Messrs. Forum:

Good afternoon.

Is there a way to separate the vibration values of the envelope from one bearing with respect to another?

I do the consultation, because they have monitored the bearings of a pump and reported that the two bearings of the pump were in poor condition and that even the bearings of the electric motor were in poor condition; however, only the bearing (coupling side) of the Pump was changed and all envelope values of both the electric motor bearings and the bearing (free side) of the pump dropped to satisfactory levels; Please support them.


Original Post

Goodnight, a query:

Is there a way to diagnose in a pump that has two bearings, which of these two bearings has a fault because there has been a case where they have diagnosed that the two bearings have a fault; however, only one bearing was changed and when it was monitored again, the failure of the other bearing that also said it had a fault disappeared, if only one bearing was changed, why the other bearing that was diagnosed as having a fault, now it has no more the fault?.


If you know the bearing numbers and the correct running speed the frequency markers in your software should line up against the peaks. Are you using skf aptitude by any chance? 

Secondly, if the enveloped acceleration drops suddenly in a bearing with no correlating maintenance activity it can suggest the bearing is starting to run to failure.

I do not know of any signal processing technique to separate one bearing vibrations from another. The common way is to have one or more measurement points on each bearing housing and use amplitude (peak value or spectral peaks) and frequency spectrum (matched to fault frequencies). Note that "envelope" is only one method of bearing fault detection. Other methods include velocity spectrum, high frequency acceleration and ultrasound (contact sensor) measurements. If bearings are close together, then a defective bearing and nearby bearing would typically be changed at same time. It is generally not wise to change a bearing based solely on envelope spectrum fault detection, unless the very early warning provides the best opportunity.


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