I have placed a FCV before pumpins station for flow control. I created a valve setting pattern same as the node on the downstream side to analyse it in EPS. but it is showing following errors:
1. FCV cannot deliver flow.
2. Maximum trials exceeded.System may be unstable.
3. Negative pressure at FCV.
4. Negative pressure at downstream junction.
5. Negative pressure at downstream pump
How can i fix these issues?
You can fix this by not using a flow control valve. While they my sound nice to a modeler, they are almost never installed in real systems and they are very expensive. There is almost always a better solution. What exactly are you trying to accomplish with the FCV?
Placing an FCV in front of a pump will cause NPSH problems which is what this model is telling you.
Hello Rahul,
See my responses below;
rahul dixit said:1. FCV cannot deliver flow
This means that the flow through the valve is less than the setting that you entered thus causing the valve to remain fully open i.e. inactive. See the below article on this for more details on resolution of this error;
What is the meaning of the notification "Valve cannot deliver flow", with regards to a Flow Control Valve (FCV)?
rahul dixit said:2. Maximum trials exceeded.System may be unstable
This message means that the maximum number of trials specified in the solver have exceeded and a valid solution is not found. You can increase the number of trials by going to Analysis > Calculation Options. Under the "Steady State/EPS Solver" section, double-click on the active calculation option to view the properties. Find the property field "Trials" and set this to a higher value, such as 400. See if this helps in resolving this notification. More details on this can be found in the below article;
Troubleshooting the Network Unbalanced or Cannot solve network hydraulic equations user notification
rahul dixit said:3. Negative pressure at FCV. 4. Negative pressure at downstream junction. 5. Negative pressure at downstream pump
This could be related to the FCV operation. Check to see if the FCV is limiting flow downstream which might be causing downstream elements demands not to be fulfilled or restricting flow to a downstream pump. See the article below for more details on this;
Problems when using a flow control valve (FCV) downstream of a pump
Let me know if this helps.
Regards,
Yashodhan Joshi
Bentley Technical Support
This Wiki article was created by Dr. Walski to support his comments in this post.
HTH,
Larry
I want to limit the water flow that can be pumped on the downstream side of a tapping point. I have a transmission main which is supposed to supply water at two different zones( say Z1 & Z2). But tapping for Z1 is on the upstream side of Z2 and also there is a pumping station for Z1, because of which Z2 is not getting the required amount of flow. So I placed a FCV on the tapping of Z1 on the upstream side of pumping station to limit the flow.
Did you get the negative pressures in the model before placement of FCV? Is the flow setting causing the negative flows i.e. check if downstream demands are satisfied.
Did you follow the troubleshooting steps mentioned in wiki provided by my colleague Yashodhan?
If required, you may upload model files for our review.
Sharing model files.
Sushma Choure
Bentley Technical Suppport