Accendo Reliability

Your Reliability Engineering Professional Development Site

  • Home
  • About
    • Contributors
  • Reliability.fm
    • Speaking Of Reliability
    • Rooted in Reliability: The Plant Performance Podcast
    • Quality during Design
    • Way of the Quality Warrior
    • Critical Talks
    • Dare to Know
    • Maintenance Disrupted
    • Metal Conversations
    • The Leadership Connection
    • Practical Reliability Podcast
    • Reliability Matters
    • Reliability it Matters
    • Maintenance Mavericks Podcast
    • Women in Maintenance
    • Accendo Reliability Webinar Series
  • Articles
    • CRE Preparation Notes
    • on Leadership & Career
      • Advanced Engineering Culture
      • Engineering Leadership
      • Managing in the 2000s
      • Product Development and Process Improvement
    • on Maintenance Reliability
      • Aasan Asset Management
      • AI & Predictive Maintenance
      • Asset Management in the Mining Industry
      • CMMS and Reliability
      • Conscious Asset
      • EAM & CMMS
      • Everyday RCM
      • History of Maintenance Management
      • Life Cycle Asset Management
      • Maintenance and Reliability
      • Maintenance Management
      • Plant Maintenance
      • Process Plant Reliability Engineering
      • ReliabilityXperience
      • RCM Blitz®
      • Rob’s Reliability Project
      • The Intelligent Transformer Blog
      • The People Side of Maintenance
      • The Reliability Mindset
    • on Product Reliability
      • Accelerated Reliability
      • Achieving the Benefits of Reliability
      • Apex Ridge
      • Metals Engineering and Product Reliability
      • Musings on Reliability and Maintenance Topics
      • Product Validation
      • Reliability Engineering Insights
      • Reliability in Emerging Technology
    • on Risk & Safety
      • CERM® Risk Insights
      • Equipment Risk and Reliability in Downhole Applications
      • Operational Risk Process Safety
    • on Systems Thinking
      • Communicating with FINESSE
      • The RCA
    • on Tools & Techniques
      • Big Data & Analytics
      • Experimental Design for NPD
      • Innovative Thinking in Reliability and Durability
      • Inside and Beyond HALT
      • Inside FMEA
      • Integral Concepts
      • Learning from Failures
      • Progress in Field Reliability?
      • R for Engineering
      • Reliability Engineering Using Python
      • Reliability Reflections
      • Testing 1 2 3
      • The Manufacturing Academy
  • eBooks
  • Resources
    • Accendo Authors
    • FMEA Resources
    • Feed Forward Publications
    • Openings
    • Books
    • Webinars
    • Journals
    • Higher Education
    • Podcasts
  • Courses
    • 14 Ways to Acquire Reliability Engineering Knowledge
    • Reliability Analysis Methods online course
    • Measurement System Assessment
    • SPC-Process Capability Course
    • Design of Experiments
    • Foundations of RCM online course
    • Quality during Design Journey
    • Reliability Engineering Statistics
    • Quality Engineering Statistics
    • An Introduction to Reliability Engineering
    • Reliability Engineering for Heavy Industry
    • An Introduction to Quality Engineering
    • Process Capability Analysis course
    • Root Cause Analysis and the 8D Corrective Action Process course
    • Return on Investment online course
    • CRE Preparation Online Course
    • Quondam Courses
  • Webinars
    • Upcoming Live Events
  • Calendar
    • Call for Papers Listing
    • Upcoming Webinars
    • Webinar Calendar
  • Login
    • Member Home

by nomtbf Leave a Comment

MTBF Use May Reduce Product Reliability

MTBF Use May Reduce Product Reliability

Is MTBF Preventing Your Product From Being Reliable?

MTBF is not reliability. Attaining a specific MTBF does not mean your product is reliable. MTBF use may be the culprit.

Therefore, working to achieve a MTBF value may actually be preventing you from creating a product that mets your customer’s reliability performance expectations.

Actively working to achieve MTBF using the common tools around MTBF may be taking you and your team down the wrong rabbit hole. You may be working to reduce the reliability of your products rather than improving them.

Let’s take a look at a couple of ways the pursuit of MTBF is harmful to your product’s reliability potential and contrary to your customer’s expectations.

