Pump Specific Speed And Four Quadrant Data In Waterhammer Simulation – Taking Another Look

Trey Walters, P.E., Applied Flow Technology, Trygve Dahl, Ph.D., P.E., Intelliquip, David C. Rogers, P.E., Rogers Engineering Hydraulics, Presented at the ASME 2020 Pressure Vessels and Piping Conference (Virtual)

In some situations, it is possible for flow to go backwards through a pump during a transient waterhammer event. Sustained reverse flow will lead to reverse rotation. Understanding and predicting the pump behavior during waterhammer under these conditions is typically accomplished using previously published four-quadrant pump data. Historically, the selection of which data to use is based on the similarity of pump specific speed. The weaknesses of using specific speed are described and an improved method of selecting appropriate four-quadrant data is given based on fundamental curve shapes for head and power in the normal operating zone.