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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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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…]

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Understanding Reliability Across an Industry

Understanding Reliability Across an Industry

The Department of Energy (DOE) Office of Energy conducted an Energy Storage Reliability Workshop this week provide a unique glimpse at how the stakeholders across an industry view reliability.

The representatives from government and private sector, including national labs, large and small companies, insurers and consultants gather to talk about the reliability of large-scale stationary energy storage systems.

Specifically, the focus of the workshop was on helping the DOE identify the specific activities and focus for their involvement in this relatively new industry segment.
[Read more…]

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The “What” & “Why” of Weibull Analysis

The “What” & “Why” of Weibull Analysis

How to conduct a Weibull analysis and the questions the analysis will generate.

Part 2 of 7

Every failure is part of a puzzle. The equipment we are maintaining is trying to communicate with the use of each and every failure.

Often the message is not obvious.

There is the immediate failure. And, if we’re paying attention we can sort out the root cause of the failure along with replacing or repairing the damaged parts. Sometimes though the damage is caused by another issue with the system. [Read more…]

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Identifying Parts Obsolescence Early

Identifying Parts Obsolescence Early

One aspect of creating a new product or system is the sourcing of parts, components, and materials.

Gone are the days of your organization providing every element of the final product. Henry Ford’s supply chain for early Ford automobiles includes their own forests, rubber plantations, and iron ore mines. [Gelderman, 1981]

We increasingly rely on the supply chain to create the necessary parts for the design’s functionality. Then to continue to supply those same parts for decades, in some cases. [Read more…]

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How Do You Select Reliability Tasks to Accomplish?

How Do You Select Reliability Tasks to Accomplish?

As reliability engineers, we have a large number of tools available.

From project planning, system modeling, data analysis, test planning, to risk identification and defect discovery, we have techniques, procedures, algorithms to help us identify and solve reliability problems.

We also may ways to apply an individual reliability task.

We could do an exploratory drop test to see what happens if anything. Or, we could conduct a full characterization study of the force signature of drops onto different surfaces and faces from a range of heights. Or something in-between.

We have options and thus need to make choices. [Read more…]

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Basic Description of a Fault Tree Analysis

Basic Description of a Fault Tree Analysis

A fault tree analysis (FTA) is a logical, graphical diagram that starts with an unwanted, undesirable, or anomalous state of a system.

The diagram then lays out the many possible faults and combination of faults within the subsystems, components, assemblies, software, and parts comprising the system which may lead to the top level unwanted fault condition. [Read more…]