MTBF is taught in many textbooks and introductory reliability courses. There may be some mention of Weibull and other distributions. You may even learn about the four functions: – reliability – probability density function (PDF) – cumulative density function (CDF) – hazard function
One of the major risks for product reliability is bad components. Either not suited for the system or adverse variation over time from the supplier.
Reading data sheets and hoping for the best is often all we have time to accomplish. For high risk (new technology, new supplier, new… something) many organizations will examine the reliability claims to some extent. Some may even conduct reliability testing in-house to validate vendor claims.
A table of numbers is not information, it is data. It is information that we need to make decisions, to notice differences and to detect patterns. It is a plot of the data that is often all that we need to interpret the data.
What do customers want when they say they want reliability?
Maybe it is that the product will work when they need it to work.
Like your car starts in the dark parking garage after a long snowy day so you can head for home. The goal is getting home.
Last year I offered a coveted NoMTBF coffee mug to the most traffic generating guest post.
This year, my challenge is for the best success story around your efforts to reduce or eliminate MTBF from use in your organization.
The basic idea is we all have a role to play to clean up the reliability profession. Using clear language is a start. Avoiding the mis-understanding around MTBF is a great start. If we all do something, great or small, toward the goal of eradicating MTBF we all benefit. Continue reading 1st Annual No MTBF Success Story Challenge
One of my regular questions with clients and students is, “How do you talk about reliability, which metrics, measures, or statements do you regularly use?”
Some have learned to avoid mentioning MTBF around me. Which is fine, and if they are really using MTBF to discuss reliability then they probably know my position.
Continue reading Provide value when talking about reliability
Sure, don’t use MTBF.
You can use that as a standard or directive or policy or however you want.
The IEC set of durability standards have been slowing shedding reference and use of MTBF. That is a good thing and I thank them for their leadership.
There are occasions when we perfectly solve the wrong problem. This is a Type III error.
Following the statistics idea of Type I and Type II errors, when a sample provides information incorrectly about a population, Type III is the error of asking the wrong question to start.
Solving the wrong problem, even perfectly, is still an error.
My wife and I are just wrapping up a two-week trip to New Zealand. As I write this I’m overlooking the lake near Queenstown.
There are parasails floating down from the hill, mountain and road bikers on the trails and roads, trampers, hang-gliders, jet boating, sailing, and bungy jumping – and dozens of other activities occurring.
Just before making an 1 hour presentation at a reliability engineering conference George asked me how to teach others what MTBF really means.
Not having given this much thought before, I asked for more details.
George works as the sole reliability engineer for a small company making specialized networking monitoring equipment.
How do your customers? And, your suppliers?
If they are all using MTBF, there is a pretty good chance one or more parties involved have some misunderstanding of MTBF. It’s common for some to think it is a failure free period. Or they don’t count early life or wear-out type failures when doing the calculation.
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Cheers,
Fred
As said by George E. P. Box. He was talking about statistical modeling and the basic idea behind actually doing the modeling.
We want to make decisions.
So this corrosion engineers walks into NoMTBF and send me a message.
Hi, I am corrosion engineer. May be you know for risk assessment of heat ex-changer tube bundle in API-581 , mean time to failure (MTTF) term is defined and used for risk assessment.
Would you please give me more information about MTTF and what history data required to calculate MTTF?
Thank u so much
Recently Glenn S. asked if I had a reference for clear definitions of MTBF and MTTF. After a bit of a search I sent him a definition or two, meanwhile he gathered a few more.
They are all basically the same, with some slight differences. What is interesting to me is the amount of variability in the interpretation and understanding.
Here’s the list Glenn collected: