BW34, PMP BW35, PMPBW36 OFF (so that no flow is pumped to AST anymore).
    and OPEN GPV-Sump-EffBox and turn PMP1 and PMP2 ON to pump the flow coming in to CCB to the injection well
    ------------------------------------------------------------------------------------------------------------------------
    If there is no flow in pipe P-BWPMPS-Disch (meaning AST feed pumps are OFF) and the HGL in AST is below 129 and above 120 (HGL has not reached 120), keep PMP BW34, PMP BW35, PMP BW 36 OFF (so that the pumps do not oscillate on and off based on small incremental HGL changes above and below 129)
    -------------------------------------------------------------------------------------------------------------------------
    Once the HGL in the AST reaches 120, then CLOSE GPS-SumpEffBox and turn OFF PMP1 and PMP2 and turn ON PMP BW34, PMP BW35, and PMP BW36 (to fill AST again)
  • 0 Offline in reply to Parsa Pezeshk

    Hello Parsa,

    I took a look at the model. Part of the issue may be with the controls. First, there are controls to turn PMP1 and PMP2 on based on some conditions. However, they cannot turn on because of the setting of the GPV GPV-Sump-EffBox. The GPV is off at all time steps, meaning that the pumps will be unable to pump into the downstream tank. 

    The other pumps (BW34, BW35, and BW36) are a part of this control as well. As these are associated with the tank CCB Wet Well, be aware of how the controls will be expected to work here. This link has details. However, the GPV feeding this tank may also have an impact on what is happening with the controls. 

    Related to the GPV, there is a control that turns this valve off, but none that will actually turn it back on. If there should be a control that turns this on, it should be included as well. If there is no control to 

    Overall, I would start with reviewing the controls and the general setup of the system to assure that everything is in order.

    Regards,

    Scott

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