Intervals from a manual assume clean power, steady load and a dry room. Real plants rarely offer all three, so the schedule has to move with the conditions.
Common questions
How often should seals be inspected?
Every 2,000 running hours on clean water, and every 500 on abrasive slurries.
Do bearings need grease on a fixed schedule?
Grease by running hours and temperature, not by the calendar. Over-greasing kills more bearings than neglect.