Abstract—Preventive maintenance can be described as
maintenance of equipment or systems before fault occurs. The main
goal of maintenance is to avoid or mitigate the consequences of
failure of equipment. It also improves reliability, decreases cost of
replacement and system downtime. Preventive maintenance helps
provide high level of availability of system function and obtains great
return on investments of hardware and software. However, very
frequent application of preventive maintenance is not economical
though. In order to obtain optimum benefit, this maintenance should
be done at proper times. This study aims at explaining the importance
of preventive maintenance mathematically. The mean time to failure
(MTTF) or the mean time between failures (MTBF) is taken as the
reliability criteria. The reliability values obtained when preventive
maintenance is applied and not applied are compared to the MTTF.