We used Unirex ep grease for our motor and fan bearing and unirex is lithium base. We did a project last year and installed 20 new motors. In the Maintenance Instructions brochure manufacturer mentionned that the motor are pregreased with polyurea mineral oil and it's compatible only with specific type of grease. We began to use grease with lithium base line in new motors bearing. Is there a problem with this ?

There is with Polyrex and lithium. I just went through this with a customer. they were using lithium based grease from the same manufacturer as the Polyrex, but the app engineer said they were NOT compatible. You can flush the dickens out of them for a while, and hope you get all the polyurea out, or you can do like we did, stop using the lithium which wasn't as good a grease as the polyurea for that app anyway, and go back to using polyurea, and THEN flush the dickens out of them. I found a mixture of food grade grease, lithium, and poly when I would clean the cavities out while greasing. What a mess.
Your call.

Dave

Best bet is don't mix grease types.
Next bet is used grease that are considered compatible based on tests of the two specific greases (not just charts).
Next best bet (and not necessarily recommended) is to allow mixing the greases if they appear compatible based on standard "grease compatibility charts" (google those words and you will find a bunch). But I am suspicious of those since there is variation within categories... not all polyurea are created equal compatibility wise (and then there's the shear-stabilized polyurea).

Some other miscellaneous comments. We use Mobilith SHC100 for the vast majority of our motors.

Polyrex EM of course is getting very common. More likely to get this within double-shielded beairngs and it's what repair organizations seem to prefer to install (putting Mobilith in the spec doesn't help if they don't read the spec).

We do have some literature from Mobil indicating that these two greases (Mobility SHC100 and Polyrex EM) are marginally compatible based on testing measuring change in worked penetration of various mixtures.

Dave - out of curiosity what do you mean by flush the Dickens....? The only way we accomplish this is to disassemble the machine, change the bearing, and hand wipe out the housing with lint free rags and alchohol, repack and reassemble.

E-Pete,

Mobilith SC and Polyrex EM are the two greases I'm talking about. The Mobil tech support said "No way" should we be mixing those two greases.
He (the tech support) also said that , yes, I could flush the mobilith out with Polyrex, and increase the grease cycle for a couple of times. We have a lot of Reliance motors that have the rectangular grease overflow. We wiped them with a wooden dowel, and greased. We let the motor run awhile, while we did another one, then came back and greased some more. When I started getting fresh blue grease on the stick, we greased one last time and buttoned it up, after wiping it out again.
I installed pressure limiting grease fittings on the motors to start with, and put vents on all of them also.

The original problem was one we saw in the motor shop when they were tearing them down. When I would tell them to grease one (spike energy) either no one would (since there wasn't one person responsible for it) or three different ones would, with three different greases.

We have changed (started) their motor greasing program for the large motors (100 to 1000 HP), and am waiting to get it stabilized to begin with others.

D

The literature I am talking about is a January 7 2002 letter from Elizabeth Bennett (Mobil) to North American Mobil customers discussing compatibility of Polyrex with other greases. I'll bet your rep can track it down if you ask. As I said "marginally compatible". I added the word marginally although that wasn't used in the letter. I wasn't recommending anyone to mix them.

I sure don't understand the purging procedure. Do you have any literature on it? I haven't seen any square fittings. Generally when we run machines after greasing, no grease comes out. If grease comes out that indicates the housing is full and I would start thinking about changing the bearing to lower the housiong level (especially large fast bearings). If the idea of the purge procedure is to fill the cavity so as to force grease out (is it?) that can't be a good thing in my mind. But greasing techniques and the theory of how it works are just one of those things that will always be subject to controversy and never seems to act the way I think it should.

Epete,

I actuall called the technical services dept. of Mobil and asked them about it. A fellow named John ? told me about it. I had suspicions after reading all I could find on the subject on the web.

The purging is not that difficult, and if you use a stick (wooden) to clean the hole out with, whether rectangular or just the 1/4 " round, you can tell what is going on. The pressure limiting (20 psi) fittings ensure you don't put a lot of pressure in at once (these guys love the electric lincoln guns), and we did it a little at a time. Whether the back cavity (most of the motors are cross flow design) is full or not I don't know, but suspect it is after we're done. There was no excessive heat the next day, so I don't think any of them were hurt that way. I do have two of them that still are running high spike, but I believe they had their feelings hurt before we started. I had asked they be greased several months prior to us doing the purge.
I am waffling back and forth now about getting one of them pulled and new bearings put in. If I do, I'll take pictures over at the shop and show what it looked like.

Dave