AWWA ACE61828

AWWA ACE61828 To Lift or Boost? Modifying the Operation of an Existing Pump Station to Maximize Energy Efficiency
Conference Proceeding by American Water Works Association, 06/17/2005

Vandermeyden, Carel

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At the Greater Cincinnati Water Works (GCWW), energy management is an importantcomponent of operating all pumping facilities. During a recent energy managementanalyses of a 35 mgd pump station, it was determined that significant energy savingscould be achieved if the pumping operation was radically changed. The normal operationof the facility was a "dump and pump" operation, where the water from the upstreamdistribution system fills the reservoir, and then the water is pumped from the reservoir tothe next pressure zone. Because the inlet pressures to the reservoir were significantlyhigher than anticipated (70 psi versus 20 psi), an innovative solution was developed toconvert the pump station from a "dump and pump" operation to a booster pumpoperation. Extensive hydraulic and economic analyses were performed to determine if theexisting pumps could be modified to efficiently operate as booster pumps, therebylowering the required horsepower usage and capturing significant energy savings.However, the pump's ability to also operate as a lift pump had to be maintained tocontinue using part of the 2.5 MG storage reservoir for water quality purposes. Thehydraulic analyses showed that by carefully trimming the pump impellers, the pumpscould be converted to pump efficiently in both the booster mode and the lift mode. Theeconomic analysis showed that the cost of modifying the existing pumps could berecovered with the projected energy savings in less than three years. The long-termelectrical savings were estimated at about 20 percent of the current electrical costs. Also,the 70-psi inlet pressure had to be reduced to about 10 psi before entering the reservoir.Throttling the water into the reservoir was causing premature failure of a critical inletvalve and resulted in undesirable pressure fluctuations on the upstream distributionsystem. In conjunction with the pump modifications, the control valve to the reservoirinlet was replaced with a unique valve called a sleeve valve. Includes tables, figures.