Abstract
This study separates the real inspection content (soft portion) within the total maintenance inspection activity and attempts to repeat the same some additional number of times during actual inspection. Effect of repetition of soft portion on inspection related time, fault detection probability and the consequence variable of down time per unit time is analyzed. Statistical test proves that both the inspection time and probability of fault detection has nearly same rate of influence on the consequence variable though in opposite direction. A factor ω is introduced to account for the proportion of soft portion over the maintenance inspection time. As the number of repetitions of soft portion is increased for a given value of ω, it is found from analysis that the new set of inspection time and probability of fault detection improves downtime per unit time until an optimum number of repetitions is reached. Improvement is better as the value of ω is on the lower side. The practitioner is to take this possibility of soft repeatable portion of maintenance inspection time into account while estimating these two input parameters when employing delay time methodology as a preventive maintenance strategy.
Highlights
While a preventive maintenance inspection of a part or a systemthat is done periodically by adopting the Delay Time Methodology (DTM), the intention is to see if there is any fault
If the fault occurs after the maintenance inspection is over, brews to a failure before inspection, it will call for a breakdown maintenance leading to more losses either by way of time or money or both.In Delay Time Analysis (DTA), the basic concept is when a fault arises in a part or a system, it gives certain indication before it mature to reach the stage of a breakdown
Some part within a system may have a set up time like a hard portion and a soft portion which is repeatable and that this soft portion alone could be responsible for the probability of fault detection
Summary
While a preventive maintenance inspection of a part or a systemthat is done periodically by adopting the Delay Time Methodology (DTM), the intention is to see if there is any fault. The proposed model: Let there exist a part, belonging to a system, that is subjected to maintenance inspection activity along with its counter parts in the system and that this part dominates the parameters inspection time ti and the probability of fault detection β.
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Published Version
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