The PM for a motor belt-drive system typically is done while the motor is running. After all, it doesn’t do you any good to listen to a non-running system or perform vibration analysis on one. A repair, of course, requires shutting the motor off.
Even though the motor disconnect is in sight, follow lockout/tagout for the whole system. This may include mechanically locking down many other parts. For example, a gust of wind could cause a large fan blade to freewheel. Ensure that