Worn/Mismatched Belts Pattern
The two-event effect of the fault, where 2XBRF is dominant, can lead to ambiguous diagnosis in spectrum analysis. This phenomenon occurs due to the belt fault striking two pulleys in one revolution, increasing 2XBRF.
Do you know the two-event effect of the fault??
As a first stage of spectrum analysis, we need to identify all forcing frequencies in the rotating equipment to detect the nature of fault(s).
One of theses frequencies is called Belt Rate Frequency (BRF) and can be observed in the spectrum due to fault or manufacturing defect in the belt.
The unexpected pattern appears when 2XBRF is dominant (as shown in below case study) rather than 1XBRF and you can face some ambiguous diagnosis in this case since the value of 2XBRF is not considered in forcing frequencies list.
The reason is due to the relation between the belt fault and the existance of two pulleys since the fault strikes the two pulleys in one belt revolution leading to increse 2XBRF
Based on this physical phenomenon, you have to consider 2XBRF and its harmonics in your analysis.
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