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Fred Schenkelberg — Thought Leader

Author of CRE Preparation Notes, Musings", NoMTBF, multiple books & ebooks>, co-host on Speaking of Reliability>/a>, and speaker in the Accendo Reliability Webinar Series.


This author's archive lists contributions of articles and episodes.

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When to Take Action on Field Failure Data?

When to Take Action on Field Failure Data?

Not much. You need just enough field failure data to identify the root cause and determine if and how to resolve the problem.

Field data will accumulate even if your program works diligently to prevent failures.

The actions taken before the reported failure will frame when you need to take action.

Gathering failure data and evaluating the trigger points for action is a reactive approach. This approach means you will only respond to problems.

You will also likely not spot the important emerging issues before they become significant problems. [Read more…]

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The Basics of Derating Electronic Components

The Basics of Derating Electronic Components

As with strength-strength analysis, derating is a means to design robust systems.

Derating is an intentional process applied to every component of a product to reduce the opportunity of a component witnessing more stress than it is capable of withstanding.

The additional robustness also reduces the amount of damage the stress may impart, thus prolonging the life of the component. [Read more…]

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A Different Way to Consider Derating Guidelines

A Different Way to Consider Derating Guidelines

The component choice an electrical engineer starts with the functional requirements of the circuit. Another consideration is the rated values of the specific component selected.

Derating guidelines provide information to compare the component rated values to select stresses or conditions. The intent is to assist the engineering team to select robust enough components for the application.

Robust here implying the component within the circuit will operate for a suitable length of time. [Read more…]

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Data Q&A with Fred and James

Data Q&A with Fred and James

A Question & Answer Period with Fred Schenkelberg and James Kovacevic on the what can be done with your data and analysis.

Data and the analyses that use the data can be tricky to manage at best, let along extremely difficult.

In this last post of the series on using the maintenance data you have, Fred and James will answer many of the common questions asked about data and the analyses. [Read more…]

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3 Ways to Provide Field Reliability Feedback to the Design Team

3 Ways to Provide Field Reliability Feedback to the Design Team

By the time a product fails in the field, the design team is focused on the next design.

They are looking to the future and not looking for field reliability feedback. We know that each failure contains valuable information.

We, as reliability professionals, often work to create as much useful information concerning failure modes and mechanisms as possible. We want to improve the design.

Yet, what happens when the design team has moved on to the next project? When the expertise to effectively make changes to the design to improve product reliability performance is no longer paid to work on the previous design?

What can you do to engage the right people to implement the necessary changes?

Here are a few ideas that I’ve seen used to effectively make good use of field failures to create meaningful field reliability feedback. [Read more…]

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The Next Step in Your Data Analysis

The Next Step in Your Data Analysis

Nothing keeps a statistician happy like a pile of data.

Part 6 of  7

As seen in the previous articles, you can easily use the data you already have to conduct a meaningful analysis. This includes Weibull, Crow-AMSAA or a Mean Cumulative Function analysis.

Digging into a well manage dataset promises to reveal insights, trends, and patterns that will help improve the line, process, or plant.

Creating a plot or calculating summaries is pretty easy with today’s tools. Yet, are you doing the right analysis or are the various assumptions valid?

One critical step in the data analysis process is making sure you are doing a valid and appropriate analysis. [Read more…]

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Environmental and Use Factors

Environmental and Use Factors

The definition of reliability includes four elements.

One of them is the intended environment where the device or system will experience a range of stresses.

The knowledge of where and how an item will operate enables:

  • The proper design to meet customer expectations
  • The essential durability during transportation, storage, and use
  • The complete accounting of applied stresses and their variations
  • The effective application of stress mitigation or reduction techniques
  • The efficient installation and monitoring of stress tracking

[Read more…]

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Petri Nets for System Reliability Modeling

Petri Nets for System Reliability Modeling

A Petri net graph is a depiction of a system using a symbolic language.

The modeling permits the analysis of complex systems or networks of systems.

It is possible to include elements of the system that are neither function or failed. In other words, it permits modeling a system when one or more of the elements are in a degraded state or under repair.

Petri net modeling is useful when the repair/restore times are long compared to operating times, as reliability block diagrams and fault tree analysis approach assume short or insignificant repair times, in most cases. [Read more…]

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Additional Reliability Specification for Your Supplier

Additional Reliability Specification for Your Supplier

Beyond the part reliability specification, you may also add conditions or requests to your reliability specification for your supplier.

The communication with your supplier should include sufficient information that they fully understand your reliability performance expectations. When buying or contracting with a supplier, you are the customer.

Be clear about your reliability requirements including constraints and conditions.  [Read more…]

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Establishing Part Specific Reliability Specifications

Establishing Part Specific Reliability Specifications

Unless you are working with raw materials directly, you rely on your suppliers to provide reliable parts.

Do you suppliers know your reliability objectives for the parts they supply?

If you didn’t tell them, they probably do not know. If you did tell them, did you make it the reliability specification clear and understandable?

As with any specification, clear communication is essential. Guessing or assuming both parties know and have the same reliability goals is, well, not a good practice. The ability of a supplier to build and deliver the parts that meet all your specification has to include a clear and understandable reliability specification.

There is a range of common reliability specifications in use, some are better than others. Let’s start with a brief review of reliability specification types.

Then briefly outline how you establish the reliability specifications for each supplied component. [Read more…]

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First Step in Analyzing Repairable Systems Data

First Step in Analyzing Repairable Systems Data

Using the right plot enables your team to know what is working or need improvement.

Part 4 of 7

Your facility has data and maybe too much data. Using simple plotting may be the key to unlocking how well your maintenance program is performing.

Building on the concept of reliability growth modeling James Kovacevic described a convenient way to quickly visualize your repairable system failure data is with a mean cumulative function (MCF) plot. [Read more…]

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Improve Decision Making with Statistics

Improve Decision Making with Statistics

We make decisions all the time. Often our decision making is with little more than a gut feeling.

When faced with a major decision we often look data to help us decide. Is the product reliable enough as designed? Which field returns indicate we should stop production?

Some decision may help us earn or lose thousands if not millions of dollars.

Deciding to delay a product launch by six months means we have no revenue for the duration. The delay may also permit us to address a design flaw that would cause half the products to fail within a few months.

The later may cause loss of market share, erosion of brand loyalty, not to mention the cost of warranty claims. [Read more…]

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Take Action to Deal with Part Obsolescence

Take Action to Deal with Part Obsolescence

Even products with relatively quick design cycles and short stays in the market deal with part obsolescence.

Long design periods along with long durations in service or in production simply increases the chance that one or more parts will become obsolete.

Designing systems with part obsolescence in mind helps. Working with suppliers to select parts with many sources, with long-term plans to produce, and with long term commitments, all may help. Even then, companies change priorities, go out of business, or simply discontinue the part you need. [Read more…]