Virtually all the bearing manufacturers and motor manufacturers give instructions to pack the beairng housing some fraction full of grease (somewhere between 1/2 and 3/4 full.. toward the lower end for fast speed large bearings).

That seems to leave some room for interpretation. Let's say it's a horizontal machine. Would you:
A - Set the endbell on it's back and pack the cavity 1/2 deep. Then when endbell is assembled to bearing, grease is at the opposite end of the cavity from bearing.
B - Set the endbell on it's side and back the bottom half (3:00 to 6:00). Then upon assembly the grease will be in contact with lower half of the bearing.
C - Put small chunks of grease into the bearing trying to trap air between chunks so when the cavity is full you have only about 50% grease by volume and 50% air by volume, and grease will be adjacent to the beairng all the way around.
D - Something else?
(of course grease will be applied directly to bearing as well).

The bottom portion of the bearing cavity should be filled. It does'nt matter if the end bell is vertical or horizontal the grease will stay in that portion of the end bell until it can be installed.

Thanks David. I was not concerned with the orientation of the endbell during packing. I just thought it painted a better picture of where the grease was going. Is your answer B? (grease ends up at the bottom of the bearing cavity after assembly in a horizontal machine?)

I should mention the motors I am most concerned with are large bearing (6313 or bigger) 3600 rpm motors. I think lubrication practices are most critical for these machines. We haven't had good luck on these machines and I'm wondering if our repacking practices contribute.

I have seen one of several of our guys packed them using method method A (grease at the far end of the cavity).

I have noticed on occasions when we open up the endbell, the grease is in the same place... has never gone near the bearing. But often I see evidence the beairng itself has gotten hot enough to form a brown stain on the bearing (but not hot enough to melt the grease clump located on the opposite end of the cavity). I am not sure the actual way the oil migrates to the beairng. If it is just migrating as film or vapor then it might be ok to pack as in method A. But I suspect that heating the grease helps to release its oil and closer is better for that (as long as the beairng is able to push the grease clear of the ball/cage path).

How did you come up with your method?
Is there any references that address this (other than just saying 50% full)?
Have you had good luck with your method (method B) even on large bearing 3600 rpm machines?

This message has been edited. Last edited by: electricpete,

I ran a vibration department at an aelectric motor shop for 15 years and worked closely with the people in the shop. The standard procedure on that type of bearing was to hand pack the bearing with grease and put grease in the end bells. I have to assume this is an EASA spec since those were the specs we went by.

Thanks. I would still like to clarify what you mean by in the endbells. When installed (horizontal motor), the grease ends up on bottom of the endbell cavity (method B) or on the end of the cavity away from the bearing (method A)?

Epete,

The EASA shop I work with here pack the bearing,and then use your "B" method when they pack the housings. On some, they don't pack the housing, but rather pump in a predetermined amount (given in the EASA info. based on bearing size, I think) after putting the end bells on. They have calibrated their grease gun, and only use the one for motors.

Dave

This message has been edited. Last edited by: RRS_Dave,

Thanks David and Dave. Method B makes pretty good sense to me (pack grease where it will end up close to the bearing). Method C makes somesense as well (a knowledgeable motor shop guy had suggested it to me recently). Method A is what I have seen our guys use at least twice and I think I will try to discourage it.

For method B, perhaps we would also smear a small circle of grease around the id to help with the sealing function (help keep contamination out and oil vapor in).

Still, I think my recommendation would carry a little more weight if I could point to a single document that identified where the grease is supposed to be packed. I checked the EASA Technical manual and it only talks about the quantity of grease, not where you add it.

This message has been edited. Last edited by: electricpete,

Pete,

Is there a reason, other than changing the grease, that you're taking the motors apart?

I was taught, for motors in place, that the best way to lubricate was to pull the drain plug, pump new grease through the fill fitting on top of the bearing housing until the expelled grease is clean, and then run the motor for about an hour with the drain plug removed to allow it to relieve itself. The half-full guideline was for during assembly in the shop. I attached a page from an EASA guide regarding this.

How_to_get_the_most_from_electric_motors.pdf (162 Kb, 23 downloads)

Joe - I am talking about repacking the housing when the bearings are changed based on vibration symtpoms.

We relubricate/regrease using a similar procedure to what you identified, except we don't pump until grease comes out... we just add the recommended amount.

In that case, like the guys said above, we would pack the bearing and the lower half of the housing before reassembling. This insures that the grease level is 1/2-3/4 full.

electricpete,

I think you brought a very good question. This question should be split in two. The first one is how much grease should be added after pump/motor is re-built and the second how much grease should be added as a part of PM program.
Some people are using SKF method to calculate amount of grease based on bearing geometry and speed. I think this is not correct. The bearing is in the housing and if calculated amount is added it’s a high chance it will not even get to bearing if cavity is substantial. I feel that there are two methods assuring proper lubrication:
1. Purging bearing with a new grease until all old grease is removed.
2. Use of ultrasound device on monthly basis and add only enough grease that it will get to the bearing.

I know facilities using any of these methods with a very good success. The other part of this discussion would be what bearing configuration to use. Should it be double shielded, one shielded (on what side) or without any shield. I think this can open a can of worms