Page 49 - Practical Machinery Management for Process Plants Major Process Equipment Maintenance and Repair

34 Major Process Equipment Maintenance and Repair

Figure 1-13. Specific speed nomogram.

crease in required horsepower input of approximately 4.8 percent; in our
example, this amounts to approximately 20 brake horsepower. The .038
in. wear performance curve on Figure 1-12 shows the worn-condition
performance characteristics of the example pump.
Figure 1-14 shows the annual power cost this extra 20 brake horse-
power will represent to you, based on 300 days per year operation.
If your power cost is 6C/kWh, your annual power cost resulting from
internal wear in this pump would be $6,440. If yours is a cctypical”
100,OOO bbl/day refinery using 25,000 pump horsepower, an overall in-
crease of 5 percent in your pump horsepower requirements could repre-
sent additional costs of WO0,OOO per year.

Maintenance practices. Normal operational wear is not the only cause of
excessive part clearances in pumps, nor are wasted dollars and fuel the
only adverse effects.
Intentional opening up of wear ring or other wearing part clearances is
used by some maintenance people to solve certain pump operating prob-
lems. Unfortunately, such practices sometimes appear to be effective-
over the short run. Over a period of time, however, such practices can
create other problems. The resulting increased internal leakages within