VIBTOOL 02.2009
36
Bearing emission window
Shock pulses are generated mainly in the interface
between rolling element and raceway. This occurs in
the loaded part of the bearing. For radial bearings, the
loaded region covers a sector of 90° centered around
the load direction. From the outer raceway, shock
pulses are transferred to the bearing housing. As the
width of the bearing is limited, direct radiation of
shock pulses is limited to a sector of ± 60° from the
perpendicular to the area of contact between the
rolling elements and the raceway. This now defines the
window of emission of the bearings. Outside the
window of emission, reflected and dampened shock
pulses can be measured. This measurement can be
good enough for trending and comparison, but does
not allow an accurate measurement of oil film thick-
ness or damage to be made.
4. Directly at the bearing
Shock pulses are dampened when they pass an interface or
are forced from their straight path. It is, therefore, impor-
tant to pick up the shock pulses before a significant part of
the signal strength is lost. A measurement directly at the
bearing is, therefore, recommended.
5. Metallic, flat, clean (preferably machine-faced)
When taking bearing measurements using VIBTOOL, care
must be taken to position it correctly. If VIBTOOL is not
held correctly against the machine, unreliable measure-
ment values and damage can occur so be sure that the
mounting surface is flat and clean (preferably machine-
faced). Remove any traces of paint, grease or dirt; other-
wise, the frequency range could be reduced due to poor
coupling.
Bearing diagnosis
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Note
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