I was wondering if anyone knows what size of particles are present in grease makeup.

Hi,
We operate a Wear Debris Analysis Laboratory and are constantly analysing grease by microscope so have a good idea of the "normal " cleanness values for grease are.
Using ISO 4407 Cleanness Codes; to compare

New Gear oil ISO 16/13 thru to ISO 19/16 Average ISO 18/15-19/15

Grease is typically more contaminated, shifting up one range code to;
New Grease ISO 17/14 thru to ISO 21/16 Average ISO 19/15 -20/15,

The new "Super Quiet" grease have all particles milled or filtered down to ISO 16/13 equivalent.

Where grease is dramatically different is once in operational use,
Note when relubricating applications we observe the dark coloured grease being extruded from the bearing housing when regreasing,
this grease is typically ISO 21/16 thru to ISO 23/20 or higher,

If we allowed our gear lubes to become this contaminated ISO 23/20 or higher would be close to failure in a gear drive but is often tolerated in grease applications.

This is how we monitor critical grease applications by microscope,
Sample by Vacuum Gun, if possible stop application and insert sample hose right between the rolling elements and pull a vacuum until 3-4 inches of hose has solid grease pulled into it,
Remove bottle from gun, cut length of hose off with grease in and force the loaded hose into bottle with cap, screw up and send to lab,

At the lab we remove the grease from the hose and as long as we have 1 CC of grease we can accurately identify contaminates and contamination level,
We monitor applications by increasing grease flow until clean samples are analysed then the grease flow is reduced over time until we are burning the grease lightly getting maximum use from the grease without causing any significant wear.
This method has giving 5-6 time bearing life increase with out increasing grease usage significantly.

Hope this assists

Regards

Rob S

www.rttech.com.au