Book Review: An Elementary Guide to Reliability
If you sort your Amazon search on ‘reliability engineering’ by price: low to high, you may find some interesting titles available for free or maybe a few pennies. Not one to resist a chance to fill another bookcase, it’s been a bit of spending spree.
One of the reasons, I am interested in older titles is to determine why MTBF is so prevalent today. So far, still looking and learning along the way.
There are many great books in our field. Sure, some are older. Some are not at all useful or helpful.
This book review is the first in what may become a monthly addition to the NoMTBF blog.
Today’s review is on the book, An Elementary Guide to Reliability (3rd) Third Edition, by G. W. A. Dummer and R. C. Winton.
Weighing in at 47 pages in a 6”x9” format, this one really is just an introduction to the topics covered. From the Introduction:
[This book] explains in simple, largely non-technical language what is meant by reliability and the various factors which make an equipment or machine reliable.
That it does or attempts to do.
The Definition of Reliability
I learned long ago to first check how the author defines ‘reliability’ in any book covering the topic. If the definition is different than my expectation, I’ll have to be careful when reading and using the book’s content.
In Chapter 2, the authors define reliability thus:
Reliability — the characteristic of an item expressed by the probability that it will perform a required function under stated conditions for a stated period of time.
This works for me.
Unfortunately, the authors quickly introduce the “most important criterion … how often the item breakdown … defined in two ways.” MTBF and MTTF.
The rest of chapter 2 describes the bathtub concept and references the British Standards Institution. Yet, they do not recognize the inability of MTBF to describe two the three sections of the bathtub curve. They do acknowledge the ‘flat’ part is actually not flat, yet often close enough to be considered flat.
How Reliability is Calculated
Let’s move on to how the suggest we measure reliability. The title of Chapter 4, “How Reliability is Calculated” is ominous. I tend to think of measuring reliability, which may be niggly on my part.
My hopes are quickly dashed as the chapter opens with a brief description of parts count predictions using failure rates, converting to MTBF, as the first way to ‘calculate’ reliability for your product or system.
After a couple pages and an example of parts count prediction, the authors mention Physics of failure and devotes two paragraphs to the approach. They suggest is applies for high-reliability items that justify the considerable expense of creating time to failure models.
Then it’s back to the parts count topic by listing examples of component steady state failure rates.
Not sure why derating garnered a paragraph in the chapter, yet in a single paragraph on the subject they suggest component derating is a good practice.
The book is aimed at those dealing with repairable systems and does touch on many of the key aspects of reliability engineering.
A very brief introduction to statistics, operating and environmental conditions, then shorts treatment on installation, operation, maintenance, and reporting of failures. I do like the discussion in the last chapter on the cost of reliability, as I agree connecting reliability activities to the business, including expenses and profits, makes good sense.
The use of MTBF pretty much limits my recommendation to — do not buy.
It’s a quick and easy read. There are examples and practical discussions, yet the focus on using MTBF to exclusively describe reliability is flawed advice.
If you have seen this title, what do you think? What’s your opinion of this short treaty on reliability engineering?
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