Definition
The P-F interval is the time between "P" (the point at which a potential failure first becomes detectable) and "F" (the point at which functional failure actually occurs). It is the maximum available window to detect, plan, and act before the function is lost: its length depends on the failure mechanism and the sensitivity of the detection method used.
Key facts
- The available action window between first detectability (P) and actual function loss (F), not a fixed universal duration.
- Its length varies by failure mechanism and by which detection method is used: a more sensitive method typically detects the potential failure earlier, lengthening the usable interval.
- Inspection or monitoring frequency must be shorter than the P-F interval to reliably catch the potential failure before functional failure.
- A short P-F interval for a given failure mode may make condition-based detection impractical, favoring a time-based preventive approach instead.
What does P-F interval reveal about failures?
The P-F interval represents the window of opportunity between the earliest point degradation can be detected by some method (P, the potential failure) and the point at which the asset actually experiences the functional failure (F): the time available to plan and execute corrective action.
How do teams use P-F interval in failure analysis?
Potential failure marks the start of the P-F interval: the first detectable evidence of degradation. Functional failure marks its end: the point performance actually drops below the required standard. The interval's length, relative to inspection frequency, determines whether a condition-based approach can reliably catch the problem in time.
FAQ
Frequently asked questions
What time span lies between a detectable early sign and a functional failure?
The P-F interval: the time between when a potential failure first becomes detectable and when the asset actually experiences functional failure, which sets the maximum available window to detect and act.
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