On-bearing Vibration Response Integration for Condition Monitoring of Rotating Machinery Doctor ...

271 Pages·2015·9.96 MB·English

by  Adrian Nembhard

On-bearing Vibration Response Integration for
Condition Monitoring of Rotating Machinery

A thesis submitted to The University of Manchester for the degree of

Doctor of Philosophy (PhD)

in the Faculty of Engineering and Physical Science

2015

Adrian D. Nembhard

School of Mechanical, Aerospace and Civil Engineering
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Table of Content

List of Tables ...................................................................................................................... 7
List of Figures .................................................................................................................... 8
Nomenclature ................................................................................................................... 14
List of Abbreviations ........................................................................................................ 16
List of Publications ........................................................................................................... 18
Abstract ............................................................................................................................ 19
Declaration ....................................................................................................................... 20
Copyright statement ......................................................................................................... 21
Acknowledgement ............................................................................................................ 22
Dedication ........................................................................................................................ 23
1 INTRODUCTION ...................................................................................................... 24
1.1 Introduction ........................................................................................................... 25
1.2 Aims and Objectives ............................................................................................. 27
1.3 Contributions to knowledge .................................................................................. 29
1.4 Report Layout ........................................................................................................ 32
1.5 Report linkages ...................................................................................................... 33
2 LITERATURE REVIEW .......................................................................................... 36
2.1 Introduction ........................................................................................................... 37
2.2 Machinery failure patterns ..................................................................................... 37
2.3 Condition monitoring ............................................................................................ 38
2.4 Vibration-based condition monitoring of rotating machinery ............................... 39
2.5 Vibration-based condition monitoring for rotor fault diagnosis............................ 41
2.5.1 Data acquisition .............................................................................................. 42
2.5.2 Data manipulation .......................................................................................... 43
2.5.3 Health assessment .......................................................................................... 44
2.6 Standard practices in vibration-based rotor fault diagnosis .................................. 44
2.6.1 Simple spectrum analysis ............................................................................... 44
2.6.2 Orbit plot analysis .......................................................................................... 45
2.6.3 Overview of standard practices ...................................................................... 49
2.7 Research on alternative methods to standard practices ......................................... 50
2.7.1 Data acquisition .............................................................................................. 50
2.7.2 Data manipulation .......................................................................................... 52
2.7.3 Health assessment .......................................................................................... 53
2.8 Vibration-based fault diagnosis for transient operation ........................................ 58
2.9 Simple mathematical modelling in vibration-based fault diagnosis ..................... 60
2.10 Summary ............................................................................................................... 62
3 EXPERIMENTAL APPROACH .............................................................................. 63
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3.1 Introduction ........................................................................................................... 64
3.2 Experimental set up ............................................................................................... 64
3.2.1 Rigid support .................................................................................................. 64
3.2.2 Flexible support .............................................................................................. 66
3.3 Experiments conducted ......................................................................................... 73
3.3.1 Rigid set up .................................................................................................... 73
3.3.2 Flexible set up ................................................................................................ 74
3.4 Summary ............................................................................................................... 75
4 EXPERIMENTAL OBSERVATIONS IN THE SHAFT ORBITS OF
RELATIVELY FLEXIBLE MACHINES WITH DIFFERENT ROTOR-RELATED
FAULTS .............................................................................................................................. 77
4.1 Introduction ........................................................................................................... 78
4.2 Experimental Set Up ............................................................................................. 82
4.2.1 Mechanical Layout and Instrumentation ........................................................ 82
4.2.2 Dynamic Characterization of Experimental Rig ............................................ 86
4.3 Experiments conducted ......................................................................................... 89
4.4 Data processing ..................................................................................................... 93
4.5 Shaft orbit observations ......................................................................................... 95
4.5.1 Residual Misalignment with Residual Unbalance - Baseline ........................ 95
4.5.2 Added Unbalance ........................................................................................... 97
4.5.3 Bow ................................................................................................................ 98
4.5.4 Crack .............................................................................................................. 99
4.5.5 Looseness ..................................................................................................... 102
4.5.6 Misalignment ............................................................................................... 103
4.5.7 Rub ............................................................................................................... 105
4.5.8 General Observations of Orbit Shapes on a different Flexible Machine (with
6mm supports) ............................................................................................................ 109
4.6 Summary ............................................................................................................. 110
5 COMBINED VIBRATION AND THERMAL ANALYSIS FOR THE
CONDITION MONITORING OF ROTATING MACHINERY ................................ 111
5.1 Introduction ......................................................................................................... 112
