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Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
Measuring Vibration - How to Select the Right Sensor
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Measuring Vibration - How to Select the Right Sensor

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Bently Nevada Webinar April 2009 …

Bently Nevada Webinar April 2009
Measuring Vibration - How to Select the Right Sensor

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  • THANKS CAN HELP ME Fundamentals of Rotating Machinery Diagnostics
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  • 1. Measuring Vibration How to Select the Right Sensor OC Asia Webinar 23 June 2009 Chris Engdahl - Field Application Engineer, SE Asia
  • 2. What is Vibration? • Vibration is the response of a system to some internal or external excitation or force applied to the system
  • 3. What Causes Vibration? • Unbalance of rotating parts • Eccentric Rotor • Bent Shaft • Misalignment • Mechanical Looseness • Rotor Rub
  • 4. What Causes Vibration? • Sleeve Bearings -Wear, Oil Whirl, Oil Whip • Rolling Element Bearings - Defects • Hydraulic & Aerodynamic Forces • Electrical Problems • Gear Problems • Belt Drive Problems
  • 5. What Causes Vibration? • Developing fault symptom • Major/dangerous machine problem • Normal operation
  • 6. Machinery Protection Systems Systems that shutdown a machine or return it to a safe or nondestructive mode of operation without human intervention. These must be high integrity systems, not susceptible to false or missed action. Must operate reliably first-time! Machinery Condition Monitoring Systems that detect change in machine condition and identify root-cause machinery failure modes for maintenance work planning. These must be highly sensitive to subtle changes in particular symptoms, and typically look for statistical variations, not single events.
  • 7. Vibration Features and Vibration Units • Displacement • The total distance travelled by the vibrating part, from one extreme limit to the other or peak to peak • Units = microns (peak to peak) UPPER LIMIT NEUTRAL POSITION LOWER LIMIT DISPLACEMENT TIME PERIOD PEAK TO PEAK DISPLACEMENT Displacement can relate to physical clearances in a machine. – OEMs usually state limits for relative displacement
  • 8. • Velocity • The speed at which displacement occurs • Because the speed is constantly changing, the peak or RMS velocity are usually selected • Units - mm/s (peak) (RMS) DISPLACEMENT Minimum Velocity Minimum Velocity Maximum Velocity TIME Vibration Features and Vibration Units Vibration Energy dissipated is proportional to VELOCITY - Vibration SEVERITY limits are set in Velocity units
  • 9. Vibration Features and Vibration Units • Acceleration • The rate of change of velocity • At the extreme limit of travel of the vibrating part, acceleration is maximum or peak • Units - g’s (peak) DISPLACEMENT Maximum Acceleration Maximum Acceleration Minimum Acceleration TIME ACCELERATION can indicate magnitude of knocks and impact events well – assessment criteria is often empirical
  • 10. Displacement / Velocity / Acceleration AccelerationDisplacement Velocity “leads” Displacement by 90 deg Acceleration “leads” Displacement by 180 deg Velocity time
  • 11. Overall Amplitude Trending Vibration AMPLITUDE is only one possible parameter. - Good for alarming and protection, but there is more information we can extract….
  • 12. The Vibration Signal 45MICRON10MICRON35MICRON30MICRON 100MICRON BAD BEARING LOOSENESS BLADE PASSING UNBALANCE The “Raw” vibration signal may be a rich source of information - or interference…… Complex Vibration Waveform Individual vibration sources generate unique symptoms. The measured vibration signal is a composite of all these.
  • 13. What is a Spectrum ? AMPLITUDE TIME AMPLITUDE FREQUENCY IMBALANCE BEARING DEFECT GEARMESH Waveform Spectrum
  • 14. Modern vibration monitoring systems* let us select a Broad Set of analysis parameters (*Bently Nevada System1)
  • 15. Obviously, there’s a lot more than just vibration amplitude….. 
  • 16. Vibration Transducers The vibration transducer must accurately detect the vibration of interest What is “of Interest”? For Protection – only symptoms of the failure mode we must protect against Typically Rotor Region (0.25X to 3X machine speed) For Condition Monitoring – we probably want to see everything….
  • 17. Vibration Transducers • Types that are commonly used are  Velocity Transducers  Accelerometers & “Velomitors”  Proximity Probes
  • 18. Displacement Probe • Probe, Extension Cable, Proximitor® Source: Machinery Malfunction Diagnosis and Correction by Robert Eisenmann Sr., Robert Eisenmann Jr., 1998
  • 19. Vibration Transducers • Proximity Probe • Used in permanent monitoring of plain bearing machines such as turbines, large pumps and large fans • “Relative” vibration measurement • Output = microns shaft non-contact pickup gap magnetic field pickup coil oscillator detector amplifier SIGNAL SENSORDC GAP METER Diagram showing non-contact transducer system
  • 20. Radial and Axial Measurement Source: Machinery Malfunction Diagnosis and Correction by Robert Eisenmann Sr., Robert Eisenmann Jr., 1998
