| the following is a discussion on the sister Linkedin NoMTBF Group recently. It was and may continue to be a great discussion. Please take a look and comment on where you stand? Do you some form of the Arrhenius reaction rate equation in your reliability engineering work?Join the discussion here with a comment, or on the Linkedin group conversion.
Fred |
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
Acceleration factors
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! Continue reading Acceleration factors
System or component testing
Fred i was asked this question and wanted to know what your thoughts were on this. R and D asked me what was the criteria to decide if to test at a component level or at a system level , my answer was that it should depend on what is the reliability and confidence level of the component
your thoughts? Continue reading System or component testing
Parts count variation
Just a short post to point to a newly added paper to the reference section. A few years ago I recalled seeing a paper that studied the difference to expect between various parts count methods and actual results. Continue reading Parts count variation
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 Continue reading No Evidence of Correlation: Field failures and Traditional Reliability Engineering
Graphical Analysis of Repair Data
With the kind permission of Wayne Nelson and Robert Abernathy we are posting an article on the analysis of repair data. As you may know, the assumptions made when using simple time to failure analysis of repairable systems may provide misleading results. Using the analysis method outlined by Wayne is one way to avoid those costly mistakes. Continue reading Graphical Analysis of Repair Data
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. Continue reading Shaping Organizational Behavior
What should we use instead of MTBF?
Giving a presentation last week and asked if anyone uses an 85/85 type test, and a couple indicated they did. I then asked why?
The response was – just because. We have always done it, or it’s a standard, or customers expected it. The most honest response was ‘I don’t know’.
They why is the test being done? Who is using the information for a decision? What is the Continue reading What should we use instead of MTBF?
Use the right fit
I’ve often railed on and on about the inappropriate use of MTBF over Reliability. The often cited rationale is, “it simpler”. And, I agree, making simplifications is often required for any engineering analysis.
It goes to far when there isn’t any reason to knowingly simply when the results are misleading, inaccurate or simply wrong. The cost of making a poor decision based on faulty analysis is inexcusable. Continue reading Use the right fit
The language we use matters
During RAMS this year, Wayne Nelson made the point that language matters. One specific example was the substitution of ‘convincing’ for ‘statistically significant’ in an effort to clearly convey the ability of a test result to sway the reader. As in, ‘the test data clearly demonstrates…’
As reliability professionals let’s say what we mean in a clear and unambiguous manner.
As you may suspect, this topic is related to MTBF. Simply saying Continue reading The language we use matters
Do not want equipment failures
I am a rock climber. Climbing relies on skill, strength, knowledge, a bit of luck, and good gear. Falling is a part of the sport and with the right gear the sport is safe.
I do not know, nor want to know, the MTBF (or MTTF) of any of my climbing gear. Not even sure this information would be available. And, all of the gear I use does have a finite chance of failing every time the equipment is in use. Part of my confidence is the that probability of failure is really low. Continue reading Do not want equipment failures
MTBF free Availability
The classic formula for availability is MTBF divided by MTBF plus MTTF. Standard. And pretty much wrong most of the time.
Recently working for a bottling plant design team we pursued the design options to improve availability and throughput of the new line. The equipment would remain basically the same, filler, capper, labeler, etc. So we decided to gather the last 6 months or so of operating data which included up and down time. Furthermore the data included time to failure and time to repair information. Continue reading MTBF free Availability
true, beneficial and timely
How Good is MTBF as a Metric?
A bolted hanger along a rock climbing route is often a very welcome site. It provides the climber with safety (by clipping the rope to the bolt); with direction (this is the way); and, with confidence. Does MTBF as a metric do the same for your organization?
As climbers we count on the bolts to provide support in case something goes wrong or we need to rest along the route.
A reliability metric is often used in the same way as a climbing bolt. The measure, whether MTBF or Reliability or Failure Rate, provides a sense of assurance that the product in question is performing as expected.
The organizations profits are or will be safe. The development team uses the measures as a guide for design and supply chain decisions. And, the measure provides confidence to the organization related to meeting customer expectations around reliability. Continue reading true, beneficial and timely
First Impressions
At first MTBF seems like a commonly used and useful measure of reliability. Trained as a statistician and understanding the use of the expected value that MTBF represented, I thought, ‘cool, this is useful’.
Then the discussions with engineers, technical sales folks and other professionals about reliability using MTBF started. And the awareness that not everyone, and at times it seems very few, truly understood MTBF and how to properly use the measure.