5.2 Experimental set up and data collection .............................................................. 116
5.3 Simulated faults and experiments ........................................................................ 118
5.4 Vibration spectrum analysis ................................................................................ 120
5.4.1 Results: Spectrum analysis - 40 Hz (2400 rev/min)..................................... 122
5.4.2 Results: Spectrum analysis - 50 Hz (3000 rev/min)..................................... 125
5.5 Combined vibration and thermal analysis ........................................................... 127
5.5.1 Theory: Computation of steady-state temperatures ..................................... 127
5.5.2 Simple linear analysis .................................................................................. 129
5.5.3 PCA-based analysis ...................................................................................... 132
5.6 Summary ............................................................................................................. 138
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6 UNIFIED MULTI-SPEED ANALYSIS (UMA) FOR THE CONDITION
MONITORING OF AERO-ENGINES .......................................................................... 140
6.1 Introduction ......................................................................................................... 141
6.2 Experimental set up ............................................................................................. 143
6.3 Spectrum analysis ................................................................................................ 146
6.3.1 Effect of speed change on spectral features ................................................. 146
6.4 Application of principal component analysis (PCA) .......................................... 151
6.5 Feature selection .................................................................................................. 153
6.5.1 Root mean square (r.m.s.) vibration amplitude ............................................ 153
6.5.2 Crest factor ................................................................................................... 154
6.5.3 Kurtosis ........................................................................................................ 155
6.5.4 Spectrum energy (SE) .................................................................................. 155
6.5.5 Feature selection summary ........................................................................... 156
6.6 Data processing ................................................................................................... 157
6.7 Results and discussion ......................................................................................... 158
6.7.1 Analysis of features from a single speed at a single bearing ....................... 159
6.7.2 Analysis of integrated features from multiple speeds at a single bearing .... 164
6.7.3 Analysis at a single speed for integrated features from multiple bearings .. 166
6.7.4 Unified Multi-speed analysis (integrated features from multiple speeds and
multiple Bearings) ...................................................................................................... 168
6.8 Summary ............................................................................................................. 170
7 DEVELOPMENT OF A GENERIC ROTATING MACHINERY FAULT
DIAGNOSIS APPROACH INSENSITIVE TO MACHINE SPEED AND SUPPORT
TYPE ................................................................................................................................. 171
7.1 Introduction ......................................................................................................... 172
7.2 Experimental set up and experiments conducted ................................................ 177
7.2.1 Mechanical layout and instrumentation ....................................................... 178
7.2.2 Experiments conducted ................................................................................ 181
7.3 Observations on orbit analysis and spectrum analysis ........................................ 186
7.3.1 Orbit plots – time domain analysis............................................................... 186
7.3.2 Amplitude spectra analysis – frequency domain analysis............................ 189
7.4 Proposed approach - data processing and analyses ............................................. 193
7.4.1 Application of principal component analysis ............................................... 193
7.4.2 Feature selection........................................................................................... 194
7.4.3 Data processing ............................................................................................ 195
7.5 Fault diagnosis - flexible support 1 (FS1) ........................................................... 199
7.5.1 Individual speed individual foundation (ISIF) analysis on FS1................... 199
7.5.2 Multi-speed individual foundation (MSIF) analysis on FS1........................ 203
7.6 Fault diagnosis – flexible support 2 (FS2) .......................................................... 204
7.7 Fault Diagnosis - combined foundations; FS1 and FS2 ...................................... 206
7.7.1 Individual speed multi-foundation (ISMF) analysis on FS1 and FS2 ......... 207
7.7.2 Multi-speed multi-foundation (MSMF) analysis on FS1 and FS2 .............. 209
7.8 Global observations ............................................................................................. 210
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7.9 Summary ............................................................................................................. 211
8 COMPARISON OF EXPERIMENTAL OBSERVATIONS IN ROTATING
MACHINES WITH SIMPLE MATHEMATICAL SIMULATIONS ........................ 213
8.1 Introduction ......................................................................................................... 213
8.2 Earlier experimental study [13] ........................................................................... 217
8.2.1 Experimental rig ........................................................................................... 217
8.2.2 Experiments conducted ................................................................................ 218
8.2.3 Experimental observations in orbit plots and simple spectra ....................... 218
8.2.4 Fault classification method with earlier proposed approach ........................ 222
8.3 Mathematical modelling – Jeffcott rotor ............................................................. 223
8.4 Fault simulation and response ............................................................................. 225
8.4.1 Healthy ......................................................................................................... 226
8.4.2 Added unbalance .......................................................................................... 230
8.4.3 Crack ............................................................................................................ 233
8.4.4 Misalignment ............................................................................................... 238
8.4.5 Rub ............................................................................................................... 242
8.4.6 Summary of fault simulations ...................................................................... 247
8.5 Fault classification – simulated data ................................................................... 250
8.5.1 Single speed (SS) classification with simulated data ................................... 250
8.5.2 Multi-speed (MS) classification with simulated data................................... 253
8.6 Summary ............................................................................................................. 254
9 CONCLUSIONS AND FUTURE WORK .............................................................. 256
9.1 Conclusions ......................................................................................................... 257
9.2 Future Work ........................................................................................................ 260
REFERENCES ................................................................................................................. 261
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List of Tables

