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عدد المساهمات : 19001 التقييم : 35505 تاريخ التسجيل : 01/07/2009 الدولة : مصر العمل : مدير منتدى هندسة الإنتاج والتصميم الميكانيكى
| موضوع: كتاب Industrial Approaches in Vibration-Based Condition Monitoring الأحد 25 ديسمبر 2022, 7:05 pm | |
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أخواني في الله أحضرت لكم كتاب Industrial Approaches in Vibration-Based Condition Monitoring Jyoti K. Sinha
و المحتوى كما يلي :
Contents Preface xiii Author xv Chapter 1 Introduction 1 1.1 Condition Monitoring 1 1.2 Condition Monitoring Techniques .1 1.3 Condition-Based Maintenance 4 1.3.1 Lead-Time-to-Maintenance (LTM) .5 1.4 Summary .9 Chapter 2 Simple Vibration Theoretical Concept . 11 2.1 Equation of Motion 11 2.2 Damped System . 13 2.2.1 Equation of Motion for Free Vibration . 14 2.2.2 Critically Damped System . 15 2.2.3 Over Damped System . 15 2.2.4 Under Damped System . 16 2.3 Forced Vibration 18 2.3.1 Example 2.1: An SDOF System .22 2.4 Concept of Modeshapes .23 2.5 Machine Vibration .25 2.5.1 Rotor Dynamics .25 2.5.2 Unbalance Responses .27 2.5.3 Machine Faults . 32 2.6 Summary . 33 References 33 Chapter 3 Vibration-Based Condition Monitoring and Fault Diagnosis: Step-by-Step Approach 35 3.1 Introduction . 35 3.2 Different Stages of Vibration Measurements and Monitoring 35 3.2.1 Bath Tub Concept . 35 3.2.2 Stage 1—Machine Installation and Commissioning 35 3.2.3 Stage 2—Machine Operation .38 3.2.4 Stage 3—Aged Machines . 42 3.3 Summary . 43 References 43viii Contents Chapter 4 Vibration Instruments and Measurement Steps . 45 4.1 Introduction . 45 4.2 Sensors and Their Mounting Approach 45 4.2.1 Displacement Sensor 45 4.2.2 Velocity Sensor . 47 4.2.3 Acceleration Sensor 48 4.2.4 Tacho Sensor 53 4.3 Vibration Measurement . 55 4.3.1 A Typical Measurement Setup . 55 4.3.2 Steps Involved in the Data Collection 57 4.3.3 Instrument Calibration and Specifications . 59 4.3.4 Concept of Sampling Frequency 61 4.3.5 Aliasing Affect and Anti-aliasing Filter 61 4.3.5.1 Observations .65 4.3.6 Concept of Nyquist Frequency, fq and the Useful Upper Frequency Limit, fu .66 4.3.7 Analog-to-Digital Conversion (ADC) 67 4.4 Conversion of the Measured Data into the Mechanical Unit .70 4.5 Summary . 71 References 71 Chapter 5 Signal Processing .73 5.1 Time Signal . 73 5.1.1 Filters 73 5.1.2 Amplitude of Vibration 74 5.1.3 Integration of Time Domain Signal . 76 5.1.4 Statistical Parameters . 78 5.1.5 Comparison between CF and Kurtosis 79 5.2 Fourier Transformation (FT) .82 5.2.1 Example 5.1: A Sine Wave Signal 83 5.2.2 Steps Involved for the Computation of FT .84 5.2.3 Importance of Frequency Resolution in Spectrum Analysis .87 5.2.4 Leakage 88 5.2.5 Window Functions .89 5.3 Computation of Power Spectral Density (PSD) 92 5.3.1 Averaging Process 92 5.3.2 Concept of Overlap in the Averaging Process 94 5.3.3 Example 5.2: An Experimental Rig .96 5.3.4 Example 5.3: An Industrial Blower 96 5.4 Conversion of Acceleration Spectrum to Displacement Spectrum and Vice Versa 99 5.5 Short Time Fourier Transformation (STFT) .100 5.5.1 Example 5.4: An Experimental Rig . 101 5.5.2 Example 5.5: An Industrial Centrifugal Pump 101Contents ix 5.6 Correlation between Two Signals 103 5.6.1 Cross Power Spectrum . 103 5.6.2 Transfer Function (Frequency Response Function) .104 5.6.3 Ordinary Coherence . 104 5.6.4 Example 5.6: Two Simulated Signals with Noise . 105 5.6.5 Example 5.7: Laboratory Experiments . 107 5.7 Concept of Envelope Analysis . 109 5.8 Summary . 111 References 111 Chapter 6 Vibration Data Presentation Formats . 