Maintworld 3/2017

CONDITION MONITORING
Figure 1.
Bearing Condition Monitoring
Using Ultrasound
Airborne & structure-borne ultrasound has become a major player in bearing condition
monitoring. Once considered just a leak detector, more maintenance & reliability
professionals are beginning to realize all of the benefits associated with using ultrasound
for condition monitoring applications. The P-F Curve, with which we have all
become familiar, reflects that trend.
ADRIAN MESSER,
CMRP, adrianm@
uesystems.com
THE I-P-F CURVE shows Ultrasound as
being the first technology that detects a
failure that is mechanical in nature such
as early stage bearing wear, or subsurface
bearing fatigue (See Figure 1.)
It has been said that at least 60 percent
of premature bearing failures can be attributed
to lubrication, whether it’s over
lubrication, under lubrication, use of
the wrong grease for the wrong application,
or use of a contaminated lubricant.
Ultrasound instruments can be used
to prevent over and under lubricated
bearings. The source of ultrasonic noise
is friction; when a bearing is in need of
grease, there is an increase in friction and
therefore an increase in noise or decibel
level. When listening to the bearing that
is in need of lubrication and watching the
decibel level on the display of an ultrasonic
instrument, as grease is applied the
inspector would notice a gradual drop in
the decibel level, eventually back down
to a more normal level. If the bearing is
already over lubricated, as soon as grease
is applied, the inspector would notice a
gradual increase in the decibel level, letting
them know that the bearing already
had enough grease.
Figure 2. PUMP 3 MTROB 007 Figure 3. PUMP 4 MTROB 010
44 maintworld 3/2017