Failure of vertical motor in sundyne Compressor 1

[engmau46]

Hi friends,

In our refinary we have many sundyne compressor. Recentily we had two failures in verticals motor in sundyne compressor. The driver side bearing was totally destroied, in both cases. We are looking for the cause. Anyone have some experience like this? Our vertical motors have two similar bearing 6314 in both side.

Thak you

Engmau46

 

[JJPellin]

We only have two Sundyne compressors. I am not sure if yours are similar to ours. A few possible issues come to mind.

Alignment of these motors is unusual and our mechanics have had some difficulties. The standard programs for vertical alignment in laser systems do not work for this arrangement. The pump is shimmed for angularity and the motor is moved laterally for offset. We had to write a specific procedure for performing this alignment. If the alignment across your coupling is poor, this could contribute to poor reliability for the lower motor bearing.

I believe our motor use oil lubricated bearings in the lower location. I did not understand if your failure was in the upper or lower location. I would suggest verifying that you are using the correct oil (or grease). Verify that you are using the correct lubrication method (oil level or grease amount).

I could be more helpful if you provide details about the lubrication method, coupling type, etc. Have you examined the failed bearings to check for evidence of the cause?


Johnny Pellin

 

[flexibox]

I agree with Johnny's comments but suggest if it was alignment then you should have experienced high vibration and its worth inspecting the coupling condition. If it is a metal membrane coupling then it should exhibit damaged membranes close to the drive bolts. Is it possible to see water contamination? Do you have vibration history?

More info will help us make more comments.

Cheers

 

[engmau46]

Hi friends, thanks for your opinion.

The motor have two bearing (SKF 6314)lubricated by grease. We were using an automatic lubricator in both bearing and the lower bearing was totaly destroied. The coupling is with metal membrane (API standard). We done a failure analysis to know what was happened but it was inconclusive. We know that the upper bearing had patterns of load paths for axial load in the both motors, but have no indication of axial load of compressor. We know too that the interference between shaft and the inner ring of bearing was in the minimal admited for this bearing (6314). I was searching other manufactures of vertical motor and every of then set in the upper bearing one angular contact (7314), I dont no why, but I think that it is cause the weight of this motor (1000 Kg).

Mauricio

 

[engmau46]

Hi friends, thanks for your opinion.

The motor have two bearing (SKF 6314)lubricated by grease. We were using an automatic lubricator in both bearing and the lower bearing was totaly destroied. The coupling is with metal membrane (API standard). We done a failure analysis to know what was happened but it was inconclusive. We know that the upper bearing had patterns of load paths for axial load in the both motors, but have no indication of axial load of compressor. We know too that the interference between shaft and the inner ring of bearing was in the minimal admited for this bearing (6314). I was searching other manufactures of vertical motor and every of then set in the upper bearing one angular contact (7314), I dont no why, but I think that it is cause the weight of this motor (1000 Kg).

Mauricio

 

[JJPellin]

In a motor that large, I would expect at least one angular contact thrust bearing. If two deep-groove radial bearings are used, one of them must be set up in a floating arrangement and the other one fixed axially. Given the new information, I have two theories that could explain the failures:

1. The motor repair shop did not install the bearings correctly. They may have installed both of them in a fixed arrangement. I have seen this on horizontal motors.
2.The bearing may have been over-greased. For motors, I believe that more fail from over-lubrication than from under-lubrication. These bearings should be hand packed with the grease cavity on one side approximately 1/3 full and the other side empty. If someone pumped these cavities full of grease, the bearing would overheat and fail quickly.

Given that fact that you are using auto-greasers, I would suspect the second option. Verify that you have the correct bearing arrangement for this motor installed in the vertical orientation. Verify that the bearings are set up correctly for floating or fixed. Verify that the new bearings are being properly greased. Verify that the auto-greaser is not set up to over-lubricate the bearings.


Johnny Pellin

 

[electricpete]

Good comments.

I can't open the attachments (can anyone else?)
I'm not familiar with Sunydyne's, what speed does the motor operate at?
Is the bearing housing accessible for vibration monitoring and when was it last monitored? (if bearing was well monitored, then imo that tends to point away from slow developing easily detectable problems like race faults and focus more toward faster developing or harder to detect problems like cage failure, inner ring spinning on shaft)

You looked at upper bearing and saw axial load, was it in one direction only? Could you confirm the direction was down? Depending on answers to these you may be able to rule out the scneario where rotor thermal expansion put the shaft in compression and loaded both bearings outward.. in which case lower bearing would take not only the compression load but also the motor weight.

I know you said bearing was wrecked and typically that makes analysis harder but maybe you can give us more details anyway. Careful inspection may show clues. Does shaft seat show signs of bearing spinning on shaft? Does outer ring show signs of spinning within housing (more than usual.. some is expected)? Which of the axial surfaces adjacent to the bearing outer rings shows signs of contact an movement? Is there fretting on only half of the bearing housing (that is sometimes indication of misalignment). Which parts show overheating? Any signs of mixing different greases? Cage intact or broken? (rules out a few things if intact... doesn't tell us much if broken).

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(2B)+(2B)' ?

 

[TD2K]

Clicking the attachments just gives me 'page not found' Pete.