Introduction to Maintenance Engineering
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Preface xxxi
Acknowledgments xxxv
Abbreviations xxxvii
1 An Overview 1
1.1 Introduction 2
1.2 Classification of Engineered Objects 4
1.3 Performance of Engineered Objects 10
1.4 Maintenance 12
1.5 Evolution of Maintenance 15
1.6 Focus of the Book 17
1.7 Structure and Outline of the Book 18
Review Questions 20
Exercises 21
References 22
Part A Maintenance Engineering and Technology 23
2 Basics of Reliability Theory 25
2.1 Introduction 26
2.2 Decomposition of an Engineered Object 26
2.3 Functions, Failures, and Faults 27
2.4 Characterization of Degradation 31
2.5 Reliability Concept and Characterization 33
2.6 Linking System and Component Failures 36
2.7 Reliability Theory 45
2.8 Summary 45
Review Questions 46
Exercises 47
References 50
3 System Degradation and Failure 51
3.1 Introduction 52
3.2 Failure Mechanisms 52
3.3 Classification of Failure Mechanisms 54
3.4 Dynamic Nature of Stress and Strength 61
3.5 Degradation of Products and Plants 62
3.6 Degradation of Infrastructures 64
Review Questions 69
Exercises 69
References 71
4 Maintenance - Basic Concepts 73
4.1 Introduction 74
4.2 Types of Maintenance Actions 74
4.3 Preventive Maintenance Actions 77
4.4 Corrective Maintenance Actions 83
4.5 Design Out Maintenance 85
4.6 Uptime and Downtime 86
4.7 Warranty and Maintenance 88
4.8 Maintenance of Products 90
4.9 Maintenance of Plants and Facilities 95
4.10 Maintenance of Infrastructures 100
4.11 Effective Maintenance 102
4.12 Summary 103
Review Questions 104
Exercises 104
References 105
5 Life Cycle of Engineered Objects 107
5.1 Introduction 108
5.2 Life Cycle Concept and Classification 108
5.3 Standard Objects 109
5.4 Custom-Built Objects 113
5.5 Reliability: Product Life Cycle Perspective 115
5.6 Life Cycle Cost 118
5.7 Summary 120
Review Questions 120
Exercises 121
References 122
6 Technologies for Maintenance 123
6.1 Introduction 124
6.2 Technology - An Overview 124
6.3 Assessing the State (Condition) of an Item 125
6.4 Sensors 129
6.5 Testing Technologies 137
6.6 Data-Related Technologies 142
6.7 Technologies for Maintenance of Products 144
6.8 Technologies for Maintenance of Plants 144
6.9 Technologies for Maintenance of Infrastructures 148
6.10 Summary 151
Review Questions 152
Exercises 153
References 154
7 Maintainability and Availability 155
7.1 Introduction 156
7.2 Maintainability - An Overview 156
7.3 Elements of Maintainability 158
7.4 Availability 161
7.5 Maintainability Process 163
7.6 Maintainability Standards 165
7.7 Relationship with Other Disciplines 166
7.8 Summary 167
Review Questions 168
Exercises 168
References 169
Part B Reliability and Maintenance Modeling 171
8 Models and the Modeling Process 173
8.1 Introduction 174
8.2 Models 174
8.3 Mathematical Modeling 178
8.4 Approaches to Modeling 182
8.5 Mathematical Modeling Process 185
8.6 Statistics versus Probability Perspectives 189
8.7 Modeling of Maintenance Decision Problems 190
8.8 Summary 191
Review Questions 191
Exercises 192
Reference 193
9 Collection and Analysis of Maintenance Data 195
9.1 Introduction 196
9.2 Data, Information, and Knowledge 196
9.3 Maintenance Data 199
9.4 Data Analysis 201
9.5 Descriptive Statistics 202
9.6 Inferential Statistics 212
9.7 Collection of Maintenance Data for Products 213
9.8 Collection of Maintenance Data for Plants 215
9.9 Collection of Maintenance Data for Infrastructures 218
9.10 Summary 220
Review Questions 221
Exercises 222
References 223
10 Modeling First Failure 225
10.1 Introduction 226
10.2 One-Dimensional Formulations 227
10.3 Two-Dimensional Formulations 230
10.4 Properties of Distribution Functions 232
10.5 Preliminary Data Analysis and Plots 236
10.6 Selection of a Mathematical Formulation 241
10.7 Parameter Estimation 242
10.8 Model Validation 246
10.9 Examples 247
10.10 Summary 253
Review Questions 254
Exercises 254
References 255
11 Modeling CM and PM Actions 257
11.1 Introduction 258
11.2 Modeling CM Actions 258
11.3 Modeling PM Actions 262
11.4 Repair Times and Downtimes 266
11.5 Maintenance Costs 269
11.6 Repair-Replace Decisions 272
11.7 Modeling Fleet and Infrastructure Maintenance 273
