Hi All,
We have received some new motors (about 800kW) and they arrived without any shaftlocks, isolaters or any other form of false brinelling prevention. The vendor says they have deep groove ball brgs and are preloaded so dont need anything more. In my experience deep groove brgs are more suseptable to false brinelling then many other brg types. Does anyone have experience with this? Will pre-loading prevent transport damange? Are deep groove brgs better at withstanding this? The motors have come from Europe to New Zealand.
Thanks in advance,
Mike

Planty,
Having worked for Reliance Electric for over 16 years, we would NEVER ship any ball bearing motor without blocking the shaft. We also placed the motors on wooden pallets for a certain amount of shock deflection.
The only time I have seen a major issue with shipping was a dynamometer manufacturer who shipped our motor with two 2500 lb. rolls on both ends of the motor shaft unsupported! The motor was shipped from Michigan to California. When it was first operated, it sounded terrible. The outer races were cracked!
I asked the engineer from the dyno firm if they had blocked the rolls. His response was that his firm had calculated the static load and it presented no problem. Static? What about the load the second the truck hits a pot hole? His eyes got as big as pie plates. His firm was getting ready to ship five more dynos to Korea without blocking the rolls! Changed that plan.
Without blocking on this motor, my guess is that you may have experienced brinelling. I have always referred to false brinelling as the marks that you see that have only polished off the final grinding marks. This 'damage' is usually of no consequence and will disappear as the bearing operates. True brinelling involves a larger displacement of material and this damage will be cause for early replacement. I would run the motor solo and look with a very high resolution (Y log scale) for any indications of BPFO or BPFI. If you see no bearing frequencies, no impacts in the time accel waveforms, then go ahead and run.

The logic of pre-loading a bearing - is it of sound practice?

I will have to say I do not believe in pre-loading. Removing all clearances and crunching the rollers just don't seem wise. With an ABEC 9 and 0.0001 or approaching zero but never pre-load. If you start and metal characteristics quickly thermal the bearing to +clearance and it continueously operates there; then.?<>!

When rotor is secured (locked) the bearings are experincing dynamic loading during transportation due to acceleration of the motor as a whole rigid body.

When rotor is unsecured ( or loose due to bearing clearance), additional dynamic loading component due to impacting of the rotor moving within the clearance on the bearings gets introduced. This type is much larger and more destructive then the first one.

David

Thanks for your replys.
I am assuming the preload is applied with springs such as belville washers, but for springs to fully resist the shock loads possible during transport they would have to be substantial.
We will test run and go from there.
Cheers