Preventive maintenance (PM) has the following meanings: 1. The care and servicing by personnel for the purpose of maintaining equipment and facilities in satisfactory operating condition by providing for systematic inspection, detection, and correction of incipient failures either before they occur or before they develop into major defects. 2. Maintenance, including tests, measurements, adjustments, and parts replacement, performed specifically to prevent faults from occurring. Preventive maintenance can be described as maintenance of equipment or systems before fault occurs. It can be divided into two subgroups: * Planned maintenance * and condition-based maintenance. The main difference of subgroups is determination of maintenance time, or determination of moment when maintenance should be performed. While preventive maintenance is generally considered to be worthwhile, there are risks such as equipment failure or human error involved when performing preventive maintena...