View Full Version : Pump open but exceeds max flow.-InfoWater

October 29, 2015, 06:47 AM
Using InfoWater and after running a scenario 3 of my pumps say open but exceeds maximum flow. Not sure what is causing this problem.

Patrick Moore
October 29, 2015, 07:35 AM

This warning message occurs when the pump is defined as using a multiple point pump curve, and the pump is supplying more flow that the last defined point on the curve.

This picture may illustrate the case more clearly:
(click for a larger image if necessary)

Generally once you know what causes this error you can troubleshoot potential causes in the model. When this occurs, it is generally a good idea to check the following as part of the troubleshooting to remove this error:
1) Are the pumps exceeding their capacity? If so this may indicate additional pumping capacity may be needed for this facility
2) Is the demand for the zone in question higher than it should be? Perhaps a large fireflow demand was not deleted and is increasing the demand beyond normal operation. Verify the total demand in the zone that is pumped too to make sure it is as expected.
3) Is the pump curve added to the model fully replicating the acceptable operating region for the pump? Review the pump curve and if need be add an additional flow point on the curve to replicate the acceptable flow region defined on the pump curve. Extending the pump curve beyond the flow range shown on the curve provided is generally not a desirable operating point for the curve which is why the model will generate warning messages just in case.
4) Are other points of supply that feed the zone in question not operating which is forcing these pumps to supply more water than they should? If so fix those controls
5) Should more pumps be turned on at this pump station to help in high flow conditions, but the pumps are missing controls to do so.
6) Are the pumps used poorly selected for the given operation so that they tend to operate on the far right of the curve? This is always a possibility. Run some quick hand calculations to verify. One method a very experienced engineer once taught me was to calculate water level on the suction side to water level on the discharge side and to add 10 psi (23.1 ft) of headloss as an initial guess. If there was a suction tank and a discharge tank you then took the difference of the maximum water level in each tank as the static lift. If its a closed zone just check the HGL difference of both zones. If this number is much lower that the head gain the pumps are operating, it could indicate (assuming everything else is correct in the model) that the pumps may not a good fit for that operation.

We hope this helps.

Innovyze Support