Week #10: MTBF & Project Discussion

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rjagodowski
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Joined: Fri Sep 04, 2015 6:59 pm

Week #10: MTBF & Project Discussion

Post by rjagodowski »

This morning we'll spend a bit of time discussing MTBF (Mean Time Between Failures) and related issues, then discuss project related issues.

MTBF from Wikipedia


Some typical MTBF numbers

Here's a study relating the Risk Assessment rates of NASA's Apollo and Space Shuttle vehicles. I've highlighted the risk rates for convenience, but you might find reading the article in its entirety very interesting. As you read it, it becomes apparent that management, engineers and politicians all have very different goals and thoughts about the U.S. manned space program. Then, and now.


U.S. Department of Energy LED Lighting Reliability Dated 2013.

MTBF vs AFR (Annualized Failure Rate) from Seagate (hard disk drive manufacturer).

Seagate Ironwolf drive datasheet showing a 1,000,000 hour MTBF for this series of hard drive.

Here's a link to MTTR, MTBF & MTTF: A Guide to Failure Metrics.

This is a great PDF document on Lessons in Industrial Automation and it is updated frequently (current version is February 2022) and it's FREE. It is over 60 MB in file size and over 3,300 pages long, so please don't print it. The part we will be looking at is section 32.3 Practical Measures of Reliability beginning on page 2633. Section 32.3.2 (page 2639) shows the common failure graph knows as the bathtub curve to relate how the likelihood of failures varies over the expected product lifetime.

You can always download the latest edition of this document here.

Another consideration which is a growing concern in manufacturing is that of "counterfeit components". This paper from Cyclops Electronics discusses the importance and prevalence of this problem.

Refer to this Wikipedia article on the great Electrolytic Capacitor Plague to get a perspective on how inferior (fraudulent) electronic components can effect countless manufacturers, products and consumers and cost multiple billions of dollars to remediate. Put in terms of the MTTF and MTBF topics discussed previously, the expected lifetime of these defective electrolyte capacitors was reduced to around 2 years from the normally expected greater than 10 year life expectancy. This became a real problem partly because many of the companies unknowingly using these defective capacitors had warranties of 2 or 3 years, or longer, and were required to service many more units than expected, at a huge cost.

Here's a link on Detecting Counterfeit ICs Without a Microscope.
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