Musings on reliability and maintenance topics

Short essays and thoughts (musings) on reliability and maintenance engineering topics. Let me know your reaction and thought, plus any questions.
ISSN 2329-0080

Achieving a Reliability Goal May Not Be the Best Plan

July 23, 2015
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Ready, Fire, Aim Reliability Goal Setting “Keeping the end in mind”, “working toward a common objective” and “providing a vision” are all convention management wisdom based on setting goals. Seeing a reliability goal is one of first tasks when creating a reliability plan. “How good (reliable) does it have to be?” That is answered with […]

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Introduction to Types of Life Testing

July 16, 2015
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Life testing My introduction to reliability engineering was my boss asking me to sort out how long a new product will last in use. The expectation was it would last for 20 years or more buried in Italian mountain concrete bridges. My first thought was about living in the Dolomites for 20 years monitoring the […]

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Do Your Statistics, It’s Good For You

July 4, 2015
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How to Encourage the Use of Statistics If nothing was uncertain we would not need statistics. Since nearly everything varies in some fashion, we need a way to describe and work with that variability. We already know this and we know about statistics as being the right set of tools. Yet we hesitate, avoid, and refuse […]

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Can a Product Have Perfect Reliability?

July 2, 2015
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What Happens When a Product Lasts Too Long? In the poem by Oliver Wendall Holmes, The One Hoss Shay, a deacon is confounded by the various parts of his carriage the fail. And, he decides to do something about it. But the Deacon swore (as Deacons do, With an “I dew vum,” or an “I […]

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Meditation and Design for Reliability

June 25, 2015
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Design for Reliability is More Than a Set of Tasks Is it possible for an individual to ‘do’ DFR? Is design for reliability something, like a specific technique, that is DFR? What is DFR and how would you recognize it if it was occurring? Like meditation, nearly anyone can strike a pose that appears similar […]

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Is Environmental Testing Part of Product Reliability?

June 18, 2015
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Is Environmental Testing Part of Product Reliability? Environmental testing is the evaluation of a product or system in one or more stress conditions. Environmental as in that which surrounds and affects a product. Consider temperature. Is the product going to experience outdoor temperatures as found in Fargo, North Dakota or Belmopan, Belize? The weather is […]

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When to Stop Testing

June 11, 2015
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When to Stop Testing Stop testing when the testing provides no value. If no one is going to review the results or use the information to make a decisions, those are good signs that the testing provides no value. Of course this may be difficult to recognize. Some time ago while working with a product […]

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Reliability and Monte Carlo Determined Tolerances

June 4, 2015
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Monte Carlo Method In the Monte Carlo method one uses the idea that not all parts have the same dimensions, yet a normal distribution describing the variation of the part dimensions is not assumed. Although the normal distribution does commonly apply, if the process includes sorting or regular adjustments or if the distribution is either […]

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Reliability and Root Sum Squared Tolerances

May 28, 2015
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Root Sum Squared Method The root sum squared (RSS) method is a statistical tolerance analysis method. In many cases the actual individual part dimensions fall near the center of the tolerance range with very few parts with actual dimensions near the tolerance limits. This of course assumes the part dimensions are tightly grouped and within […]

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Quick Introduction to Worst Case Analysis

May 21, 2015
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Worst-Case Tolerance Analysis Worst-case tolerance analysis is the starting point when creating a tolerance specification. It is a conservative approach as it only considers the maximum or minimum values of part variation—whichever leads to the worst situation. Setting tolerances such that the system will function given the expected variation of manufactured components improves that ability of […]

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