Book Review

Contents

• Chapter 1 - Impact of Maintenance
• Chapter 2 - Financial Implications and Cost Justification
• Chapter 3 - Role of Maintenance Organization
• Chapter 4 - Benefits of Predictive Maintenance
• Chapter 5 - Machine-Train Monitoring Parameters
• Chapter 6 - Predictive Maintenance Techniques
• Chapter 7 - Vibration Monitoring and Analysis
• Chapter 8 - Thermography
• Chapter 9 - Tribology
• Chapter 10 - Process Parameters
• Chapter 11 - Ultrasonics
• Chapter 12 - Visual Inspection
• Chapter 13 - Operating Dynamic Analysis
• Chapter 14 - Failure Mode Analysis
• Chapter 15 - Establishing a Predicitive Maintenance Program
• Chapter 16 - A Total-Plant Predictive Maintenance Program
• Chapter 17 - Maintaining the Program
• Chapter 18 - World Class Maintenance

Our Review

If you plan to buy one book on Predictive Maintenance, this, I believe, is currently the best book on the market. This is not to say that it does not have its shortcomings, and I will discuss some of these later in this review, but overall, this book comes closest to being a comprehensive introduction to the Predictive Maintenance technologies currently available, and their practical application.

The book is pitched at Maintenance Engineers and Maintenance Managers who need to make decisions regarding what Predictive Maintenance technologies they should apply in their organizations, and who may also be called upon to interpret the recommendations given to them by Condition Monitoring specialists. It succeeds admirably in providing the correct information, with the appropriate amount of detail, for this readership. This book is not a detailed "how to" guide for budding Predictive Maintenance technicians, nor does it aim to be.

The book commences with an discussion of the impact that maintenance has on organizations, and a brief discussion of alternative maintenance improvement approaches. One of the key messages of the opening chapter, and one that is repeated throughout the book, is that Predictive Maintenance technologies are capable of far more than just breakdown prevention. Mobley argues strongly that these technologies can also be used as Maintenance QA tools, as well as plant or process optimization tools. When applied in this manner, predictive maintenance technologies can be an integral part of proactive, as well as predictive and preventive, maintenance strategies. This initial chapter also recognises that technology alone cannot provide improvement - associated improvements in other aspects of the management of maintenance are also necessary in order to unlock the potential benefits of predictive maintenance technologies.

Chapter 2 attempts to outline the benefits of utilising Predictive Maintenance Technologies. By necessity, this chapter is fairly generic, but does detail the types of benefits that are likely to accrue, and provides a worked example of the justification for Predictive Maintenance.

Chapter 3 expands more on the Objectives of Maintenance, the benefits of effective Preventive Maintenance, and the associated organisational issues to be addressed in successfully implementing a Predictive Maintenance program.

Chapter 4 discusses in more detail, the benefits of Predictive Maintenance, and quotes the results of a survey 0f 1,500 plants that had implemented predictive maintenance programs. Among the more interesting statistics from this survey was the selection of Vibration Analysis as the msot beneficial predictive maintenance technique by 54.6% of respondents. The chapter also discusses the responses to questions regarding changes or improvements that respondents believed should be made to their existing programs. This makes for some very interesting reading.

Chapter 5 discusses the normal failure modes and monitoring techniques that can prevent failures for common machine-train components. It is a slightly curious position for this chapter, as it assumes some knowledge of the techniques themselves (which are not discussed until later), but does assist in providing a very practical focus relatively early in the book. Various machine-train components are discussed, including motors, turbines, chains, couplings, gearboxes, compressors, fans and more.

Chapter 6 then moves on to give an overview of the various predictive maintenance techniques covered in the book. These include:

• Vibration Monitoring
• Thermography
• Tribology
• Visual Inspections, and
• Ultrasonics

There is also a very brief discussion of electrical testing techniques. If there is a weakness in this book, it is that it does have a very mechanical focus, and there is generally little in depth discussion of electrical predictive maintenance techniques. Further, it is fairly clear that Mobley's own area of specialist expertise is in Vibration Analysis, as there is particular emphasis on this technique. However, given the previously quoted result that 54.6% considered Vibration Analysis to be their most beneficial Predictive Maintenance technique, perhaps this slight bias can be forgiven.

