400HP vertical mounted motor on cooling tower water pump. MOB (Fafnir 6226 ball) has fluting. First time I have seen fluting signature oppose one another from inner race to outer race. Is this common in thrust loaded vertical mounted motors? Second question, MIB (7228 SKF ball) has distinct rolling element paths in four separate location on outer and inner bearing races. These do not intersect around the races. I am at a loss as to why this pattern was discovered on a destruct test of bearing. Might this be a signature of the motor hunting magnetic center? Has anyone ever seen this pattern? Will post picture of inner race of MIB if able. Need a little help on this. Thanks!!

JB
I can't make out much from the picture you posted, I think it is probably the one showing four ball paths, because I don't see any fluting marks. Try holding your camera a little further away and if you are using a macro setting don't use the zoom with it, just get a little closer. I am not sure I understand what you mean "First time I have seen fluting signature oppose one another from inner race to outer race." because I almost always see fluting on both inner and outer races. Please send some more pictures and info.

I have seen multiple ball paths although not sure of reason. I have also seen ball paths that are not continuous and will post some pictures that are all from the same VFD driven motor. As far as I know any motor with ball bearings does not hunt magnetic center, only plain bearing motors. Fluting almost always can be told by the balls having a frosted appearance.

Here is the same bearing outer race

Here is the same bearing inner race.

Randall you are correct in that the paths you see in the picture are the rolling element paths around the inner race. I only have a proscope (the one used on TV's CSI) for inspection. I am limited to 10X that picture is as far away as I am able to get and remain focused. I will post another of the motor outboard bearings inner and outer races, maybe it will clarify what I spoke of. What I meant by opposing with regards to the fluting of the outboard bearing is the fluting signature is on one side of the inner race and at discharge through the rolling elements it migrates to the opposite (180 degrees)side of the outer race. I hold the preloaded thrust bearing responsible for this pattern switch. Am I correct in this assumption? With regards to the motor inner bearing rolling element paths, I believe the distinct are from thermal growth experienced by the rotor at different operating speeds. This due to increasing heat as speed increases. What are your thoughts on this?

Randall your pictures are what I am use to seeing with fluting. The signature is maintained in the middle of the races. Mine is one each side of each race opposite one another. Hope this is clearer.

Mtr inboard inner race

Mtr inboard bearing outer Race

Mtr outboard bearing inner race

JB, I am still a little confused by your descriptions and pictures. Do you have a regular digital camera instead of the inspection scope? I am not any sort of expert in this field but have had some bearing failure analysis training and always do an analysis of bearings removed because of calls I have made. Your theory of thermal growth changing the ball path sounds correct to me. As far as the mechanisms of the actual electrical path and how it causes the patterns, I don't have a clue.

Randall security at this job prevents me from having a digital camera. I'll try another description. Laying the bearing on a work bench with the inner race touching the bench the fluting pattern on the inner race is next to the work bench surface on the flange closest to the bore of the bearings inner race. (Flange closest to the bore of the inner race, see previous picture outboard bearing inner race.) The outer race is on top resting on the rolling elements as installed. The fluting pattern on the outer race is on the outside edge of the flange as the rolling elements contact after the bearing is preloaded. (See picture of outboard bearing outer race previous.) Therefore, each race has an opposing fluting pattern on opposite flanges of the outboard thrust bearing. My apologies for the lack of visual supporting data. My access to this forum is limited, so responses lag in time. I destruct test all bearings I can get my hands on have learned a lot. This fluting signature I have never seen and I believe that the thrust load results in a path of least resistance. Therefore, leading to the cross race discharge to ground. Thanks for your response and interest, look forward to conversing again on bearings. I will try and do better with the pictures next time