ADASH Ltd.
Adash 4900 – Vibrio M
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Vibrations in frequency bands – gearboxes/bearings.
When we need to find the failure on not simple machines (e.g. gearbox) then it is very useful to know
the vibration values in several frequency bands.
The screen No. 6 shows measurement acceleration values in three frequency bands:
0.5 – 1,5 kHz, 1.5 – 5 kHz and 5 kHz – 16 kHz.
Example:
We are going to show the analysis procedure on a signal obtained on a seating of an inlet
transmission shaft with the speed frequency 25 Hz (1500 rpm) and with a gear with 65 teeth. So called
tooth frequency can be obtained by simple multiplication of the shaft revolution frequency (in Hz) by
the number of teeth.
f
GMF =
f
speed
*
z
f
GMF
gear mesh frequency
f
speed
speed frequency
z
number of teeth
In our example the tooth frequency is 1625 Hz (so approx. 1,6 kHz).
What are the possibilities?
The transmission is OK and tooth frequency of 1,6 kHz slightly increases vibrations in the second
frequency band.
Bearing failure - vibrations are concentrated in the last frequency range 5 – 16 kHz
