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Basics of Vibration
Vibration theory & analysis
What is Vibration?
Vibration Terms
Time Waveform Analysis
complex time waveform
individual vibration signals
combine to form a complex
time waveform showing ...
Scale Factors
– When comparing overall vibration signals, it is
imperative that both signals be measured on the
same frequ...
Measurements & Units
Displacement (Distance)
mils or micrometer, mm
Velocity (Speed - Rate of change of displcmt)
in/sec o...
10 100 1,000 10,000
Frequency (Hz)
10
1.0
0.1
1
0.01
100
Displacement (microns)
Acceleration
(g's - 9,81m/sec2)
Velocity (...
Multi-Parameter Monitoring
Same Data in Velocity and Acceleration
Velocity
Spectrum
Acceleration
Spectrum
On the same bear...
Accelerometers
• Rugged Devices
• Operate in Wide Frequency
Range (Near 0 to above 40 kHz)
• Good High Frequency Response
...
What is vibration?
Complex signal?
FFT Signal Processing
Tim
e
Amplitude
Tim
e
Amplitude
Frequency
Amplitude
Narrow Bands with trend
T re n d o f
B a la n c e
A la rm
Amplitude
S u b -
H a rm o n ic 1 X 2 X B e a rin g B e a rin g ...
Alarm Types – Narrow Bands
A2 - 8.2.4. BPFI Pomp PNV
P1/K10 -PNV POMP NIET-KOPP VERTIKAAL
Label: BPFI with 1xrPM modulatio...
Overall Vibration
• The total vibration energy
measured within a specific
frequency range.
– includes a combination of all...
Alarm Types – Overall Alarm
• Look to the global vibration level
A2 - 8.2.4. BPFI Pomp PNV
P1/K10 -PNV POMP NIET-KOPP VERT...
Analyse of data: Spectra,
Waveform and Trends
Vibration
» -Imbalance
» -Misalignment
» -Looseness
» -Bearing problems
» -Belt problems
» -Gear problems
» -Lubrification...
Vibration analysis
• "Of all the parameters that can be measured non
intrusively in industry today, the one containing the...
SIGNATURE ANALYSISSIGNATURE ANALYSIS
• Which frequencies exist and what are the
relationships to the fundamental exciting
...
Vibration analysis
Unbalance
COUPLE UNBALANCECOUPLE UNBALANCE
• 1800 out of phase on the same shaft
• 1X RPM always present and normally dominates
• Am...
OVERHUNG ROTOR
UNBALANCE
OVERHUNG ROTOR
UNBALANCE
• 1X RPM present in radial and axial directions
• Axial readings tend to...
Diagnosing UnbalanceDiagnosing Unbalance
• Vibration frequency equals rotor
speed.
• Vibration predominantly RADIAL
in dir...
Vibration analysis
Misalignment/Bent shaft
ANGULAR
MISALIGNMENT
ANGULAR
MISALIGNMENT
• Characterized by high axial vibration
• 1800 phase change across the coupling
...
PARALLEL
MISALIGNMENT
PARALLEL
MISALIGNMENT
• High radial vibration 1800 out of phase
• Severe conditions give higher harm...
MISALIGNED BEARINGMISALIGNED BEARING
• Vibration symptoms similar to angular
misalignment
• Attempts to realign coupling o...
BENT SHAFTBENT SHAFT
• Bent shaft problems cause high axial vibration
• 1X RPM dominant if bend is near shaft center
• 2X ...
OTHER SOURCES OF HIGH
AXIAL VIBRATION
OTHER SOURCES OF HIGH
AXIAL VIBRATION
a. Bent Shafts
b. Shafts in Resonant Whirl
c. ...
Vibration analysis
Mechanical looseness
MECHANICAL
LOOSENESS (A)
MECHANICAL
LOOSENESS (A)
• Caused by structural looseness of machine feet
• Distortion of the bas...
MECHANICAL
LOOSENESS (B)
MECHANICAL
LOOSENESS (B)
• Caused by loose pillow block bolts
• Can cause 0.5, 1, 2 and 3X RPM
• ...
MECHANICAL
LOOSENESS (C)
MECHANICAL
LOOSENESS (C)
• Phase is often unstable
• Will have many harmonics
• Can be caused by ...
Vibration analysis
Sleeve bearing/Rotor rub
SLEEVE BEARING
WEAR / CLEARANCE
PROBLEMS
SLEEVE BEARING
WEAR / CLEARANCE
PROBLEMS
• Later stages of sleeve bearing wear wi...
ROTOR RUBROTOR RUB
• Similar spectrum to mechanical looseness
• Usually generates a series of frequencies which
may excite...
OIL WHIP INSTABILITYOIL WHIP INSTABILITY
• Oil whip may occur if a machine is operated at 2X the
rotor critical frequency....
OIL WHIRL
INSTABILITY
OIL WHIRL
INSTABILITY
• Usually occurs at 42 - 48 % of running speed
• Vibration amplitudes are some...
Resonance
typically 10% or greater
RESONANCERESONANCE
• Resonance occurs when the Forcing
Frequency coincides with a Natural
Frequency
• 1800 phase change oc...
BELT PROBLEMS (A)BELT PROBLEMS (A)
• Often 2X RPM is dominant
• Amplitudes are normally unsteady, sometimes pulsing with e...
BELT PROBLEMS (D)BELT PROBLEMS (D)
• High amplitudes can be present if the belt natural
frequency coincides with driver or...
HYDRAULIC AND
AERODYNAMIC FORCES
HYDRAULIC AND
AERODYNAMIC FORCES
• If gap between vanes and casing is not equal, Blade Pa...
HYDRAULIC AND
AERODYNAMIC FORCES
HYDRAULIC AND
AERODYNAMIC FORCES
• Flow turbulence often occurs in blowers due to variati...
HYDRAULIC AND
AERODYNAMIC FORCES
HYDRAULIC AND
AERODYNAMIC FORCES
• Cavitations will generate random, high frequency
broad...
BEAT VIBRATIONBEAT VIBRATION
• A beat is the result of two closely spaced frequencies going
into and out of phase
• The wi...
Vibration analysis
Electrical
ELECTRICAL PROBLEMSELECTRICAL PROBLEMS
• Stator problems generate high amplitudes at 2FL (2X line
frequency )
• Stator ecc...
• Electrical line frequency.(FL) = 50Hz = 3000 cpm.
60HZ = 3600 cpm
• No of poles. (P)
• Rotor Bar Pass Frequency (Fb) = N...
