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All articles listed in reverse chronological order.

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Hartley’s Test for Variance Homogeneity

Hartley’s Test for Variance Homogeneity

The Hartley test is an extension of the F distribution-based hypothesis test checking if two samples have different variances.

The F test works with two samples allowing us to compare two population variances based on the two samples. This test does not work for three or more populations. We could conduct multiple pairwise comparisons, yet the probability of an erroneous result is significant.

Bartlett’s Test and Levene’s Test are non-parametric checks for homogeneity of variances. Bartlett’s Test pretty much expects the underlying data to be normally distributed.

Levene’s Test is a better choice when you’re not sure the data is normal. Both are conservative and time-consuming to calculate.

We need another way to check for equal variances. [Read more…]

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Introduction to the 6 Sigma Design Approach

Introduction to the 6 Sigma Design Approach

Sigma, σ, is the Greek character we use to represent standard deviation. 6 σ represents the spread of data about the mean. For data with a normal distribution 6 σ includes 99.7% of the data.

The 6 σ design approach incorporates knowledge of the variation that will occur within the design such that the design has is unlikely to fail.

According to Mikel J. Harry, the foundation of excellence in product quality rests on achieving six sigma product quality. [1]  [Read more…]

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Achieving Cost Effectiveness with Performance Management

Achieving Cost Effectiveness with Performance Management

Welcome to part six of my 10-part series of blogs called “Uptime Insights”, where we explore a journey of excellence in maintenance.

To stay on top, managers must implement strategies that keep operations performing at high levels. In these articles, I will show you how to achieve excellence in maintenance – a critical business process in any capital intensive industry.

Uptime Insights Part Six:

Achieving Cost Effectiveness with Performance Management

The work management process is essential to keeping costs under control in maintenance but how will you know if you are doing well if you don’t measure what you are doing and the results you get?

Performance management is another essential for maintenance management. Costs are important, results are important and so are the processes you use to turn costs into results.

Performance management is central to managing those processes so you get the most output for the least input – the greatest cost effectiveness. [Read more…]

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Focus on the Foundation: It Will Sustain You

Focus on the Foundation: It Will Sustain You

As Engineers, Craft and Maintenance people, we have a tendency to be excited by the technological advancements that become available.

This is not a bad thing provided we do not let them become the flavor of the month or take our attention away from what we are here to do. Enable Reliability and Maintenance.

Often we find much information on the advanced technical topics such as Reliability Engineering, Life Cycle Costing, or various CBM technologies. When properly deployed, these techniques allow us to further our success in Reliability and Maintenance.

But what about the foundations that make these interesting techniques successful? [Read more…]

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How to Correct a Failing Lean Six Sigma Program

How to Correct a Failing Lean Six Sigma Program

Guest Post by David Patrishkoff (first posted on CERM ® RISK INSIGHTS – reposted here with permission)

We are living in a time of great disruption and uncertainty.

Every organization is facing great risks. Some of these risks are visible and many others are hidden.

So, it’s crucial that every company develops and implements tools to identify, mitigate and transform risks into dramatic improvements and even disruptive innovations. [Read more…]

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Isolation Valves for Different Services

Isolation Valves for Different Services

Valves can be used to both isolate and regulate liquid and gas flow.

Valve used for isolation duties must provide secure, tight shut-off. Consideration must be given to the nature of the process chemical, the quality of sealing and the impact of outside environmental occurrences.

Keywords: bubble tight, design pressure, leakage rate, fire rated, differential pressure. [Read more…]

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The Sum of Squares Concept

The Sum of Squares Concept

The data analysis course professor tended to focus on the practical application of statistics.

Avoiding statistical theory was fine with me. Learning statistics for me was on how to solve problems, optimize designs, and understanding data.

Then one lecture started with the question, “Why do we sum squares regression analysis, ANOVA calculations, and with other statistical methods?” He paused waiting for one us to answer.

We didn’t. I feared the upcoming lecture would include arcane derivations and burdensome theoretical annotations. It didn’t. [Read more…]

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The Fundamental Set of Reliability Engineering Tools

The Fundamental Set of Reliability Engineering Tools

In a single meeting, you may need to structure a reliability model, create estimates, outline test plans, and discuss a field failure. The breadth of tools and knowledge to be effective is staggering.

No two problems, questions, situations, or industries are the same. Thus, the solutions you provide must differ as well. If you enjoy a complete set of reliability engineering tools at your disposal, you are well situated to address any question.

[Read more…]

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Building Excellence in Materials Management

Building Excellence in Materials Management

Welcome to part five of my 10-part series of blogs called “Uptime Insights”, where we explore a journey of excellence in maintenance. To stay on top, managers must implement strategies that keep operations performing at high levels.

In these articles, I will show you how to achieve excellence in maintenance – a critical business process in any capital intensive industry.

Uptime Insights Part Five:

Building Excellence in Materials Management

Without parts, many jobs can’t be done.  There’s no point planning and scheduling work if you can’t rely on materials management to provide the parts when you need them.  If you want excellence in maintenance you need excellence in materials management. [Read more…]

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See How Easily You Can Succeed in Reliability: 7 Critical Steps in Making Reliability a Way of Life

See How Easily You Can Succeed in Reliability: 7 Critical Steps in Making Reliability a Way of Life

Why is it that Reliability Programs often fail and are not sustained? Bringing about such a change in a large organization is often one of the most difficult tasks that we undertake.

This undertaking requires a shift in mindset and in the ways people work. People love the status quo and are often afraid of the change. We must show them that there is nothing to be afraid of and that the change will be beneficial.

[Read more…]

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The Unpredictability of Uncertainty

The Unpredictability of Uncertainty

Guest Post by Geary Sikich (first posted on CERM ® RISK INSIGHTS – reposted here with permission)

Introduction 

Recently I wrote an article titled “Can You Calculate the Probability of Uncertainty?” The article posited that the heavy dependence on mathematics to determine the probability of risk realization may actually create “false positives” regarding the basis for the determination of probability.

My point was that there is too much uncertainty, things that we just do not know, to be able to calculate the probability of uncertainty with any degree of confidence. I received several comments from readers telling me that I was confusing the issue and that determining the probability of risk is all about “uncertainty”.

I have to say that this gave me pause to think. And, my conclusion is that risk is all about the probability of identified certainties that carry an uncertain realization. [Read more…]

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Performance Reviews for the Crew

Performance Reviews for the Crew

One method to provide a formal means of appraising people’s performance is by using performance reviews. The employee and manager together use a structured check sheet to work through keys duties of the employee.

They address both the good, and not so good, aspects of performance. The end result is an unbiased assessment of the employee’s current performance and a plan to improve it over the coming year.

Keywords: rating scale, verifiable, performance standards. [Read more…]

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Bartlett’s Test for Homogeneity of Variances

Bartlett’s Test for Homogeneity of Variances

A common assumption when comparing three or more normal population means is they have similar (the same) population variances.

ANOVA and some DOE analysis results rely on the underlying data having similar variances. If this assumption is not true, the conclusions suggested by the ANOVA or DOE may be misleading.

It doesn’t take long to check. [Read more…]

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Plot Your Derating Guidelines

Plot Your Derating Guidelines

The concept of derating is similar to the mechanical engineering concept of a stress–strength analysis.

The intent is to ensure that the selected component or the mechanical design has sufficient strength to withstand the expected applied stresses.

Components operating at or near their rated values have short lives. Consequently, the general practice is to use components for materials well below their rated values to extend the operating life of the items.

This is where derating comes into play. [Read more…]