Table 3.1 Details of main components used on mechanical rig with flexible supports ....... 70
Table 3.2 Summary of experimental approach used in present study .................................. 76
Table 4.1 Summary of experiments conducted in present rotor orbit study ........................ 93
Table 5.1 Summary of experimental procedure used......................................................... 120
Table 7.1 Summary of experiments conducted .................................................................. 185
Table 7.2 Summary of different approaches considered in the present study ................... 194
Table 7.3 Features used in previous studies done .............................................................. 195
Table 8.1 Summary of model parameters .......................................................................... 249
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List of Figures

Figure 1.1 Flow diagram showing logical progression of research undertaken in the current
study as presented in Chapters 4-8, part 1 .................................................................... 34
Figure 1.2 Flow diagram showing logical progression of research undertaken in the current
study as presented in Chapters 4-8, part 2 .................................................................... 35
Figure 2.1 Trends in maintenance expectations [43] ........................................................... 38
Figure 2.2 Fundamental components in rotating machinery ................................................ 40
Figure 2.3 Condition monitoring data processing flow diagram [51] .................................. 41
Figure 2.4 Typical set up for a vibration-based condition monitoring system .................... 43
Figure 2.5 One machine with possibilities for different foundation set up which results in
different dynamic characteristics including different natural frequencies. ................... 58
Figure 3.1 Experimental rig mechanical layout with relatively rigid supports [20] ............ 65
Figure 3.2 Experimental Rig with relatively rigid supports major dimensions ................... 65
Figure 3.3 Schematic of software and instrumentation used in the experiment for the rigid
support .......................................................................................................................... 66
Figure 3.4 Mechanical layout of experimental rig with relatively flexible supports ........... 67
Figure 3.5 Dimensions of main components on rig with flexible supports ......................... 68
Figure 3.6 Close up of bearing pedestal from (a) rigid support and (b) flexible support .... 69
Figure 3.7 Schematic of instrumentation used for testing with flexible supports ................ 71
Figure 3.8 Details of accelerometer and thermocouple configuration for: a) rigid supports
and b) flexible supports ................................................................................................ 72
Figure 3.9 Details of instrumentation used at Bearing 1 (B1) ............................................. 73
Figure 4.1 Mechanical layout of experimental rig ............................................................... 83
Figure 4.2 Close up of: a) Bearing 4 side view with Disc 3 and pedestal and b) Bearing 4
end view ........................................................................................................................ 84
Figure 4.3 Schematic of experimental rig instrumentation .................................................. 85
Figure 4.4 Details of eddy current probe mounting at Bearing 1 of experimental rig ......... 85
Figure 4.5 Schematic of rig dimensions and measurement location .................................... 86
Figure 4.6 Schematic of experimental rig set up for modal testing ..................................... 87
Figure 4.7 Frequency Response Function (FRF) in the vertical direction at position 4
obtained during modal testing ...................................................................................... 88
Figure 4.8 Mode shapes of experimental rig with 10 mm supports for first two observed
