Category Archives: MTBF

Mean Time Between Failures or MTBF is a common metric for reliability and is often misused or misunderstood.

Is MTBF better than nothing

Is using MTBF better than not using any reliability measure?

This is the core of a blog entry mean-time-between-failure-why-people-do-not-use-the-1-metric-for-equipment-reliability by Ricky Smith, ” Mean Time Between Failure Why People Do Not Use the 1 Metric for Equipment Reliability” (which seems to be removed from his blog at the moment) a few months ago. The recommendation and example described highlights the benefit of using MTBF over not making any reliability measurements.

Continue reading Is MTBF better than nothing

Calculating MTBF from data

There are occasions when we have either field or test data that includes the duration of operation and whether or not the unit failed. This can be, say, 10 large motors. For sake of argument, the test ran each motor for 1,000 hours and when a motor failed it was repaired quickly and returned to the test. There were 3 failures. Continue reading Calculating MTBF from data

MTBF to PoF

Received this questions the other day.

So if we were to go from a MTBF requirement of 7,500 hours @ 40 degrees C how would we address this requirement as a PoF? Would we say the PoF is 90% reliable after 7,500 hours of operation? Or would we state this as something else?

The discussion is on how to move towards using physics of failure (PoF) type approaches rather than parts count. The underlying question is about how to set reliability goals. Continue reading MTBF to PoF

Reality

wpid-reality-2013-09-8-09-44.jpg Phillip K. Dick (Brain Pickings, http://www.brainpickings.org/index.php/2013/09/06/how-to-build-a-universe-philip-k-dick/) Or stated another way

Reliability, is that which when you stop measuring it doesn’t go away.

Product’s fail. That is a reality. It is messy, confusing and not always obvious why. Product fail. They cease to function, they are the wrong color, they are too expensive, they were a mistaken purchased, or they degrade, crack, discolor, or fracture.

Continue reading Reality

Clarity

Moving toward clarity reliably

I recently saw a quote with the notion to stop complaining and do something positive. Which happens to work with my mother’s admonishment

If you have nothing good to say, say nothing.

So, while I’ve been railing against MTBF and then suggesting a better metric, my message on use something else has gotten lost. Recently on a Linkedin group discussion someone suggests yesbx.com as a sister site to nomtbf.com.

Maybe it is time to focus on a positive message around a replacement metric to MTBF. You already know my position on MTBF. So what do I recommend. Continue reading Clarity

End MTBF Debating

The End of MTBF Debating

Endless debate on merits of MTBF is meaningless as more than one has told me. My neighbor has a bumper sticker that says Endless War with the ‘less’ crossed out and written above it ‘this’. Instead of endless debate, how about we just end this now. Stop using MTBF and all related grand averages. Use the statistics, distributions and knowledge you have to provide accurate estimates and summaries.

Continue reading End MTBF Debating

Replacing MTBF with Bx

A Guest Post by Jim McLeish titled:

Replacing MTBF/MTTF with Bx/Lx Reliability Metrics 

Jim McLeish – Mid-West Regional Manager – DfR Solutions
(Rochester Hills Michigan)

jmcleish@dfrsolutions.com

http://www.linkedin.com/in/jimmcleish 

Expanded from the RIAC Reliability Information Analysis Center Linkedin Group Discussion on

“Great challenge for change from Fred – No MTBF!”

“Endless discussion and it seems there’s no real solution to get rid of MTBF”

See original and ongoing Linkedin discussion here.

 

I am absolutely astonished that the reliability profession and its noted experts are unable to develop a better metric to characterize reliability performance and specify reliability requirements.  I respectfully submit that there is a simple and eloquent solution that has successfully been used in the ball bearing and machine industry for decades (that actually predates MTBF/MTTF), that should be considered as a replacement to MTBF/MTTF. Continue reading Replacing MTBF with Bx

Someone had to do it

Take on MTBF, that is.

In a conversion with a colleague I mentioned the amount of traffic the NoMTBF site has been enjoying. For what started simply as a device for a discussion, the No MTBF movement has turned into quite an endeavor. We talked about the idea that unless someone starts and stays with the effort, MTBF will continue to erode the credibility of reliability engineering. We talked about the idea that unless we started the discussion to only use MTBF when it is proper to do so, that we would be plagued by the rampant misunderstanding and misuse for decades to come.

Continue reading Someone had to do it