I have model with different scenario, the required scenario is named "PH-improvements" .when i make run notification " pump can not deliver flow or head " for example PS1-2 can not deliver flow or head .
Hi Mohamed
This "Communities Feedback Forum" is specifically for discussions and questions relating to the operation of the overall Communities pages.
The question you've raised here appears to be regarding a specific Bentley software package.
Would you be able to provide details for which software and version this is regarding.
We can then assign your query to the most appropriate support team or discussion forum associated with this software.
RegardsAndrew BellTechnical SupportBentley Systems
the issue is related to watergems but i did not receive any reply
Hello Mohamed,
I cannot see the model uploaded by you but here is some related information which may help you regarding the issue.
This user notification would occur when your pump is operating beyond the pump curve specified. See this article which can help you troubleshoot this issue: User Notification: "Pump cannot deliver flow or head"
You can see if the boundary downstream of the pump is lower than the upstream boundary. If the pump head is not required to overcome downstream elevation you could be seeing negative head values in system head curves.
Let me know if this helps.
I sent to you the model by email
I reviewed the model and when I first validated it, gives me error that the following GPV is not connected to the reservoir. You need to check the CONNECTIVITY. I bypassed the flow just to check the further errors and making pipes and GPV inactive (as shown below)
Following are the observations (errors) -
1. The network is unbalanced - the system is not able to converge due to instability.
The "Network Unbalanced" user notification means that the program could not converge on a balanced solution within the maximum number of trials. Between calculation iterations, the program checks the relative change in flow, which has a default value of 0.001. If the relative flow change is below the "Accuracy" value designated in the calculation options, the time step is balanced or is said to have converged. If the relative flow change is greater than the Accuracy value, the program will try another iteration. If the program reaches the maximum number of trials without finding a solution, the "Network Unbalanced" user notification is generated.
I request you to check the troubleshooting steps mentioned in Troubleshooting the Network Unbalanced or Cannot solve network hydraulic equations user notification wiki article. Kindly check the following settings -
- General model set up.
- Multi-point pump curves
- GPV's
2. Tanks are getting empty and full -
When the water level in the tank reaches the minimum or the maximum (as specified in the properties) during an extended period simulation (EPS), a built-in altitude valve will close the adjacent pipe. An empty tank will close the downstream pipe since it cannot drain anymore and a full tank will close the upstream pipe since it can't fill anymore. Once the opposite conditions occur in the system, the pipe(s) will automatically open back up. please see the following wiki article.
What happens when a tank becomes empty, full, overflows?
Typically you would have controls in place that monitor the tank level and either turn on/off an upstream pump (if the source is at a lower elevation), or open and close a valve (if the source is at a higher elevation and feeds the tank by gravity). See the following article in our wiki for more information on controls:
Creating Controls - Conditions, Actions, and Control Sets (CONNECT Edition and V8i SELECTseries 6)
If your demands have a diurnal pattern applied, then the demand at a particular timestep may be greater than the sum of the downstream base demands (if the pattern multipliers are greater than 1.0) and if the FCV was set to the sum of the base demands, then the downstream demand and tank outflow may be greater than the FCV setting at some times, and thus drain the tank. Try graphing flow in the pipe downstream of the tank.
3. Pump can not deliver flow or head -
This message can occur if the pump was trying to operate at the shutoff point (zero flow) or the pump would have to add more head to the system than is specified in the shutoff head, in order to elevate the water up to the downstream boundary condition. It will also be generated if the pump is operating beyond the defined pump curve. See this article which can help you troubleshoot this issue: User Notification: "Pump cannot deliver flow or head"
Kindly share the updated model after reviewing, if you still see the issues.