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Adding FCV, while pressure not changed!

Dear All

I've a model with two scenarios, Average and Peak, when I added a flow control valve on the average scenario, nothing changed! as image below

on the other hand when I placed the FCV on the Peak scenarios there was a drop in pressure as shown below

Is there any problem in the model? may you help us?

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  • Yaqoub,

    A Flow control valve will throttle to attempt to keep the flow at or below the desired flow setting. In your first screenshot, the flow through the FCV is most likely already below the setting which means the valve is fully open and hence you have no headloss through it. In the second screenshot the flow appears to be equal to your flow setting, so it is throttling (partially closing, with headloss) in order to restrict the flow to that amount. The headloss you see is the headloss needed to cause the network to balance on that reduced flow. See more in this article: Why do I see such a large headloss through my FCV, PSV or PRV?

    With that said - what does this FCV actually represent? We have found in many cases that an FCV is used in cases where it may not be the best choice. See more in the following article and in the blog post linked to at the bottom of it: Using a Flow Control Valve (FCV)


    Regards,

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

  • Many thanks for your feedback

    But how can the larger flow need throttling of the valve while smaller flow need to be fully opened!

    second screenshot showing peak flow with value of 49,000 m3/day while the first one showing the average flow of 33,000 m3/day?

    please clarify?

  • Where does the water flow to in your model? WaterGEMS is demand driven, so if the total combined demand behind the FCV that is supplied through the FCV in the first scenario is lower than the setting of the FCV, the FCV will not throttle. If the total combined demand behind the FCV rises to above the flow setting of the FCV (second scenario), the FCV will throttle to keep it's flow setting. Water will have to be supplied from other sources in your model in this case, if the source upstream of the FCV is the only source in the system, errors will be generated. 

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  • Where does the water flow to in your model? WaterGEMS is demand driven, so if the total combined demand behind the FCV that is supplied through the FCV in the first scenario is lower than the setting of the FCV, the FCV will not throttle. If the total combined demand behind the FCV rises to above the flow setting of the FCV (second scenario), the FCV will throttle to keep it's flow setting. Water will have to be supplied from other sources in your model in this case, if the source upstream of the FCV is the only source in the system, errors will be generated. 

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