113 6.1 Introduction . 113 6.2 Normal Operation Condition . 113 6.2.1 Overall Vibration Amplitude . 113 6.2.2 Vibration Spectrum 113 6.2.3 The Amplitude—Phase versus Time Plot 115 6.2.4 The Polar Plot . 115 6.2.5 The Orbit Plot . 116 6.3 Transient Operation Conditions . 117 6.3.1 The 3D Waterfall Plot of Spectra . 117 6.3.2 The Shaft Centerline Plot . 118 6.3.3 The Orbit Plot . 118 6.3.4 The Bode Plot . 119 6.4 Summary .120 References 120 Chapter 7 Vibration Monitoring, Trending Analysis and Fault Detection . 121 7.1 Introduction . 121 7.2 Types of Faults .125 7.3 Rotor Faults Detection . 125 7.3.1 Mass Unbalance .125 7.3.2 Shaft Bow or Bend .126 7.3.3 Misalignment . 127 7.3.4 Shaft Crack .128 7.3.5 Shaft Rub 128 7.4 Other Machine Fault Detection . 129 7.4.1 Mechanical Looseness . 129 7.4.2 Blade Passing Frequency (BPF) . 129 7.4.3 Blade Vibration and Blade Health Monitoring (BHM) .129 7.4.4 Electric Motor Defects . 129 7.5 Gearbox Fault Detection 130x Contents 7.6 Anti-friction Bearing Fault Detection . 137 7.6.1 Crest Factor (CF) 141 7.6.2 Kurtosis (Ku) 141 7.6.3 Envelope Analysis 142 7.7 Experimental Examples 143 7.7.1 Example 7.1—Roller Bearing Defect . 143 7.7.2 Example 7.2—Rotor Faults 144 7.8 Industrial Examples . 147 7.8.1 Example 7.3—Fan with Unbalance Problem . 147 7.8.2 Example 7.4—Gearbox Fault . 148 7.9 Machines Having Fluid Bearings 151 7.10 Field Rotor Balancing 153 7.10.1 Single Plane Balancing—Graphical Approach 153 7.10.2 Single Plane Balancing—Mathematical Approach 155 7.11 Summary . 157 References 157 Chapter 8 Experimental Modal Analysis 159 8.1 Experimental Procedure 159 8.1.1 Impulsive Load Using the Instrumented Hammer . 159 8.2 Modal Analysis 162 8.3 Experimental Examples 170 8.3.1 Example 8.1—A Clamped-Clamped Beam . 170 8.3.2 Example 8.2—Experimental Rotating Rig-1 . 178 8.3.3 Example 8.3—Experimental Rotating Rig-2 . 181 8.4 Industrial Examples . 183 8.4.1 Example 8.4—Horizontal Centrifugal Pump 183 8.4.2 Example 8.5—Vertical Centrifugal Pump . 186 8.4.3 Example 8.6—Wind Turbine . 188 8.5 Summary . 191 References 191 Chapter 9 Operational Deflection Shape (ODS) . 193 9.1 Simple Theoretical Concept 193 9.2 Industrial Examples . 198 9.2.1 Example 9.1—Steam Turbo-Generator (TG) Set . 198 9.2.2 Example 9.2—Gearbox Failure .202 9.2.3 Example 9.3—Blower with Frequent Bearing Failure .204 9.3 Summary .207 References 207Contents xi Chapter 10 Shaft Torsional Vibration Measurement 209 10.1 Measurement Approach .209 10.2 Extraction of Torsional Vibration Signal . 210 10.2.1 Time Domain Zero-Crossing Approach 210 10.2.2 Demodulation Approach 212 10.3 Experimental Examples 213 10.3.1 Example 10.1—Blade Vibration . 213 10.3.2 Example 10.2—A Diesel Engine . 216 10.4 Summary . 218 References 218 Chapter 11 Selection of Transducers and Data Analyzer for a Machine 219 11.1 Introduction . 219 11.2 Calculation of Machine Faults Frequencies 219 11.3 Selection of Accelerometer 221 11.4 Analysis Parameters 221 11.4.1 Time Domain Analyses 222 11.4.2 Frequency Domain Analyses .222 11.4.3 Time-Frequency Analyses 222 11.5 Features Required in the Data Analyzer .222 11.5.1 Specifications .223 11.5.2 Data Analysis Capabilities .223 11.5.3 Data Trending and Storage .224 11.6 Summary .224 Chapter 12 Future Trend in VCM .225 12.1 Introduction .225 12.1.1 Future IIoT-Based CVCM Approach .227 12.2 Approach 1: Suitable for Existing Old Plants 227 12.3 Approach 2: Suitable for New Plants .229 12.4 Summary .230 References 231 Index 233 Index Note: Page numbers in italic and bold refer to figures