ELECTRICAL PROBLEMSELECTRICAL PROBLEMS
• Loose stator coils in synchronous motors generate high
amplitude at Coil Pass Fre...
ELECTRICAL PROBLEMSELECTRICAL PROBLEMS
• Phasing problems can cause excessive vibration at 2FL
with 1/3 FL sidebands
• Lev...
ELECTRICAL PROBLEMSELECTRICAL PROBLEMS
• 1X, 2X, 3X, RPM with pole pass frequency sidebands
indicates rotor bar problems.
...
Vibration analysis
Gear
CALCULATION OF GEAR
MESH FREQUENCIES
CALCULATION OF GEAR
MESH FREQUENCIES
20 TEETH20 TEETH
51 TEETH51 TEETH
1700 RPM1700 R...
GEARS
NORMAL SPECTRUM
GEARS
NORMAL SPECTRUM
• Normal spectrum shows 1X and 2X and gear mesh
frequency GMF
• GMF commonly w...
• Gear Mesh Frequencies are often sensitive to load
• High GMF amplitudes do not necessarily indicate a
problem
• Each ana...
GEARS
TOOTH WEAR
GEARS
TOOTH WEAR
• Wear is indicated by excitation of natural frequencies
along with sidebands of 1X RPM ...
GEARS
GEAR ECCENTRICITY AND BACKLASH
GEARS
GEAR ECCENTRICITY AND BACKLASH
• Fairly high amplitude sidebands around GMF sug...
GEARS
GEAR MISALIGNMENT
GEARS
GEAR MISALIGNMENT
• Gear misalignment almost always excites second order or
higher harmonics...
GEARS
CRACKED / BROKEN TOOTH
GEARS
CRACKED / BROKEN TOOTH
• A cracked or broken tooth will generate a high amplitude at
1X...
GEARS
HUNTING TOOTH
GEARS
HUNTING TOOTH
• Vibration is at low frequency and due to this can often be
missed
• Synonymous w...
Vibration analysis
Bearings
Outer Race
(BPFO)
Inner Race
(BPFI)
Ball Spin
(BSF)
Cage or Train FTF
D0
D1DB
Note : shaft turning outer race fixed
F = frequency in cpm
N = number of balls
BPFI = Nb/2 · (1+(Bd/Pd)cosӨ) · RPM...
ROLLING ELEMENT
BEARINGS STAGE 1 FAILURE MODE
ROLLING ELEMENT
BEARINGS STAGE 1 FAILURE MODE
• Earliest indications in the ...
ROLLING ELEMENT
BEARINGS STAGE 2 FAILURE MODE
ROLLING ELEMENT
BEARINGS STAGE 2 FAILURE MODE
• Slight defects begin to ring...
ROLLING ELEMENT
BEARINGS STAGE 3 FAILURE MODE
ROLLING ELEMENT
BEARINGS STAGE 3 FAILURE MODE
• Bearing defect frequencies a...
Examples
Singing Propeller
0 50 100 150 200 250 300 350 400
0
0.06
0.12
0.18
0.24
0.30
0.36
FrequencyinHz
RMSVelocityinmm/Sec
0 50 ...
LFPS 1 024
Route Spectrum
28-JUL-06 21:56:44
OVRALL= 2.79 V-DG
RMS = 2.76
LOAD = 100.0
RPM= 92.
RPS = 1.53
80 100 120 140 ...
Singing Propeller
Conclusion
After thorough measurements/analysis our conclusion is that the port side propeller suffers
f...
Bearing damage
SF8000.182 645 AKSEL REIMHJUL 1. LAGER RADIELL
Route Spectrum
10-MAY-05 12:07:36
OVRALL= 10.23 V-DG
RMS = 1...
Bearing damage
Trend Display
of
1. - 20. kHz
-- Baseline --
Value: 1.143
Date: 26-FEB-03
0 200 400 600 800 1000
0
0.5
1.0
...
FAG6322 (outer race)FAG6322 (outer race)
Bearing damage
Outer ring
SF8000.129 716 AKSELREIMHJUL 2. LAGER RADIELL
Route Spectrum
01-MAR-05 09:47:29
OVRALL= 15.10 V-...
Bearing damage
Outer ring
Observing powerful
increasement in the area 1-20
kHz (which represents the are
of bearing noise)...
Bearing damage
Outer ring (large transmission)
Observing increasement in the area
1-20 kHz (which represents the are of
be...
,
Trend Display
of
2. -20. kHz
-- Baseline --
Value: .00000
Date: 28-MAY-98
0 200 400 600 800 1000 1200
0
0.5
1.0
1.5
2.0
...
Bearing damage on inner race motor sideBearing damage on inner race motor side
Bearing damage on inner race drive sideBearing damage on inner race drive side
Bearing damage
Outer ring (thrust bearing)
Observing increasement in the area
1-20 kHz (which represents the are of
bearin...
Gear damage
Input crown wheel
Time-waveform indicates that there is
a pulsation on time per revolution.
This supports the ...
Gear damage
Intermediate shaft
,
WaveformDisplay
07-OCT-*3 13:16
RMS = .1089
LOAD = 100.0
RPM = 296.
RPS = 4.94
PK(+) = .7...
Broken tooth on the intermediate shaftBroken tooth on the intermediate shaft
Resonance problem
Case
On two main gears several tie-/anchor bolts for the pinion bearings on the first gear
step broken j...
rpm and a lower maximum gearmesh. In addition to this we also achieved to obtain
the power by increasing the pitch curve.
...
BSC - Port-gear-1500hz
Port-HF -V05 VERTIKALT
Analyze Spectrum
08-SEP-07 01:41:06
RMS = 29.24
LOAD = 86.0
RPM= 1100.
RPS =...
Unbalanced flexible coupling
• Initial vibration analysis revealed
mechanical unbalance in the coupling.
• Unbalance is indicated by a dominating
1.st ...
Generator with a unbalanced/damaged coupling elements
035 - GENERATOR 2
Gen 2 -P05 GENERATOR, DE,VERTIKAL
Route Spectrum
2...
The outer steel ring of the coupling was turned 180 degrees vs. the
rubber elements - wich in this case was the rebalancin...
Before vs. after dynamic balancing – reduced 1.st order
035 - GENERATOR 2
Gen 2 -P05 GENERATOR, DE,VERTIKAL
Route Spectrum...
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B. basic of vibration

  1. 1. Basics of Vibration Vibration theory & analysis
  2. 2. What is Vibration?
