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.
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.
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:
Mean-Time-Between-Failure (MTBF) as defined by the MIL-STD-721C Definition of Terms for Reliability and Maintainability (12 June 1981) is
[a] basic measure of reliability for repairable items: The mean number of life units during which all parts of >the item perform within their specified limits, during a particular measurement interval under stated >conditions.
MTBF is widely used to describe the reliability of a component or system. It is also often misunderstood and used incorrectly. In some sense, the very name “mean time between failures” contributes to this misunderstanding. The objective of this paper is to explore the misunderstood nature of MTBF and its impact on decision making and program costs.
As annual milestones occur, like the approach of the new year or the end of a project, we often take time to reflect. Did we accomplish what we had set out to accomplish? Are we making progress? Are we making a difference?
Part of this process is having a goal to start.
All models are wrong, some are useful. ~ George E. P. Box
If you know me, you know I do not like MTBF. Trying to predict MTBF, which I consider a worthless metric, is folly.
So, why the article on predicting MTBF?
Predicting MTBF or creating an estimate is often requested by your customer or organization. You are being specifically asked for MTBF for a new product.
You have to come up with something.
Wayne Nelson once said during a conference, “The words we use matter”. I agree. I think using MTBF in conversation should be avoided. This is not a surprise those that know me.
We do and should have meaningful conversations about reliability. To improve those conversations consider the words you use. Reliability is the probability of survial over some duration for stated set of conditions and expected function. It is the probability and duration that often gets muddled.
Continue reading How to have clear reliability conversations
In January 2006, Jim Renfroe, Executive Vice President (Retired), Haliburton, published an essay titled,
Interpreting Reliability Metrics with Confidence. He discussed reliability, it’s defintion, importance, and working with suppliers to achieve higher product reliabilty. He also said,
MTBF or MTTF can be misleading