Why is my pump not performing to the manufacturer’s published performance curve?
by Jim Elsey
I often talk with pump owners/operators who question why a given pump is not performing to the manufacturer’s published performance curve. Of course, there is a long list of reasons why this problem can occur, and I will explain a list of potential issues in this column. One possible answer is that the pump is performing just fine but it could be that you are not measuring the performance correctly.
Initially, understand that pump performance tests conducted in the field (in situ testing in the owner/operator’s system) are rarely as accurate as a factory test. The disjunct is normally due to the accuracy, calibration schedule and placement of the instruments. Other pertinent factors are the size and geometry of the piping. Further, there is a long list of items that includes the proper calculations, methods and compensation of/for the readings for torque-speed, atmospheric pressure, acceleration head, temperature, specific gravity, viscosity, air entrainment, net positive suction head available (NPSHa), critical submergence, Newtonian properties, friction losses and elevation corrections to a specific datum point.
Additionally, pumps tested at the test facility will have the proper settings, clearances and lubrication. They also have the positive benefit of being new.