  3. 3. Vibration Terms
  4. 4. Time Waveform Analysis complex time waveform individual vibration signals combine to form a complex time waveform showing overall vibration frequency low freq. high freq. time overall vibration
  5. 5. Scale Factors – When comparing overall vibration signals, it is imperative that both signals be measured on the same frequency range and with the same scale factors.
  6. 6. Measurements & Units Displacement (Distance) mils or micrometer, mm Velocity (Speed - Rate of change of displcmt) in/sec or mm/sec Acceleration (Rate of change of velocity) G’s or in/sec2 or mm/sec2
  7. 7. 10 100 1,000 10,000 Frequency (Hz) 10 1.0 0.1 1 0.01 100 Displacement (microns) Acceleration (g's - 9,81m/sec2) Velocity (mm/sec) Common Machinery Operating Range Amplitude (microns, mm/sec, g’s Sensor Relationships
  8. 8. Multi-Parameter Monitoring Same Data in Velocity and Acceleration Velocity Spectrum Acceleration Spectrum On the same bearing cap, low freq. events (imbalance, misalignment, etc.) show best in the velocity spectrum; while high freq. events (bearing faults, gearmesh) show best in the acceleration spectrum
  9. 9. Accelerometers • Rugged Devices • Operate in Wide Frequency Range (Near 0 to above 40 kHz) • Good High Frequency Response • Some Models Suitable For High Temperature • Require Additional Electronics (may be built into the sensor housing)
  10. 10. What is vibration? Complex signal?
  11. 11. FFT Signal Processing Tim e Amplitude Tim e Amplitude Frequency Amplitude
  12. 12. Narrow Bands with trend T re n d o f B a la n c e A la rm Amplitude S u b - H a rm o n ic 1 X 2 X B e a rin g B e a rin g G e a rs B e a rin g 1 x 2 x .3 in /s e c .1 in /s e cT im e (D a y s ) T im e (D a y s ) T re n d o f B e a rin g s 1 0 x
  13. 13. Alarm Types – Narrow Bands A2 - 8.2.4. BPFI Pomp PNV P1/K10 -PNV POMP NIET-KOPP VERTIKAAL Label: BPFI with 1xrPM modulations. Route Spectrum 30-jan-96 15:14:51 OVERALL= 13.52 V-DG RMS = 13.46 LOAD = 100.0 RPM = 2987. (49.78 Hz) 0 500 1000 1500 2000 2500 0 2 4 6 8 10 12 14 Frequency in Hz RMSVelocityinmm/Sec Fault Limit Freq: Ordr: Spec: 475.00 9.542 .06356 Imbalance Misalignment Looseness Bearing
  14. 14. Overall Vibration • The total vibration energy measured within a specific frequency range. – includes a combination of all vibration signals within measured frequency range – does not include vibration signals outside measured frequency range – produces a numerical value
  15. 15. Alarm Types – Overall Alarm • Look to the global vibration level A2 - 8.2.4. BPFI Pomp PNV P1/K10 -PNV POMP NIET-KOPP VERTIKAAL Label: BPFI with 1xrPM modulations. Route Spectrum 30-jan-96 15:14:51 OVERALL= 13.52 V-DG RMS = 13.46 LOAD = 100.0 RPM = 2987. (49.78 Hz) 0 500 1000 1500 2000 2500 0 3 6 9 12 Frequency in Hz RMSVelocityinmm/Sec Fault Limit Freq: Ordr: Spec: 1321.9 26.55 .119
  16. 16. Analyse of data: Spectra, Waveform and Trends
  17. 17. Vibration » -Imbalance » -Misalignment » -Looseness » -Bearing problems » -Belt problems » -Gear problems » -Lubrification » -Electrical problems » -Resonance » -Sleeve Bearing problems » -Other
  18. 18. Vibration analysis • "Of all the parameters that can be measured non intrusively in industry today, the one containing the most information is the vibration signature." Art Crawford • Vibration Analysis is the foundation of a predictive maintenance program
  19. 19. SIGNATURE ANALYSISSIGNATURE ANALYSIS • Which frequencies exist and what are the relationships to the fundamental exciting frequencies. • What are the amplitudes of each peak • How do the peaks relate to each other • If there are significant peaks, what are their source
  20. 20. Vibration analysis Unbalance
  21. 21. COUPLE UNBALANCECOUPLE UNBALANCE • 1800 out of phase on the same shaft • 1X RPM always present and normally dominates • Amplitude varies with square of increasing speed • Can cause high axial as well as radial amplitudes • Balancing requires Correction in two planes at 180o
  22. 22. OVERHUNG ROTOR UNBALANCE OVERHUNG ROTOR UNBALANCE • 1X RPM present in radial and axial directions • Axial readings tend to be in-phase but radial readings might be unsteady • Overhung rotors often have both force and couple unbalance each of which may require correction
  23. 23. Diagnosing UnbalanceDiagnosing Unbalance • Vibration frequency equals rotor speed. • Vibration predominantly RADIAL in direction. • Stable vibration phase measurement. • Vibration increases as square of speed. • Vibration phase shifts in direct proportion to measurement direction. 900 900
  24. 24. Vibration analysis Misalignment/Bent shaft
  25. 25. ANGULAR MISALIGNMENT ANGULAR MISALIGNMENT • Characterized by high axial vibration • 1800 phase change across the coupling • Typically high 1 and 2 times axial vibration • Not unusual for 1, 2 or 3X RPM to dominate • Symptoms could indicate coupling problems
  26. 26. PARALLEL MISALIGNMENT PARALLEL MISALIGNMENT • High radial vibration 1800 out of phase • Severe conditions give higher harmonics • 2X RPM often larger than 1X RPM • Similar symptoms to angular misalignment • Coupling design can influence spectrum shape and amplitude RadialRadial 1x1x 2x2x 4x4x
  27. 27. MISALIGNED BEARINGMISALIGNED BEARING • Vibration symptoms similar to angular misalignment • Attempts to realign coupling or balance the rotor will not alleviate the problem. • Will cause a twisting motion with approximately 1800 phase shift side to side or top to bottom
