Instead of Reliability Prediction

Abstract

Chris and Fred discuss reliability prediction and how it can relate to the ‘design’ phase when there is no data. How do you ‘predict reliability?’

Key Points

Join Chris and Fred as they discuss what reliability prediction is. There are quite a few answers to this question … and some of them can be helpful!

Topics include:

• What is ‘reliability prediction’ #1? Depends on who you ask. Reliability prediction is often seen as looking up a book or standard of ‘failure rates’ for specific ‘types’ of components. These ‘prediction tables’ include generic descriptions of things like ball valves, small two stroke engines and so on. The many problems with this is that these tables are not compiled with a lot of rigour, neglects the fact that the ‘same’ component from different suppliers can much more or less reliable than any other … and once you have a ‘number’ for that component reliability is never thought of again.
• What is ‘reliability prediction’ #2? What it should be is a more analytical, considered approach to looking at your design and analyzing what it’s reliability is. And this doesn’t need ‘data.’ There is nothing wrong with engineering judgment, and then understanding the (lack of) confidence in the results. This is OK. But it allows you to work out which ‘vital few’ components drive reliability performance. And those are the ones you study.
• What is ‘reliability prediction’ #3? Not the MTBF. That is the only number you get from those tables. But the MTBF is not reliability.
• … and why aren’t we trying to IMPROVE reliability before MEASURING it? Good question! There are many companies out there that make really reliable stuff without ever measuring how reliable it is. That’s right. So if you haven’t finished designing your product (presumably because there are more design changes to be made to improve the design), then why would you even try to come up with a number beforehand?

Enjoy an episode of Speaking of Reliability. Where you can join friends as they discuss reliability topics. Join us as we discuss topics ranging from design for reliability techniques to field data analysis approaches.

SOR 984 Instead of Reliability PredictionChristopher Jackson

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