Flow control valve (FCV) elements are the most abused elements in WaterGEMS/WaterCAD. If I had my way, I would eliminate them as model elements.
In the many years I have been working with water and wastewater systems, I can’t recall ever seeing an actual valve that behaves the way that the FCV model element behaves. There are always better ways to model valves that control flow. Before you insert one in a model, you need to ask yourself if you really have a valve that will behave this way. According to the WaterGEMS/WaterCAD help.
“FCVs are used to limit the maximum flow rate through the valve from upstream to downstream. FCVs do not limit the minimum flow rate or negative flow rate (flow from the To Pipe to the From Pipe).”
If you search for flow control valves on Google or Bing, you won’t see any listed for the large sizes that exist in water and wastewater systems, and perform as described above. That’s because there are better ways to control water systems and disadvantages to using an FCV that the model describes.
A model FCV is at least four different components:
Plus, you’d need a power supply and associated wiring and possibly a method to transmit information about the valves back to the control room, usually through the SCADA system.
Another problem with an FCV is that you have it set for a given flow (say 40 L/s) and the downstream demand is higher (50 L/s) with no other source, the model will not run correctly because it can’t solve the equations.
The instance where you can use one is in a scenario where you want to use the model to prove to someone that the FCV is a bad idea.
But I could be wrong. If somebody has a good application of FCVs in a real system, send it to me at firstname.lastname@example.org. If you have a picture of such a valve on a big pipe, send it to me. There must be some exceptions to what I wrote above, and I’m always willing to learn.
If you want to look up past blogs, go to https://blog.virtuosity.com/tag/water-and-wastewater.
If you want to contact me (Tom), you can email email@example.com.