and tables, respectively. A acceleration sensors, 48–53 acceleration spectrum, 100, 145, 205 on anti-friction bearing, 138 to displacement spectrum, conversion, 99, 99 on gearbox, 150 for healthy machine, 123 response, 164 size defects, 123, 124 accelerometer, 48, 48–49, 49 mounting, 51, 52, 53 in non-dimensional form, 51 selection, 221 specifications, 52 accuracy, 60 acoustic emission monitoring, 3 ac signal, 116 ADC (analog-to-digital conversion) process, 58, 61, 66 aged machine, 42 aliasing effect, 61, 63–66 AM (amplitude modulation), 109 amplification factor, 20–21, 32 amplitude with DAQ device, 69 FRF, 106, 106, 167, 168, 174 linearity, 51 phase versus time data, 115, 116 spectrum, 85, 94, 162, 173 unbalance force, 32 vibration, 74–76, 76, 113, 114 amplitude modulation (AM), 109 analog-to-digital conversion (ADC) process, 58, 61, 66 angular displacement, 211 anti-aliasing filter, 61, 63–67, 66, 67, 73 anti-friction bearing fault detection, 137–140, 138, 139 CF, 141 envelope analysis, 142–143 Ku, 141–142 averaging process, 92–93, 93, 94 key elements, 96 overlap in, 94–95 B band pass (BP) filter, 73, 74, 222 bath tub concept, 35 life cycle model, 36 modification, 43 beam acceleration response, 172 bearing(s), 38, 118 anti-friction, 38, 137, 137–140, 138 blower with failure, 204–206 CF/Ku for, 142 details, 144, 220 failed drive-end motor, 147 fluid, 151–152 FRF phase plots, 198 journal, 151 machine vibration on, 30 measurements, 39, 40 pedestal, 129, 184, 185, 199 resonance response, 139 roller, 137, 143, 143–144 STFT plot, 102 vibration acceleration, 29, 195, 205 vibration sensors, 56 Blade Health Monitoring (BHM), 129 Blade Passing Frequency (BPF), 129 Blade Tip Timing (BTT) method, 129 blade vibration, 129, 213, 213–216, 214, 214 Bode plot, 119, 120 BPF (Blade Passing Frequency), 129 BP (band pass) filter, 73, 74, 222 Breakdown Maintenance (BM), 4 BTT (Blade Tip Timing) method, 129 bump test, 159 C calibration chart, 59 cantilever beam, 24, 24 modeshapes, 25 vibration mode, 26, 27 carrier frequency, 109 CBM, see Condition-based Maintenance (CBM) centralized VCM (CVCM) system, 227, 227 centrifugal force, 27, 29, 29 CF (Crest Factor), 78, 141, 222234 Index clamped-clamped beam, 170, 170–178, 171, 174, 176, 177 CM, see Condition Monitoring (CM) coherence composite spectrum approach, 230 computation, 162 FRF and, 108 function plot, 106, 107 ordinary, 104–105 two simulated signals with noise, 105, 105–106, 106 complimentary solution, 18–19 Condition-based Maintenance (CBM), 4, 4–5 CM leading, 6 machines for, 5 Condition Monitoring (CM), 1, 2, 36 leading to CBM, 6 techniques, 1, 3 Crest Factor (CF), 78, 141, 222 critically damped system, 15, 16 cross power spectrum, 103–104 CVCM (centralized VCM) system, 227, 227 D D’Alembert Principle, 11 damped SDOF system, 14 damped system, 13–14 under, 16–17, 18 critical, 15, 16 over, 15–16, 16 damping ratio, 15 HPP method, 179 data acquisition (DAQ) device, 45, 56, 67 ADC using 16-bit, 68 collected data for, 70 multi-input channels, 58 signal amplitudes with, 69 data analyzer, 222 capabilities, 223 data trending and storage, 224 specifications, 223 data collection steps, 57, 57–58 data sampling rate, 61 dc signal, 116 Debris analysis, 3 demodulation approach, 212 diesel engine, 216, 218 Digital FT (DFT), 84–85 displacement sensors, 45–46 displacement spectra, 100 Doppler effect, 47–48 dynamic equilibrium, 11 E eddy current probe, 45–46 electric motor defects, 129–130 encoder, 209–210, 210, 213 signal, 215 envelope analysis, 222 signal processing, 109–111, 110 steps, 135, 