Table of Contents
Advertisement
ADASH Ltd.
Vibrations on frequency range – gearboxes/bearings.
When we need to find the failure on not simple machines (e.g. gearbox) then is very usefull to know
the vibration values in several frequency bands.
The screen No. 6 shows measurement values in three frequency bands:
0.5 – 16 kHz
the whole vibration area occurring in transmissions due to friction in bearings, bite of
gears, abrasion of limiting rings etc. (beyond low-frequency phenomena the imbalance
etc., which we measure using the first four screens)
1.5 – 16 kHz
in the area from 1.5 kHz we can find driving wheel gear frequencies of most
transmissions
5 kHz – 16 kHz this range is typical for bearing defects, where the high-frequency signal occurs as a
consequence of bad lubrication, abrasion, bearing wear or overload.
Attention: Please note that the ranges overlap. They all have the upper frequency 16 kHz. What does
it mean for analysis? The following examples should help you to understand their significance:
- All values are the same:
All vibrations are in the last range. If they were in the lower ranges also, the highest range
would have to have a lower value.
- In the first two ranges the value is the same, the last range value is lower:
The vibrations are in the range 1.5 - 5 kHz. They are not above 5 kHz, this would express itself
in the last range. They are not under 1.5 kHz, the value in the first range would have to be
higher than in the second one.
- The first range has the highest value:
The vibrations are in the range 0.5 - 1.5 kHz. The reasoning is the same as in the previous
example.
- The value in the higher range is larger than in the lower one:
This must be a measurement error. It is logically impossible to have a higher value in the last
range, than in the middle one. The reason is their overlapping.
36
Adash 4900 – Vibrio III
Advertisement
Table of Contents
