Reliability Assessment: A Guide to Aligning Expectations, Practices, and Performance. Daniel Daley

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       Chapter 8Everything in Between

       • Failure Mapping

       Chapter 9Conclusion

       AppendixWide-Hart Assessment

       References for Further Reading

       Index

Introduction

       Climate is what we expect, weather is what we get.

       Mark Twain

      A number of years ago, I heard someone refer to a concept called the “device mentality.” It was a way of describing a naïve viewpoint of complex devices. For instance, a young driver with a “device mentality” would view a car as simply being a steering wheel, an accelerator, and a brake. You push the accelerator to make it go. You push the brake to make it stop. And you turn the wheel to choose the direction. All other details are unimportant.

      I have occasionally used this concept when describing issues related to reliability. As it turns out, people with a device mentality create a problem for people in the reliability business. They neither know nor care how their actions makes things fail. However, if it is possible to engage these individuals in caring how a thing works and what they can do to avoid causing damage, reliability will improve.

      Although the most obvious example of an individual with a device mentality is a young person operating an automobile, many individuals you would expect to have a thorough understanding of reliability still remain quite naïve. Even some fairly senior managers of companies that depend on complex machinery for their source of income have a limited understanding of the things that result in high reliability and those that do the opposite.

      The reason for introducing the device mentality is that the same people who view a car as little more than a steering wheel, an accelerator, and a brake also expect their vehicle to operate flawlessly with little or no maintenance forever. This same paradigm exists with people who operate complex equipment.

      There is an entire spectrum of how well people understand reliability. At one extreme are folks with the device mentality who are clueless. At the other extreme are individuals who understand the subject very well. Generally speaking, if you were to create a graph showing the number of people at each point on the spectrum, it would not be a normal distribution. Most people are pretty naïve about reliability. Most people just expect things to work and not be an inconvenience to them.

      As mentioned above, even individuals who regularly deal with complex systems are often poorly informed concerning what makes a system reliable and what is likely to make in unreliable. If you were to ask them to characterize their expectations concerning the reliability of their systems, they would say they expect excellent reliability. If you were to ask them again why they have those expectations, they would say that their systems were designed to the highest standards and constructed with the finest materials. Although those factors have some bearing on reliability, there are many, many other factors that are equally if not more important.

      So, for the moment, if we accept the premise that many people have a na^ïve or distorted notion of reliability, the next question should be, “so what?”

      Recently I read an article in the business section of the local newspaper about a bio-fuel plant filing for bankruptcy. The explanation provided by the owners was that uncontrollable outages during early operation resulted in economic losses. Apparently they blamed the problems on “gremlins.” More likely, the individuals who owned the plant knew little about reliability. Maybe the people who engineered and constructed the plant provided the owners with slick brochures showing people with smiling faces working in a clean, smoothly operating plant. The owners might have been provided with a tour through a smoothly operating facility. Everything they saw suggested that you simply turned the key and the plant started up and ran forever flawlessly cranking out money.

      Nowhere in the process of purchasing, designing, or building the facility did anyone mention anything about reliability or what was needed to achieve it. No one mentioned:

      •There are choices that can be made during the design process that will provide a more reliable configuration.

      •There are choices that can be made during procurement that will provide more robust equipment.

      •There are choices that can be made during construction, commissioning, and start-up that will ensure the systems start-up and operate smoothly.

      •There are different ways the plant can be operated that will affect reliability.

      •There are different ways to maintain the plant that will affect reliability.

      •There are ways to provide routine inspection and oversight that will identify failure mechanisms at work and defects before they can cause a failure.

      •There are steps that can be taken during modifications and renewal that will ensure that inherent reliability is maintained or improved.

      If only someone would have told the owners about all these issues, maybe they would have made choices that would have prevented all the problems leading to the bankruptcy.

      As the title of this book implies, the objective is to provide an approach to “aligning yout reliability expectations.” That title may be a little misleading to some. A better title might be, “Developing realistic expectations for reliability” or, better yet, “Finding out how bad things really are.” Independent of the title, at the conclusion of this book, the reader should understand:

      1.What elements determine reliability

      2.How to evaluate how well you are currently dealing with those elements

      Rather than spending more time worrying over the most appropriate title, let’s focus on the meaning of “aligning reliability expectations.” Let’s begin by carefully defining the terms.

      For our purposes, the definition of “expectation” is a level of performance that is considered reasonable or “due.” Although it may seem I am being overly precise, it is important to clearly separate feelings from facts. An “expectation” may be viewed as being reasonable or due even though the facts or tangible evidence may not support those feelings.

      The term “reliability” is intended to go beyond the textbook definition of reliability. In this context, I am using the term reliability to embrace the concepts of reliability, availability, and maintainability.

      More specifically, these terms have the following definitions:

      •Reliability is the instantaneous likelihood that a system or device will fail during a specific interval of time.

      •Availability is a measure of the percentage of time a system can perform its intended function.

      •Maintainability is a measure of the ability to restore the full inherent reliability in a ratable period of time.

      Thus, reliability is used somewhat like the term expectation. It is applied in a manner that exposes the concept that most people feel when they use the term. They typically use the term to represent СКАЧАТЬ