Good Morning,
I am attaching pictures of a 22330 bearing (self-aligning double row) that ran for only three months. It is on the commutator end of a 1500hp motor. Prior to dismantle; my vibe data picked up BPFI and FTF faults, which were quite obvious once dismantled. My question to those more experienced in RCA than myself (pretty much everyone): What do you think is the most probable cause? I was leaning toward contamination (through the exit hole) of the lubrication. The pitting was only on the outboard side, and note the discoloration of the grease. However, notice the roller's pattern...almost like it was a stationary fault. Any advice,input, or pointers would be greatly appreciated.
I have come across some literature that points to "axial compression" as being a possible cause
Thanks, Jeff

This message has been edited. Last edited by: Jeff4,

close_up_ir.pdf (89 Kb, 436 downloads) rollers

Jeff,

Did you contact the bearing manufacturer and have them look at it? Generally they will tell what they think the wear or failure mechanism was based upon what they see.

Waiting for them to call/email back.
Thanks
Jeff

Jeff,
It looks like haevy spalling and possibly could be caused by local overloading. Did it show any bearing misalignment?

Jeff,

It looks like excessive axial loading was present based on the fact that just one race has been affected. In this case one race takes up the axial load while the other one gets unloaded. As far as spacing between spalls is concerned, that may not be important or indicative of something.

How did rollers look like?
Can you post the data?

David

Good morning,
Alex & David; bearing misalignment did pop up in conversation, but we have no data thatpoints to that being the cause.
The axial loading theory has grabbed my attention as well. They are reassembling the motor today. I have the vibration data showing the FTF and BPFI and will post it later (hopefully) today.
Thanks for responses
the roller pics are in the other post

Jeff

Hi jeff
It's very difficult to make a call on this as there is not really enough info, however if the damage on raceway is evenly spaced around the rollers I too would look at stationary faults.
Has the motor sat idle for a while, near to a vibration source?
If so your fault may have been caused by false brinelling.
Incorrect clearance/handling may also have caused a load related defect to the bearing.

Type false brinelling into google for examples

Jeff-
Just from looking at the pictures and reading your post, it looks like to me that some of the possible cause could be: Incorrect mounting, which will cause axical loading or an excessive preloading condition. The extent of the flaking around one entire raceway indicates that the axial load has been very heavy in relation to the radial load. You may want to check the fit to make sure that the clearances are ajusted accordingly. Also if there is a high temperature differential between shaft and housing, ther may not be enough room for termal expansion, that can be checked by going back to the manufacture of the bearing and looking at the design to determin what the termal expansion is. I'm not an expert by far but we do run a lot of spherical roller bearings, in our paper machine rolls, refiners, ect. We have run into this very problem with our refiners and the out come was to much axial loading. Instead of the rotor moving on the shaft like it was designed, the rotor would become stuck or locked in place causing the shaft and bearings to be loaded instead of the rotor itself. We had to rework the splines on the shaft and in the rotor to allow for some additional floating. Hope this helped.

Jeff,
How about some more info on this one.
Direct coupled or other?
Motor load?
Recently rebuilt or stored spare (how long)?
If stored spare, was the motor rotated?
Lubricant?

From the photos, it certainly looks like thrust loading although this could be from a variety of sources either internal to the motor or external.

Looking at the pictures and the fact that it only ran for 3 months would point to severe overloading (preload caused by thermal expansion) as the cause of failure. I have seen this type of failure when rotor shafts are rebuilt and the bearing shoulder to shoulder dimension is mistakenly changed. At any rate you need to take caution on rebuild to assure that the floating bearing has enough clearance in the housing to allow for thermal growth. As Chad Tuttle alluded to the first place to look would be the internal alignment and clearances.

quote:

Originally posted by Jeff4:
However, notice the roller's pattern...almost like it was a stationary fault. Any advice,input, or pointers would be greatly appreciated.

We can't really tell from the pictures, since we don't have the cage comparison. But if there really is a pattern of damage occuring at ball spacing, it would be a very strong indicator pointing toward damage while stationary as you suggested.

That might include: A - vibration while secured, B - trauma to the bearing before installed (dropped the bearing and didn't tell anyone), or C - trauma to the bearing during installation. D - damage during transport - improperly blocked shaft.

A doesn't seem particularly likely if only installed a short period (although you can check vib on the housing while secured for an idea). B doesn't seem particularly likely to give a pattern resembling an axial load. C seems like could certainly be a pattern associated with mishandling during installation.... specifically pushing on the outer ring vs inner ring while driving onto the shaft would create defects on one inner ring. Over time they get worse and worse. If this were the case (bearing already bad upon completion of installation), you can go back to the old vibration data and examine it on a log scale you should be able to see harmonics of inner race frequency present ever since the first data recorded after installation (although they might have started so small they didn't catch your attention)

(I noticed many of these items mentioned already - just wanted to bring them up again with my own spin)

Is there any possibility of a current flowing through the bearing?
The only other cause I can think of would be excessive loading.

There is a definite pattern to the failure. Axial Loading, maybe, but without more pics and info, I would lean to the rotor not centered or even a drive problem causing the rotor positioning to vary. All of which should be checked out.

Jeff,
It appears from the images that one of the causes would be axial loading, but could also be due to fluting caused by High VFD wave frequencey and/or inadequate grouding of the motor.

Jeff, the few times we have experienced such severe damage after an installation usually means something may have been assembled wrong. The damage is too severe to be from shaft current leakage. It looks like the bearing had no clearance at stratup and may have been under severe axial loading at startup. Possibly a bearing cap or spacer was not right or the bearing width was wrong. I would check the stackup of all the parts. Root cause analysis is very important here to avoid a repeat.

For my idea after inspecting your picture,I think it may came from high electricity current(see the melting spot) that electrical machines have this phenomenon.Failure did not show me exactly the wear due to fatique loads.

with best regards
prasong D.

If the outer race is held how can the bearing be self aligning

Spherical roller bearing with spherical outer race. You can tilt the inner ring with respect to the outer ring and you are still riding on a spherical section of the outer race (just a different section).

What type of coupling was mounted on the shaft?

Jeff,

Any word on the cause?