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Category: Reliability Analysis

  • Random failure and the MTTF

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    by

    Murray Wiseman
    in

    Nowlan and Heap said that the (conditional) probability of occurrence of most failure modes is constant throughout the life of a component. They described this behavior as being that of “random” failure. What is the Mean Time to Failure (MTTF) of a randomly failing part? In cases of random failure the formula for a component’s reliability (survival) over…

  • Safety Instrumented Systems

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    by

    Murray Wiseman
    in

    Safety in a plant is provided by layers of protection. The diagram from Emerson SIS Course shows the Safety Instrumented System (SIS) as the “safety layer” providing the final preventive layer before the mitigation layers must engage. Typically, safety instrumented systems (commonly known as Emergency Shutdown (ESD), Emergency Venting (ESV) or Safety Interlock Systems) consist of the three elements…

  • So you’re getting an EAM

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    by

    Murray Wiseman
    in

    Maintenance engineers are constantly aware of obstacles impeding their organization’s maintenance goals. Hence they explore specific actions, activities, and projects that would remove those barriers and support the goals. In the context of their on-going EAM investment, given real day-to-day time and human resource constraints, how can the maintenance department leverage its substantive knowledge and data to achieve physical…

  • Expected failure time for an item whose maintenance policy is time-based

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    by

    Daming Lin
    in

    Let Tc be the time of a cycle, tp the preventive maintenance time interval,  and T the failure time. The expected life cycle Tc will be the planned maintenance time tp multiplied by the probability that planned maintenance does occur, plus the expected failure time (knowing that failure occurs before tp) multiplied by the probability that failure…

  • The reliability data Catch 22

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    by

    Murray Wiseman
    in

    Ever wonder why poor historical work order data in the CMMS has been tolerated all these decades? One reason is that the fix is a human one. And human behavior is difficult to change. We tend to avoid difficult human problems, ultimately seeking a technological solution to everything. But there’s also a kind of paradox…