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Charles Phelps
Field Engineer
GE Energy
312 Thompson Ave
Lehigh Acres, FL 33972
Sleeve Bearing Diagnostics UsingProximity Probes
Basic Concepts of Rotor Dynamics
RELATIVE PHASE
Relative Phase
ONE CYCLESignal A (Y)
Signal B (X)
Am
plit
ud
e
Time
ONE CYCLE
1. Two Signals
2. Same Frequency
3. Same Units
4. Either Signal May Be Reference
5. Relative Phase is0 to 180 degreesLeading or Lagging
0°
0°
-V
-V
Once Per Turn Reference Pulse
ONE REVOLUTION
ONE REVOLUTION
Shaft Balancing
Shaft Crack Detection
Shaft / Structural Resonance Detection
Shaft Mode Shape
Direction of Precession
Location of Fluid-Induced Instability Source
0.2 2.0
TimeAmplitude Time
Volts/div.
ms/ div.
Timebase Vibration Characteristics
1. Vibration Amplitude2. Vibration Frequency3. Phase4. rpm5. Direction of Precession6. Signal Shape 7. Gap
(from proximity probe)
Y
X
X to Y (counterclockwise)
Y
X
Y
X
Direction of Precession
Given X to Y Precession (ccw) and (ccw) Rotation: Precession = Forward
1. Vibration Amplitude (X & Y)2. Absolute Phase (X & Y)3. Relative Phase4. Relative Frequency (X & Y)
vs Running SpeedX vs Y
5. Direction of Precession
6. Shape
Amplitude
Orbit Vibration Characteristics
YX
X = Y =5.6 mils pp 5.4 mils pp
Amplitude
Orbit Vibration Characteristics
Given X to Y (ccw) Rotation:
Forward Precession
1. Vibration Amplitude (X & Y)2. Absolute Phase (X & Y)3. Relative Phase4. Relative Frequency (X & Y)
vs Running SpeedX vs Y
5. Direction of Precession
6. Shape
A B C D E F
Shaft Deflection Shape
Different Bearings, Same Speed with Keyphasor® Marker.
**
***
**
6.0
4.0
2.0
0.0-2.0 0.0 2.0
07:26:407:26:1
07:24:5
07:23:307:19:2
07:17:1
07:15:0
TRAIN: 115 MW TG 45 deg Ref: -9.76 voltsPoint ID: BRG #1 VERT 315 deg Ref: -9.28 voltsPoint ID: BRG #1 HORIZ Var: PROBE GAP TRANSIENT FILE30 SEP 88 07:02:52 to 30 SEP 88 07:42:15
AVERAGE SHAFT CENTERLINE POSITION
AMPLITUDE 0.20 mils/div X to Y (CCW) ROTATION
UP
Average Shaft Centerline Position
0.5X 1X 2X
Oscilloscope Spectrum Analyzer
1/2X Vibration
Vibration Signal
TIME
COMPLEX WAVEFORM
1X3X
6X8X
+ + + + +
+ + + + +
+ + + + +
+ + + + +
+ + + + +
Y
X
-1X
0 1X
2.5
2.0
0
2xB
2xA
A
A
B
B
A
B
1.5
1.0
0.5
UP POINT: Bearing 1 Vibration vertical
POINT: Bearing 1 Vibration horizontal
2.0 mil/div X to Y (CCW) Rotation 5.00 ms/div 4935 rpm
Full Spectrum
Am
plit
ud
e:
(mil
pp
/div
)A
B
B
A
A
B
ReverseVibration
ForwardVibration
1.0 mil/div X to Y (CCW) RotationFrequency(Orders)
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
40
30
20
10
0-4000 -2000 0 2000 4000
Reverse Vibration Components
Forward Vibration Components
FREQUENCY: 200 cpm/div X to Y (CCW) Rotation
POINT: PT BRG 4 VERT 0°POINT: PT BRG 4 VERT 90°14 SEP 93 13:17:44 4890 rpm
POINT: Dual Vibr OB VERT
POINT: Dual Vibr OB HORIZ
10 mils/div DIRECT
X to Y (CCW) Rotation
5.00 ms / div 4890 rpm
Full Spectrum
Up
1X
AM
PL
ITU
DE
: 1
0.0
mils
/div
Full Waterfall Plot
HOW TO MAKE PHASE MEASUREMENTS
RELATIVE PHASE
Relative Phase
ONE CYCLESignal A (Y)
Signal B (X)
Am
plit
ud
e
Time
ONE CYCLE
1. Two Signals
2. Same Frequency
3. Same Units
4. Either Signal May Be Reference
5. Relative Phase is0 to 180 degreesLeading or Lagging
Deflection Shape
A
B
0°
0°
-V
-V
Once Per Turn Reference Pulse
ONE REVOLUTION
ONE REVOLUTION
0° 360°
Absolute Phase Measurements
Timing (in degrees) between two (2) points on a vibration signal, the Keyphasor® pulse and positive peak in vibration.
