The primary goal of maintenance is to avoid the consequences of failure
of equipment. This may be by preventing the failure before it actually
occurs which preventive maintenance and condition based maintenance help
to achieve. It is designed to preserve and restore equipment reliability
by replacing worn components before they actually fail. Preventive
maintenance activities include partial or complete overhauls at
specified periods, oil changes, lubrication and so on. In addition, a
record of equipment deterioration can be documented so worn parts can be
replaced or repaired before they cause system failure. The ideal
preventive maintenance program would prevent all equipment failure
before it occurs.