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Hi friends,

                   Recently we changed three roller bearings of roller press with new one and after one month running we analysed the grease sample of all bearings.Surprisingly all three new bearings were stated in critical condition with bearing wear particle around 700 microns.Re sampling of grease of three bearings was done and the result was same.But we are not finding any defects in the spectrum.

What could be reason for high bearing wear particle in a new bearing ?

Thanks in advance.

 

Regards

Sagar

Tags: High, Wear Particles, bearing

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Hi Sagar,

What particle wear elements in your grease analysis because in our previous oil analysis on our ball mill trunion bearing which is lubricated with gear oil and sealed with lithium soap base EP2 grease and contaminated the oil due to defective rubber seal, the results was the wear elements found is high molybdenum, molybdenum element can be found particularly in greases uses MoS2 as additives.

Thanks. Morse

RM

[quote]all three new bearings were stated in critical condition with bearing wear particle around 700 microns[/quote]

I'm not familiar with tests on grease. Can you explain what you mean by this? 700 microns is the size of one particular particle? Of how many particles? What is the name of the test you're doing?

Assuming it is abnormally high large iron particles, I'm with rgf…. more likely came from something other than bearing race/ball degradation. I tend to think bearing degradation is easy to detect in vib (assuming you look carefully) long before wear particles will show up although I know others may have differeing opinions).

 If it were an oil sample I'd ask for analytical ferrography in attempt to narrow it down. I don't know if similar applies to grease samples.

RM
Last edited by Registered Member

Now that I think about it a 700 micron particle is huge in the oil contamination world. I would think that it maybe a sampling thing. In my experience its tough to get a good grease sample from a bearing unless it is laying on the shop bench. The grease tests basically wash the carrier from the grease (lithium/calcium etc.) and test the base oil. Rich Wurzbach from MRG is the grease testing guru.  http://www.mrgcorp.com/index.html

RM

Hi RGF,

              Grease is directly supplied from the grease barrel with 55 pulse per minute.Cage is of steel.

As per my previous experience,when ever we opened the bearing the outer race was having heavy scoring and it gets cracked after opening.

Hi E'pete,

              total wear particle concentration is 497.(limit 100). PLP is 30%. I think for grease also same procedure is followed as oil.Please find the attached spectrum of the roller brg. RPM=16.8.Bearing= KRW 12.70.01 four row cylindrical roller bearing.

Attachments

Images (1)
  • roller nde
RM

I overlooked that this is a slow-speed application 17rpm.  I don't have any machines like that, but I understand bearing defects are a lot harder to see in vibration for those applications. Others can contribute better about how best to detect bearing defects on slow speed bearings.

I gather maybe you've had several bearing problems and in the past they were detectable both by grease sampling and vibration. Now upon installing a new bearing it shows similar symptoms by grease and not vibration.   In that case obviously one possibility to consider would be that the housing was not completely cleaned after last episode and what you're seeing in your sample is wear from the last bearing.  That's just speculation, but it's about all I can contribute. Hopefully someone else can chime in.

 

 

 

RM
Last edited by Registered Member

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