Machinery condition monitoring : principles and practices

256 Pages·2015·23.16 MB·English

by  Amiya R Mohanty

Mechanical Engineering M
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H
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“This book brings together condition monitoring content in a single text, a N
definite improvement over the single discipline-based texts that are currently on T
the market. The approachable writing style and limited use of equations make Y
the text desirable reading for the practitioner, not just the academic reader.”
—Nancy L. Denton, Purdue University, West Lafayette, Indiana, USA
“Like the author, I have struggled to find one suitable resource book on this
M MACHINERY
broad subject. In my opinion, this book will solve that problem for a significant
number of instructors as well as practitioners of machine condition monitoring.” A
—Chris Mechefske, Queen’s University, Ontario, Canada C
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Find the Fault in the Machine
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C O N D I T I O N
Drawing on the author’s more than two decades of experience with machinery E
condition monitoring and consulting for industries in India and abroad, R
Machinery Condition Monitoring: Principles and Practices introduces the
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practicing engineer to the techniques used to effectively detect and diagnose

faults in machines. Providing the working principle behind the instruments, the C
important elements of machines as well as the technique to understand their O
MONITORING
conditions, this text presents every available method of machine fault detection
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occurring in machines in general, and rotating machines in particular.
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A Single-Source Solution for Practice Machinery Conditioning Monitoring I
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Since vibration is one of the most widely used fault detection techniques, the O PRINCIPLES AND PRACTICES
book offers an assessment of vibration analysis and rotor-dynamics. It also
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covers the techniques of wear and debris analysis, and motor current signature
analysis to detect faults in rotating mechanical systems as well as thermography, M
the nondestructive test NDT techniques (ultrasonics and radiography), and
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additional methods. The author includes relevant case studies from his own
experience spanning the past 20 years, and detailing practical fault diagnosis N
exercises involving various industries ranging from steel and cement plants to I
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gas turbine driven frigates. While mathematics is kept to a minimum, he also
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provides worked examples and MATLAB® codes.
A M I Y A R . M O H A N T Y
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Machinery Condition Monitoring: Principles and Practices presents the I
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latest techniques in fault diagnosis and prognosis, provides many real-life
practical examples, and empowers you to diagnose the faults in machines all G
on your own.
K20592
ISBN: 978-1-4665-9304-6
90000
9 781466 593046
K20592_COVER_final.indd 1 11/11/14 3:58 PM

MACHINERY
CONDITION
MONITORING
PRINCIPLES AND PRACTICES

MACHINERY
CONDITION
MONITORING
PRINCIPLES AND PRACTICES
AMIYA R. MOHANT Y
Indian Institute of Technology
Mechanical Engineering Department
Kharagpur, West Bengal, India
Boca Raton London New York
CRC Press is an imprint of the
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MATLAB® is a trademark of The MathWorks, Inc. and is used with permission. The MathWorks does
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Dedicated to the memory of my father.
Professor Aswini Kumar Mohanty
(1941–1995)

Contents
Preface .....................................................................................................................xv
Acknowledgments .............................................................................................xvii
About the Author ................................................................................................xix
1. Introduction .....................................................................................................1
1.1 Machinery Condition Monitoring ......................................................1
1.2 Present Status ........................................................................................2
1.3 Fault Prognosis ......................................................................................3
1.4 Future Needs .........................................................................................3
2. Principles of Maintenance ............................................................................5
2.1 Introduction ...........................................................................................5
2.2 Reactive Maintenance ...........................................................................6
2.3 Preventive Maintenance .......................................................................6
2.4 Predictive Maintenance........................................................................7
2.5 Enterprise Resource Planning .............................................................9
2.6 Bath Tub Curve ....................................................................................10
2.7 Failure Modes Effects and Criticality Analysis (FMECA) ............11
2.7.1 Implementation of FMECA for Machinery
Maintenance .......................................................................11
2.7.2 Risk Priority Number for FMECA ......................................12
3. Fundamentals of Machinery Vibration ...................................................13
3.1 Introduction .........................................................................................13
3.2 Single Degree-of-Freedom Motion ...................................................13
3.3 Forced Vibration Response ................................................................15
3.4 Base Excitation .....................................................................................17
3.5 Force Transmissibility and Vibration Isolation ..............................17
3.6 Tuned Vibration Absorber .................................................................19
3.7 Unbalanced Response ........................................................................20
3.8 Characteristics of Vibrating Systems................................................21
3.9 Vibration of Continuous Systems .....................................................23
3.10 Mode Shapes and Operational Deflection Shapes .........................25
3.11 Experimental Modal Analysis ..........................................................26
4. Rotordynamics ..............................................................................................29
4.1 Introduction .........................................................................................29
4.2 Simple Rigid Rotor-Disc System .......................................................29
4.3 Unbalance Response and Critical Speed .........................................29
4.4 Journal Bearings ..................................................................................31
vii
viii Contents
4.5 Oil Whirl and Oil Whip .....................................................................33
4.6 Squeeze Film Dampers.......................................................................34
4.7 Condition Monitoring in Large Rotor Systems ..............................34
5. Digital Signal Processing ...........................................................................35
5.1 Introduction .........................................................................................35
5.2 Classification of Signals .....................................................................35
5.3 Signal Analysis ....................................................................................36
5.4 Frequency Domain Signal Analysis .................................................40
5.4.1 Fourier Series ..........................................................................40
5.4.2 Fourier Integral ......................................................................41
5.4.3 Discrete Fourier Transform ..................................................43
5.5 Fundamentals of Fast Fourier Transform ........................................44
5.5.1 Representation of Fourier Transform Data ........................46
5.5.2 Autopower Spectrum ............................................................47
5.5.3 Cross-Power Spectrum ..........................................................47
5.5.4 Frequency Response Function .............................................47
5.5.5 Coherence Function ...............................................................48
5.6 Computer-Aided Data Acquisition ...................................................49
5.7 Signal Conditioning ............................................................................52
5.7.1 Signal Filtering .......................................................................52
5.8 Signal Demodulation ..........................................................................55
5.9 Cepstrum Analysis .............................................................................58
5.10 Examples ..............................................................................................58
5.10.1 Natural Frequency of a Cantilever Beam ...........................58
5.10.2 Compressor Vibration ...........................................................60
5.10.3 Engine Vibration ....................................................................60
6. Instrumentation ............................................................................................63
6.1 Introduction .........................................................................................63
6.2 Measurement Standards ....................................................................63
6.3 Measurement Errors ...........................................................................64
6.4 Calibration Principles .........................................................................64
6.5 Static and Dynamic Measurements..................................................65
6.6 Frequency Response ...........................................................................65
6.7 Dynamic Range ...................................................................................66
6.8 Basic Measuring Equipment ..............................................................67
6.8.1 RMS/Peak Meters ..................................................................67
6.8.2 Signal Amplifiers ...................................................................67
6.8.3 Oscilloscope ............................................................................68
6.8.4 Signal Generators ...................................................................68
6.8.5 Signal Filters ...........................................................................69
6.8.6 Power Supply ..........................................................................69
6.8.7 Counters ..................................................................................70