Bob Assistant - Reference Manual
2023-04-04 - Version 1.0
50
VII.
Frequently Asked questions
7.1.
Why monitor vibrations and their drift?
When the state of a rotating machine changes, vibration drift is the first measurable symptom:
However, a distinction must be made between breakdowns due to wear or tear (slow drift) and breakage
(fast drift). The increase in the level of the anomaly can therefore sometimes occur only a few days before
the failure. The maintenance team will always be the most able to analyse and intervene on the equipment
when BoB ASSISTANT reports an anomaly.
7.2.
What are the main causes of vibration anomaly?
Possible cause
Corresponding frequency
Off balance
Rotation frequency
Misalignment
2 x rotation frequency
Bearing fault
3 to 10 x rotation frequency [2kHz - 60KHz]
Instability
Natural frequency of the equipment
Belt fault
Rotation fre harmonics
Fan fault
Number of blades x natural frequency
Electrical fault
Line frequency (50Hz) + harmonics
Gear
Natural frequency x number of gears
Natural frequency
resonance
Natural frequency