  28. 28. BENT SHAFTBENT SHAFT • Bent shaft problems cause high axial vibration • 1X RPM dominant if bend is near shaft center • 2X RPM dominant if bend is near shaft ends • Phase difference in the axial direction will tend towards 1800 difference
  29. 29. OTHER SOURCES OF HIGH AXIAL VIBRATION OTHER SOURCES OF HIGH AXIAL VIBRATION a. Bent Shafts b. Shafts in Resonant Whirl c. Bearings Cocked on the Shaft d. Resonance of Some Component in the Axial Direction e. Worn Thrust Bearings f. Worn Helical or Bevel Gears g. A Sleeve Bearing Motor Hunting for its Magnetic Center h. Couple Component of a Dynamic Unbalance
  30. 30. Vibration analysis Mechanical looseness
  31. 31. MECHANICAL LOOSENESS (A) MECHANICAL LOOSENESS (A) • Caused by structural looseness of machine feet • Distortion of the base will cause “soft foot” problems • Phase analysis will reveal aprox 1800 phase shift in the vertical direction between the base plate components of the machine
  32. 32. MECHANICAL LOOSENESS (B) MECHANICAL LOOSENESS (B) • Caused by loose pillow block bolts • Can cause 0.5, 1, 2 and 3X RPM • Sometimes caused by cracked frame structure or bearing block
  33. 33. MECHANICAL LOOSENESS (C) MECHANICAL LOOSENESS (C) • Phase is often unstable • Will have many harmonics • Can be caused by a loose bearing liner, excessive bearing clearance or a loose impeller on a shaft
  34. 34. Vibration analysis Sleeve bearing/Rotor rub
  35. 35. SLEEVE BEARING WEAR / CLEARANCE PROBLEMS SLEEVE BEARING WEAR / CLEARANCE PROBLEMS • Later stages of sleeve bearing wear will give a large family of harmonics of running speed • A minor unbalance or misalignment will cause high amplitudes when excessive bearing clearances are present
  36. 36. ROTOR RUBROTOR RUB • Similar spectrum to mechanical looseness • Usually generates a series of frequencies which may excite natural frequencies • Sub harmonic frequencies may be present • Rub may be partial or through a complete revolution. Truncated waveform
  37. 37. OIL WHIP INSTABILITYOIL WHIP INSTABILITY • Oil whip may occur if a machine is operated at 2X the rotor critical frequency. • When the rotor drives up to 2X critical, whirl is close to critical and excessive vibration will stop the oil film from supporting the shaft. • Whirl speed will lock onto rotor critical. If the speed is increased the whip frequency will not increase. oil whirl oil whip
  38. 38. OIL WHIRL INSTABILITY OIL WHIRL INSTABILITY • Usually occurs at 42 - 48 % of running speed • Vibration amplitudes are sometimes severe • Whirl is inherently unstable, since it increases centrifugal forces therefore increasing whirl forces
  39. 39. Resonance typically 10% or greater
  40. 40. RESONANCERESONANCE • Resonance occurs when the Forcing Frequency coincides with a Natural Frequency • 1800 phase change occurs when shaft speed passes through resonance • High amplitudes of vibration will be present when a system is in resonance
  41. 41. BELT PROBLEMS (A)BELT PROBLEMS (A) • Often 2X RPM is dominant • Amplitudes are normally unsteady, sometimes pulsing with either driver or driven RPM • Wear or misalignment in timing belt drives will give high amplitudes at the timing belt frequency • Belt frequencies are below the RPM of either the driver or the driven • Often 2X RPM is dominant • Amplitudes are normally unsteady, sometimes pulsing with either driver or driven RPM • Wear or misalignment in timing belt drives will give high amplitudes at the timing belt frequency • Belt frequencies are below the RPM of either the driver or the driven WORN, LOOSE OR MISMATCHED BELTSWORN, LOOSE OR MISMATCHED BELTS BELT FREQUENCY HARMONICS
  42. 42. BELT PROBLEMS (D)BELT PROBLEMS (D) • High amplitudes can be present if the belt natural frequency coincides with driver or driven RPM • Belt natural frequency can be changed by altering the belt tension • High amplitudes can be present if the belt natural frequency coincides with driver or driven RPM • Belt natural frequency can be changed by altering the belt tension BELT RESONANCEBELT RESONANCE RADIAL 1X RPM BELT RESONANCE
  43. 43. HYDRAULIC AND AERODYNAMIC FORCES HYDRAULIC AND AERODYNAMIC FORCES • If gap between vanes and casing is not equal, Blade Pass Frequency may have high amplitude • High BPF may be present if impeller wear ring seizes on shaft • Eccentric rotor can cause amplitude at BPF to be excessive • If gap between vanes and casing is not equal, Blade Pass Frequency may have high amplitude • High BPF may be present if impeller wear ring seizes on shaft • Eccentric rotor can cause amplitude at BPF to be excessive BPF = BLADE PASS FREQUENCY
  44. 44. HYDRAULIC AND AERODYNAMIC FORCES HYDRAULIC AND AERODYNAMIC FORCES • Flow turbulence often occurs in blowers due to variations in pressure or velocity of air in ducts • Random low frequency vibration will be generated, possibly in the 50 - 2000 CPM range • Flow turbulence often occurs in blowers due to variations in pressure or velocity of air in ducts • Random low frequency vibration will be generated, possibly in the 50 - 2000 CPM range FLOW TURBULENCEFLOW TURBULENCE
  45. 45. HYDRAULIC AND AERODYNAMIC FORCES HYDRAULIC AND AERODYNAMIC FORCES • Cavitations will generate random, high frequency broadband energy superimposed with BPF harmonics • Normally indicates inadequate suction pressure • Erosion of impeller vanes and pump casings may occur if left unchecked • Sounds like gravel passing through pump • Cavitations will generate random, high frequency broadband energy superimposed with BPF harmonics • Normally indicates inadequate suction pressure • Erosion of impeller vanes and pump casings may occur if left unchecked • Sounds like gravel passing through pump CAVITATIONCAVITATION
