Unusual problems with centrifugal pumps

Solutions to these puzzling pump problems may help you to resolve some of the difficulties that you encounter with pumps. 

At first sight, a centrifugal pump seems to be one of the simplest of machines. In practice, however, it is capable of posing an enormous spectrum of different problems [1]. Occasionally, one comes across problems that seem to defy everything we know about centrifugal pumps. We shall report on four such cases. 

In a chemical process plant, two identical pumps were installed side by side, to transfer liquid from the same source into the same pressurized container. Each pump had been provided with a separate suction and a separate discharge line. Also, the two pumps were never used simultaneously. While one ran, the other served as a standby. 

Everything about these two systems seemed to be identical — except that one pump performed perfectly, whereas the second operated with great noise and vibration. The troublesome pumping system was dismantled several times, but nothing wrong could be found. 

The author realized that the successful pump s pipe loop had a 2-in.-dia. discharge, with a reducer connecting directly to a IVa-in. pipeline. However, the troublesome loop had a 6-ft length of of 2-in.-dia. pipe connected to the pump s discharge, and only after this length was the line reduced to IVa in. 

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Yedidiah, S., Unusual Problems with Centrifugal Pumps, Chem. Eng, V. 93, No. 23, 1986. 

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