Presentation on theme: "Unit III Module 3 - On Condition Task"— Presentation transcript:
1Unit III Module 3 - On Condition Task The P-F IntervalAccording to NAVAIR RCM Guideline
2Unit III Module 3 - On Condition Task NAVAIR P-F IntervalThe following describes NAVAIR  methods based on the classic CBM:Determining the P-F Interval, andDetermining the Inspection Interval NAVAIR RCM Guideline
3NAVAIR Methods for determining PF intervals: Unit III Module 3 - On Condition TaskNAVAIR Methods for determining PF intervals:Laboratory testing (in conjunction with accelerated life testing (ALT)), Analytical methodsEvaluation of in-service data - AE (Age Exploration), and engineering judgement based on inputs from operators and maintainer, (i.e. Classic RCM method) andKnowledge of the item’s design and of applications consisting of similar components. Note: NAVAIR does not provide details about the above methods in its guide.
4PF used only for starting Inspection Interval Unit III Module 3 - On Condition TaskPF used only for starting Inspection IntervalThe PM task interval is determined by using some fraction of the PF interval. This fraction will depend on the consequences of failure and the effectiveness of the proposed task.I = PF/nWhere:I = Inspection intervalPF = potential failure to functional failure intervaln = number of inspections in the PF interval
5Unit III Module 3 - On Condition Task Determining nn = ln (Pacc) / ln (1-θ)Where:θ = Probability of detecting a potential failure with one occurrence of the proposed On Condition task, assuming the potential failure existsPacc = Acceptable probability of failureNote: θ can only be determined practically in a LRCM program that tracks CBM hits and misses.
6Unit III Module 3 - On Condition Task Error in the GuideThe next slide illustrates an error by NAVAIR regarding the P-F interval. It is a commonly held misconception …
8Unit III Module 3 - On Condition Task Implies that functional capability will drop off as the system approaches a potential failure state (point B).In fact, in most cases, especially in complex systems, the equipment's functions remain fully operational at the potential failure pointFunctional Failure:Task DevelopmentAFunctional CapabilityBPOTENTIALFAILUREDEFINED POTENTIALFAILURE CONDITIONDEFINED FUNCTIONALFAILURE CONDITION-403,CFUNCTIONALFAILUREOPERATING AGEIIIInspection IntervalTASK INTERVAL PRACTICAL?PF Interval
9Unit III Module 3 - On Condition Task Functional Failure:Task DevelopmentIn the original on-condition model by Nowlan and Heap, and in Moubray's book "RCM II", the vertical axis is correctly labelled "Condition“ or “Failure Resistence”AConditionFunctional CapabilityBPOTENTIALFAILUREDEFINED POTENTIALFAILURE CONDITIONDEFINED FUNCTIONALFAILURE CONDITION-403,CFUNCTIONALFAILUREOPERATING AGEIIIInspection IntervalTASK INTERVAL PRACTICAL?PF Interval
10Unit III Module 3 - On Condition Task ConclusionThe P-F Interval is a good, but subjective, first approximation developed during an RCM analysis in the absence of data based on the recollection by the analysts of potential and functional failures that have occurred.Age exploration techniques (e.g. EXAKT and LRCM) during the In-Service (IS) phase of operation should be used to confirm inspection frequencies and refine predictive models for the continuous improvement in Remaining Useful Life Estimation (RULE).