  46. 46. BEAT VIBRATIONBEAT VIBRATION • A beat is the result of two closely spaced frequencies going into and out of phase • The wideband spectrum will show one peak pulsating up and down • The difference between the peaks is the beat frequency which itself will be present in the wideband spectrum • A beat is the result of two closely spaced frequencies going into and out of phase • The wideband spectrum will show one peak pulsating up and down • The difference between the peaks is the beat frequency which itself will be present in the wideband spectrum WIDEBAND SPECTRUM ZOOM SPECTRUM F1 F2
  47. 47. Vibration analysis Electrical
  48. 48. ELECTRICAL PROBLEMSELECTRICAL PROBLEMS • Stator problems generate high amplitudes at 2FL (2X line frequency ) • Stator eccentricity produces uneven stationary air gap, vibration is very directional • Soft foot can produce an eccentric stator STATOR ECCENTRICITY, SHORTED LAMINATIONSSTATOR ECCENTRICITY, SHORTED LAMINATIONS AND LOOSE IRONAND LOOSE IRON
  49. 49. • Electrical line frequency.(FL) = 50Hz = 3000 cpm. 60HZ = 3600 cpm • No of poles. (P) • Rotor Bar Pass Frequency (Fb) = No of rotor bars x Rotor rpm. • Synchronous speed (Ns) = 2xFL) • Slip frequency ( FS )= Synchronous speed – Rotor rpm. • Pole pass frequency (FP )= Slip Frequency x No of Poles. •• Electrical line frequency.(Electrical line frequency.(FLFL) =) = 50Hz = 3000 cpm.50Hz = 3000 cpm. 60HZ = 36060HZ = 3600 cpm0 cpm •• No of poles.No of poles. ((PP)) •• Rotor Bar Pass Frequency (Rotor Bar Pass Frequency (FbFb) =) = No of rotor bars x Rotor rpm.No of rotor bars x Rotor rpm. •• Synchronous speed (Synchronous speed (NsNs)) == 2xFL2xFL)) •• Slip frequency (Slip frequency ( FFSS )=)= Synchronous speedSynchronous speed –– Rotor rpm.Rotor rpm. •• Pole pass frequency (Pole pass frequency (FFPP )=)= Slip Frequency x No of Poles.Slip Frequency x No of Poles. FREQUENCIES PRODUCED BY ELECTRICAL MOTORS. FREQUENCIES PRODUCED BY ELECTRICAL MOTORS. PP
  50. 50. ELECTRICAL PROBLEMSELECTRICAL PROBLEMS • Loose stator coils in synchronous motors generate high amplitude at Coil Pass Frequency • The coil pass frequency will be surrounded by 1X RPM sidebands SYNCHRONOUS MOTORSYNCHRONOUS MOTOR (Loose Stator Coils)(Loose Stator Coils)
  51. 51. ELECTRICAL PROBLEMSELECTRICAL PROBLEMS • Phasing problems can cause excessive vibration at 2FL with 1/3 FL sidebands • Levels at 2FL can exceed 25 mm/sec if left uncorrected • Particular problem if the defective connector is only occasionally making contact POWER SUPPLY PHASE PROBLEMSPOWER SUPPLY PHASE PROBLEMS (Loose Connector)(Loose Connector)
  52. 52. ELECTRICAL PROBLEMSELECTRICAL PROBLEMS • 1X, 2X, 3X, RPM with pole pass frequency sidebands indicates rotor bar problems. • 2X line frequency sidebands on rotor bar pass frequency (RBPF) indicates loose rotor bars. • Often high levels at 2X & 3X rotor bar pass frequency and only low level at 1X rotor bar pass frequency. ROTOR PROBLEMSROTOR PROBLEMS
  53. 53. Vibration analysis Gear
  54. 54. CALCULATION OF GEAR MESH FREQUENCIES CALCULATION OF GEAR MESH FREQUENCIES 20 TEETH20 TEETH 51 TEETH51 TEETH 1700 RPM1700 RPM 31 TEETH31 TEETH HOW MANY TEETH ON THIS GEAR?HOW MANY TEETH ON THIS GEAR? 8959 RPM8959 RPM
  55. 55. GEARS NORMAL SPECTRUM GEARS NORMAL SPECTRUM • Normal spectrum shows 1X and 2X and gear mesh frequency GMF • GMF commonly will have sidebands of running speed • All peaks are of low amplitude and no natural frequencies are present 14 teeth 8 teeth GMF= 21k CPM 2625 rpm 1500 rpm
  56. 56. • Gear Mesh Frequencies are often sensitive to load • High GMF amplitudes do not necessarily indicate a problem • Each analysis should be performed with the system at maximum load GEARS TOOTH LOAD GEARS TOOTH LOAD
  57. 57. GEARS TOOTH WEAR GEARS TOOTH WEAR • Wear is indicated by excitation of natural frequencies along with sidebands of 1X RPM of the bad gear • Sidebands are a better wear indicator than the GMF • GMF may not change in amplitude when wear occurs 14 teeth 1500 rpm 8 teeth 2625 rpm GMF = 21k CPM
  58. 58. GEARS GEAR ECCENTRICITY AND BACKLASH GEARS GEAR ECCENTRICITY AND BACKLASH • Fairly high amplitude sidebands around GMF suggest eccentricity, backlash or non parallel shafts • The problem gear will modulate the sidebands • Incorrect backlash normally excites gear natural frequency
  59. 59. GEARS GEAR MISALIGNMENT GEARS GEAR MISALIGNMENT • Gear misalignment almost always excites second order or higher harmonics with sidebands of running speed • Small amplitude at 1X GMF but higher levels at 2X and 3X GMF • Important to set Fmax high enough to capture at least 2X GMF
  60. 60. GEARS CRACKED / BROKEN TOOTH GEARS CRACKED / BROKEN TOOTH • A cracked or broken tooth will generate a high amplitude at 1X RPM of the gear • It will excite the gear natural frequency which will be sidebanded by the running speed fundamental • Best detected using the time waveform • Time interval between impacts will be the reciprocal of the 1X RPM TIME WAVEFORM
  61. 61. GEARS HUNTING TOOTH GEARS HUNTING TOOTH • Vibration is at low frequency and due to this can often be missed • Synonymous with a growling sound • The effect occurs when the faulty pinion and gear teeth both enter mesh at the same time • Faults may be due to faulty manufacture or mishandling fHt = (GMF)Na (TGEAR)(TPINION)
  62. 62. Vibration analysis Bearings Outer Race (BPFO) Inner Race (BPFI) Ball Spin (BSF) Cage or Train FTF
  63. 63. D0 D1DB Note : shaft turning outer race fixed F = frequency in cpm N = number of balls BPFI = Nb/2 · (1+(Bd/Pd)cosӨ) · RPM BPFO = Nb/2 · (1-(Bd/Pd)cosӨ) · RPM BSF = Pd/2Bd · (1-((Bd/Pd)cosӨ)2) · RPM FTF = ½ (1-((Bd/Pd)cosӨ)) · RPM
