DFO-103 - page 48

1360RPM
1698RPM
48
Determine the increasedbearing lifeof aSize365Class II fanoperatingat 1360
RPM.Assume the fanpitchdiameter (11.2 inches) listed inTable1will beused.
1. CalculateoperatingRPMasapercent of thedesignRPMinTable1.
2. Calculate fansheavepitchdiameter as apercent of thedesign fan sheave
pitchdiameter inTable1.
3. Locate intersectionof 80%of designRPMand100%of design fansheave
diameter inTable 2.The increased bearing life is 5 times the designmini-
mumbearing lifeor 375,000hoursminimumaverage life.
Bearing life may be substantially in-
creasedor decreasedbyvariations in
theoperatingspeedor changes in the
V-belt drive. Table 1 lists the design
speeds (RPM), motor horsepower,
and fan sheavepitchdiameters.Table
2 plots the increase or the decrease
in bearing life when the RPM or fan
sheave pitch diameter is changed
fromthe values inTable1.
BearingLife
Table1:
Table2:
= .801 x 100=80.1%
Use80%
11.2" (actual dia.)
11.2" (designdia.)
=1.0 x 100=100%
Example
1...,38,39,40,41,42,43,44,45,46,47 49,50,51,52
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