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How to connect a in-line storage tank into two pumps

Hello, I'm modelling a large size existing water supply network with many boosters through the network. There is also a tank with a pumping station through the network to provide water for a further network. So my question is how can I model a the the connected pumps to the storage tank?

I put the following conditions for both pumps :

If the tank level is below 10%, then pump status is OFF, else: Pump status is ON

But no flow is discharged by the pumps:

the error messages are:

Pump "PMP-22 cannot deliver flow or head."

and  "Tank T1-Tech Institute 1 is full."

Parents
  • Hello,

    The connection between the tank and the pump looks fine in the screenshots. 

    The following link has information on the pump notification: User notification "Pump cannot deliver head or flow".

    What is downstream of the pumps? If there is no other tank or reservoir and there are no demands, I would not expect flow from the pumps. The pumps would only deliver flow if there are demands downstream of it or a tank/reservoir to pump against.

    There are also controls on the pump. Make sure the pump controls are set up properly. If you are basing the control on a tank level, use the "<=" or ">=" operators. If you are using just the "=", you can have cases where the control is not applied because the condition is not exactly the value you are using.

    if that doesn't help, we will likely need to see a copy of the model.

    Regards,

    Scott

  • Also - 

    If the tank level is below 10%, then pump status is OFF, else: Pump status is ON

    I noticed you mentioned "else" - if you created only one controls, you should create two controls instead, one to turn the pump on and one to turn it off, with a range between it. For example one to turn the pump off if the tank level is below 10% and the other to turn it back on if the tank level is above 80%. This and more are mentioned in the following article: Troubleshooting Controls in WaterCAD and WaterGEMS


    Regards,

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

  • Dear all, 
    Many thanks for your responses. In fact,the problem was the water demands that were zero through the network after the pump. So now the water flows.
    But the message indication "Tank is full" persist and I don't know what is the problem. 


    Could you please help ?

    Thank you in advance.

    Regards

  • Hello Gashin, 

    Could you please check if controls are indeed followed, meaning pumps turn on when tank level is above 80 %? Create graph for tanks and pumps together to observe whether the controls are followed or not. Tank has separate inlet, check that path as well. 

    Also check pipe headlosses, it appears that there is large headloss in pipes by looking at user notifications, which would make pumps to add more head than required. 

    As mentioned by Scott in his earlier reply, if required provide copy of the model.

    Regards,

    Sushma Choure

    Bentley Technical Suppport

Reply
  • Hello Gashin, 

    Could you please check if controls are indeed followed, meaning pumps turn on when tank level is above 80 %? Create graph for tanks and pumps together to observe whether the controls are followed or not. Tank has separate inlet, check that path as well. 

    Also check pipe headlosses, it appears that there is large headloss in pipes by looking at user notifications, which would make pumps to add more head than required. 

    As mentioned by Scott in his earlier reply, if required provide copy of the model.

    Regards,

    Sushma Choure

    Bentley Technical Suppport

Children
  • Tanks become full because the inflow exceeds to outflow over time. That's a trivial statement. What does it mean for you?

    You need to look into increasing the outflow but if you have a fairly low demand downstream, that's not feasible. Then you can decrease the inflow. This can be done by turning off some pumps upstream of the tank or if that's not feasible, throttling the inflow to the tank using a control valve.  This can also be done by shutting off inflow to the tank when it gets to about 98% full and opening it when the level drops to say 60%.

    It's good to test out a lot of operational alternatives like this (e.g. peak demand/low demands, controlling inflow vs. outflow,... ) before you construct the pump station and your options become limited.

  • Also, what is the purpose of the tank on the suction side. Is it there to provide surge protection NPSH, or storage for the zone from which it is fed?

    The overflow for that tank should be consistent with the hydraulic grade in the zone that feeds it. One way to keep it from getting stuck full, is to make it taller and consistent with that HGL. The elevation of the overflow should be consistent with the other tanks in the zone.

  • Dear Tom, 

    Sorry for my late response. Many thanks for your complete response.

    Indeed the reason is storig water for the zone from which it is fed.

    Also, this is an existing system that I try to model. We are not yet 100% sure about the population of the city to have the exact water demands. But we are not so far from the reality. 

    How can I put the control valve for the tank?

  • Dear Sushma, Sorry for my late response. Thank you for your response. 

    I made the graph, in fact the graph shows that the tank water level varies slightly. The tank has almost 3m of height with following descriptions:

    And in controls I put if level is between 30% and 80% pump off and if less than 30% pump on:

    Is it correct?

    Could you please help?