Centrifugal pumps fundamentals of operation

Centrifugal pumps are dynamic machines, which means that they convert velocity into feet of head. 

One day, the plant experiences a partial power failure. Three of the six pumps shown in Fig. 34.1 shut down. A few moments later, the manhole covers on top of the sump blow off. Geysers of water spurt out of the manholes. What has happened  

This is an example of water, or hydraulic, hammer. But what causes water hammer  

Let s consider the change in the water velocity in the 3-mi pipeline when half the pumps failed. The velocity in the pipeline dropped from 8 down to 4 ft/s. Velocity is a form of energy, called kinetic energy. Energy can take several different forms  

About 250 years ago, Daniel Bernoulli first noticed two important things about energy  

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The water flow has only increased by 2.5 percent by starting the fourth pump. This does not usually indicate a pump malfunction. More likely, it is an indication that all four pumps are operating on the flat portion of their pump curve, (see Chap. 34, "Centrifugal Pumps Fundamentals of Operation.") To get more water flow, you will need to reduce restrictions in the circulating system. 

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