Motor Transportation? 4

[THooper]

Good morning experts!!,

I purchased a couple large new rebuilt 1500hp, ac ball bearing motors. When performing pre-testing we found that both motors have bad load end bearings and sound very rough.

My question is, If the shaft has not been properly supported with a shaft bearing locking device, which these motors arrived without, could transit vibration possibly cause damage to the bearings?

I know if proper maintenance is not performed while in storage, equipment, and earth vibration can cause inner and outer bearing race circular depressions damage like I am seeing on both load end bearings, looking like they have been exposed to vibration during standstill. Note: Both motors were just fresh rebuilds.

New large motors from Oem's are always shipped with a dampening base or a shaft lock bar.

They are saying it is highly unlikely the damage was caused from transit across five states and probably received a couple bad bearings from their supplier. Has anyone heard of bearing damage caused from not supporting the shaft in transprtation?

Kind Regards,
motorhead1

 

[electricpete]

Absolutely. It's called "false brinelling".

If you cut open the bearing and see marks on the races spaced at the exact distance corresponding to ball-spacing, that is proof-positive that the damage occured while the bearings were stationary.

Stationary bearings under load cannot tolerate as much vibration as rotating bearings because the lubricant film at the point of contact cannot be maintained over time and metal-to-metal contact develops and the vibration causes "false brinelling".

If I can find a web reference I will post it.

 

[jbartos]

Suggestion: Visit

http://www.oit.doe.gov/bestpractices/explore_library/pdfs/emmay99.pdf

http://www.oit.doe.gov/bestpractices/explore_library/energymatters/may1999_root_cause.shtml

http://www.emersonbearing.com/failures/false.html

http://www.iie.org.uk/talking/forum.asp?cid=1&fid=1

http://www.timken.com/products/bearings/services/valueadd/prevent.asp

(false brinelling and fretting)

http://www.lubrizol.com/GreaseReference/glossary.htm

(definitions of false brinelling and fretting)
etc. for more info.
Also, there is not any industry standard mentioned for transportation of the large motors, whether or not it was followed.

 

[ctolbert]

This happened to me with a 500hp motor only being transported 5 miles.

I was there during the testing at the rewinder and everything passed perfectly. The testing at my mill was a total failure. The drive end bearing was damaged in transport or during installation. We could not prove which one caused it (the people from timken called it "false brinelling" something that I never heard of until then.)

The rewinder had to repeat the entire process with extreme care. The second time around, everything worked. It was such a pain....

Thanks,
Carl