Understanding Pump Curves

Pump performance curves are the least used, least consulted, least appreciated, and least understood aspect of the world of industrial pumps. The plant personnel who most need their pump curves, meehanics and operators, generally don t have the curves and accompanying information at their disposal. The people who control the performance curves store them in a file, in a drawer, in a cabinet that s almost never opened. They don t share the information contained in the curves with the people who need it. Maybe it s because they themselves don t understand the information to share it. In the next few paragraphs and pages, we re going to explain the pump performance curves. This might be the most important chapter of the book. 

Up to this point, you probably didn t understand the crucial importance of the pump curve. With the information provided in this chapter, and this book, we suggest that you immediately locate and begin using your pump curves with suction and discharge gauges on your pumps. 

Since the flow calculations need to be repeated at various points on the pump curve, a computer program would be useful. The program AXIAL-RADIAL was developed by the author in Qbasic, a language easy to understand by most engineers, but experts may modify it to PASCAL, C+, Fortran, or other languages as it suits their needs. It calculates both hydraulic and axial loads on the pump impeller. 

In reality, the performance curve is easy to understand. It isn t rocket. science. The performance curve indicates that the pump will discharge a certain volume or flow (gpm) of a liquid, at a certain pressure or head (H), at an indicated velocity or speed, while consuming a specific quantity of horsepower (BHP). The performance curve is actually four curves relating with each other on a common graph. These four curves are ... 

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