11.8 Summary 273
Review Questions 274
Exercises 275
References 276
12 Modeling Subsequent Failures 277
12.1 Introduction 278
12.2 System Characterization for Modeling 278
12.3 Mathematical Formulations for Modeling 280
12.4 Subsequent Failures with Only CM Actions 283
12.5 Subsequent Failures with Both CM and PM Actions 285
12.6 Data?-Based Modeling 287
12.7 Summary 295
Review Questions 296
Exercises 296
References 298
Part C Maintenance Decision Models and Optimization 299
13 Optimal Maintenance 301
13.1 Introduction 302
13.2 Framework for Optimal Maintenance Decisions 302
13.3 Maintenance Policy 303
13.4 Decision Parameters 304
13.5 Objective Function 305
13.6 Optimization Model 306
13.7 Information 306
13.8 Optimization 307
13.9 Summary 308
Review Questions 308
Exercises 308
Reference 309
14 Maintenance Optimization for Non?-Repairable Items 311
14.1 Introduction 312
14.2 Preliminaries 312
14.3 Infinite Time Horizon 314
14.4 Group Replacement 322
14.5 Finite Time Horizon 323
14.6 Inspection Policies 325
14.7 Summary 327
Review Questions 327
Exercises 328
Reference 329
15 Maintenance Optimization for Repairable Items 331
15.1 Introduction 332
15.2 Preliminaries 332
15.3 Group I Scenarios 334
15.4 Group II Scenarios 338
15.5 Group III Scenarios 344
15.6 Multi-Item Policies 350
15.7 Summary 351
Review Questions 352
Exercises 352
References 354
16 Condition-Based Maintenance 355
16.1 Introduction 356
16.2 Characterization of Degradation 357
16.3 Approach to CBM 359
16.4 Diagnostics, Prognostics, and CBM 364
16.5 Summary 382
Review Questions 384
Exercises 384
References 386
Part D Maintenance Management 389
17 Maintenance Management 391
17.1 Introduction 392
17.2 Management 393
17.3 Maintenance Management 401
17.4 Maintenance Organization 403
17.5 Approaches to Maintenance 407
17.6 Risk and Maintenance 410
17.7 Maintenance Management System 415
17.8 Summary 417
Review Questions 418
Exercises 418
References 419
18 Maintenance Outsourcing and Leasing 421
18.1 Introduction 422
18.2 Outsourcing 422
18.3 Maintenance Outsourcing 424
18.4 Framework for Maintenance Outsourcing Decision Making 426
18.5 Optimal Decisions 429
18.6 Leasing 436
18.7 MSCs for Products and Plants 438
18.8 Infrastructures 444
18.9 Summary 447
Review Questions 448
Exercises 449
References 450
19 Maintenance Planning, Scheduling, and Control 451
19.1 Introduction 452
19.2 Maintenance Planning 452
19.3 Tactical-Level Maintenance Planning 454
19.4 Operational-Level Maintenance Planning 458
19.5 Maintenance Control 462
19.6 Maintenance Control System 464
19.7 Maintenance of Products 465
19.8 Maintenance of Plants 468
19.9 Maintenance of Infrastructures 470
19.10 Summary 471
Review Questions 472
Exercises 472
Reference 473
20 Maintenance Logistics 475
20.1 Introduction 476
20.2 Logistics 476
20.3 Key Elements of Maintenance Logistics 478
20.4 Service Facilities 479
20.5 Human Resources 480
20.6 Inventories 480
20.7 New Item Inventory Management 484
20.8 Repairable Items Inventory Management 487
20.9 Maintenance Logistics for Products 488
20.10 Maintenance Logistics for Plants 491
20.11 Maintenance Logistics for Infrastructures 492
20.12 Summary 493
Review Questions 494
Exercises 494
References 495
21 Maintenance Economics 497
21.1 Introduction 498
21.2 Basic Concepts and Terms 498
21.3 Capital Investment 502
21.4 Cost Elements of Capital Investment 505
21.5 Life Cycle Cost 506
21.6 Capital Equipment Replacement 509
21.7 Buy versus Lease Decisions 515
21.8 LCCA for Products and Plants 519
21.9 LCCA for Infrastructures 520
21.10 Summary 522
Review Questions 523
Exercises 523
References 525
22 Computerized Maintenance Management Systems and e-Maintenance 527
22.1 Introduction 528
22.2 Role of Technology in Maintenance Management 528
22.3 Computerized Maintenance Management Systems (CMMSs) 530
22.4 e-Maintenance 534
22.5 Applications of e-Maintenance 538
22.6 Summary 543
Review Questions 544
Exercises 545
References 546
Part E Case Studies 547
23 Case Studies 549
23.1 Introduction 549
23.2 Case Study 1 - Hydraulic Pump Maintenance 549
23.3 Case Study 2 - Maintenance of Rail Track 559
Part F Appendices 575