Vibration Signal
Time
Phase Lag
Keyphasor ®
SignalDegrees of
Rotation
NOTE: Frequency must be the same or harmonically related.
HOW TO INTERPRET STEADY STATE DATA FORMATS
0.2 2.0
Timebase Vibration Characteristics
TimeAmplitude Time
1. Vibration Amplitude2. Vibration Frequency3. Phase4. rpm5. Direction of Precession6. Signal Shape 7. Gap
(from proximity probe)
Volts/div.
ms/ div.
0.2 2.0
TimeAmplitude Time
Volts/div.
ms/ div.
Timebase Vibration Characteristics
1. Vibration Amplitude2. Vibration Frequency3. Phase4. rpm5. Direction of Precession6. Signal Shape 7. Gap
(from proximity probe)
Y
X
X to Y (counterclockwise)
Y
X
Y
X
Direction of Precession
Given X to Y Precession (ccw) and (ccw) Rotation: Precession = Forward
0.2 2.0
TimeAmplitude Time
Volts/div.
ms/ div.
Timebase Vibration Characteristics
1. Vibration Amplitude2. Vibration Frequency3. Phase4. rpm5. Direction of Precession6. Signal Shape7. Gap
(from proximity probe)
Sinusoidal
Relative Vibration Frequency
A B
1/2X 2X
Amplitude
Orbit Vibration Characteristics
1. Vibration Amplitude (X & Y)2. Absolute Phase (X & Y)3. Relative Phase4. Relative Frequency (X & Y)
vs Running SpeedX vs Y
5. Direction of Precession
6. Shape
1. Vibration Amplitude (X & Y)2. Absolute Phase (X & Y)3. Relative Phase4. Relative Frequency (X & Y)
vs Running SpeedX vs Y
5. Direction of Precession
6. Shape
Amplitude
Orbit Vibration Characteristics
YX
X = Y =5.6 mils pp 5.4 mils pp
Amplitude
Orbit Vibration Characteristics
X = Y =180° 270°
1. Vibration Amplitude (X & Y)2. Absolute Phase (X & Y)3. Relative Phase4. Relative Frequency (X & Y)
vs Running SpeedX vs Y
5. Direction of Precession
6. Shape
Amplitude
Orbit Vibration Characteristics
X leads Y by 90°
1. Vibration Amplitude (X & Y)2. Absolute Phase (X & Y)3. Relative Phase4. Relative Frequency (X & Y)
vs Running SpeedX vs Y
5. Direction of Precession
6. Shape
Amplitude
Orbit Vibration Characteristics
1X
1. Vibration Amplitude (X & Y)2. Absolute Phase (X & Y)3. Relative Phase4. Relative Frequency (X & Y)
vs Running SpeedX vs Y
5. Direction of Precession
6. Shape
Amplitude
Orbit Vibration Characteristics
Given X to Y (ccw) Rotation:
Forward Precession
1. Vibration Amplitude (X & Y)2. Absolute Phase (X & Y)3. Relative Phase4. Relative Frequency (X & Y)
vs Running SpeedX vs Y
5. Direction of Precession
6. Shape
Amplitude
Orbit Vibration Characteristics
Circular
1. Vibration Amplitude (X & Y)2. Absolute Phase (X & Y)3. Relative Phase4. Relative Frequency (X & Y)
vs Running SpeedX vs Y
5. Direction of Precession
6. Shape
A B C D E F
Shaft Deflection Shape
Different Bearings, Same Speed with Keyphasor® Marker.
