Accendo Reliability

Your Reliability Engineering Professional Development Site

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Wrong Conclusions

Here is a podcast by Chris Peterson of H and H Environmental Systems which includes her thoughts on the MTBF topic. She also explores how making even ‘obvious’ assumptions may lead to the wrong conclusions.

[soundcloud url=”http://soundcloud.com/handh-testing-lab/aug-7-podcast-using”]

Chris records a podcast almost everyday and many are enjoyable, fun, and and provide something to think about as you go about your day. If you like the podcast above, check out her growing list of available podcasts.

Embedded podcast with permission of Chris.

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Use Lognormal Distribution

The lognormal distribution has two parameters, μ and σ. These are not the same as mean and standard deviation, which is the subject of another post, yet they do describe the distribution, including the reliability function.

$latex \displaystyle R(t)=1-\Phi \left( \frac{\ln (t)-\mu }{\sigma } \right)$

Where Φ is the standard normal cumulative distribution function, and t is time. [Read more…]

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Where does 0.7eV come from

This post is a conversation first held on the LinkedIn group No MTBF. I’m capturing a portion of the contributions here to continue the discussion or to widen the audience. Reminds me of always assuming 95% confidence is the right value when designing a test, or assuming constant failure rate. So, let the conversation continue, starting with the original post. [Read more…]

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Datasheet MTBF

Some many years ago I ran across a data sheet for a cooling fan (used to cool a desktop computer, for example) that listed the fan’s life as 50,000 hours MTBF. The big bold lettering was on the data sheet and was the only use of bold on the entire data sheet. One couldn’t miss it. The computers we used these fans within had a one year warranty, plus were expected to operate for a home computer user for about 5 years. Thus, we would expect the fan to also operate for five years without failure. [Read more…]

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I must not MTBF

I must not MTBF. MTBF is the mind-killer. MTBF is the little-death that brings total obliteration. I will face my MTBF. I will permit it to pass over me and through me. And when it has gone past I will turn the inner eye to see its path. Where the MTBF has gone there will be nothing. Only Reliability will remain.

  • Bene Gesserit Litany Against Fear. (with apologies)

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Why HALT is not HALT

An excellent short white paper by Craig Hillman that is worth reading. It underscores whey I claim HALT is the second worst 4 letter acronym in our profession. See the paper at http://www.dfrsolutions.com/uploads/white-papers/Why_HALT_Is_Not_HALT.pdf

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Acceleration factors

Acceleration factors
gear used for a rock climbing anchor
Gear for anchor during rock climbing

Temperature acceleration factor for ALT planning (question posted to Linkedin Society of Reliability engineers group, 5/7/12

Hello, can anyone advise me how to calculate temperature acceleration factor for a complex system including cards, RF elements, cables, motors and moving parts? Is the Arrhenius model valid for such systems, or there are more precise models? Thank you! [Read more…]

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No Evidence of Correlation: Field failures and Traditional Reliability Engineering

Historically Reliability Engineering of Electronics has been dominated by the belief that 1) The life or percentage of complex hardware failures that occurs over time can be estimated, predicted, or modeled and 2) Reliability of electronic systems can be calculated or estimated through statistical and probabilistic methods to improve hardware reliability.  The amazing thing about this is that during the many decades that reliability [Read more…]

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Shaping Organizational Behavior

When conducting a Human Reliability Assessment (HRA) we use the terminology: errors of commission or errors of omission. It behoves every professional to question why we focus upon one metric in preference to all others, in an objective and constructive manner in order to discern whether we are exposing our organization to errors of professional omission or commission. Obviously the other conclusion is that we are doing the right thing and this is also an empowering piece of knowledge. [Read more…]