I'm not going to waste my time looking for documentation. I'll draw on my forty something years of experience instead.
The best thing you can do is keep records from day one and look at trends. Are the megger readings starting to decline? Are amp readings changing and/or no longer balanced? What about temperature? Are you willing to pay for vibration analysis?
I would prioritize based on lead time to acquire a new motor and what the loss of that motor means to your operations. For example a 100 HP chill water pump motor might not be in stock locally and could render you unfit for business on a hot summer day. However a 5 HP AHU motor might be delivered and changed out in under 4 hours and only effect a small area.
Excellent reply and I will add based on similar years of experience.
I had 20+ years as an instructor and taught many motor classes, and found the following to be usefull...
NEMA has a lot of good information on motors,
https://www.nema.org/standards/view...edium-squirrel-cage-induction-motor-standards
Motor manufacturers are a great source of info, at Baldor is the 100 page Cowern Papers by a former Baldor district manager and technical writers, its
excellent https://www.baldor.com/mvc/DownloadCenter/Files/9AKK107303
NFPA has 70B, recommended practice for electrical maintenance.
https://www.nfpa.org/codes-and-stan...s/list-of-codes-and-standards/detail?code=70B
IEEE would be worth checking, you would need to do a document search and them pay for any articles of interest
Biddle has A Stitch In Time, Guide to practical insulation testing,
excellent
Take good readings from day 1, open circuit volts, running volts, running amps, and megger readings, A one time reading does not tell you the trend. Meg the motor, correct for temperature and plot on the special graph paper. Its much better to do a
Dielectric Absorption Ratio test as it tells you a lot about the motor condition, much more than a 1 time megger test.
The other comments are spot on, correct overload settings, keep the motor clean and dry, don't overgrease, use the correct grease, do vibration analysis and balancing. I also like to record the RPM when running loaded (its related to Back EMF)
A motor is dumb, it will keep pulling current (review what back EMF is) if ioverloaded, and it will generator excessive heat (not enought back EMF).
Make sure the motor operates in its +/- 5% of voltage range. Keep it clean and dry.
So there is some homework for you.
On motor life, I haven't seen such a recommendation. Suggest you contact Baldor or Reliance or ?? and ask them
I had motors that were in installed in WWII and lasted 70 years, these were the big old T frame that had lots of copper and ran cool.
Let us know how it goes and what you would recommend.