1. Vibration Monitoring & Analysis

2. Vibration Monitoring What is Vibration ?
It is motion of mechanical parts back and forth from its position of rest /neutral position.

3. Vibration Monitoring What causes Vibration ? Induced Force &
Freedom for Movement

4. Harmful Effects of Excess vibration
Vibration Monitoring
Harmful Effects of Excess vibration
Increased load on BRGs: Reduced BRG Life
Higher Forces on Mountings:
Foundation Loosening and Damage of Support Structure
Increased Stresses of M/c : Risk of fatigue
components

5. Harmful Effects of Excess vibration
Vibration Monitoring
Harmful Effects of Excess vibration
Decreased Equipment efficiency.
Reduced Output Quality.
Increased Maintenance Cost due to more Component Failures and Unplanned Operations
Unsafe Operating Environment

6. Vibration Monitoring Problem Identifications
Unbalance
Misalignment
Mechanical Looseness
Antifriction / Sleeve Bearing Defects
Gear Defects

7. Vibration Monitoring Problem Identifications
Belt Defects
Impeller / Blade Defects
Bent Shaft
Electrical Problems
Resonance

8. Vibration Monitoring Fundamental Realities All Machines vibrate.
An increase in vibration level is a sign of trouble & amplitude of Vibration depends on the extent of defect in the machinery components
Each trouble will create vibration with different characteristics

9. VIBRATION FUNDAMENTALS90
Upper Limit
Neutral Position
180
TIME
Lower Limit
Period(T)
(1 complete cycle)
270

10. Characteristics of Vibration
Vibration characteristics are
Amplitude
Frequency Hz or CPM
Phase Angle or clock face
Displacement
Velocity
Acceleration

11. Parameter Selection Frequency sensitivity Displacement <600CPM
Velocity
600-60,000CPM
Acceleration
>60,000CPM
Spike Energy/SEE
Ultrasonic range

12. Frequency sensitivity

13. Vibration Monitoring
Displacement
Velocity
Acceleration

14. FFT FAST FOURIER TRANSFORM.
THE PROCESS OF TRANSFORMING TIME DOMAIN SIGNAL TO FREQUENCY DOMAIN.
THE TIME DOMAIN SIGNAL MUST
FIRST BE SAMPLED AND
DIGITIZED.

16. Time Domain - overall data is the sum of all exciting and reacting forces
Imbalance
Rolling
Element
Bearing
Coupling
chatter
Gearmesh
Time
Resultant Complex
Waveform

17. Enables precise evaluation of machinery condition and prediction
Spectrum Analysis
Enables precise evaluation of machinery condition and prediction

18. Fmax, LINES, AVERAGES.
Fmax REPRESENTS THE MAXIMUM FREQUENCY RANGE IN CPM OR HZ TO BE SCANNED BY THE INSTRUMENT.
Fmax SHOULD NOT BE SET TOO HIGH SO THAT THE RESOLUTION AND ACCURACY SUFFERS OR IT SHOULD NOT BE TOO LOW SO THAT WE MISS SOME IMPORTANT HIGH FREQUENCIES.

19. GUIDELINES FOR SETTING Fmax.
FOR MACHINES HAVING ANTI-FRICTION BEARINGS:- Fmax = 60 x RPM
FOR MACHINES HAVING SLEEVE BEARINGS:- Fmax = 20 x RPM
FOR GEAR BOXES:- Fmax = 3.25 x GMF

20. LINES OF RESOLUTION THE RESOLUTION IS THE NUMBER OF LINES
OR CELLS WHICH ARE USED TO CALCULATE AND DISPLAY THE FREQUENCY SPECTRUM.
THE BANDWIDTH CAN BE CALCULATED BY DIVIDING Fmax BY THE LINES OF RESOLUTION.
THE GREATER THE NUMBER OF LINES , THE BETTER IS THE ACCURACY.

