Problems when using a flow control valve (FCV) downstream of a pump

  Applies To 
  Product(s): WaterCAD, WaterGEMS
  Version(s): 08.11.XX.XX
  Area:  Modeling
  Original Author: Mark Pachlhofer, Bentley Technical Support Group


When using a flow control valve (FCV) to regulate flow in the system downstream of a pump station there are negative pressures in many nodes or the model is unbalanced/unstable.

Problem ID#: 67804


There could be multiple issues here:

1) The FCV's could be limiting the demand to a number lower than the total of the fixed demands you have in your model. If you add up the flow settings for all the FCV's that are active in your model they should be equal to or greater than the total fixed demand on the nodes in your model.

2) If the FCV's are providing right around the same flow as is demanded from the model the calculation engine can have trouble mathematically converging. Try adjusting the convergence check frequency, convergence check cut off, and the dampening limit in the calculation options to resolve this. You can also slightly increase the flow setting in the FCV's or if the demands in the model are actually pressure dependent demands then setting up a pressure dependent demand function might also help.

See Also

Ill-conditioning User Notification