136 equation of motion, 11–13 for free vibration, 14–15 SDOF, 31 experimental modal analysis, 159, 162–169, 163, 164 clamped-clamped beam, 170–178 impulsive load using hammer, 159–162 procedure, 159 experimental rig, 213 PSD, 96 rotating rig-1, 178–180, 179, 180, 181 rotating rig-2, 181–183, 182 STFT analysis, 101, 102 with vibration instruments, 28 vibration spectrum plots, 146 F fan-gearbox-motor (FGM), 148 Fast FT (FFT), 85, 174 fault detection process, 225 faults types, 125 field rotor balancing, 153–157 filtering process, 222 fluid bearings, 151–152 forced vibration, 18–22, 21 force sensor, 161 forward calculation procedure, 71, 71 Fourier transformation (FT), 82 computation, 84–87, 85 frequency resolution, importance, 87–88, 88 leakage, 88–89, 89 sine wave signal, 83, 83 window functions, 89–92, 90 frequency domain analyses, 222 frequency modulation (FT), 109 frequency ratio, 22 frequency response function (FRF), 104, 195–196, 198 amplitude/real/imaginary/phase, 167, 174 bearing pedestal, 185 and coherence plots, 108 computation, 162 measured, 175 non-dimensional, 169 two simulated signals with noise, 105, 105–106, 106 zoomed view, 169 FSIV (full scale input voltage), 67–68 FS (full scale) reading, 60 FT, see Fourier transformation (FT); frequency modulation (FT)Index 235 full scale input voltage (FSIV), 67–68 full scale (FS) reading, 60 G gearbox conditions, 134 failure, 202, 202–203, 203 fault, 148–151, 150 fault detection, 130–135, 131, 135 single stage, 130 spectrum plots, 133 typical vibration, 132 vibration spectra, 134 gear mesh frequency (GMF), 131, 149, 150 gear ratio (GR), 130 gearwheel frequency, 212 H half-power point (HPP) method, 168–169 high pass (HP) filter, 73, 74, 212 high pressure (HP) turbine, 198, 200 horizontal centrifugal pump, 183–186, 184, 185, 186, 227, 228 I IAS, see instantaneous angular speed (IAS) impulse-response method, 159, 179 impulsive response, 138, 140, 142 industrial blower system, 204, 204–206 industrial centrifugal pump, 101–103, 102, 103 industrial IoT 4.0, 227, 227 inertia force, 11 influence coefficient method, 126, 153 in situ modal tests, 159, 186–188 instantaneous angular speed (IAS), 210–212 response at EO5, 215, 216 16-cylinder diesel engine, 217 spectra, 217 waveforms, 216 instrumented hammer, 159, 160, 172 force sensor in, 161, 170 impact heads, 161 for modal testing, 171 intermediate pressure (IP) turbines, 198, 200 ISO codes, 38–39, 41–42, 122 K kurtosis (Ku), 79, 141–142, 222 L laser velocity sensor, 47–48 Lead-Time-to-Maintenance (LTM), 5–8 estimating, 8 for machine, 7 parameters, 8 leak detection monitoring, 3 linearity, 60 Lower LTM (LLTM), 7 low pass (LP) filter, 73, 74 low pressure (LP) turbines, 198, 200 LTM, see Lead-Time-to-Maintenance (LTM) lubricant monitoring, 3 M MAC (modal assurance criteria), 176–177, 178 machine critical speeds, 119 machine fault detection, 129 BHM, 129 BPF, 129 electric motor defects, 129–130 mechanical looseness, 129 machine faults classification, 228 frequencies, 219, 220–221 machine vibration, 32, 33 machine learning (ML) approach, 227–228 machine vibration, 25 on bearing housing, 30 machine faults, 32, 33 rotor dynamics, 25–26, 28, 29 under rotor unbalance, 31 sinusoidal response, 31, 32 unbalance responses, 27, 29–32, 30 magnification factor, 20 mass unbalance, 125–126 mean LTM (MLTM), 8 mean-time-to-failure (MTTF), 1 mechanical looseness, 129 ML (machine learning) approach, 227–228 modal assurance criteria (MAC), 176–177, 178 modal testing, 162; see also experimental modal analysis modeshapes concept, 23–25, 