natural frequencies in: a) vertical and b) horizontal direction ...................................... 89
Figure 4.9 Rub fault apparatus mounted near Bearing 1 ..................................................... 90
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Figure 4.10 Seeding of misalignment in vertical direction at Bearing 1 by 2× 0.8 mm
shims under Bearing 1 .................................................................................................. 91
Figure 4.11 Details of looseness fault at Bearing 3 ............................................................. 92
Figure 4.12 Details of crack showing close up of notch and shim ...................................... 92
Figure 4.13 Sample of processing method for Rub showing: a) vertical response, b)
horizontal response and c) tachometer reference signal with start and stop point for 1
cycle .............................................................................................................................. 94
Figure 4.14 RMRU unfiltered orbits for 10 mm supports at B1 for: a) 600 rev/min (10 Hz),
b) 1200 rev/min (20 Hz), c) 1800 rev/min (30 Hz) and d) 2400 rev/min (40 Hz) ....... 95
Figure 4.15 RMRU orbits for 10 mm supports at B1 for: a) 600 rev/min (10 Hz), b) 1200
rev/min (20 Hz), c) 1800 rev/min (30 Hz) and d) 2400 rev/min (40 Hz) ..................... 96
Figure 4.16 RMRU orbits for 10 mm supports at B4 for: a) 600 rev/min (10 Hz), b) 1200
rev/min (20 Hz), c) 1800 rev/min (30 Hz) and d) 2400 rev/min (40 Hz) ..................... 97
Figure 4.17 Added Unbalance orbits for 10 mm supports at B1 for: a) 600 rev/min (10 Hz),
b) 1200 rev/min (20 Hz), c) 1800 rev/min (30 Hz) and d) 2400 rev/min (40 Hz) ....... 97
Figure 4.18 Bow orbits for 10 mm supports at B1 for: a) 600 rev/min (10 Hz) and b) 1200
rev/min (20 Hz) ............................................................................................................. 99
Figure 4.19 Crack orbits for 10 mm supports at B1 for : a) 600 rev/min (10 Hz), b) 1200
rev/min (20 Hz), c) 1800 rev/min (30 Hz) and d) 2400 rev/min (40 Hz) ................... 100
Figure 4.20 Crack orbit for 10 mm supports at B1 for: a) 1710 rev/min (28.5 Hz); approx.
half of the second natural frequency (56.67 Hz) ........................................................ 101
Figure 4.21 RMRU orbit at B1 for half of a) 50.66 Hz (1st) natural frequency and b) 56.76
Hz (2nd) natural frequency ......................................................................................... 101
Figure 4.22 Looseness orbits at B1 for: a) 600 rev/min (10 Hz), b) 1200 rev/min (20 Hz),
c) 1800 rev/min (30 Hz) and d) 2400 rev/min (40 Hz) ............................................... 103
Figure 4.23 Misalignment orbits at B1 for: a) 600 rev/min (10 Hz), b) 1200 rev/min (20
Hz), c) 1800 rev/min (30 Hz) and d) 2400 rev/min (40 Hz) ....................................... 104
Figure 4.24 Rub orbits at B1 for: a) 600 rev/min (10 Hz), b) 1200 rev/min, (20 Hz), c)
1800 rev/min (30 Hz) and d) 2400 rev/min (40 Hz) ................................................... 105
Figure 4.25 Rub orbits at B1 over 2 shaft rotations for: a) 600 rev/min (10 Hz), b) 1200
rev/min (20 Hz), c) 1800 rev/min (30 Hz) and d) 2400 rev/min (40 Hz) ................... 107
Figure 4.26 Simple amplitude spectra at 40 Hz from B1 of 10 mm supports for: (a) RMRU
vertical, (b) RMRU horizontal, (c) Rub vertical and (d) Rub horizontal .................. 108
Figure 4.27 Residual Misalignment with Residual Unbalance orbits at B1 for: a) 600
rev/min (10 Hz), b) 1200 rev/min (20 Hz), c) 1800 rev/min (30 Hz) and d) 2400
rev/min (40 Hz); ......................................................................................................... 109
Figure 4.28 Orbit for 6 mm supports at B1 for : a) Added Unbalance, b) Crack, c)
Looseness, d) Misalignment, e) Rub at 1800 rev/min (30 Hz) and f) Bow at 600
rev/min (10 Hz); ......................................................................................................... 110
Figure 5.1 Experimental rig mechanical layout ................................................................. 117
