Need Help on Motor Bearing Failure

Were the bearings pre-loaded when reassembled? If yes, was the motor test run in the vertical axis and the loading checked afterwards?

I don't know. A motor overhaul shop did the work so I will ask. I am not familiar with Pre-loading vertical motor bearings. I will have to research that. Thanks!

Obviously water found it's way in and washed out lubricant. Was housing weld-sleeved? I bet it was. There's a pocket or crack there somewhere.

Also any chanse the opposite side sleaving was too tight for bearing to travel on thermal expansion? Still lubricant dissapearing with no trace without washing makes no sense. Temp to achieve this in that short time is EXTREMELY high.

The pump is about 2 feet under the motor. No water is around the bottom bearing. If I look at the picture it doesn't look like the bearing was greased enough. If a bearing got hot and failed and initially had enough grease, do you think it would look this dry?

The bearings look like there never was any lubricant but the rust indicates that it ran really hot for awhile so maybe the grease ran out and led to the failure. That raises the question as to why they got so hot. TonyS mentioned two, and a third would be the vertical adjustment of the thrust bearing so that there would be no axial load on the bottom bearings. One more thing, the spec sheet for the Mobil Polyrex EM indicates there's a Mobil Polyrex EM 103 that is specifically for vertical bearings.

"Mobil Polyrex EM 103 is more specifically recommended for applications such as vertically mounted bearings, or very large motors where a stiffer grease consistency may be required by the OEM, and low noise properties are not required."

Those upper bearings have to take the weight of the motor rotor plus the pump rotor, was the pump reassembled and tested vertically as a unit?

This being a hollow shaft motor it is difficult test run at repairers place.The alignment problem can also be ruled out in Hollow shaft motors.This may need a continous monitoring and also involve the bearing manufacturer.

you have to make a thermograph test for the motor components and i want to ask what was the bearing temp. after start up by 2 hrs and 48 hrs if u got the records,also This may need a continous monitoring as nesubra said.

I wish you had included a few more pictures. I can't see any lubricant left anywhere. You can also see the bearing experienced high temps (you can tell by looking at the cage), which could have happened before all the lubricant was gone.

One suggestion, only use a bearing recommended by the motor manufacturer.

I'd be looking at clearances, bearing seals (making sure the bearing is sealed and not exposed) and would only use a bearing from a source trusted by the manufacturer. If possible I'd also have another motor builder take a look. The place you used might be the entire story.

If you are using a VFD, you might have eddy current problems, possibly related to the sleeves.

I have had similar issues with motors over the years and have found a couple of useful items to check off the list.

1. I have come to understand that all motor shops are not qualified on all motor types.

2. It is best (when possible on specialized motors) to return to the manufacture for repairs when there is problem. They have the specifications and knowledge to do it right.

3. Never re-sleeve either bearing surfaces.

Now having said this, it maybe possible to find a local motor shop who can do the job correctly and properly test run afterward. I do not know your area, so not fare for me to say. But I would contact Siemens and ask lots of questions.

You are absolutely right.

That fact that there is no grease residue at all indicates that it got very, very hot.

I don't know what caused it, but you might find this link informative. They don't use those bearings anymore because they need frequent relubrication. You may want to look into an upgrade.

http://www.sea.siemens.com/us/internet-dms/dt/ElectricMotorsComm/ElectricMotors/Docs/Sleeve%20vs%20Antifriction%20Bearings_Selection%20of%20the%20optimal%20bearing.pdf

The bearing looks like a regular ball bearing. Not know for a large thrust carrying ability. It also looks like that was a sealed bearing at one time, note the groove on the inner race and the counter bore in the outer race. Your post states that it was "lubricated with Mobil Polyrex EM" that would mean that someone would have to remove and replace the seal, a tricky operation to get back in and not have it just fall out. Was the seal-shield any place around when it was disassembled?. If it was a plain bearing, without seal or shield it is likely that what ever lube was in it was spun out by centrifugal force. But I don't see any grease reside. Also if there was grease in it the should be burned charcoal material around the area.

Is there a chance that this thing had an angular contact bearing in it originally? I think you stated that the housing had to be sleeved. It's possible that who ever did that used a different ID-OD bearing to make the repair and used a regular ball bearing. Also it may be that in the sleeving operation the length dimension was miss interpreted and when the motor was bolted back together a large thrust force was applied and maintained while the motor was running, of coarse the bearing on the other end should have failed also, but possibly the weight of the armature may have made the lower bearing fail more spectacularly.

Sleeving a bearing is a poor way to repair. I personally would have had the shaft and housing metal sprayed and turned back to size.

When rebuilding a motor with thrust bearing I've always been careful to retain the shims used to load the bearings, but at times it wasn't always possible. Then it would be a case of shimming the bearing until all play was gone and then test running the motor vertically. After a short run the play and temperature would be checked and the shims adjusted accordingly. Then an 8 hour test run.

The shims I'm referring to are for axial play.

Dear,

Please have a close look at the picture. I can see the bearing was hammered, forcibly inserted the bearing into the housing. There might be a chance that sme metallic burrs are entered in to the housing, at the time of over hauling process. ( considering all the installatin / design parameters ok, as it was running for 20 years )

this metaalic burrs or euivalant waste material may have caused the faults. As cleaning agent's purity is also doubt ful, as 2 similar break downs occurred after over hauling.

I want to thank everyone for the great comments. It gives me a lot to look into.

Here are answers to a few questions you asked.

1) The motor was test run at the Motor Shop for 20 minutes prior to delivery and installation. After installation the motor was coupled to the pump and put in-service. It was tested for vibration and temperature the first day and a few days later. The bearings failed the first time in 10 days and the bottom bearing failed again in 7 days.

2) We don't monitor continuous. We are looking into that.

3) There is no VFD

4) Thank you for the comment to Never Re-Sleeve.

5) The bearing that failed is the guide bearing not the thrust bearing. The bearing installed is the bearing number on the nameplate of the motor.

6) Thank you for the Mobil Polyrex EM 103 information.

I am looking into all of your comments and recommendations.

Thank you