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Electric motor grease recommendation for high D*N?
2

Electric motor grease recommendation for high D*N?

Electric motor grease recommendation for high D*N?

(OP)
We have an electric motor application for 2-pole motor with 6316 greased bearings.

D (bore in mm) is 80mm
N is 3600rpm
D*N = 288,000

Bearing housing typically runs 150F - 180F.

We use Mobilith SHC100 for all our motor applications.  Very few problems, except in this application we seem to have poor bearing life and examination upon removal of bearings shows signs of overheating (grease darkens, some varnish deposited on bearing surfaces).

I am looking for ways to solve this problem.

I don't believe there is any abnormal loading on the bearing and I believe our fill practices are good (pack bearing full and cavity 1/2 full.

Mobil tells us this grease is limited to approx 250,000 D*N.

I read in the Machinery Tribology handbook that grease lubrication becomes challenging in the range 200,000 - 300,000, and generally not practical above 300,000.

Does anyone have recommendations for a good grease to use in high D*N number applications such as this?

Also I the handbook mentioned that much higher D*N numbers 400,000-600,000 were achievable in greased bearings if precision bearings (better ABEC tolerance?) were used with machined (vs fabricated steel) cages.  Any thoughts or experience on this?

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RE: Electric motor grease recommendation for high D*N?

We use LE 1275 as the primary grease in our high speed electric motors.  Not too exotic but we have found it to be quite effective.  No sure about our D*N numbers but a number of the motors are highly loaded, varying loads.  

http://www.le-inc.com/Literature/Product%20Flyers/1274-1275%20Flyer.pdf

RE: Electric motor grease recommendation for high D*N?

There are a couple of companies that produce high speed greases (more appropirately greases for high speed applications) that I remember.  One is Klueber and the other is Lubcon.  We had bearings running at 1.5x10^6 DMn (100 mm PD bearing running at 15000 RPM) with steel balls and a temperature increase on the outer ring of 20 deg.C.
These were ABEC 9 SNFA spindle bearings.   
Regardless of accuracy, the companies have the products and the know-how to help you reduce friction and operating temperature.   Klueber has more formulations, but Lubcon is the one I woild call first.  Their Thermoplex grease is quite good!
 

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