Maintenance which is carried out at regular intervals of either time, output, cycles of operation etc. is known as Fixed Time Maintenance. To minimise disruption Fixed Time Maintenance is, where possible, carried out off-line i.e. when production has stopped.

Fixed Time Maintenance will only be effective where the failure characteristic is time dependent with the failure occurring within the life of the equipment, and where the total cost of the repair is substantially less than the cost of allowing the equipment to breakdown.

Unfortunately, time dependent failures are a relatively uncommon characteristic in a complex plant, resulting in FTM having a negligible or occasionally detrimental effect on improving equipment performance.

The more predictable the time to failure, the more effective Fixed Time Maintenance is. This does not necessarily mean that FTM is the optimum strategy to use for time dependent failures, as Condition Based Maintenance can sometimes be more economic if it can be applied.