Page 157 - Know and Understand Centrifugal Pumps

Know and Understand Centrifugal Pumps

aforementioned reasons up to this moment, and even including
vibration, damaged and misapplied bearings.
The problem could be maintenance, operation, or design, or a
combination of any or all these factors. In all honesty, you should never
see this set of evidence marks because it indicates a lack of control. Now
because the mechanic cannot control operational problems or design
problems, the first phase to correct this situation is to control the
mechanical maintenance factors, like alignment, proper bolting and
torque sequences, be sure shafts are straight and round, and
dynamically balance all rotary components. Reinstall the pump and wait
for the next failure. Once the maintenance factors are under control,
there should appear a clear vision and path to resolve any operational
and/or design weaknesses.

The sweet zone

Consider the following graph, Figure 9-14. Radial loading on the shaft
rises if the pump is operated too far to the left or right of the best
efficiency zone. Another interpretation of the same concept is to say
that the maintenance and problems rise when the pump is operated
away from its BEP. Many pumps have a rather narrow operational
window. These pumps can be very efficient if they are correctly
specified and operated. This is discussed completely in Chapters 7 and 8
Pump Curves and System Curves.

B.E.P. FLOW I GPM
Figure 9-14
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