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EM MAIIL TIP T PS A Learn ning Publicaation from Full Spectrrum Diagno ostics
Vo ol. 81 Februa ary 2012
What abo out th he “Big”” Stu uff?
Inttrodu ucing g the Vibrration n Ana alysis Pe eriodiic Ta able
EMAIL TIPS Volume 81 February 2012 A New Look You may have noticed a new look to the Email Tips publication. We hope you like it! The hope is that Full Spectrum Diagnostics can add some real world insights into machinery maintenance and vibration analysis through a more visual format. The magazine format is provided by Issuu.com. It is our goal to promote sharing of ideas and solutions through our training side of the business and offer a view from the trenches via the field engineering and diagnostics side of the business. In the coming months when we’ve worked some of the bugs out of this publication we will be inviting our readers to comment and critique our efforts. Till then bear with us as we struggle to produce a product that is both worthwhile, credible and of value to the reader.
Features:
Cover: The cover features one of industries largest drive systems. The Amclyde (National Oilwell Varco) shipboard crane system. The crane features a Whip, Boom, and Main Hoist with lifting capacity of 600 metric tons. This crane is used to assemble sections natural gas pipeline on the ocean floor world-wide. It has all the features that make vibration analysis problematic. Variable Frequency Drives (VFD’s), Low speed / High Load operation, High speed / Low Load operation, Multi reduction reversible Gear drives, and rigid support frame designed with enough give to accommodate severe load conditions. Oh yeah, did I mention the ocean? It’s a nightmare to monitor, much less trend.
The Time Waveform – Monitoring low speed rolling element bearings. The Spectrum – Sidebands in the FFT provide indications of deterioration in bearings and gears. Ultra Sonics – The FFT processor will create a spectrum based on the type of Time Waveform provided as an input. Definitions: Ultrasonic Demodulation explained as a generic technology. 2012 Training Schedules – Something for Everyone Core Training Courses Concentrated Training Courses
A New Concept: This issue of Email Tips includes an introduction of an original concept in vibration analysis. The Vibration Analysis Periodic Table was unveiled during two Vibration Institute meetings in November and December of 2011. The reception was very good and this format of fault classification by frequency content and directional response will be incorporated into all of the Full Spectrum Diagnostics training courses by the end of 2012. Eventually, a drill down interactive and self-guided program will be available. Currently, full color Laminated 8 ½ x 11 inch cardstock prints of the table will be available by the Email Tips publication date. See page 8.0.
Time Domain Tips: Time Waveform (TWF) Analysis in low-speed applications can be superior to Spectral analysis in detecting rolling-element bearing defects. What is considered ‘low speed” to one analyst may be different to the next. FSD asks the reader to consider low speed as any rotating frequency below 600 RPM. As speed is reduced (below 600 RPM) the need for TWF Analysis increases. In a Rolling Element Bearing (REB) the defects may appear in the spectrum at 2.2x–12.2x the rotor speed, (which doesn’t especially make them “low speed” events at shaft speeds of 600 RPM). However; it’s the centrifugal loads in the bearing that make the impacts between the rolling elements and the raceways visible in the spectrum. These impacts are significantly reduced at lower rotor speeds.
Impact Pulsing in the Time Waveform (Low-Speed)
In the unfiltered Time Waveform these impacts are quite evident above other noise sources as each ball or roll crosses a race defect. Look for an amplified repeating pattern of peaks spaced at nonsynchronous intervals. Remember that an outer race defect will be fairly constant in amplitude, whereas inner race defects tend to have modulated amplitudes as the defect moves in and out of the bearing load zone.
Frequency Domain Tips: Pay attention to SIDE BANDS in your spectra. Side Bands are caused by modulation in the vibration signal, either Frequency Modulation, or more commonly Amplitude Modulation. Common sources of Amplitude Modulation are rotating bearing defects (in and out of the bearing load zone) and electrical field disruptions in AC motors resulting in 2x electrical line frequency modulation around Rotor Bar Passing Frequency (RBPF). Frequency Modulation results from non-uniform gear wear or gear tooth spacing variation from the manufacturing process, changes in torque, or actual gear speed variations. Some minor amplitude sidebands are expected, however it is the trended changes in amplitude and number of sideband sets that typically indicates problems developing in rotating machinery. The example (right) shows Ball Spin Frequency (BSF) with FTF (Cage) frequency sideband modulation. Modulation is created as the rolling elements move in and out of the bearing load zone.
