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Machinery Vibration Analysis and Maintenance


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This practical workshop provides a detailed examination of the detection, location and diagnosis of faults in rotating and reciprocating machinery using vibration analysis. The basics and underlying physics of vibration signals are first examined. The acquisition and processing of signals is reviewed followed by a discussion of machinery fault diagnosis using vibration analysis, and rectifying the unidentified faults. The workshop is concluded by a review of the other techniques of predictive maintenance such as oil and particle analysis, ultrasound and infrared thermography. The latest approaches and equipment used together with current research techniques in vibration analysis are also highlighted in the workshop.


Published in: Engineering, Technology, Business

Machinery Vibration Analysis and Maintenance

  1. 1. Technology Training that
  2. 2. Technology Training that If you are interested in further training or information, please visit: OR Like us on Facebook: OR Follow us on Twitter: @IDCandEIT
  3. 3. Technology Training that Maintenance Philosophies
  4. 4. Technology Training that Vibration in everyday life
  5. 5. Technology Training that Useful Vibration
  6. 6. Technology Training that Vibration Monitoring
  7. 7. Technology Training that Vibration Basics Any external force has to overcome structure’s properties: - Mass - Stiffness - Damping A force cause vibration!
  8. 8. Technology Training that Vibration Basics Vibration can be described in terms of: - Acceleration - Velocity - Displacement Single degree of freedom system: - Forced vibration response - Free vibration response - Resonance is free vibration Frequency is the number of vibration cycles / time!
  9. 9. Technology Training that Vibration Basics
  10. 10. Technology Training that System Response 2g 10N
  11. 11. Technology Training that Nature of Vibration - SHM • X = Xo sin w t • X = Disp. at instant t • Xo = Maximum disp. • w = 2 .p. f (rad/s) • f = frequency (Hz) • t = time (seconds)
  12. 12. Technology Training that Wave Terminology
  13. 13. Technology Training that Wave Terminology - Phase • A time lag of T is a phase angle of 360º. • A time lag of T/4 will be a phase angle of 90º. The two waves are out of phase by 90º !
  14. 14. Technology Training that A Fast Fourier Transform Also called the Frequency Domain or Vibration Spectrum
  15. 15. Technology Training that Harmonics
  16. 16. Technology Training that Frequency and Time Domains • FFT is the Frequency Domain • Time Waveform is the Time Domain
  17. 17. Technology Training that Frequency Analysis
  18. 18. Technology Training that Overall Amplitude • It is the total vibration amplitude over a wide range of frequencies. • Acceleration, Velocity, or Displacement.
  19. 19. Technology Training that Which to choose?
  20. 20. Technology Training that “Real world” vibration levels
  21. 21. Technology Training that Vibration Terminology • Displacement [peak-peak] • Velocity [peak] • Velocity [rms] – Velocity rms tends to provide the energy content in the vibration, whereas the Velocity peak depicts more of the intensity of vibration. • Acceleration [peak]
  22. 22. Technology Training that Machinery Fault Diagnosis • Vibration analysis is used to monitor the state of a machine. • Detailed analyses can be made concerning the health of the machine and any faults, which may be arising or may have already arisen. • The need for higher reliability and availability of critical machinery forces the use of this technique of PdM.
  23. 23. Technology Training that Common Machinery Faults • Unbalance • Bent shaft • Eccentricity • Misalignment • Looseness • Belt drive problems • Gear defects • Bearing defects • Electrical faults • Oil whip / whirl • Cavitation • Shaft cracks • Rotor rubs • Resonance • Hydraulic + aerodynamic forces
  24. 24. Technology Training that Unbalance - Static • Amplitude due to unbalance will vary with the square of speed • The FFT will show 1 × rpm frequency of vibration. • It will be predominant • Phase difference is as shown
  25. 25. Technology Training that Unbalance - Couple • Amplitude varies with square of speed • Predominant 1 × peak • May cause high axial along with radial vibrations. • Phase difference is 180º on shaft ends in both planes.
  26. 26. Technology Training that Unbalance - Overhung Rotors • Amplitude varies with square of speed. • Predominant 1× peak • May cause high axial along with high radial vibrations. • Axial plane phase difference is 0º. Radial direction phase is unsteady.
  27. 27. Technology Training that Bent Shaft • Bend near centre: 1× is predominant • Bend at ends: 2× is predominant • No phase difference in radial direction at one location. • 180º phase difference in axial plane.
  28. 28. Technology Training that Misalignment • After unbalance, misalignment is the major cause for high vibrations. • Two kinds of misalignment: – Angular - shaft ends meet an angle. – Parallel - shaft ends are parallel but have an offset.
  29. 29. Technology Training that Angular Misalignment
  30. 30. Technology Training that • Predominant peak is 1× • 1×, 2 ×, 3 × may be present. • High axial vibration with 1 × and 2× • Axial phase difference across the coupling is 180º. Angular Misalignment
  31. 31. Technology Training that Bent Shaft - Angular Misalignment • Difference between angular misalignment and a bent shaft is differentiated only by phase difference. • In misalignment, phase difference is 180º across the coupling.
  32. 32. Technology Training that Parallel Misalignment
  33. 33. Technology Training that • The predominant peak is at 2× • Vibrations in radial direction are higher than in the axial direction. Parallel Misalignment
  34. 34. Technology Training that • Phase difference in radial direction across the coupling is 180º. Parallel Misalignment
  35. 35. Technology Training that Misaligned Bearing • Cocked bearing show high axial vibrations • Opposite ends have an axial plane phase difference of 180º. • FFT may show peaks of 1×, 2× and 3×
  36. 36. Technology Training that Misalignment - Orbits
  37. 37. Technology Training that Mechanical Looseness • Internal assembly looseness: – Bearing liner in its cap. – Sleeve or rolling element bearing. – Impeller on a shaft. • Looseness at machine to base plate interface: – Loose bolts. – Cracks in the frame structure or bearing pedestal. • Structure looseness: – Weakness of machine feet, baseplate or foundation. – Loose hold-down bolts, distortion of frame or base.
  38. 38. Technology Training that Internal Looseness • Phase is unstable. • Radial vibrations taken at 30º. Will see different spectrums for each (directional). • FFT will show harmonics of × or even ×.
  39. 39. Technology Training that Looseness at Machine to Base Plate interface
  40. 40. Technology Training that Structure Looseness • Measure each bolt, one at a time.
  41. 41. Technology Training that Resonance • Every body has a resonance frequency. • Frequency is dependant on mass, stiffness and damping. • Forced and free vibrations (e.g. ringing of bell). • Resonance is free vibrations. • Bump test is simple technique to find resonant frequency of stationary mass or system.
  42. 42. Technology Training that Bump Test
  43. 43. Technology Training that Thank You For Your Interest If you are interested in further training or information, please visit: OR Like us on Facebook: OR Follow us on Twitter: @IDCandEIT