Defining Failure Properly Upfront Can Increase P-F Interval, Simplify Maintenance Management & Reduce Cost Of Ownership

The P-F Interval is the time taken or the 'warning period' to prepare and act to correct any deviations from ‘functional’ parameters that indicates the onset of ‘functional failure’.

Maintenance can be done safely and efficiently simplified if we define properly upfront ‘what constitutes failure’. What are the operational parameters (i.e. the upper and lower control limits), of both the process and equipment, that once strayed from will indicate the onset of ‘functional failure’?

Defining failure properly will give us longer P-F Intervals and the opportunity to be more proactive and less reactive in maintenance which will lead to reduction in the cost of ownership as well.

Defining what functional failure looks like is the foundation of any effective maintenance strategy. Without that clarity, it becomes difficult to distinguish between acceptable performance drift and true failure onset. The functional failure definition shapes the way we detect, plan and respond. It directly impacts how we leverage the P-F Interval.

Proactive maintenance truly begins with a shared understanding of failure criteria.

Adapting P-F Interval To Manual And Online Equipment Condition Monitoring

In this shared post a KPI called MTTA (Mean Time To Acknowledge Failure) is introduced. It is a new terminology for me but not a new concept as this KPI tries to measure and get an understanding of maintenance’s responsiveness to plant issues and to help improve operational efficiency.

MTTA is not the period before the P-F Interval but is the period within the P-F Interval when data is obtained and failure (as in machine literally stopped running) is eventually observed (the ‘primary effect’ in Apollo RCA terminology). MTTA is more applicable to online monitoring and its description, in essence and to a large extent, is a maintenance KPI attempting to measure our reactiveness in a firefighting maintenance mode since the maintenance strategy appears to be rtf (run-to-fail) after onset of failure was first detected.

Conclusion

In my view, production equipment need not be seen to come to a catastrophic stop and maintenance reacting to it. Maintenance can be done safely and efficiently simplified if we take the time to define properly upfront ‘what constitutes failure’ or what are the operational parameters (i.e. the upper and lower control limits), of both the process and equipment, that once strayed from will indicate the onset of ‘functional failure’.