Inner Raceway Crack in Low-Speed Bearing
Ball Spin Frequency with FTF (Cage) Frequency Sidebands
Sidebands in the Velocity FFT Spectrum
Ultrasonic Domain Tips: The Harmonics generated in the Demodulated Spectrum of your analyzer are a function of the Fast Fourier Transform (FFT) algorithm. The multiples of the bearing fault are created in the processor’s attempt to define the enveloped time waveform. Many ultrasonic software routines simplify the filtered ultrasonic waveform by enveloping and rectifying the high-frequency signal, which will typically appear as a repeating saw-tooth or impulse time waveform pattern. The FFT tries to mathematically reproduce this time signal resulting in odd, even, or odd & even multiples of the fundamental frequency (harmonics). The result is a series of non-synchronous harmonics that tell the analyst that the source is a repetitive pulsation, or more plainly, that the source is indeed a bearing fault. FFT Signal Processing Frequency Response
Definitions & Nomenclature: Ultra-Sonic Demodulation “.….the Recovery, from a Modulated Carrier, of a Signal having substantially the same characteristics as the Original Modulated Signal…….” Ultrasonic Demodulation analysis relies on a carrier frequency to allow the analyst to “see” the related fault frequency in a rolling element bearing or gear problem. What the vibration analyst detects in this “ultrasonic” measurement is the excitation of the carrier frequency. The carrier frequency is excited by sharp impacts between the rollers and the raceway fault. The Carrier Frequency can be a resonance response of the bearing, retainer, support housings, or more commonly, the ringing of the accelerometer used in the measurement! The impact produces series of classic ring-down responses in the TWF, which includes the ultrasonic carrier frequency. The impact rate (each roller passing a raceway defect) itself is not a “highfrequency” phenomena. The key to Ultrasonic Demodulation is as simple as the ringing of a bell. It’s not important to describe the actual ringing frequency of the bell (carrier), but rather the number of times the bell was rung (bearing defect rate). Assuming we know the spacing of the rolling elements in the bearing, we can determine how often the “bell” will be rung, if a bearing fault is present. Demodulation removes the carrier frequency, but retains the impact rate as a series of pulses in the TWF. The FFT of this TWF can determine if the impact rate is related to a bearing or gear fault.
Ultrasonic Demodulation Enveloping
The Demodulated Frequency Spectrum
2012 CORE VIBRATION TRAINING SCHEDULE
2012 SPECIALTY VIBRATION TRAINING SCHEDULE
IMPLEMENTING A SUCCESSFUL PdM PROGRAM
MODAL & ODS ANALYSIS 2
JUN 19-20 Cameron, WI 2012-PdM-01
MAR 20-22 Davenport, IA 2012-ODS-01 JUL 24-26 St. Paul, MN 2012-ODS-02
Tuition: $ 945.00 / 2-day Format Proficiency Test: Included
INTRODUCTION TO VIBRATION ANALYSIS FEB 21-22 MAR 13-14 MAR 27-28 APR 17-18
St. Paul, MN Brookfield, WI Harrisburg, PA Knoxville, TN
2012-INT-01 2012-INT-02 2012-INT-03 2012-INT-04
Tuition: $ 945.00 / 2-day Format Proficiency Test: Included
St. Paul, MN Cedar Rapids, IA Wheeling, WV Chicago, IL Charlotte, NC New Orleans, LA
CONC TIME WAVEFORM ANLAYSIS JUN 05-06 Cedar Rapids, IA 2012-TWF-01 NOV 27-28 Chillicothe, OH 2012-TWF-02 Tuition: $ 945.00 / 2-day Format Proficiency Test: Included
CONCENTRATED SPECTRUM ANALYSIS
VIBRATION ANALYSIS I MAR 06-09 APR 10-13 APR 24-27 SEP 11-14 DEC 11-14 DEC 18-21
For In-Plant Training: ModalGuy@aol.com Tuition: $ 1,595.00 / 3-day Format One Month ME’scope Software Included
2012-VA1-01 2012-VA1-02 2012-VA1-03 2012-VA1-04 2012-VA1-05 2012-VA1-06
JUN 26-27 Brookfield, WI 2012-CSA-01 JUL 17-18 Davenport, IA 2012-CSA-02 OCT 02-03 St. Paul, MN 2012-CSA-03 Tuition: $ 945.00 / 2-day Format Proficiency Test: Included
CONCENTRATED PHASE ANALYSIS
Tuition: $ 1,295.00 / 3-day Format Certification Exam: $ 200.00
SEP 18-19 Davenport, IA 2012-CPA-01
VIBRATION ANLAYSIS II
Tuition: $ 945.00 / 2-day Format Hands-on Exercises: Included
MAR 20-23 MAY 08-11 MAY 22-25 JUL 10-13 SEP 25-28
Leesport, PA Chicago, IL Cumming, GA St. Paul, MN Cedar Rapids, IA
2012-VA2-02 2012-VA2-03 2012-VA2-04 2012-VA2-05 2012-VA2-06
Tuition: $ 1,395.00 / 3-day Format Certification Exam: $ 200.00
CONCENTRATED RE BEARING & GEAR ANLAYSIS OCT 16-17 Cedar Rapids, IA 2012-BGA-01 Tuition: $ 945.00 / 2-day Format Proficiency Test: Included
VIBRATION ANALYSIS FOR MOTOR SHOPS VIBRATION ANALYSIS IIIa OCT 23-26 Leesport, PA 2012-VA3-01 Tuition: $ 1,595.00 / 4-day Format Certification Exam: $ 200.00
AUG 28-30 Charlotte, NC 2012-VAM-01 DEC 04-06 St. Paul, MN 2012-VAM-02 Tuition: $ 1,295.00 / 3-day Format Hands-on Exercises: Included
PRACTICAL VIBREATION ANALYSIS IIIb PRECISION BALANCING AUG 21-24 St. Paul, MN 2012-PVA-01 Tuition: $ 1,595.00 / 4-day Format Certification Exam: $ 200.00
!!! NEW !!!