Relative Phase
X leads Y by 10° - 15°
Relative Phase
X leads Y by 170° - 175°
Vibration Frequency vsRotative Speed
X = 1X, Y = 2X
180° OF ORBITING360° OF ROTATION
Frequency Ratio Using Orbits
120° OF ORBITING360° OF ROTATION
120° ORB 1360° ROT 3
= = X
180° ORB 1360° ROT 2
= = X
240° OF ORBITING360° OF ROTATION
240° ORB 2360° ROT 3
= = X
**
***
**
6.0
4.0
2.0
0.0-2.0 0.0 2.0
07:26:407:26:1
07:24:5
07:23:307:19:2
07:17:1
07:15:0
TRAIN: 115 MW TG 45 deg Ref: -9.76 voltsPoint ID: BRG #1 VERT 315 deg Ref: -9.28 voltsPoint ID: BRG #1 HORIZ Var: PROBE GAP TRANSIENT FILE30 SEP 88 07:02:52 to 30 SEP 88 07:42:15
AVERAGE SHAFT CENTERLINE POSITION
AMPLITUDE 0.20 mils/div X to Y (CCW) ROTATION
UP
Average Shaft Centerline Position
0.5X 1X 2X
Oscilloscope Spectrum Analyzer
1/2X Vibration
Vibration Signal
TIME
COMPLEX WAVEFORM
1X3X
6X8X
+ + + + +
+ + + + +
+ + + + +
+ + + + +
+ + + + +
Y
X
-1X
0 1X
2.5
2.0
0
2xB
2xA
A
A
B
B
A
B
1.5
1.0
0.5
UP POINT: Bearing 1 Vibration vertical
POINT: Bearing 1 Vibration horizontal
2.0 mil/div X to Y (CCW) Rotation 5.00 ms/div 4935 rpm
Full Spectrum
Am
plit
ud
e:
(mil
pp
/div
)A
B
B
A
A
B
ReverseVibration
ForwardVibration
1.0 mil/div X to Y (CCW) RotationFrequency(Orders)
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
. .. . . .. . .
40
30
20
10
0-4000 -2000 0 2000 4000
Reverse Vibration Components
Forward Vibration Components
FREQUENCY: 200 cpm/div X to Y (CCW) Rotation
POINT: PT BRG 4 VERT 0°POINT: PT BRG 4 VERT 90°14 SEP 93 13:17:44 4890 rpm
POINT: Dual Vibr OB VERT
POINT: Dual Vibr OB HORIZ
10 mils/div DIRECT
X to Y (CCW) Rotation
5.00 ms / div 4890 rpm
Full Spectrum
Up
1X
AM
PL
ITU
DE
: 1
0.0
mils
/div
Full Waterfall Plot
HOW TO INTERPRET STARTUP AND SHUTDOWN PLOTS
0 500 1000 1500 2000 2500 3000 3500 4000
4
3
2
1
0
180
240
300
360
60
120
180
240
Slow Roll Phase
Slow Roll Amplitude
1X Bode Plot
Slow Roll Vector
Amplitude: 1.0 mils pp
Phase: 225 Deg. Lag
Slow roll speed range (no dynamic data).rpm
* **
***
**
****
******* * *
0°
90°
180°
270°2205 2250
2280
23702385
2400
2415
2310
2430
2445
24602475
25052685
277529853615300
1845
2145
2610
Uncompensated Polar Plot
4.0 mil pp Full Scale X to Y (CCW) Rotation
Slow Roll Vector
0 500 1000 1500 2000 2500 3000 3500 4000
4
3
2
1
0
180
240
300
360
60
120
180
240
180°
1X Bode Plot
rpm
Uncompensated
Compensated
Plot of High Spot
Angle of Heavy Spot
Uncompensated
Compensated
Balance Resonance
********
* *****
***
0°
90°
180°
270°90°
90°300
20702205 2250
2280
2310 2370
238524052415
2430
24452460
25052610
27753615
1X Compensated Polar Plot
Amplitude and Direction of Response at Balance Resonance
Amplitude and Direction of Response Above Balance Resonance
Direction of Mass Unbalance
4.0 mil pp Full Scale X to Y (CCW) Rotation
180
240
300
360
60
120
180
10
8
6
4
2
00 1000 2000 3000 4000 5000 6000 7000
Vertical and Horizontal 1X Bode Plot
Split Critical
Inboard Horizontal
Inboard Vertical
Structural Resonances
rpm
Split Critical and Structural Resonances
***
**
*
**
*****
***
***
**
0°
90°
180°
270°