  64. 64. ROLLING ELEMENT BEARINGS STAGE 1 FAILURE MODE ROLLING ELEMENT BEARINGS STAGE 1 FAILURE MODE • Earliest indications in the ultrasonic range • These frequencies evaluated by Spike EnergyTM gSE, HFD(g) and Shock Pulse • Spike Energy may first appear at about 0.25 gSE for this first stage gSE ZONE BZONE A ZONE C ZONE D
  65. 65. ROLLING ELEMENT BEARINGS STAGE 2 FAILURE MODE ROLLING ELEMENT BEARINGS STAGE 2 FAILURE MODE • Slight defects begin to ring bearing component natural frequencies • These frequencies occur in the range of 30k-120k CPM • At the end of Stage 2, sideband frequencies appear above and below natural frequency • Spike Energy grows e.g. 0.25-0.50gSE ZONE A ZONE B ZONE C ZONE D gSE
  66. 66. ROLLING ELEMENT BEARINGS STAGE 3 FAILURE MODE ROLLING ELEMENT BEARINGS STAGE 3 FAILURE MODE • Bearing defect frequencies and harmonics appear • Many defect frequency harmonics appear with wear the number of sidebands grow • Wear is now visible and may extend around the periphery of the bearing • Spike Energy increases to between 0.5 -1.0 gSE ZONE A ZONE B ZONE C ZONE D gSE
  67. 67. Examples
  68. 68. Singing Propeller 0 50 100 150 200 250 300 350 400 0 0.06 0.12 0.18 0.24 0.30 0.36 FrequencyinHz RMSVelocityinmm/Sec 0 50 100 150 200 250 300 350 400 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 FrequencyinHz RMSVelocityinmm/Sec Starboard side Port side
  69. 69. LFPS 1 024 Route Spectrum 28-JUL-06 21:56:44 OVRALL= 2.79 V-DG RMS = 2.76 LOAD = 100.0 RPM= 92. RPS = 1.53 80 100 120 140 160 180 200 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 FrequencyinHz RMSVelocityinmm/Sec Freq: Ordr: Spec: Dfrq: 142.28 93.24 .186 1.534 •• Sideband activity around theSideband activity around the troubled frequency (140 Hz)troubled frequency (140 Hz) •• The modulation/sidebandThe modulation/sideband activity tells us that theactivity tells us that the troubled frequency is workingtroubled frequency is working along with the rpm of thealong with the rpm of the shaft.shaft. •• Dfrq (Delta frequency) =Dfrq (Delta frequency) = 1.534 Hz (*60sec)= 92 RPM1.534 Hz (*60sec)= 92 RPM •• 92 rpm = shaft speed when92 rpm = shaft speed when measurements were taken.measurements were taken. Singing Propeller Describing the frequency spectra
  70. 70. Singing Propeller Conclusion After thorough measurements/analysis our conclusion is that the port side propeller suffers from a phenomenon called a singing propeller. The conclusion is justified by: • A frequency of approximately 140 Hz is causing the noise/vibration. • This frequency is independent from rpm within the troubled range of propeller revolution (60-105 rpm). • The ~140 Hz frequency only appears on the port side propeller shaft. This was confirmed by single propeller transit on both starboard and port side. • The ~140 Hz frequency measured has sideband (modulation) which is directly connected to the speed of the port side shaft. This indicates that the troubled frequency is situated somewhere along this shaft. • There is no other “rpm independent” component along port side shaft line that can be a source to this frequency. The size and weight to the propeller can possibly fit to the “singing” frequency. Recommendation Grinding an anti singing edge on the propeller. Result: The grinding of the propeller blades were carried out and the singing tone disappeared
  71. 71. Bearing damage SF8000.182 645 AKSEL REIMHJUL 1. LAGER RADIELL Route Spectrum 10-MAY-05 12:07:36 OVRALL= 10.23 V-DG RMS = 1.71 LOAD = 100.0 RPM= 2937. RPS = 48.95 0 20 40 60 80 100 0 0.2 0.4 0.6 0.8 1.0 Frequencyin Order RMSAccelerationinG-s Ordr: Freq: Spec: 5.436 266.08 .03517 >FAG 6322 F=BPFI : 5.44 F F F F F F F F F F SF8000.182 645 AKSEL REIMHJUL 1. LAGER RADIELL Route Spectrum 10-MAY-05 12:07:36 OVRALL= 10.23 V-DG RMS = 1.71 LOAD = 100.0 RPM= 2937. RPS = 48.95 0 20 40 60 80 100 0 0.2 0.4 0.6 0.8 1.0 Frequencyin Order RMSAccelerationinG-s Ordr: Freq: Spec: 3.540 173.27 .01331 >FAG 6322 E=BPFO : 3.56 E E E E E E E E E E Observing frequencies that matches ball pass frequencies inner race (fault frequencies BPFI) on bearing FAG 6322 Observing frequencies that matches ball pass frequencies outer race (fault frequencies BPFO) on bearing FAG 6322
  72. 72. Bearing damage Trend Display of 1. - 20. kHz -- Baseline -- Value: 1.143 Date: 26-FEB-03 0 200 400 600 800 1000 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 Days: 10-JAN-03 To 10-MAY-05 RMSAccelerationinG-s Date: Time: Ampl: 10-MAY-05 12:07:40 4.281 OFF ROUTE ORP OFF ROUTE MEASUREMENTPOINTDATA Label: WF 63 1RER-1 / Route Spectrum 10-MAY-05 12:09:49 (Demod-HP 1000 Hz) OVRALL= 1.49 A-DG RMS = 1.50 LOAD = 100.0 RPM= 2937. RPS = 48.95 0 2 4 6 8 10 12 14 16 18 20 22 0 0.2 0.4 0.6 0.8 1.0 Frequencyin Order RMSAccelerationinG-s Ordr: Freq: Spec: 5.433 265.94 .715 >FAG 6322 F=BPFI : 5.44 F F F Observing powerful increasement in the area 1-20 kHz (which represents the are of bearing noise) This supports the assumption of a bearing damage under development Also the demodulated measurement indicates fault frequencies from the bearing inner ring on bearing FAG 6322
  73. 73. FAG6322 (outer race)FAG6322 (outer race)