MAY 01-02 Cedar Rapids, IA 2012-BAL-02 AUG 07-08 Brookfield, WI 2012-BAL-03 NOV 13-14 Wheeling, WV 2012-BAL-04 Tuition: $ 945.00 / 2-day Format Hands-on Exercises: Included
THE VIBRATION FAULT GUIDE The Vibration Fault Guide is a 110-page indispensable asset for every vibration analyst, as well as a helpful tool to bridge the gap between the analyst and his management staff. Some 45 Rotating Machinery Faults are Identified and defined. Conveniently sized at 3” x 6”, it easily fits in your pocket for everyday use!
GUÍA DE FALLAS DE VIBRACIÓN Este manual consta de 110 páginas y fue compilado por Full Spectrum Diagnostics como referencia rápida para la industria de Mantenimiento Predictivo y Monitoreo de Condición. La guía incluye ejemplos de espectros, formas de onda, definiciones de fallos y reglasde análisis de fase para aproximadamente unos 45 problemas que se pueden presentar en maquinaria rotativa. También incluimos varios estándares de especificaciones de vibración, guías para definición de bandas de alarmas, fórmulas y definiciones de Procesamiento de Señales. Es suficientemente pequeño como para llevarlo en la bolsa de su camisa ( 3.5” X 6.0”), pero su contenido es tan grande que podría ser considerado como una guía de referencia esencial para la industria del Monitoreo de Condición.
THE VIBRATION TECHNIQUES GUIDE The Vibration Analysis Techniques Guide is a 108-page pocket sized information treasure trove. Information on dozens of analysis techniques, specifications and data presentation formats are included. If you liked the Vibration Fault Guide, your next educational step should be the Vibration Analysis Techniques Guide get yours now at:
Order now at: http://www.fullspec.net/store.html Or by Phone @ (763) 577-9959
BULK DISCOUNTS & BUNDLE PACKAGES AVAILABLE!
THE VIBRATIION ANALYSIS WALL W CHA ART This 46” 4 x 36” Fulll-Color Lam minated Vibra ation Analysiis tool is the ultimate com mpanion to the t Vibration n Fault Guide e and the Vib bration Tech hniques Guid de reference es. Over 40 dominant ro otating mach hinery proble ems are outline ed, based on: Fau ult Direction / Amplitude / Frequencyy / Phase an nd Time Wavveform Attrib butes And d categorize ed, based on n: Synchrono ous / Harmonic / Non-Syynchronous AC / DC / Aero-Hydro o and Gearin ng Groupings ore.html Orderr now at: Htttp://www.fulllspec.net/sto Or byy Phone @ (763) 577-99 959
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THE VIBRATION ANALYSIS PERIODIC TABLE This Full Color Laminated 8 ½ x 11 inch card-stock table provides a “quick-look” method of distinguishing one machinery fault from another and suggests Diagnostic Tests or formula that may be used to build a case and make the call! Faults are classified by Frequency Content and grouped in similar patterns: Synchronous / Harmonic / Sub-Harmonic Sub-Synchronous / Non-Synchronous / Modulated (Sidebands) Faults are Color classified Directionally: [ Radial ] / [ Axial ] / [ Radial & Axial ] Faults are Foot Noted to the Vibration Fault Guide for a more detailed reference. If you liked the Vibration Fault Guide, your next educational step should be the Vibration Analysis Periodic Table! Get yours now at: www.fullspec.net, or by phone at 763-577-9959
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