Your Reliability Engineering Professional Development Site
A series of articles devoted to the eradication of the misuse of MTBF.
ISSN 2168-4375
Plus, we explore other commonly misused or misunderstood reliability-related topics and what one should do instead. A little understanding will help you get better results with your efforts.
Note: This is a reposting with editing, updating, etc. of the articles that first appeared at NoMTBF.com.
MTBF comes up a bit too often. When it does I have found rolling my eyes and arguing against using MTBF is not very effective.
So, what should a knowing reliability professional do instead?
Let’s explore four questions that you can ask that may help others find the value in no longer talking about MTBF. [Read more…]
Received a short question last week. The person writing seems to already know the answer, yet asked:
If we replace an item after a duration equal to the MTTF value, we would avoid failures, right?
Well, no, most likely not, was my response. What is your response? How would you answer this question? [Read more…]
We establish reliability goals and measure reliability performance.
They are not the same thing. Goals and measures, while related, are not the same nor serve the same purpose. [Read more…]
Just when I thought we had experienced every possible MTBF definition confusion, here’s another.
This one is courtesy of the thread concerning the impact on reliability when adding redundancy to a system. [Read more…]
In a Q&A forum, the response to a question concerning failure rate and repair times for a redundant system demonstrated yet another person confusing MTBF with something it is not.
The responder to the question mentioned that the reference to repair time implied the need for MTBF as a metric. Then went on to describe MTBF as the duration of repair time, which should not change given a redundant system over a non-redundant system. [Read more…]
[Note: I wrote and published this article in August 2016, almost 10 years ago. The overall house hasn’t failed yet some windows leak when it’s raining (replaced), the water heater and furnace have both failed (replaced, repaired), and we are enjoying the house as our home. And, while I do get out for walks, I do not play Pokémon Go anymore.]
Seriously, while out walking, listening to a podcast, and playing Pokémon Go, I found an open house to view. A week later our offer was accepted, and next week we close.
I would not have been out walking that Sunday afternoon if not out playing Pokémon Go.
Glad there are no dangerous cliffs nearby. [Read more…]
Spending too much on reliability and not getting the results you expect? Just getting started and not sure where to focus your reliability program? Or, just looking for ways to improve your program?
There is not one way to build an effective reliability program. The variations in industries, expectations, technology, and the many constraints shape each program. Here are three suggestions you can apply to any program at any time. These are not quick-fix solutions, nor will you see immediate results, yet each will significantly improve your reliability program and help you achieve the results you and your customers expect. [Read more…]
Have you ever heard the claim that “We use MTBF, as it’s working just fine”?
They may be profitable and successful in the marketplace. Is MTBF serving them well?
Probably not.
One way help the folks claiming MTBF is alright is to illustrate using a better reliability metric may provide an improvement over using MTBF. Asking a few questions may find the inevitable chink in the MTBF armor.
In today’s complex product environment, becoming more and more electronic, do the designers and manufacturers really understand what IS Reliability ??
It is NOT simply following standards to test in RD to focus only on Design Robustness as there is too much risk in prediction confidence, it only deals with the ‘intrinsic’ failure period and rarely has sufficient Test Strength to stimulate failures. [Read more…]
One of the benefits of reliability engineering is that failure happens.
Everything made, manufactured, or assembled will fail at some point. It is our desire to have items last long enough that keep working for us. Since failures happen, our work includes dealing with failures.
We use our biases every day to make choices.
We select the beige sweater because we have a color bias concerning our sweaters.
Many of our biases help us quickly make decisions. We rely on biases to move through the day. Many of our biases are under the surface, unconsciously guiding our daily decisions. Mostly, biases are good or at least inconsequential.
The problem is the bias that shields us from achieving our goals. [Read more…]
If you sort your Amazon search on ‘reliability engineering’ by price: low to high, you may find some interesting titles available for free or maybe a few pennies. Not one to resist a chance to fill another bookcase, it’s been a bit of a spending spree.
One of the reasons I am interested in older titles is to determine why MTBF is so prevalent today. So far, still looking and learning along the way.
There are many great books in our field. Sure, some are older. Some are not at all useful or helpful.
This book review is the first in what may become a monthly addition to the NoMTBF blog.
Today’s review is on the book, An Elementary Guide to Reliability (3rd) Third Edition
, by G. W. A. Dummer and R. C. Winton. [Read more…]
One technique to calculate a product’s MTBF is to count the number of failures and divide by the tally of operating time.
You already know, kind reader, that using MTBF has its own perils, yet it is done. We do not have to look very far to see someone estimating or calculating MTBF, as if it were a useful representation of reliability… alas, I digress.
Counting failures would appear to be an easy task. It apparently is not. [Read more…]
If you have been a reliability engineer for a week or more, or worked with a reliability engineer for a day or more, someone has asked about testing planning. The conversation may have started with “How many samples and how long will the test take?”
You have heard the sample size question.
Did you notice the speed limit signs in your neighborhood today?
If like me, you went about your commute or regular travels relatively blind. You watched for the neighbor’s dog that jumped into the road last week, yet didn’t register seeing the speed limit sign.
It’s a cognitive burden to notice the mundane or known. [Read more…]
