Rolling Element Bearing Problem
Rolling Element Bearing Problem
Rolling Element Bearing Problem
The vibrations caused by bearings are called bearing tones. All antifriction bearings generate
more or less high levels of lagertoner. The more worn the bearing becomes the higher the
levels of the bearing tones are.
An incorrect bearing generates vibrations not exact multiples of 1xRPM, i.e. asynchronous
vibration components. Except these components bearing faults can also generate a broad
banded noise.
Fundamental Train Frequency (FTF) = The rotational speed of the train, usually 0.4
multiplied with the rotational speed. FTF seldom appears in vibration spectrums as the train
hardly carry any load.
Ball rotation frequency (BSF) = The balls or rollers rotaional speed. A hole in a ball/roller
causes BSP to appear in the frequency spectrum.
Ball passage frequency, outer race (BPFO) = The rate of which the ball/roller passes a
defect in the outer race. This frequency is estimated as:
the number of rollers x rotational speed x 0.4.
Ball passage frequency, inner race (BPFI) = The rate of which a ball/roller passses a defect
in the inner race. The level of BPFI is often slightly lower than BPFO as the vibration is
generated further away from the transducer. The vibration has to pass through the roller and
the outer rece before it is registrated. BPFI is estimated as
the number of rollers x rotational speed x 0.6.
Bpfi, with
Defect inner ring, Asynchronous
multiples and Amplitude Radial load increase
increased single Radial peaks with
side band on 1 modulated level
defect sideband on 1 X
X
Bpfi and
Defect inner ring, two High, broadband noise,
significant Radial Broadband
or three small defects constant increase in level
multiples
Damaged fundamental
Broadband
train, broken at one Radial Broad band Low level on noise
noise
place
High frequency
Bad pretension or oil Natural bearing
noise Radial Broad band
film frequency
haystack
Number of multiples
Note:
X = speed (RPM)
ftf = fundamental train frequency (approx. = 0,38X to 0,42X)
bsf = ball rotation frequency (approx. = 1,5X to 3X)
bpfi = ball pass frequency, inner ring (approx. = 4X to 10X)
bpfo = ball pass frequency, outer ring (approx. = 2X to 7X)
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