Page 116 - Subyek Teknik Mesin - Forsthoffers Best Practice Handbook for Rotating Machinery by William E Forsthoffer

Pump Best Practices Best Practice 2 .23
Fig 2.23.2 Performance change vs. impeller
diameter change (Courtesy of Union Pump Company)

The variation of pump performance with changes in speed integrity of the pump coupling and driver with the vendor
also follows the affinity laws, but with a higher level of accuracy before proceeding with the change. The mechanical design of
than do changes in impeller diameter. the process system must also be confirmed for the revised
When the performance is known for a pump operating at pressures and flow rates (refer to Figure 2.23.3).
a lower speed (e.g. 1150 rpm) and it is desired to operate at The data used for this example is taken from an actual pump
a higher speed (e.g. 1750 rpm), the affinity laws can be used to operating at 1150 rpm. The affinity law calculation results
calculate performance at the new speed, and the converse is also compare favorably with the same pump operating at 1750 rpm
true. However, it is good practice to verify the mechanical (refer to Figure 2.23.4).

Fig 2.23.3 Performance change versus speed change

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