21. FREQUENCY RESOLUTION = Fmax total lines of resolution
Bandwidth =
total lines of resolution
total lines of resolution
lines or bins or cells
of resolution
Amplitude
Fmax
Frequency

22. Spectrum Data Collection Time
FFT Calculation Time = Time to calculate FFT from Time Waveform [assuming no overlap processing]
(60) ( #FFT Lines) (#Averages)
FFT Calculation Time =
Frequency Span
Where: #FFT = Number of FFT Lines or Bins in Spectrum
# Averages = Number of Averages
Frequency Span measured in CPM

23. FFT SPECTRUM

24. OVERALL VIBRATION
Total summation of all the vibration,with no regard to any particular frequency.

25. OVERALL VIBRATION
Overall vibration is the total vibration energy measured within a frequency range. Measuring the “overall” vibration of a machine or component, a rotor in relation to a machine, or the structure of a machine, and comparing the overall measurement to its normal value (norm) indicates the current health of the machine. A higher than normal overall vibration reading indicates that “something” is causing the machine or component to vibrate more.

26. Overall Vibration Total summation of all the vibration,with no
regard to any particular frequency.
OA =
OA=Overall level of Vibration Spectrum , Ai = Amplitude of each FFT line
n = No. of FFT Lines of resolution , NBF= Noise Bandwidth for Window chosen 2 2 2
A A ………………………+An
NBF

27. NOTE: Don’t be concerned about the math, the condition monitoring instrument calculates the value. What’s important to remember is when comparing overall vibration signals, it is imperative that both signals be measured on the same frequency range and with the same scale factors.

28. What is Phase?
The position of a vibrating part at a given instant with reference to a fixed point or another vibrating part.
The part of a vibration cycle through which one part or object has moved relative to another part.
The unit of phase is degree where one complete cycle of vibration is 360 degrees.

29. Phase is a measurement, not a processing method
Phase is a measurement, not a processing method. Phase measures the angular difference between a known mark on a rotating shaft and the shaft’s vibration signal. This relationship provides valuable information on vibration amplitude levels,shaft orbit, and shaft position and is very useful for balancing and analysis purposes.

30. Vibration Phase

31. Additional
Illustration on
Phase

32. PHASE AN ILLUSTRATION 32 Micron 30 Micron 10 degrees 10 degrees
Shaft centre line moves up and down in a planer fashion

33. PHASE AN ILLUSTRATION 32 Micron 30 Micron 190 degrees 10 degrees
Shaft center line moves up and down in a rocking fashion

34. MACHINE TRAIN MISALIGNMENT
TURBINE
G/B
HP COMP
LP COMP
AXIAL PHASE
(degrees)
Note: All phase readings corrected for pickup direction

35. Comparing Overall Levels Across Mounting Interfaces

36. Phase application C B A A 5 Microns, 10 degrees
B 7 Microns, 12 degrees
C 25 Microns, 175 degrees
Bolt at C is loose

37. Vibration Analysis of
Common Problems

38. Vibration Analysis Unbalance
Amplitude proportional to the amount of unbalance
Vibration high normally in radial direction (may be also in axial direction incase of overhung and flexible rotors ).
1* RPM vibration is greater than 80% (normally) of the overall reading.

39. Vibration Analysis Unbalance
Horizontal and vertical 1* RPM amplitude should be nearly same, although it also depends on system rigidity on the particular direction.
Other frequency peaks may be less than 5% of the 1*RPM amplitude
Phase shift of 90 deg. When sensor moves from horizontal to vertical.

40. UNBALANCE
Operating conditions such as load, flow condition and temperature effect unbalance
Balance under normal operating conditions
Changes in track and pitch angle of fan blades can result in “Aerodynamic Unbalance”

41. Typical Spectrum For Unbalance

42. MISALIGNMENT BIGGEST PROBLEM INITIALLY
Operating temperature can affect alignment
Machines aligned cold can go out when warm
Bases or foundations can settle
Grouting can shrink or deteriorate
Increases energy demands

43. MISALIGNMENT Forces shared by driver and driven (not localized)
Level of misalignment severity is determined by the machines ability to withstand the misalignment
If coupling is stronger than bearing the bearing can fail with little damage to the coupling

