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Articles in support of small community water and wastewater operators.

Featured Videos: Pump Curves and Pump Selection Basics

Featured Videos: Pump Curves and Pump Selection Basics

Pump curves inform operators to select and run pumps at optimal efficiency for their system. Whether preparing for a certification exam or looking to refresh your knowledge of pump hydraulics, this week’s featured videos will teach you how to read pump curves, calculate system curves, and use these curves to select an ideal pump for your system.

For any given pump, flow will impact pressure head, efficiency, horse power requirements, and vulnerability to pump damage. This video reviews three different pump curves starting with a very simple curve and moving to more complex curves with increasing pump information. Understanding performance, efficiency, horsepower, and net positive suction head (NPSH) curves is essential in selecting the proper pump for your system’s needs. After covering the basics, this video introduces concepts that will help operators to select and run pumps at recommended operating zones to maximize pump life and reduce operational costs.

Once you start to feel comfortable with these concepts, the next step is learning how to compare pump curves to your own system. For pump curves to be useful during selection, you must first have a system curve of your own. Prepare for a bit of math because this next video walks through the calculations needed to develop a simplified equation that graphs system pressure head (Hp) as a function of flow rate (Q) squared. When watching the video, remember that z1 is the starting elevation and z2 is the final elevation.

With a well developed knowledge of pump curves and system curves, selecting a new pump becomes much easier. This last video demonstrates how to compare the system curve to the pump curve . When comparing these two graphs, the pump’s best efficiency point should be fairly close to the system operating point. Other considerations include how much power is required to operate the pump and the net positive suction head available to avoid pump cavitation. 

These videos simplify many of the factors that go into a real system, however they offer a good foundation for operators to better understand the theory behind pump curves and pump selection.