Appendix A: Introduction to Probability Theory 577
A.1 Basics of Probability 577
A.2 Random Variables 578
A.3 Characterization of a Univariate Random Variable 579
A.4 Some Basic Univariate Discrete Distribution Functions 580
A.5 Some Basic Univariate Continuous Distribution Functions 581
A.6 Bivariate Random Variables 587
A.7 Sums of Independent Random Variables 590
References 591
Appendix B: Introduction to Stochastic Processes 593
B.1 Basic Concept 593
B.2 Characterization of a Stochastic Process 593
B.3 Classification of Markov Processes 594
B.4 Point Processes 596
B.5 Poisson Processes 597
B.6 Renewal Processes 599
B.7 Marked Point Processes 603
References 604
Appendix C: Introduction to the Theory of Statistics 605
C.1 Introduction 605
C.2 Descriptive Statistics 605
C.3 Inferential Statistics 609
References 612
Appendix D: Introduction to Optimization 613
D.1 Introduction 613
D.2 Case A 615
D.3 Case B 617
D.4 Case C 619
D.5 Case D 622
References 623
Appendix E: Data Sets 625
Data Set E.1 Battery (Component of a Bus) 625
Data Set E.2 Automobile (Repair Costs) 625
Data Set E.3 Photocopier 625
Data Set E.4 Throttle Valve (Automobile Component) 628
Data Set E.5 Valve Seat Replacement for Diesel Engines 628
Data Set E.6 Heavy Vehicle 628
Data Set E.7 Buses 628
Data Set E.8 Buses 629
Data Set E.9 Hydraulic Pumps 631
Data Set E.10 Shock Absorber 634
References 634
Index 635
1
An Overview
Learning Outcomes
After reading this chapter, you should be able to:
- Define maintenance and explain its importance from a strategic business perspective;
- List the three main aspects of maintenance;
- Provide a classification of engineered objects;
- Describe reliability and non-reliability performance measures of engineered objects;
- Describe the factors that affect performance degradation;
- Recognize the consequences of poor maintenance;
- Describe the main categories of maintenance costs;
- Explain that there is a trade-off between preventive maintenance effort and maintenance costs;
- Explain that there are maintenance decision-making problems at the strategic, tactical, and operational levels;
- Describe the evolution of maintenance over time and the new trends;
- Understand the structure of the book.
1.1 Introduction
Modern societies use a range of engineered objects for many different purposes. The objects are designed and built for specific functions. These include a variety of products (used by households, businesses, and government in their daily operations), plants, and facilities (used by businesses to deliver goods and services) and a range of infrastructures (networks such as rail, road, water, gas, electricity; dams, buildings, etc.) to ensure the smooth functioning of a society.
Every engineered object is unreliable in the sense that it degrades with age and/or usage and ultimately fails. A dictionary definition of failure is "falling short in something expected, attempted, desired, or in some way deficient or lacking." From an engineering point of view, an engineered object is said to have failed when it is no longer able to carry out its intended function for which it was designed and built. Failures occur in an uncertain manner and are influenced by several factors such as design, manufacture (or construction), maintenance, and operation. In addition, the human factor is also important in this context.
The consequence of a product failure may vary from mere inconvenience (for example, a dishwasher failure) to something serious (for example, an automobile brake failure leading to economic and possibly human loss). The failure of an industrial plant or commercial facility may have major economic consequences for a business as it affects the delivery of goods and services (outputs of the business) and the revenue generation. The daily loss in revenue as a result of the product being out of action due to failure may be very high. Rough estimates (circa 2000) for the revenue lost due to engineered objects being out of action are as follows:
- Large aircraft (A340 or Boeing 747) ~ $500 000/day;
- Dragline (used in open cut mining) ~ $1 million/day;
- A large manufacturer (for example, Toyota) ~ $1-2 millions/hour.
