Top 5 Popular NoMTBF Posts

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Summer Break

Taking a week off away from the article writing so in the vain of summer reruns, providing a list to the top five posts from the NoMTBF site.

In no particular order:

  • Replacing MTBF with Bx - 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.
  • MTBF: What is it Good For? - MTBF: What is it Good For? Guest post by Andrew Rowland, CRE, ReliaQual Associates, LLC I.  INTRODUCTION The mean time between failure (MTBF) is arguably the most prolific metric in the field of reliability engineering. The MTBF is used as a metric throughout a product’s life-cycle; from requirements, to validation, to operational assessment. Unfortunately, MTBF alone doesn’t … Continue reading MTBF: What is it Good For? →
  • Where does 0.7eV come from - This post is a conversation first held on the LinkedIn group No MTBF. I’m capturing a portion of the contributions here to continue the discussion or to widen the audience. Reminds me of always assuming 95% confidence is the right value when designing a test, or assuming constant failure rate. So, let the conversation continue, starting … Continue reading Where does 0.7eV come from →
  • The Worst Reliability Requirement - Most of us have seen reliability specified using a requirement like the following: The Zeus 5000 SUV shall have an MTBF of 144,269.5 miles with a 90% confidence. Some readers may not have seen reliability requirements specified in any other way.  What they have always seen has read something like:  The widget shall have an … Continue reading The Worst Reliability Requirement →
  • Why The Drain in the Bathtub Curve Matters - Most reliability engineers are familiar with the life cycle bathtub curve, the shape of the hazard rate or risks of failure of a electronic product over time. A typical electronic’s life cycle bathtub curve is shown in figure 1.

 

Enjoy these again or for the first time.

Customer Reliability Talk

Engineering, Maintainability

How do your customers talk about reliability

And, what can you do about it?

As engineers laying out a factory or designing a new product we have to meet the reliability expectations of our customers. It would be great if the system would not fail or need repair, yet that is often not the case. Continue reading Customer Reliability Talk →

Why do we talk about reliability?

MTBF,

Why do we talk about reliability?

  • To make decisions
  • To estimate reliability
  • To understand risk

We talk about reliability because it matters. The ability to estimate reliability allows us to make design and development decisions. The ability to monitor reliability allows us to adjust the design, suppliers or expectations about a product. Continue reading Why do we talk about reliability? →

The Common Useful Life Assumption

Engineering

If we only measure Useful Life

Does that mean the early life failures and wear out failures don’t count?

Designing to keep the useful life failure rates low is good design practice. This generally means a design that is robust, operates smoothly, incurs little temperature rise, and is as simple as it needs to be to function. Continue reading The Common Useful Life Assumption →

If not MTBF

MTBF

If not MTBF, then what should we use instead?

 

MTBF has issues. It is commonly mis-understood and mis-used. I find it hard to interpret and use for any meaningful discussion of reliability.

The entire premise of the NoMTBF site is to encourage you to not use MTBF.

There are exhaustive writings on setting meaningful goals and metrics in the business literature. A couple of tenants seem common: Continue reading If not MTBF →

Searching for MTBF

MTBF

Are you searching for MTBF?

I would ask why would you do that, yet I probably know.

You are looking for reliability information about a component or system. You want to know something about the expected failure rate or durability. Will it last long enough to meet your design and customer requirements?

Or, you have heard of MTBF and want to understand the acronym and metric. Maybe how to calculate the value from test results or field data. Continue reading Searching for MTBF →

MTBF Requirement Reaction

MTBF

Let’s talk about an appropriate MTBF Requirement Reaction

Every now and then we receive a customer request concerning reliability. If asked most customers would prefer no failures, low-cost of maintenance or ownership, and trouble-free long-term performance. And, many also realize that failures do occur. Thus a series of discussions occur to find the economically viable solution for both parties. Part of this discussion may include a poorly worded reliability requirement.

How you respond can help to improve the discussion and accelerate the finding of the right solution.

Continue reading MTBF Requirement Reaction →

Failure Dates not Rates

MTBF

Ask for failure dates not failure rates.

Just because the vendor provide the data convenient for an MTBF calculations should you settle?

No.

You have some questions to ask and some better information to gather. You may have a decision to make and using the best possible data helps you and your team make the right decision more often.

Continue reading Failure Dates not Rates →

Persuasion and Influence

Engineering

Persuasion and Influence

Reliability engineers usually work in support of an organization. We support a development team as they design a new product. We support a factory as they operate equipment to produce products. We support using our specialized knowledge to create and maintain reliable products or assets.

The teams we work with consider cost, time, function, technology, environmental impact and many other factors as they find a viable solution. Reliability is just one of the many considerations.

Continue reading Persuasion and Influence →

Required Case History for Reliability Engineers

Engineering

One for the (Reliability) Books

Guest post by Kirk Gray

The GM Ignition switch failure case history should be required reading for all reliability engineers.

It is rare to have insight into any internal company history of serious electronic and electromechanical failures. Failure analysis and the causes of electronics or electromechanical systems failure can be a difficult investigation for any manufacturing company. Disclosure of the history and data is rarely if ever published due to the potential liability and litigation costs as well as loss of reputation for reliability and safety.

Continue reading Required Case History for Reliability Engineers →

Talking about Reliability

Engineering, MTBF

How do you talk about reliability?

“The language we use matters.” Wayne Nelson

When we talk about our products or equipment, we may refer to the expected durability of the system.

  • How long it will work before failure?
  • How long before we have to make repairs?
  • Will it work when we need it to work?

Our customers and investors also want to know how long will it last.

Continue reading Talking about Reliability →

Expecting MTBF

MTBF

What to Expect from MTBF

What do we really want?

When using the term, MTBF, many believe they are talking about the reliability of a device or system. A high MTBF numbers means it is a reliable item.

What we really want is the device to work over some duration without failure (or with few failures). It should perform a function as expected in the desired environment.

Continue reading Expecting MTBF →