Raymond® Vertical Mills Motor Bearing Failure

Maybe the shafts are out of alignment. Or maybe where an axial thrust bearing is needed, a radial only bearing has been installed.

??

Sorry!! I forgo mentioned Bearing Size, Bearing used are ACBB 7216 @Drive end and 6316C3 at NON Drive end with insulated bearing,

Application run through VFD

I'm with you on this one...

I bet the first time the bearing was replaced, it was replaced with a bearing the same size and appearance, but missing some axial bearing functionality in some way.....appearances can be deceptive with bearings!

So he will have to talk to the manufacturer to find out what is required.

Maybe the equipment manufacturer took the wrong motor off the spares shelf and installed one for horizontal usage......just a thought!!

The best sugggestion is to stop wasting time and contact the manufacturer directly. Their telephone details may be found using any internet search engine, if indeed the equipment manual cannot be found.

Both or one of them more frequently ? In the second case which one ?

What means "frequently" to you ? How long between two successive failures ?

Raymond's mill with vertical flange motor? It is supposed to be driven with a horizontal axis motor (foot mounted).

Check up whether your motor is designed to be used with variable frequency or not.

What is the motor loading vis a vis rated load?

You are probably not following the proper maintenance procedures....Contact the company and get a list of maintenance procedures including recommended materials and suppliers...

Might also try electrostatic grounding ring on bearing...
http://hpac.com/motors-drives/extending-motor-life-sustainable-shaft-gounding-0510/index1.html
http://www.est-aegis.com/

What is the type of motor and starter used?. Are they suitable for the kind of duty it has to do?. Is the load suddenly applied?. Is it overloaded?.Did you check the alignment?. Did you record/measure the variation of motor current during starting and running for a few hours?.

You said the non drive side has an insulated bearing and does not fail. The drive side does not have an insulated bearing and fails frequently.

I would look into a grounding system for the motor shaft. VFD's can produce unwanted currants in the rotor shaft seeking ground, causing the bearings to fail.

I suggest you contact the VFD and motor manufacturers to get the best information for your installation.

Where does he say that the noninsulated bearing fails and the other not ?

Of course it can be possible that the non insulated fails first and its failure leads to the other failure. Your suggestion to check the motor grounding is sane.

Seems to me there was a post a while back about VFDs generating eddy currents in motor bearings. there was a link to a company that makes a grounding ring for the motor bearing that stops the bearing failures. -- JHF

Install a Ceramic Axial Thrust Bearing and be done with it.

No grounding rings needed, the ceramic coating on the bearing will remove any chance of etching of the bearings due to the drive. This will insure armature isolation, and prevent feed back through the bearings to the motor casing.