  • 21. Proximity Probe Advantages • Measures Shaft Dynamic Motion • Measures Shaft Static Position • Excellent Signal Response Between DC and 90,000 CPM (1.5 kHz) • Flat Phase Response Throughout Transducer Operating Range • Simple Calibration • Solid State Electronics • Rugged and Reliable Construction • Available in Many Physical Configurations • Suitable for Installation in Harsh Environments • Multiple Machinery Applications for the Same Transducers
  • 22. Proximity Probe Disadvantages • Sensitive to Surface Imperfections and Magnetism • Sensitive to Material Properties • Shaft Surface must be Conductive • Low Dynamic Signal Response Above 90,000 CPM (1.5 kHz) • External Power Source Required • Correct Probe to Proximitor® Cable Impedance Must Be Maintained (e.g. 5 or 9 meters) • Minor Temperature Sensitivity (before API 670 4th edition) • Sensitive to Interference from Adjacent Proximity Probes – Cross- talk! • Sensitive to Probe Mounting Bracket Resonance(s) • Potentially Difficult to Install
  • 23. Velocity Transducer Source: Machinery Malfunction Diagnosis and Correction by Robert Eisenmann Sr., Robert Eisenmann Jr., 1998
  • 24. Transducer Installation Source: Machinery Malfunction Diagnosis and Correction by Robert Eisenmann Sr., Robert Eisenmann Jr., 1998
  • 25. Velocity Advantages • Measures Casing Absolute Motion • Easily Attached to Machinery Externals, Piping, Baseplates or Structures • Good Signal Response Between 900 and 90,000 CPM (15 and 1,500 Hz) • Self-Generation Signal Electronics • No Special Wiring Required • Available in Several Configurations
  • 26. Velocity Disadvantages • Sensitive to Mounting Fixture and Transducer Orientation • Unable to Measure Shaft Vibration or Position • Poor Signal Response Below 900 CPM (15 Hz) Above 90,000 CPM (1.5 KHz) • Operates Above Transducer Natural Frequency of 600 CPM (10 Hz) • Potential for Failure due to Fatigue of Moving Internal Parts • Temperature Sensitive, Typical Upper Limit of 250°F, Lower Limit of 30°F
  • 27. Accelerometer Source: Machinery Malfunction Diagnosis and Correction by Robert Eisenmann Sr., Robert Eisenmann Jr., 1998
  • 28. Accelerometer Advantages • Measures Casing or Structural Absolute Motion • Easily Attached to Machinery, Piping, Baseplates or Structures • Good Signal Response Between 900 and 600,000 CPM (15 >10,000 Hz) • Flat Phase Response Throughout Transducer Operating Range • Solid State Electronics with Rugged and Reliable Construction • Operates Below Mounted Natural Resonant Frequency • Special Units Available for High Temperature Applications (>1,200°F)
  • 29. Accelerometer Disadvantages • Sensitive to Mounting Technique and Surface Condition • Unable to Measure Shaft Vibration or Position • External Power Source Required • Low Dynamic Signal Response Below 600 CPM (10 Hz) • Transducer Cable Sensitive to Noise, Motion, and Electrical Interference (particularly in charge-mode accels) • Temperature Limitation of 250°F for ICP® Transducers • Extended Frequency Range Often Requires Signal Filtration • Double Integration Often Suffers from Low Frequency Noise
  • 30. What Vibration Transducers see: frequency Velocity unbalance Sealrub Bearingdefect General“noise” Consider we have various vibration components of similar energy, at different frequencies Rotor Region ¼X to 3X Prime Spike 1.Epx to 7.EPx
  • 31. amplitude frequency frequency tisplacemen Velocity D Velocity What Proximity Transducers see:
  • 32. amplitude frequency Velocity What Acceleration Transducers see: frequencyVelocityonAccelerati
  • 33. frequency unbalance Sealrub Bearingdefect General“noise” DynamicRange Transducer frequency range •Good resolution between approx 5Hz and 2kHz •Limited higher frequency response What Velocity Transducers see:
  • 34. frequency unbalance Sealrub Bearingdefect Generalnoise DynamicRange Transducer frequency range •Excellent resolution for Rotor Region data •Poor SNR for high frequency components What Proximity Transducers see:
  • 35. frequency unbalance Sealrub Bearingdefect Generalnoise DynamicRange Transducer frequency range •Good resolution for high frequency components •Poor SNR for Rotor Region data What Acceleration Transducers see:
  • 36. DynamicRangethatmonitorsees Why are we interested in SNR? Example: 8-bit resolution Analogue-to- Digital data acquisition input signal must be divided up into 256 discrete steps.
  • 37. DynamicRangethatmonitorsees Why are we interested in SNR? “Rotor Region” Data Up to 3 or 4 X running speed frequency Example: 8-bit resolution Analogue-to- Digital data acquisition input signal must be divided up into 256 discrete steps. So the useful data we want looks like this
  • 38. DynamicRangethatmonitorsees Why are we interested in SNR? “Rotor Region” Data Up to 3 or 4 X running speed frequency Example: 8-bit resolution Analogue-to- Digital data acquisition input signal must be divided up into 256 discrete steps. So the useful data we want looks like this 3500 has 16-bit resolution , 1900/65A and ADRE 408 support 24-bit A/D This is why we need to consider: 1. What sort of data do we expect to see? 2. What are the characteristics of the transducer and monitor? This is how the Waveform is acquired…. Imagine what this does to the Vibration Spectrum. Consider the sort of resolution you would see on trend plots…
  • 39. What Transducer should you use : 1. To Protect 600 rpm Fin Fan with Rolling Element Bearings. 2. To Monitor a 7,500rpm precision gearbox with 57 teeth (gear mesh ~ 7.5 kHz) Remember: The ideal transducer for PROTECTION may not be ideal for CONDITION MONITORING !

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