  74. 74. Bearing damage Outer ring SF8000.129 716 AKSELREIMHJUL 2. LAGER RADIELL Route Spectrum 01-MAR-05 09:47:29 OVRALL= 15.10 V-DG RMS = 4.14 LOAD = 100.0 RPM= 2622. RPS = 43.70 0 1000 2000 3000 4000 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 FrequencyinHz RMSAccelerationinG-s Freq: Ordr: Spec: 300.17 6.869 .00788 >SKF NU2224 E=BPFO : 299.6 E E E E E E E E E E SF8000.129 716 AKSELREIMHJUL 2. LAGER RADIELL Trend Display of 1. -20. kHz -- Baseline -- Value: .986 Date: 03-FEB-03 0 100 200 300 400 500 600 700 800 0 1 2 3 4 5 6 7 Days: 03-FEB-03 To 01-MAR-05 RMSAccelerationinG-s ALERT FAULT Date: Time: Ampl: 01-MAR-05 09:47:37 5.531 Observing powerful increasement in the area 1-20 kHz (which represents the are of bearing noise) This supports the assumption of a bearing damage under development Observing frequencies that matches ball pass frequencies outer race (fault frequencies BPFO) on bearing SKF NU2224
  75. 75. Bearing damage Outer ring Observing powerful increasement in the area 1-20 kHz (which represents the are of bearing noise) This supports the assumption of a bearing damage under development Observing frequencies that matches ball pass frequencies outer race (fault frequencies BPFO) on bearing TMK HH840200 (HH840249/210) 003 - GEAR SN: 61.88.6032.01.01 G0008 -086 GEAR,INNG.AKS 1.LAGER RADIAL Route Spectrum 06-JUN-05 21:04:14 OVRALL= 21.82 V-DG RMS = 6.58 LOAD =1550.0 RPM= 1505. RPS = 25.09 0 1000 2000 3000 4000 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 2.7 Frequencyin Hz RMSAccelerationinG-s Freq: Ordr: Spec: 255.02 10.17 .102 >TMK HH840210/249 E=BPFO : 256.5 E E E E E E E E 003 - GEAR SN: 61.88.6032.01.01 G0008 -086 GEAR,INNG.AKS 1.LAGER RADIAL Trend Display of 1. - 20. kHz -- Baseline -- Value: 2.937 Date: 12-MAR-03 0 200 400 600 800 1000 0 1 2 3 4 5 6 7 8 Days: 09-JAN-03 To 06-JUN-05 RMSAccelerationinG-s Date: Time: Ampl: 06-JUN-05 21:04:15 6.656
  76. 76. Bearing damage Outer ring (large transmission) Observing increasement in the area 1-20 kHz (which represents the are of bearing noise) This supports the assumption of a bearing damage under development , Trend Display of 2. -20. kHz -- Baseline -- Value: .00000 Date: 28-MAY-98 0 200 400 600 800 1000 1200 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Days: 09-JAN-02 To 03-JAN-05 RMSAccelerationinG-s ALERT FAULT Date: Time: Ampl: 09-JAN-02 11:03:24 .340 , Trend Display of 2. -20. kHz -- Baseline -- Value: .00000 Date: 28-MAY-98 0 200 400 600 800 1000 1200 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Days: 09-JAN-02 To 03-JAN-05 RMSAccelerationinG-s ALERT FAULT Date: Time: Ampl: 03-JAN-05 14:04:35 .551 Observing powerful increasement in the area 1-20 kHz (which represents the are of bearing noise) This supports the assumption of a bearing damage under development Input shaft motor side Input shaft drive side
  77. 77. , Trend Display of 2. -20. kHz -- Baseline -- Value: .00000 Date: 28-MAY-98 0 200 400 600 800 1000 1200 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Days: 09-JAN-02 To 03-JAN-05 RMSAccelerationinG-s ALERT FAULT Date: Time: Ampl: 09-JAN-02 11:03:24 .340 Bearing damage Outer ring (large transmission) Points of observedPoints of observed damages on same type ofdamages on same type of bearingbearing Due to earlier observation in this trending tool on this particuDue to earlier observation in this trending tool on this particularlar shaft, our conclusion is that there is a bearing damage.shaft, our conclusion is that there is a bearing damage.
  78. 78. Bearing damage on inner race motor sideBearing damage on inner race motor side
  79. 79. Bearing damage on inner race drive sideBearing damage on inner race drive side
  80. 80. Bearing damage Outer ring (thrust bearing) Observing increasement in the area 1-20 kHz (which represents the are of bearing noise) This supports the assumption of a bearing damage under development Route Spectrum 03-NOV-*3 14:37 OVRALL= 18.24 V-DG RMS = 2.30 LOAD = 100.0 RPM = 1500. RPS = 25.00 0 400 800 1200 1600 2000 0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 2.4 Frequency in Hz RMSAccelerationinG-s Freq: Ordr: Spec: 247.50 9.900 1.047 >SKF NU1026 E=BPFO E E E E E E E E Trend Display of 1. - 20. kHz -- Baseline -- Value: .00000 Date: 16-JUL-96 0 100 200 300 400 500 600 700 0 2 4 6 8 10 12 Days: 22-JAN-*2 To 03-NOV-*3 RMSAccelerationinG-s ALERT FAULT Date: Time: Ampl: 03-NOV-*3 14:37:54 9.625 Observing frequencies that matches ball pass frequencies outer race (fault frequencies BPFO) on bearing SKF NU1026
  81. 81. Gear damage Input crown wheel Time-waveform indicates that there is a pulsation on time per revolution. This supports the assumption of a gear damage. Possible broken tooth. Observing harmonic rpm frequencies on the input shaft of this gear , Route Spectrum 03-FEB-04 14:37:03 OVRALL= 3.31 V-DG RMS = .4406 LOAD = 100.0 RPM= 278. RPS = 4.63 0 100 200 300 400 500 600 700 0 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 FrequencyinHz RMSAccelerationinG-s Freq: Ordr: Spec: 25.19 5.437 .02161 Time in mSecs AccelerationinG-s 0 40 80 120 160 200 240 Plot Span -4 4 29-NOV-02 13:34:02 12-JUN-03 12:04:11 12-SEP-03 11:49:13 07-OCT-03 13:09:16 08-JAN-04 12:22:13 03-FEB-04 14:26:02 Time: Ampl: 32.15 -.906
  82. 82. Gear damage Intermediate shaft , WaveformDisplay 07-OCT-*3 13:16 RMS = .1089 LOAD = 100.0 RPM = 296. RPS = 4.94 PK(+) = .7243 PK(-) = .8067 CRESTF= 7.41 0 100 200 300 400 500 600 -1.0 -0.8 -0.6 -0.4 -0.2 -0.0 0.2 0.4 0.6 0.8 1.0 Time in mSecs AccelerationinG-s Time: Ampl: Dtim; Freq: 240.57 .559 195.61 5.112 , Route Spectrum 07-OCT-*3 13:20 (Demod- HP 500 Hz) OVRALL= .0701 A-DG RMS = .0700 LOAD = 100.0 RPM = 76. RPS = 1.27 0 5 10 15 20 25 30 35 40 45 50 0 0.01 0.02 0.03 0.04 Frequencyin Hz RMSAccelerationinG-s Freq: Ordr: Spec: 5.094 3.998 .02843 Time-waveform indicates that there is a pulsation on time per revolution. This supports the assumption of a gear damage. Demodulated measurement shows that there is a harmonic frequency of 5.094 Hz. 5.094 Hz x 60 Hz = ~300 RPM which is close to the intermediate shaft speed. Therefore it is likely to believe that there is a tooth damage on this shaft