When the Requested MTBF is Not What The Customer Wants

Some customers may request 50,000 hours MTBF when they really want a very low failure rate probability over 50,000 hours of product use. They meant a duration of 50k hours, not a chance of failing every hour of 1:50k. They didn’t know how to ask for what they wanted. You should ask any time someone asks for MTBF what they really want.

What is a customer really wants high availability over a short duration, or they want to reduce repair times, or they cannot tolerate any failures over a 12 hour mission duration? If they only ask for some MTBF value, is that sufficient for you to create a product that will meet their needs. Probably not.

Reliability Testing Assuming MTBF

When we assume a constant hazard rate, which is common when using MTBF, we can use the memoryless feature of the exponential distribution. Therefore we can test 50 units for 1,000 hours each and count the number of failures that occur… if only one or none, we have ‘proved’ the 50,000 hour MTBF. All good.

The may catch early life failures complicating the test analysis and results, yet certainly would not reflect any product actual reliability performance over a duration of 50k hours. We actually learn very little about how the product performs after 1,000 hours.

The sad part is products with known wear out failure mechanisms are tested using these methods, thus avoiding the messy business of wear out failures clouding reliability testing results.

Assuming Away Early Life and Wear Out Issues

If customer would just use the product during the ‘useful life’ portion of the bathtub curve. Draw as a low failure rate over an extended duration with a few early life failures for a short duration, plus eventually something wears out long after the product has been retired.

Customers do not control the ‘useful life’. The product design does, with a dash of manufacturing, too. Design and build a reliable product, and it may have a low failure rate over the duration a customer may want to use the item.

If we assume away the the early life and wear out portions in order to focus on the useful life, we have a couple of problems:

First, we’re delusional in thinking there is a flat part of the curve that we can assume will naturally occur.

Second, our assumptions do not change what actually causes the product fail. We still have design and manufacturing issues that cause failures. Some occur early, some later, rarely at a low and random rate.

Third, customers do not care about your assumptions, it is the actual performance that matters.

Use Reliability Instead of MTBF

One way out this nest of problems is to avoid using MTBF. Instead use reliability, or the probability of successful operation, over a specified duration. Include the details on the environment, use profile, and what we consider a failure, and you are making progress.

Using MTBF makes everything easier. From apportionment, test planning, and design we can simply assume away many problems that will cause the product to fail. The problem is products that are not reliable fail.

Does your team use MTBF (or MTTF) and do you regularly have ‘surprise’ field failures? If you use reliability directly could you have avoided the issue? I suspect so. What is your story?

Filed Under: Uncategorized

« Software Design For Reliability
Root Cause Analysis: The Key To Breaking The Reactive Cycle »

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

[popup type="" link_text="Get Weekly Email Updates" link_class="button" ]

[/popup]

The Accendo Reliablity logo of a sun face in circuit

Please login to have full access.




Lost Password? Click here to have it emailed to you.

Not already a member? It's free and takes only a moment to create an account with your email only.

Join

Your membership brings you all these free resources:

  • Live, monthly reliability webinars & recordings
  • eBooks: Finding Value and Reliability Maturity
  • How To articles & insights
  • Podcasts & additional information within podcast show notes
  • Podcast suggestion box to send us a question or topic for a future episode
  • Course (some with a fee)
  • Largest reliability events calendar
  • Course on a range of topics - coming soon
  • Master reliability classes - coming soon
  • Basic tutorial articles - coming soon
  • With more in the works just for members
Speaking of Reliability podcast logo

Subscribe and enjoy every episode

RSS
iTunes
Stitcher

Join Accendo

Receive information and updates about podcasts and many other resources offered by Accendo Reliability by becoming a member.

It’s free and only takes a minute.

Join Today

Dare to Know podcast logo

Subscribe and enjoy every episode

RSS
iTunes
Stitcher

Join Accendo

Receive information and updates about podcasts and many other resources offered by Accendo Reliability by becoming a member.

It’s free and only takes a minute.

Join Today

Accendo Reliability Webinar Series podcast logo

Subscribe and enjoy every episode

RSS
iTunes
Stitcher

Join Accendo

Receive information and updates about podcasts and many other resources offered by Accendo Reliability by becoming a member.

It’s free and only takes a minute.

Join Today

Recent Articles

  • test
  • test
  • test
  • Your Most Important Business Equation
  • Your Suppliers Can Be a Risk to Your Project

© 2025 FMS Reliability · Privacy Policy · Terms of Service · Cookies Policy