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The Practical Pumping Handbook ..............

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Entrainment I jlati~en ,,,,~,,:, I

1

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Poor NPSHA High Low ..... .................... I
Piping Too Low Flow Rate Flow F~quen~eY' 1
l

Raise Level Increase Adjust
in NPSHA Flow
Wet Well Rate

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Irrevocable
System
Condition

Upgrade
System Impeller New
Change Material Pump

Figure 11.2 Hydraulic causes of vibration chart

When little difference is experienced, that indicates an Air Entrainment
problem that is not immediately susceptible to changes in flow rate.

11.2.2 Uncurable conditions
While the various possible cures for these hydraulic problems arc clearly
identified, it is recognized that, on many occasions, the appropriate
cure cannot be implemented. For example, it is difficult to raise the
level of the liquid in the wet well, if that wet well happens to be an

m 184