44. Three Types of Misalignment
Combination (most common)
Angular
Parallel or Offset

45. General Characteristics Of Misalignment
Radial vibration is highly directional
1X, 2x, and 3x running speed depending on type and extent of misalignment
Angular 1x rpm axial
Parallel x rpm radial (H & V)
Combination 1,2,3x rpm radial and axial

46. Typical Spectrum for Misalignment

47. Vibration Analysis Misalignment
Angular Misalignment
High axial vibration
( Greater than 50% of the radial vibration)
1* , 2*, 3* RPM normally high.
180 deg. Out of phase across the coupling

48. Angular Misalignment Produces predominant 1x rpm component
Marked by 180 degree phase shift across the coupling in the axial direction

49. Vibration Analysis Misalignment
Off-Set Misalignment
High Axial vibration. Also shows high radial vibrations.
1*, 2*, 3* RPM high. 2* often larger than 1*
In case of severe misalignment, much high harmonics (4* - 8*) or even a whole series of high frequency harmonics will be generated.
180 deg. Out of phase across coupling

50. Parallel Or Offset Misalignment
Produces a predominant 2x rpm peak in the spectrum
Marked by 180 degree phase shift across the coupling in the radial direction.

51. Typical Spectrum for Misalignment

52. Axial Phase Showing Misalignment

53. Other Types Of Misalignment

54. Vibration Analysis Mechanical Looseness
Caused by structured looseness / weakness of machine feet, base plate or foundation; also by deteriorated grouting, loose base bolts and distortion of the frame or base.
Radial vibration high
2* RPM & 1* RPM dominant
180 deg. Phase differences between mating surfaces which have looseness between them.

55. Vibration Analysis Mechanical Looseness
Caused by structured looseness / weakness of machine feet, base plate or foundation; also by deteriorated grouting, loose base bolts and distortion of the frame or base.
Radial vibration high
2* RPM & 1* RPM dominant
180 deg. Phase differences between mating surfaces which have looseness between them.

56. Looseness
Looseness produces
2X RPM Freq.

57. Vibration Analysis Mechanical Looseness
Caused by looseness in bearing housing bolts and cracks in the frame structure.
Radial vibration high
2* RPM normally dominant. 0.5*, 1* and 3* RPM may also be present
Substantial Phase difference between mating surfaces which have looseness between them

58. LOOSENESS Not an exciting force
Allows exciting frequencies already present to exhibit much higher amplitudes
Loss or reduction in normal stiffness
Caused by:
loose mounting bolts
deterioration of grouting
cracked welds

59. Two Types Of Looseness Looseness of Rotating Components
Loose Rotors
Bearings Loose on the Shaft or in Housing
Excessive Sleeve Bearing Clearances
Looseness of Support System
Loose Mounting Bolts
Grouting Deterioration
Cracks
Poor Support
Frame Distortion

60. Looseness Of Rotating System
Rattling condition cause impacts due to excessive clearance in a rolling element or sleeve bearing
Impacts cause multiple running speed harmonics to appear in the spectra
Identified by:
multiple harmonics
unstable phase
highly directional radial vibration

61. Typical Spectrum for Looseness of Rotating System

62. Looseness Of Support System
FFT readings show 1x rpm, 2x rpm, and 3x rpm components
Structural looseness / weakness will cause high 1xrpm peak in FFT
Identified by
Highly directional radial vibration
Bouncing
Taking comparative phase readings across interfaces and look for amplitude variation
Typically loose in vertical direction

63. Looseness Of Support System

64. Modern Trend in
Vibration Technology

65. Condition Monitoring System Integration
WALKAROUND
OFF- LINE
Condition Monitoring System Integration
CENTRALISED
PROTECTION
DISTRIBUTED
CONTINUOUS
SURVEILLANCE
ON - LINE
PERIODIC
ON-LINE
ANALYSIS
NETWORK
DCS
SOFTWARE
PdM TECHNOLOGIES
CMMS

