Infant Mortality in Sealed Motor Bearings

Saturday, June 27, 2020

Sealed bearing get a charge of grease on assembly at the OEM, I have witnessed this during a plant tour in Wurzburg Germany.

The standard grease in most sealed bearings is lithuim based and has a grease depletion life of aproximately 10,000  hours, this forces asset owners into an annual overhaul of continuous run motors.

Recently I ultrasonic cleaned two bearings for my wind  turbine and found a shocking discovery.

I weighed the bearing before & after and found a massive difference in grease charge 5grams versus 12 grams in a 6208 2RS bearings.

The before & after weights are written on the boxes.

The total weight is within 1 gram and resolution of my scales, but once Ultrasonic cleaned the difference is 6 grams. One bearing is heavier than the other, which corresponds to the assembly. The machines match inner and outer races with balls to get the right clearance.

What I found is the heavier bearing of 368 grams cleaned got 5 grams of grease, versus the lighter bearing of 12 grams.

Here is the before cleaning photos


The lefthand one has 5 grams, and righthand one 12 grams. That is a massive difference.

It appears the grease charge is controlled by total weight, therefore a tradeoff between metal or grease.

This means bearings that are under charged will have a significant service life shortening.

Not many people would check Grease charge, if any and take what is given. You expect an OEM product to be "fit for Use" that expectation is now in question.

3Phi Reliability can extract seal without damage, ultrasonic clean and repack with a high performance grease that can see a service life of ten years. We can provide actual grease charge weights on individual bearings.  Only for clients of Motor Management.

This has enormous cost benefits and precise grease charges stop Electric Motor Failures.


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