Vibration Signatures of failed Sleeve Bearing 1

[LummyKem]

Hello All,

Can someone help with informations of Vibration Characteristics / Signatures of bad sleeve bearing such as wiped bearing, e.t.c.

Thanks for your contributions

 

[MachEng]

Reviewing what everyone has been suggesting I would like to add to my earlier comments. The diagnostician should not just rely on an isolated symptom such as an increased radial vibration to diagnose a faulty bearing. One should examine the spectrum trend if this is available comparing it with the base line. Examine all other symptoms looking for operating variances to the base line. If no base line is available then one has to really on experience to make a call but then this increases the risk of your credibility suffering if you are wrong.

The vibration frequency spectrum for a wiped bearing will sometimes also have higher harmonics of the 1X RS involved because of the reduced stiffness in the bearing journal. A 2X RS could also be present on its own indicating a mis-alignment between the two journals on the shaft due to one having an increased clearance hence the dynamics can manifest the 2X's frequency because of the internal angular alignment between the journals.

Oil sampling can be very useful on some machines however, I have not experienced good results when the reservoir is very large in capacity the increase in babbit per volume may be very tiny, hence not very detectable. I am generalising here so I don't want to incite anyone who has experienced something different.

Regarding the comment that at every start the shaft wipes babbit from the bearing. I suggest that this would only occur when the machine has been sitting for a long period idle. If it is started on a regular bases there should be sufficient fresh or active oil in the journal to immediately lift the shaft off the babbit surface. I have seen bearings operate for many years with minimal wear such as GE frame 3 gas turbine aircompressor rotor journals.The main thing is to always ensure the lubricating oil is serviceable by testing it on a regular interval.

I trust this is useful and good websites for the technical data would be Bently Nevada, CSI, and Technical Associates of Charlotte.



DANIEL C. SMAISTRLA
judasmai@optusnet.com.au

Equipment: Centrifugal Pumps and compressors; Steam and Gas Turbines; Reciprocation Engines and
Compressors

Specialties: Machinery diagnostics, design application of compressors, FEED,Detail Design,construction,commissioning and maintenance.

 

[LummyKem]

@MachEng,
Thanks once again for your valuable contribution.