66. Overall Data Acquistion
4-20mA
MONITOR
THE DCS
time waveform
DCS OUTPUT

67. this is what the DCS records
Overall Data Trends-
this is what the DCS records
current value
changes over time
lo alarm
hi alarm
The limitation is that it does not adequately reflect changes at higher frequencies which can increase by 100% but only add 1% to the overall energy level

68. Vibration Analysis transducer time waveform Protection Monitor
and / or
Data Collector
Vibration Spectrum
time waveform
transducer

69. Band Alarms, associate with each rotating element
frequency bands
hi alarm
lo alarm

70. Band Trending, the new way forward
lo alarm
hi alarm
changes over time
Trend and alarm the:
Machine unbalance
Alignment
Gear mesh
Bearings etc

71. Emonitor Odyssey: spectrum band alarming though its diagnostic tools feature for both On & Off line gives advanced machinery analysis and reduces False Alarms

72. EMONITOR Odyssey: Frequency Band Trends
Frequency Trend of Single Measurement

73. DIAGNOSTICS - the advantage of frequency band trending
Root cause analysis is a complex machine specific exercise considering all eventualities
Expert systems are a one off diagnosis and do not show a trend
Frequency band trending is specific to root cause analysis
Band alarming also indicates vibration signals that are outside the established norms
Trending alignment, unbalance, gear meshing and bearing condition condition is more specific
A complex issue simplified without the need of specialist customisation and regular updates

74. DCS Limitations - Summary
We have shown that putting total belief in the DCS vibration trend is highly risky
Machinery failures still happen with on-line vibration monitoring with 4-20mA data to the DCS. Most causes are due to higher frequency signals swamped by the overall levels.
Advanced machinery protection through Frequency Band Trending and Alarming - more specific than an Expert system.
The latest S/w based Analysers incorporates Narrow Band Alarming. They offer machinery protection and narrow band alarming.
A lower cost solution is periodic manual Data Collection.

75. ESHAPE: Modal analysis using phase for advanced diagnosis and better understanding of system response

76. On line Vibration and other monitors
Innovative, fully-digital design
Exceeds API 670 specification
Widely-used system
Fully field programmable
Low installation cost
ModBus protocol

77. TYPICAL APPLICATION

78. POWER PLANT INTEGRATION
DCS
OPERATIONS
ENGINEERING
ODYSSEY
SERVER
DATA
LOGGER
VIBRATION ANALYSER FS HP LP
GEN EX
BFP ID
BFP FD
CWP PA
TURBINE SUPERVISORY
STATOR END WINDING
GATEWAY
TO CMMS
AUXILIARIES

79. Plant Integration with LAN or WAN
DCS
ENGINEERING
ODYSSEY
CLIENT SERVER
VIBRATION ANALYSER
ETHERNET
CONTROL ROOM No 1
CONTROL ROOM No 2
CONTROL ROOM No 3 FS HP LP
GEN EX FS HP LP
GEN EX FS HP LP
GEN EX
GATEWAY
TO CMMS
ANURAKSHAN
TG 1
TG 2
TG 3

80. NETWORKING THE INFORATION - LAN / WAN e.g.
RIHAND
TALCHER
PLANT OPERATIONS
VINDHYACHAL
NOIDA HQ CM CELL
GATEWAY
TO CMMS
ANURAKSHAN
KAYAMKULAM
UNCHAHAR

81. Hyperlink to equipment
Using PlantLink
Vibration Trend Plot
Digital Picture of Plant
Hyperlink to equipment
Hierarchy
Automatic notification on Equipment Alarm Status
Click on Measurement Label to link to plots or other views.

82. Information however you want it !

83. X-Window Screen Captures

84. Scenario of Instruments &Sensors & Probes
Velocity sensors are made in India
Accelerometers range over 150 types
standard
Low frequency
High temperature (Gas Turbines)
Special application
Eddy current probes - comprehensive range
Others available for process measurement

85. Vibration Datacollectors
Many vendors
Select on ‘Fitness for Purpose’
Intrinsic Safety
Dust & Moisture proof
Diagnostic Capability