22352295
2340
23852400
2415
24452460
247525052610
26852775
27453285
300 20552065 2400
2415
24452475
*
Polar Plot
Balancing EffectMu Before
BalancingMu After
Balancing
4.0 mil pp Full Scale X to Y (CCW) Rotation
0°
90°
180°
270°
Frequently Observed Polar Plot
High Speed
Two Mass Rotor System
Vertical Probe
Vertical Probe
Mass
0° 0°
90°90°
180° 180°
270° 270°
Split Translational Resonance
INBOARD OUTBOARD
High Speed High Speed
0° 0°
90°90°
180° 180°
270° 270°
Translational and Pivotal Resonance
High SpeedHigh Speed
INBOARD OUTBOARD
Typical Flexible Rotor Mode ShapesP1 P2P3P4
Typical Rotor
P3
Cylindrical / Translational Mode P2
Pivot / Conical Mode
P1
P4Third Mode Node Locations are Affected by System Stiffness
**
**
**
**
*
*
*
3.0
2.0
1.0
0.0 -1.0 0.0 1.0
9500
94009200
8700
8000
7600
5500
45001200
500
300
Average Shaft Centerline
Amplitude 0.20 mils / div X to Y (CCW) Rotation
(Not Orbit or Polar Plot)Top
4000
3000
2000
1000
00 1000 2000 3000 4000 5000 6000 7000 8000
1X2X
3X
Half Cascade Plot
Frequency (cpm) Hanning Window
Full Cascade Plot
HOW TO EVALUATE PRELOADS (MISALIGNMENT) AND RADIAL POSITION MEASUREMENTS
Direct MeasurementsVibration and Position
Rotor Speed
Bearing Temperature
Indirect DataProcess Data
Performance Data
Radial Preloads
Gravitational
Fluidic Preloads
Bearing Preloads
Internal MisalignmentParallel and Angular Misalignment
Pipe Strain
Thermal Warping
Axial PreloadsGravity (Vertical Machines)
Fluidic
Process Thrust Loads
Differential Expansion
Orbit Plot Can Show Preloads
(Misalignment)(No Resonance Near Twice Rotative Speed)
Rare Common Rare
Orbit Plot Can Show Preloads
(Misalignment)(Resonance Near Twice Rotative Speed)
Rare Common Rare
Orbit and Position Indicators of Preload
Y X
Y = - 6.8 VdcX = - 7.2 Vdc
Normal Orbit and Position
BEARING
AVERAGE SHAFT CL
CL
Normal steady load downward, such as gravity.
RO
TN
Orbit and Position Indicators of Preload
Y X
Y = - 6.2 VdcX = - 5.8 Vdc
AVERAGE SHAFT CL
BEARING CL
Abnormal Orbit and Position
RO
TN
Gap Voltage Measurement
PROVIDES:Shaft Centerline PositionShaft Attitude AngleEccentricityShaft Trend PlotsAlignment Along Shaft
Radial Position Calculation
Y
X
Y = - 10 VdcX = - 10 Vdc
Vertical Transducer 200 mV/mil
Horizontal Transducer 200 mV/mil
Diametral Clearance 10 mils
Rotor (Not to Scale)
Shaft Centerline
Radial Position Calculation
Y
X
Y = - 9.6 VdcX = - 10.2 Vdc
Vertical Transducer 200 mV/mil
Horizontal Transducer 200 mV/mil
Diametral Clearance 10 mils
Rotor (Not to Scale)
Shaft Centerline
Vertical Transducer200 mv/mil
to Scale)
Radial Position Calculation
Left 1 milUp 2 mils
Y = - 9.6 VdcX = - 10.2 Vdc
Horizontal Transducer 200 mV/mil
Shaft Centerline
Y
X
**
**
**
**
*
*
*
3.0
2.0
1.0
0.0 -1.0 0.0 1.0
9500
94009200
8700
8000
7600
5500
45001200
500
300
Amplitude 0.20 mils / div X to Y (CCW) Rotation
Top
Average Shaft Centerline Position
TurbineGenerator
Shaft Centerline Plot Can Show Misalignment
AXIAL (THRUST) POSITION
DIFFERENTIAL EXPANSION
Thrust Collar
12 Max
12 Max
Axial Position Measurements