  83. 83. Broken tooth on the intermediate shaftBroken tooth on the intermediate shaft
  84. 84. Resonance problem Case On two main gears several tie-/anchor bolts for the pinion bearings on the first gear step broken just after a couple of hundred hours, and therefore Maskindynamikk AS was engaged to identify and analyze the vibration in these two gears. It was soon discovered to be abnormally high levels of vibration in a specific speed-/load area around these bolts (close to maximum speed), and these vibrations were amplified by the gearmesh frequencies of the input shaft. This was the first observation that pointed in the direction of a possible resonance – problem Additional examination was therefore carried out to identity this resonance-problem. An element analysis was carried out to sort which of the gear components had natural frequencies in this frequency range (resonant area). This was not a easy case as more than one component could be involved in this. Thru this investigation it was revealed that the bolts had radial natural frequencies which were amplified (excited) by 1st level gearmesh frequency. The resolution to the problem was therefore divided in two. First stage involved redesigning and replacing the bolts with others with lower natural frequencies, and thereafter to change the propeller curve so that we achieve a lower maximum
  85. 85. rpm and a lower maximum gearmesh. In addition to this we also achieved to obtain the power by increasing the pitch curve. BSC - Port-gear-1500hz Port-HF -V05 VERTIKALT Analyze Spectrum 08-SEP-07 00:48:28 RMS = 8.38 LOAD = 73.0 RPM= 1050. RPS = 17.50 0 400 800 1200 1600 0 2 4 6 8 10 FrequencyinHz RMSVelocityinmm/Sec Freq: Ordr: Spec: 716.90 40.97 6.594 BSC - Port-gear-1500hz Port-HF -V05 VERTIKALT Analyze Spectrum 08-SEP-07 01:00:27 RMS = 23.05 LOAD = 80.0 RPM= 1080. RPS = 18.00 0 400 800 1200 1600 0 2 4 6 8 10 12 14 16 18 FrequencyinHz RMSVelocityinmm/Sec Freq: Ordr: Spec: 735.77 40.88 13.37 The two engines is running at 1060 rpm which gives a gearmesh of 718 Hz with a amplitude of 6.7 mm/s. This is normal The two engines is running at 1080 rpm which gives a gearmesh of 736 Hz with a amplitude of 13.4 mm/s. An 2.5% increasement on the gearmesh frequency doubles the amplitude, and this clearly indicates a resonance problem
  86. 86. BSC - Port-gear-1500hz Port-HF -V05 VERTIKALT Analyze Spectrum 08-SEP-07 01:41:06 RMS = 29.24 LOAD = 86.0 RPM= 1100. RPS = 18.33 0 400 800 1200 1600 2000 0 3 6 9 12 15 18 21 24 27 30 33 FrequencyinHz RMSVelocityinmm/Sec Freq: Ordr: Spec: 753.53 41.10 26.38 BSC - Port-gear-1500hz Port-HF -V05 VERTIKALT Analyze Spectrum 16-SEP-07 10:04:08 RMS = 2.59 LOAD = 15.0 RPM= 600. RPS = 10.00 0 200 400 600 800 1000 1200 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 FrequencyinHz RMSVelocityinmm/Sec 722.55 836.46 Freq: Ordr: Spec: 837.00 83.70 .220 The two engines is running at 1100 rpm which gives a gearmesh of 753 Hz with a amplitude of 26.4 mm/s. An 5.8% increasement on the gearmesh frequency increases the amplitude four times, and this definitely indicates a resonance problem The two engines is running at low and variable rpm with 1st order gearmesh around 350-400 Hz. This gives a 2nd order gearmesh frequency in the are 700-850 Hz. Also the 2nd order is strongly amplified something which confirms our assumption. This proves that there is a resonance problem in this area (700-800Hz) The measurement technique which were used her is called “rpm sweeping with peak-hold function” which means that you sweep a frequency area to map possible resonance problems
  87. 87. Unbalanced flexible coupling
  88. 88. • Initial vibration analysis revealed mechanical unbalance in the coupling. • Unbalance is indicated by a dominating 1.st order frequency amplitude. • Unbalance can have different reasons – Insuficcient dynamic balancing. – Coupling damages, as here where the stress between the rubber elements and the inner ring (steel) has excedeeded the force limits and the rubber elements were damaged after only a few months
  89. 89. Generator with a unbalanced/damaged coupling elements 035 - GENERATOR 2 Gen 2 -P05 GENERATOR, DE,VERTIKAL Route Spectrum 20-SEP-07 15:20:28 OVRALL= 22.12 V-DG RMS = 20.32 LOAD = 100.0 RPM = 1800. RPS = 30.00 0 40 80 120 160 200 0 2 4 6 8 10 12 14 16 18 Frequency in Hz RMSVelocityinmm/Sec Freq: Ordr: Spec: 30.00 1.000 13.10 1.orden
  90. 90. The outer steel ring of the coupling was turned 180 degrees vs. the rubber elements - wich in this case was the rebalancing trick to reduce the 1.st order vibration levels from 18 to 4 mm/s
  91. 91. Before vs. after dynamic balancing – reduced 1.st order 035 - GENERATOR 2 Gen 2 -P05 GENERATOR, DE,VERTIKAL Route Spectrum 20-SEP-07 15:20:28 OVRALL= 22.12 V-DG RMS = 20.32 LOAD = 100.0 RPM = 1800. RPS = 30.00 0 40 80 120 160 200 0 2 4 6 8 10 12 14 16 18 Frequency in Hz RMSVelocityinmm/Sec Freq: Ordr: Spec: 30.00 1.000 13.10 035 - GENERATOR 2 Gen 2 -P05 GENERATOR, DE,VERTIKAL Route Spectrum 28-SEP-07 10:54:16 OVRALL= 10.82 V-DG RMS = 10.49 LOAD = 100.0 RPM = 1801. RPS = 30.01 0 40 80 120 160 200 0 2 4 6 8 10 Frequency in Hz RMSVelocityinmm/Sec Freq: Ordr: Spec: 30.00 1.000 4.018
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Vibration

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