Equipment Reliability Engineering Basics
Reliability Analysis Example
These equipment reliability examples are used to convey the basics of reliability engineering. Learn the 4 system reliability factors that must all be addressed at Equipment Reliability Examples, Reliability Engineering Basics
How do you Measure the Reliability of a Glass?
Some glasses survive for centuries, others less than a week. The glass is not such a good example to equate to equipment component reliability because ALL glasses, regardless of design, are close to being equally vulnerable, so the only things helping them to survive are how they are treated and the intensity of use (i.e. Operator precision). Most other things can be designed to be more inherently reliable.
The use of a drinking glass as an example, though not a true reflection of what happens in operating equipment (because glasses are failed by accident, i.e. a Poisson event, and not by being worked under load conditions), will still help us to envisage the concepts of reliability. As we go through the glass example, we need to remember that it is not really the same as a part in a machine, and we cannot directly relate the failure behavior of a drinking glass to the reliability of parts in operating equipment.
Measuring the Number of Failures:
From personal experience, we can plot our own history of glass breakage onto a graph. In the slide, you see the number of glasses broken in a household during a thirty-year period listed by the failure mechanism that caused the breakages. You can see that of the 24 glasses broken over 30 years, dropping is the main reason for breaking glasses.
Make sure you understand that the timescale of use is important. The best glasses that come out only for Xmas and weddings last longer because the time in use, and so at risk, is less. In such situations, there is less chance for things to go wrong because they are not put in circumstances where failure is possible.
Measuring the Rate of Failures:
Once we know the number of glasses broken over a period of time, we can work out a lot about the chance of glasses being broken in that household.
It would be risky to assume that what happened to glasses in one household is the same for every other household. Whether we could claim what happens in my house to glasses is the same as would happen in every house is too much to assume. To be sure how representative the treatment of glasses in my house was compared to the real world, you would need to do a do random sampling of many other households.
We also need to consider that the stock of glasses can be managed in two ways - 1) do not replace any until the last one is broken and then get a new set, or 2) replace a glass each time it is broken so we always have 24 glasses. One must distinguish between the estimate of the rate of failure from a sample of 24 that are run to failure, and the rate of failure in a stock maintained at 24 by replacing those broken – they are not the same.
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