Definition 1.1
Maintenance is the combination of all technical, administrative, and managerial actions during the life cycle of an item intended to retain it in, or restore it to, a state in which it may perform the required function (CEN, 2001).
In a sense, maintenance may be viewed as actions to compensate for the unreliability of an engineered object. Building in reliability is costly and is constrained by technical limits and economic considerations. However, not having adequate reliability is costlier due to the consequence of failures. Thus, maintenance becomes an important issue in this context. Table 1.1 shows the maintenance costs (as a fraction of the operating costs) in different industry sectors, as reported in Campbell (1995).
Table 1.1 Maintenance as a percentage of operating cost.
Industry sector Maintenance cost (%) Mining (highly mechanized) 20-50 Primary metals 15-20 Electric utilities 5-15 Manufacturing processing 3-15 Fabrication/assembly 3-5There are several aspects to maintenance and they may be grouped broadly into the following three categories:
- Technical (engineering, science, technology, etc.);
- Commercial (economics, legal, marketing, etc.);
- Management (from several different perspectives - manufacturer, customer and maintenance service provider when maintenance is outsourced).
This implies that maintenance decisions need to be made in a framework that takes into account these issues from an overall business perspective. Figure 1.1 shows the link between maintenance (strategic and operational) and production from a business perspective.1
Figure 1.1 Maintenance from a business perspective.
In this book we discuss all of these aspects and this chapter gives a broad overview of the book.
The outline of the chapter is as follows. Section 1.2 deals with the classification of engineered objects and presents some examples that are used in later chapters to illustrate different concepts and issues. The performance of an engineered object degrades with age and/or usage and this is the focus of Section 1.3, where we look at both reliability and non-reliability performance measures. Maintenance consists of actions to ensure the desired performance and this is discussed in Section 1.4, where we look at a range of such types of maintenance, the consequence of poor maintenance, maintenance costs, and so on. Although maintenance has been practiced since the dawn of civilization (maintaining shelters to live, stone tools, etc.), the theory of maintenance evolved only recently (in the early part of the twentieth century). Since then it has been growing at an ever-increasing pace and this issue is discussed in Section 1.5, where we look at both the past and future trends. These sections provide the background to highlight the focus of the book, which is discussed in Section 1.6. We conclude the chapter with a brief outline of the various chapters of the book in Section 1.7.
1.2 Classification of Engineered Objects
Engineered objects may be grouped into three broad categories, as indicated in Table 1.2.
Table 1.2 Classification of engineered objects.
Products Consumer: Household appliances, automobiles, and so on Commercial and Industrial: Also referred to as equipment, machinery, and so on Defense: Ships, tanks, planes, and so on Plants Collection of several elements: Power plant composed of boiler turbine, generators, and so on Infrastructures Discrete: Buildings, dams, and so on Distributed networks: Rail, road, gas, water, and so onEach of these categories may be subdivided, and this is discussed in subsequent sections.
1.2.1 Products
Products may be classified into three groups, as indicated in Table 1.2. Each group may be divided into two subgroups: (i) standard (or off-the-shelf) and (ii) custom-built.
- Consumer products: These are mostly standard products (for example, television sets, appliances, automobiles, and personal computers) that are consumed by society at large. (These products are also consumed by businesses and government agencies.) As such, the number of customers is large, with a small to medium number of manufacturers. The complexity of the product may vary considerably, and the typical small consumer is often not sufficiently well informed to evaluate product performance, especially in cases involving complex products (computers, cars, etc.).
- Commercial and industrial products: These may be either standard or custom-built (for example, mainframe computers, CNC machines, pumps, X-ray machines, and aircraft), with a small number of customers and manufacturers. The technical complexity of such products and their mode of usage may vary considerably. The products may be either complete units, such as cars, trucks, pumps, and so forth, or product components needed by another manufacturer, such as batteries, drill bits, electronic modules, turbines, and so on.2
- Defense products: These are specialized products (for example, military aircraft, ships, rockets) with a single customer and a relatively small number of manufacturers. The products are usually complex and expensive and involve state-of-the-art technology with considerable research and development effort required from the manufacturers. These products are usually designed and built to customers' requirements.
1.2.2 Plants and Facilities
Plants are used to produce a variety of goods. They may be classified into several categories, as indicated in Table 1.3.
Table 1.3 Classification of plants.
Industry sector Operations and outputs Mining Extracting and enriching raw materials (for example, ore,...