25 Machine Condition Monitoring and Fault Diagnostics

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Chris K. Mechefske

Queen’s University

25.1 Introduction ....................................................................... 25-2

25.2 Machinery Failure ............................................................. 25-2

Causes of Failure † Types of Failure † Frequency

of Failure

25.3 Basic Maintenance Strategies ............................................ 25-4

Run-to-Failure (Breakdown) Maintenance † Scheduled

(Preventative) Maintenance † Condition-Based

(Predictive, Proactive, Reliability Centered,

On-Condition) Maintenance

25.4 Factors which Influence Maintenance Strategy .............. 25-7

25.5 Machine Condition Monitoring ...................................... 25-8

Periodic Monitoring † Continuous Monitoring

25.6 Transducer Selection ......................................................... 25-10

Noncontact Displacement Transducers † Velocity

Transducers † Acceleration Transducers

25.7 Transducer Location .......................................................... 25-14

25.8 Recording and Analysis Instrumentation ........................ 25-14

Vibration Meters † Data Collectors † Frequency-

Domain Analyzers † Time-Domain Instruments †

Tracking Analyzers

25.9 Display Formats and Analysis Tools ................................ 25-16

Time Domain † Frequency Domain † Modal Domain †

Quefrency Domain

25.10 Fault Detection .................................................................. 25-21

Standards † Acceptance Limits † Frequency-Domain

Limits

25.11 Fault Diagnostics ............................................................... 25-25

Forcing Functions † Specific Machine Components †

Specific Machine Types † Advanced Fault Diagnostic

Techniques

Summary

The focus of this chapter is on the definition and description of machine condition monitoring and fault diagnosis.

Included are the reasons and justification behind the adoption of any of the techniques presented. The motivation

behind the decision making in regard to various applications is both financial and technical. Both of these aspects

are discussed, with the emphasis being on the technical side. The chapter defines machinery failure (causes, types,

and frequency), and describes basic maintenance strategies and the factors that should be considered when deciding

25-1

© 2005 by Taylor & Francis Group, LLC

which to apply in a given situation. Topics considered in detail include transducer selection and mounting location,

recording and analysis instrumentation, and display formats and analysis tools (specifically, time domain,

frequency domain, modal domain, and quefrency domain-based strategies). The discussion of fault detection is

based primarily on standards and acceptance limits in the time and frequency domains. The discussion of fault

diagnostics is divided into sections that focus on different forcing functions, specific machine components, specific

machine types, and advanced diagnostic techniques. Further considerations on this topic are found in Chapter 26

and Chapter 27.

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