Hi Rosana,
IMO, both preventive and predictive maintenance are activities that involve inspection, repair if necessary, of a given subject.
The differences are how often and the sourced data that conclude the activity.
Predictive maintenance is resulted in known failure facts or historical failure data. From those data, we have known that the subject IS going to fail. and the frequency is set from there.
Preventive maintenance is regular frequency inspection activity set by recommendation, experience or common practice.
Example of this is the case of our car. Changing oil every 6 months and replacing tires every 80,000 Km are cases of predictive maintenace because we know that if we don't do that the car will give us trouble.
Checking the oil level every month (some cases, daily) to see if there is any leak, visual inspection on tires every morning to see if there is any nail, etc. is the case of preventive maintenance. Again, the frequency is based on each individual car condition, road condition in the driving area.
That was my thought, see if anybody has other opinions? or better way to explain it.
Paul N.