Preventive maintenance (PM)

Regularly scheduled servicing of machinery or other equipment using appropriate tools, tests, and lubricants. This type of maintenance can prolong the useful life of equipment and machinery and increase its efficiency by detecting and correcting problems before they cause a breakdown of the equipment.


Source: Handbook of water and wastewater treatment plant operations

Wikipedia:  https://en.wikipedia.org/wiki/Maintenance_(technical)#Preventive_maintenance