System Design and Strategy Corrections Stabilize Pump Station Operations

The control strategy for the City of Roseville’s closed pressure Zone 2 pump station had become unstable during the transition from summer to winter demands. Bennett Engineering Services performed troubleshooting DPPS pumps, analyzed the cause of abnormal operation of two variable-frequency drive-controlled pumps, and determined a course of action to remedy the problem.

The team interviewed the station operations and maintenance staff to get an overall assessment of the problems, reviewed the SCADA-reported operating conditions, pump shop drawings and system control strategies, and the station’s pump curves. They recommended several levels of modifications to the operations strategy. Based on pump curves obtained from the original pump tests, engineering calculations were made to provide a pump station system curve to display the pressure/flow characteristics of the VFD pumps at a range of speeds. This system curve was then used to analyze the problems with the existing control strategy. Three system-fix options were prepared, requiring small to large budgets and requiring oversight ranging from manual to fully automatic.