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