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I have a site where lubrication of motors has mostly been ignored, partly in response to the rhetoric about the dangers of "over lubrication" that has been flying about for a number of years now.  When they started talking about a "lubrication program" I became concerned because I've seen how that usually turns out, especially when there are a lot of folks involved, none of whom are expert on lubrication.

So I convinced them to let me do it, at least on the large air compressor and fan motors.  First, what grease should we be using?  The 'tags' on the motors (Weg & Siemens) seem to recommend Mobil Polyrex EM which is a polyurea-based grease formulated especially (?) for motor bearings.

But at least some of these motors have been lubed (sporadically) with lithium-based grease which seems to be popular for the synthetics and specialty greases that so many are trying to sell.  What I've learned so far (and yes, I am no expert) is that polyurea and lithium are not generally compatible unless the polyurea is "sheer stable" and I'm not seeing much said about that by any of the grease mfgs.

I have a few fan motor bearings that don't seem to "stay" quiet after they've been lubed in response to a "call" I've made for lubrication.  I'm wondering now if mixing incompatible greases might be the cause.  I don't yet know what the various motor rebuild shops are using for rebuilds, but apparently at least one (of the better ones in my opinion) seems to have recommended a Mystik synthetic (lithium based) and it's been used on motors which did not come out of their shop... what if the OEM or last rebuilder used polyurea grease? 

Part of the problem is that there is no clear "ownership" of motors in the plant.  Some areas have folks who are dedicated "lubricators" and some don't.  Electricians grease motors in some areas, and mechanics in others.  

What has your experience been with this issue?  Am I going to regret opening this can of worms?

"The trend is your friend"

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Reply with quote  #2 
We use Shell Gadus S3 T100 which is a polyurea based grease with mineral oil. We used to use Castrol Longtime PD2 which is a Lithium based grease with mineral oil. We had Shell do a compatibility test for us before we swapped from the PD2 to the Gadus and they compared well. If you know what 2 greases you are mixing like if you are replacing one type used with another, you should be to get them tested for compatibility. AS you said though you do need to be very careful because if you do mix 2 incompatible greases and will be disaster. 

On the who does it question. We have one lube tech who looks after everything on our site. This ensures that the same lubricants are used in the correct machines. We use tagging and other things as well. I have found having electrical people with any input with lubrication is dangerous. When I started at my current job one of the first things I heard from the electrical side was that they complained all the motors were being over greased because they were finding it in the windings during rebuilds. The I found out that when the electricians went and did inspections and found a motor they thought was too warm they would go to the lube tech and tell him to add more grease. Normally here  the increased motor bearing temperature was not due to lubrication at all. 
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