24 cantilever beam, 25 for clamped-clamped beam, 177 experimental rig-1, 181 experimental rig-2, 183 extraction, 176–177 machine, 193, 194 measured, 183 at natural frequency, 184, 184 normalized, 176 pump assembly and, 187 rotor, 28236 Index motor defects, features, 130 motor-gearbox-fan unit, 149, 202, 202 N natural frequency, 12 noise monitoring, 3 non-destructive test (NDT) techniques, 1, 3 non-dimensional CF, 142 normal operation condition amplitude, 115, 115 orbit plot, 116–117, 117 polar plot, 115, 115 vibration amplitude, 113, 114 vibration spectrum, 113, 114, 115 O ODS, see operational deflection shape (ODS) analysis oil whip/whirl, 151–152, 152 operational deflection shape (ODS) analysis, 36 at critical speeds, 201 gearbox failure, 202–203 at gear mesh frequency, 203 industrial blower system, 204–206 at motor-blower unit, 206 motor-gearbox-fan, 203 at operating speeds, 202 rotating machine, 193, 194 simple theoretical concept, 193–198 steam TG set, 198–201 values at 1× and 2×, 197, 197, 199 orbit plot, 127, 152 normal operation condition, 116–117, 117 at rotor speed, 128, 128 transient operation conditions, 118 ordinary coherence, 104–105 oscillation, 11–13, 13 over damped system, 15–16, 16 P PA-Fan, see primary air fan (PA-Fan) particular integration, 19 pCCS (poly coherent composite spectrum), 230 P-F (Potential Failure) curve, 40, 41 phase distortion, 51 phase versus time plot, 115, 115 piezoelectric accelerometers, 48 Planned Preventive Maintenance (PPM), 4 polar plot analysis, 154–155 poles, representation, 17, 17 poly coherent composite spectrum (pCCS), 230 power spectral density (PSD), 93 averaging process, 92–95, 93, 94 experimental rig, 96, 97 industrial blower, 96–98, 98 primary air fan (PA-Fan), 147, 147–148, 148 proximity probes, 45–46, 47, 116 PSD, see power spectral density (PSD) pulse train waveform, 210 from gearwheel, 211 spectrum, 212 pumps/piping assembly, 187, 220 horizontal centrifugal, 183–186, 228 industrial centrifugal, 101–103, 102 schematic layout, 187 stool, stiffening, 188 vertical centrifugal, 186–188 R reference signal, 53 Reliability and Maintenance Index (RMI), 6–7 repeatability, 60 reproducibility, 60 resonance, 20 fluid, 151–152 frequency, 52, 137, 139 response built-up, 20, 21 reverse calculation procedure, 71, 71 RMI (Reliability and Maintenance Index), 6–7 RMS, see root mean square (RMS) roller bearing defect, 143, 143–144, 145 root mean square (RMS), 74–76, 113 amplitude, vibration, 114 time wave forms, 76 velocity, 124 vibration values, 124 vibration velocity, 147 rotating machine representation, 121, 122 rotor balancing, 155, 156, 157 dynamics, 25–26, 28, 29 faults, 126, 144; see also rotor faults detection misalignment, 127 rig speed profile, 215 with single plane unbalance, 30 solid point on, 30 unbalance estimation, 155 unbalance force, 29 rotor faults detection mass unbalance, 125–126 misalignment, 127 shaft bow/bend, 126–127 shaft crack, 128 shaft rub, 128–129 running speeds/GMFs, 149, 150 run to failure, 4Index 237 S sampling frequency, 61, 61, 62 at 2/1 kHz, 750 Hz, 63–64, 64 at 10/5 kHz, 63, 63 at 500/400 Hz, 65, 65 collected signals, 62 sine wave, 63 SDOF, see single degree of freedom (SDOF) system seismometer, 47 sensitivity method, 153 sensors and mounting approach, 45 acceleration, 48–53 displacement, 45–46 tacho, 53, 53–54, 54, 55 velocity, 47–48, 48 shaft bow/bend, 126–127 shaft centerline plot, 118, 119 shaft crack, 128 shaft misalignment, 146 shaft response, 138 shaft rubs, 128–129 conditions, 146 simulation, 147 short time Fourier transformation (STFT), 100–101 analyses, 198–199, 201 experimental rig, 101 industrial centrifugal pump, 101–103, 102, 103 signal processing correlation between signals, 103–108 FT, 82–92 PSD, computation, 92–98 STFT, 100–103 time signal, 73–82, 92 signal waveforms, 80, 82 sine waveform, 89, 91 single degree of freedom (SDOF) system, 11, 22–23, 162 and behavior, 12 damped, 14 under damped, 18 with natural period, oscillation, 13 responses, 22 on vibrating object, 49 single plane balancing, 153 graphical approach, 153, 153–155 mathematical approach, 155–157 single stage gearbox, 130 small instrumented hammer, photograph, 160 spectrum analysis, 194, 212 frequency resolution in, 87, 87–88, 88 measured vibration, 196 spectrum/spectra acceleration, see acceleration spectrum amplitude, 85, 94, 162, 173 coherence composite, 230 cross power, 103–104 displacement, 100 gearbox, 133, 134 IAS, 217 measured force, 163 normal operation condition, 113, 114, 115 plots, 85, 86, 87, 95, 205 pulse train waveform, 212 3D waterfall plot, 117–118, 118 time domain signal and, 140 velocity, 99, 100 vibration, 130 waterfall plot, 101 spring-mass system, 11–12, 23, 46 steam TG set, 198–201; see also turbo-generator (TG) set STFT, see short time Fourier transformation (STFT) T tacho sensors, 53, 53–54, 54, 55 tacho signal, 53–54, 153, 154 temperature monitoring, 1, 3 TG, see turbo-generator (TG) set thermography, 3 3-D waterfall plot, 117 time domain analyses, 222 time domain signal, 73, 140 integration, 76–78, 77 into segments, 93 and spectrum, 140 using STFT analysis, 101 time domain zero-crossing approach, 210–212, 214 time-frequency analyses, 222 time signal, 73 CF versus Ku, 79–82, 81, 82 filters, 73–74, 75 statistical parameters, 78–79, 79, 80 time domain signal, integration, 76–78, 77 vibration amplitude, 74–76, 76 time wave-forms, 161 torsional vibration, 209 transient operation conditions Bode plot, 119, 120 orbit plot, 118 shaft centerline plot, 118, 119 spectra, 3D waterfall plot, 117–118, 118 transient response, 19 transition piece (TP), 188 trial-and-error approach, 36 trial run, 154 turbo-generator (TG) set, 55, 56, 198, 201238 Index U under damped system, 16–17, 18 Upper LTM (ULTM), 7 V VCM, see vibration-based condition monitoring (VCM) velocity sensors, 47–48, 48 velocity spectra, 99, 100 vertical centrifugal pump, 186–188 vibration acceleration, 193, 195 spectrum plots, 205 vibration-based condition monitoring (VCM), 11, 32, 122, 225, 226 data processing in, 226 limitations in, 225, 227 machine, 38–39 measurement interval, 40–41 measurement locations and directions, 39, 39, 40 procedure, 38 software and instrumentations, 40 vibration severity limits, 41, 41–42 vibration data fusion concept, 229, 229 vibration data presentation formats normal operation condition, 113–117 transient operation conditions, 117–120 vibration displacement signal, 141, 154 velocity versus acceleration spectra, 123, 124 vibration measurements and monitoring stages ADC, 67–69 aged machine, 42 aliasing affect and anti-aliasing filter, 61, 63–67, 66, 67 bath tub concept, 35 data collection steps, 57–58 instrument calibration and specifications, 59–60 machine installation and commissioning, 35–37, 37 machine operation, 38–42 Nyquist frequency, 66–67 sampling frequency, 61, 61, 62, 62 setup, 55–57 vibration monitoring, 3 vibration severity limits, 41, 41–42 vibration spectrum, 130 vibration transducer, 46 vibration velocity signal, 140 W wind turbine, 188, 189, 190, 191 Z zebra reflective strip, 209, 210
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