Chapter 7 weighs in at a solid 57 pages long, and gives an excellent introduction to Vibration Analysis. The coverage is extensive, without being overly technical (although there are a few formulae in here, for the mathematically minded). Aspects covered in this chapter include the various, and extensive, applications for Vibration Analysis, Vibration Sources, an introduction to Machine Dynamics, Vibration Data Types and Formats (including time domain data, frequency-domain, single or multi-channel data etc.) Also covered are a variety of options for data collection, and a variety of analysis techniques.

Chapter 8 moves on to discuss Thermographic techniques, including coverage of the basic theories of infra red thermography, a discussion of things to look for when selecting infrared thermographic equipment, and possible applications for thermography. In this latter section, all of the applications listed are electrical, but thermography can also have useful application in mechanical scenarios, to check, for example, for the location of pipe blockages, external inspection of refractory condition in furnaces etc.

Chapter 9 covers Tribology, and provides an introduction to the various oil analysis techniques and their application, but I would have liked to have seen a little more detail in this chapter, covering, for example, the situations in which different tribological tests are appropriate, and providing assistance in interpreting the results that are returned from these tests.

Chapter 10 discusses Process Parameters, such as flow, temperature, pressure etc. Mobley makes the very valid point that rotating equipment in identical condition may give very different Vibration readings under different operating conditions. It is well known, for example, that many electric motors that are lightly loaded will demonstrate greater vibration than the same motor when it is heavily loaded. Interpreting vibration readings, therefore, is fraught with danger, unless the conditions that equipment is operating under at the time the readings are taken are also recorded, and used in interpreting the results. This chapter discusses a wide variety of equipment types (including pumps, fans, steam traps, control valves and more), and the typs of process information that should be monitored for each of these equipment types.

Chapter 11 gives a three page summary of ultrasonics. This is barely enough to do credit to this technique, nor discuss the various applications of this technology, its strengths and its weaknesses. This chapter also makes the rather contentious claim, often proposed by Vibration Analysts, that "the use of ultrasonics to monitor bearing condition is not recommended". I believe that the independent jury is still considering its verdict on this matter, and that this book would have been better served by providing a more objective review of the possible strengths, and weaknesses, of ultrasonics in this type of application, rather than dismissing it out of hand.

Chapter 12 discusses Visual Inspection, on its own a rather interesting inclusion in this book, as there are many people who would consider that Visual Inspection is not a Predictive Maintenance technique. I am certainly not one of them, and it is a pleasure to see coverage of this topic in a book such as this.

One of Mobley's key propositions in this book is that Predictive Maintenance techniques can, and should, be used for much more than predictiing equipment failures. He argues that these techiques can be used to contribute to Total Plant Optimisation. In Chapter 13 of the book, he attempts to demonstrate this, with reference to an example of a pumping system, and demonstrates that these techniques can be used to assist with the identification of design, installation and operating issues, as well as maintenance issues.

Chapter 14 discusses a wide variety of failure modes that can be detected using vibration analysis. These include such failure modes as imbalance, mechanical looseness, misalignment etc. There is also some discussion of vibration-related equipment-specific failure modes, for various rotating equipment types, including process rolls, jackshafts etc. However, there is no discussion of failure modes that can be detected using other Predictive Maintenance techniques in this chapter.

Chapter 15 provides a comprehensive look at all the practical tasks involved in establishing a Predictive Maintenance program, from the activities needed to garner support for the program, through selecting the appropriate software, and more. It is an excellent chapter, only marred by one "clanger" when it insists that the primary deterninant of the frequency of Predictive Maintenance inspections is equipment criticality. As anyone familiar with RCM principles knows, equipment criticality determines whether it is worth doing Predictive Maintenance at all, but the frequency of measurement is actually determined by the Lead Time to Failure, or PF Interval.

Finally, Chapters 16, 17 and 18 discuss the practicalities of getting the most out of your PdM program, and these chapters provide a comprehensive discussion of the major items that need to be in place if the PdM program is to work properly, and if full value is to be obtained from this program. This includes the requirement for an effective Planning and Scheduling process, proper work instructions, methods for recording and analysing history, effective supervision, and more.

In summming up, this book is an excellent introduction to a variety of predictive maintenance technologies, and their practical application. While the book has a bias towards mechanical techniques, and is particularly strong in its discussion of vibration analysis, there is sufficient detail here for this book to represent great value for many maintenance engineers, planners and supervisors. I suspect that those who have bought this book will find themselves returning to it periodically, to refer to the large quantities of practical information that is contained in it. Highly recommended.

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