5kV motor heaters

[mull982]

I am on a new construction project for which we have several 5kV motors that have been sitting On-Site waiting to be installed and operated. The motors have been sitting for some time now, and most of the time have not been stored very well.

I have been telling the contractor for some time now that because these motors have been sitting around not running, we need to periodaclly turn the shafts, as well as hook up the heaters inside the motors. The contractor has been arguing with me that this is not necessary.

What are some reasons I can back my argument with, as to why we need to to routinely spin the shafts and put the heaters on the motors?

 

[cornbread]

Rotationg the shaft will keep from flatspotting the bearing and shaft deformation. Heaters will naturally keep the moisture out of the windings. You don't want to find out after installation that the motor has a low megger reading.

 

[coulter]

...What are some reasons I can back my argument with, as to why we need to to routinely spin the shafts and put the heaters on the motors?

Few times I have speced, "keep the motor heaters energized", it was part of the mfg direction. Recomend: Call the mfg and ask for their storage spec.

carl

 

[zog]

Do acceptance testing before you energize them.

 

[Jraef]

Any kind of vibration at the site, however minor some people may think it is, can cause what is called "False Brinelling" of the bearings. I don't know of any motor manufacturer who does not recommend periodic rotation when stored.

Google that terminology, you will see some articles about it, such as these:
False Brinelling article
Engineer's Edge definition

The heating requirement is a function of temperature and humidity. No need to heat if you are storing them in Saudi Arabia in the summer, but pretty much anywhere in North America will require it. All that is necessary for hygroscopic infiltration of the winding insulation is a period of time where the motor is warm, say above 70F, followed by a period of time where it drops below the dew point, maybe even as high as 40F depending on atmospheric humidity levels. That pretty much covers most of N. America.

 

[zbang]

Who owns the motors at the moment? If you do, the contractor has no business refusing to do this ("a charge may apply"). If they own the motors, you could refuse to accept them as having been improperly stored. Definitely check with the mfg on this.