Root Cause Analysis

Dear All,

Reccently I met a very strange anti-friction bearing failure pattern on a geared compressor. The details pls see attached.

Any comment will be welcome.

Thanks.

Attachment(s)

TA3000_Bullgear_bearing failure.doc   2.93 MB 1 version

Dear Lux,

Very interesting case of failure of bearing,

analyzing of evidences:

1.- Only one ball was damaged.

2.- The location of failure in inner face of thrust bearing.

possible causes,

1.- Not enough axial play during bearing Installation, that's mean the bearing was preloaded axially.

2.- Bad quality of bearing, it is possible to find fakes bearing  in market.

3.- Excessive axial load due to coupling pre-stretch.

Lack of thrust bearing temperature reading, was a factor that early action were not taken.

Regards.

Hello Sir,

Good to see your response.

Yes, it is very strange to current bearing failure status. In addition, during the investigation, we also found this compressor got surge many times in the past becasue this machine was always running at turndown mode due to low demand from customer.----this should actually contributed to this bearing failure.

Thanks,

LUX

Good morning Xuefeng Lu,

we have a similar problem with a TA3000 where the DE bearings failed. We replaced all the bearings, seals and bull gear bearings. when we commissioned the compressor, the gear was noisy and had an excessively high axial vibration on the DE side indicating mechanical looseness. We stripped the compressor again, replaced the bull gear bearings with a new set, recommissioned and had exactly the same problem. We then decided to replace the bull gear shaft and rebalance the bull gear. The whole assembly was within 13 microns both axially and perpendicular as per the limits for this type of gear. We replaced the DE bearing housing too. 

We assembled and recommissioned the compressor and it is doing exactly the same. Stage vibrations are good. We have no idea where to proceed from here.

What did you do to rectify the problem?