Figure 5.2 Schematic of software and instrumentation ...................................................... 117
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Figure 5.3 Details of crack simulation: (a) locations tested, (b) crack dimensions and (c)
shim details ................................................................................................................. 118
Figure 5.4 Details of apparatus used for rub simulation .................................................... 119
Figure 5.5 Details of Misalignment simulation at Bearing 3 ............................................. 119
Figure 5.6 Time waveform sample of the measured vibration data ................................... 121
Figure 5.7 Acceleration spectra at bearing 2 for all faults at 40 Hz................................... 124
Figure 5.8 Comparison of spectral features for all conditions tested at 40 Hz .................. 125
Figure 5.9 Acceleration spectra at bearing 2 for all faults at 50 Hz................................... 126
Figure 5.10 Comparison of spectral features for all conditions tested at 50 Hz ................ 127
Figure 5.11 Bearing heat transfer model ............................................................................ 128
Figure 5.12 Sample showing progression of temperature trends in curve fitting process: a)
transient curve fitting and b) generation of steady-state curves ................................. 130
Figure 5.13 Linear combined approach: a) Temperature and vibration scatter and b)
Proposed linear combined diagnostic trend ................................................................ 131
Figure 5.14 PCA flow process ........................................................................................... 134
Figure 5.15 PCA-based approach without Temperature - 40 Hz .................................... 135
Figure 5.16 PCA-based approach with Temperature - 40 Hz ......................................... 136
Figure 5.17 PCA-based approach without Temperature - 50 Hz .................................... 137
Figure 5.18 PCA-based approach with Temperature - 50 Hz ......................................... 138
Figure 6.1 Layout of rotating machinery experimental rig ................................................ 144
Figure 6.2 Measured mode shapes (dots represent measurement locations) of experimental
rig: (a) mode l: 67.14 Hz and (b) mode 2: 142.2 ....................................................... 145
Figure 6.3 Sample of Frequency Response Function (FRF) in the horizontal direction;
measured on long shaft near bearing 2 during modal testing ..................................... 145
Figure 6.4 Amplitude Spectra from Bearing 2 at 2400 rev/min (40 Hz) for: a) healthy, b)
crack near Bearing 1, c) crack near Bearing 2, d) crack near Bearing 3, e)
misalignment and f) rub near Bearing 4 ..................................................................... 147
Figure 6.5 Amplitude Spectra from Bearing 2 at 3000 rev/min (50 Hz) for: a) healthy, b)
crack near Bearing 1, c) crack near Bearing 2, d) crack near Bearing 3, e)
misalignment and f) rub near Bearing 4 ..................................................................... 148
Figure 6.6 Comparison of spectral features at 2400 rev/min (40 Hz) for all conditions
tested ........................................................................................................................... 150
Figure 6.7 Comparison of spectral features at all speeds for all conditions tested ............ 151
Figure 6.8 Basic example of a Principal Component representation of two correlated
variables X and Y ....................................................................................................... 153
Figure 6.9 Time waveform sample of a measured vibration signal 𝑦(𝑡), where t is time in
seconds ........................................................................................................................ 154
Figure 6.10 Actual sample of the amplitude spectrum 𝑌𝑓 of function 𝑦𝑡 between
frequencies 𝑓1 and 𝑓𝑤 ............................................................................................... 156
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