failure analysis case studies by using vibration analysis t~

7/30/2019 Failure Analysis Case Studies by Using Vibration Analysis T~

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Failure Analysis Case Studies by using Vibration Analysis

Technique

1- Bearing Premature Fatigue

Problem Initiation and definition :

The problem was initiated by the operator. He noticed that high vibration

level was sensed by human sense. Vibration measurements were carried out

by condition monitoring engineer as he received the order.

Measuring procedures and used instrumentations :

The condition monitoring engineer select the measuring point which is near

to the expected fault. An axial vibration data ware collected using

piezoelectric accelerometer mounted with magnet. The accelerometer have

the following characteristics ( natural frequency F= 200 order 0f the

machine rotational speed, the accelerometer sensitivity = 100 mV/g) The

accelerometer signal was sent to the CSI model 2120 equipped condition

monitoring and diagnosis programs.

Analysis:Bearing outer race defect was detected in the 4th mode as indicated from

the time signal and FFT plot where BPFO was presented at 12.21 order

according the bearing type and it needs to be changed As Soon As possible.

This defect resulted from

excessive axial load causes edge loading and overstressing of the raceway

and result in premature fatigue. This is easily recognized as the damage is

clearly restricted to one side..

Follow Up:After changing the bearing and revising the assembly . the problem was

disappeared where vibration measurements identical to that described in

Measuring procedures and used instrumentations were carried out.


2/10

WAVEFORM DISPLAY15-Jul-99 10:03:42RMS = 4.89

PK(+) = 14.75PK(-) = 18.71CRESTF= 3.83

0 100 200 300 400 500 600

-25

-20

-15

-10

-5

0

5

10

1520

Time in mSecs

AccelerationinG-s

CF ALARM

CF ALARM

PK ALARMPK ALARM

SPIN - FINISHING HOLDER

HOLDER#16 -IHA INNER BRG.HOLDER AXIAL (HIGH FRQ)

Label: Befor e changing the bearing

ROUTE SPECTRUM15-Jul-99 10:03:42

OVRALL= 36.75 V-DGPK = 36.51LOAD = 100.0RPM = 507.RPS = 8.44

0 100 200 300 400 500 600 700 800

0

2

4

6

8

10

12

14

1618

Frequency in Hz

PKV

elocityinmm/Sec

Freq:

Ordr:Spec:

103.13

12.213.648

>SKF 61836M AE=BPFO : 102.5

E E E E E E E

WAVEFORM DISPLAY

22-Jul-99 08:49:03RMS = .3284PK(+) = 1.39PK(-) = 1.16CRESTF= 4.23

0 100 200 300 400 500 600 700

-2.0

-1.5

-1.0

-0.5

0

0.5

1.0

1.5

2.0

Time in mSecs

AccelerationinG-s

CFALARM

CF ALARM

PK ALARM

PK ALARM


HOLDER#16 -IHA INNER BRG.HOLDER AXIAL(HIGH FRQ)

Label: After changing the bearing

ROUTESPECTRUM22-Jul-99 08:49:03


0 100 200 300 400 500 600

0

2

4

6

8

10

12

14

1618

Frequency in Hz

PKVelocityinmm/Sec

Freq:Ordr:Spec:

7.125.9955.086


3/10

2- Bearing Fatigue


The problem was initiated by the PM Craw. They noticed that high vibration

level was sensed by human sense. Vibration measurements were carried out

by condition monitoring engineer as he received the order.

Measuring procedures and used instrumentations :The condition monitoring engineer select the measuring point which is near

to the expected fault. An axial vibration data ware collected usingpiezoelectric accelerometer mounted with magnet. The accelerometer have





Analysis:Bearing outer race defect was detected in the 4th mode as indicated from

the time signal and FFT plot where BPFO was presented at 12.1order

according the bearing type and it needs to be changed As Soon As possible.

This defect resulted from

excessive axial load due to severe looseness causes general outer race

annular damage.

..

Follow Up:After changing the bearing and revising the assembly . the problem was

disappeared where vibration measurements identical to that described in

Measuring procedures and used instrumentations were carried out.


4/10

WAVEFORM DISPLAY15-Jul-99 10:03:42RMS = 4.89

PK(+) = 14.75PK(-) = 18.71CRESTF= 3.83

0 100 200 300 400 500 600

-25

-20

-15

-10

-5

0

5

10

1520

Time in mSecs

AccelerationinG-s

CF ALARM

CF ALARM

PK ALARMPK ALARM


HOLDER#16 -IHA INNER BRG.HOLDER AXIAL (HIGH FRQ)

Label: Befor e changing the bearing

ROUTE SPECTRUM15-Jul-99 10:03:42


0 100 200 300 400 500 600 700 800

0

2

4

6

8

10

12

14

1618

Frequency in Hz

PKV

elocityinmm/Sec

Freq:

Ordr:Spec:

103.13

12.213.648

>SKF 61836M AE=BPFO : 102.5

E E E E E E E

WAVEFORM DISPLAY

29-Jun-02 11:51:45

RMS = 7.27

PK(+) = 19.50

PK(-) = 20.49

CRESTF= 2.82

0 50 100 150 200 250 300 350 400

-25

-20-15

-10

-5

0

5

10

15

20

Time in m Secs

A

ccelerationinG-s

CF ALARM

CF ALARM

PK ALARMPK ALARM

Spin - FINSHING HOLDER

HOLDER#17 -UOA UPPER BRG.HOLDER AXIAL(HIGH FRQ)

Lab el: BEFORE CHANGING THE BEARING

ROUTE SPECTRUM

29-Jun-02 11:51:45

OVRALL= 38.49 V-DG

PK = 38.38

LOAD = 100.0

RPM = 626.

RPS = 10.44

0 200 400 600 800 1000

0

3

6

9

12

15

18

21

24

27

30

Frequency in Hz

PK

Velocityinmm/Sec

Freq:

Ordr:

Spec:

126.25

12.10

4.069

>SKF 61836MA

E=BPFO : 126.6

E E E E E E E


5/10

WAVEFORM DISPLAY

30-Jun-02 16:13:32RMS = 1.11PK(+) = 6.42

PK(-) = 6.42CRESTF= 5.77

0 100 200 300 400 500 600

-8

-6

-4

-2

0

2

4

6

8

Time in mSecs

Acce

lerationinG-s

CF ALARM

CF ALARM

PK ALARM

PK ALARM

Spin - FINSHING HOLDER

HOLDER#17 -UOA UPPER BRG.HOLDER AXIAL(HIGH FRQ)

Labe l: AFTER CHANGING THE BEARING

ROUTE SPECTRUM30-Jun-02 16:13:32

OVRALL= 20.01 V- DG

PK = 19.92LOAD = 100.0RPM = 565.

RPS = 9.42

0 100 200 300 400 500 600 700 800

0

3

6

9

12

15

18

21

24

27

Frequen cy in Hz

PKVeloci

tyinmm/Sec

Freq:Ordr:Spec:

9.375.9955.998

B=1X HARMONIC

: 9.42

BBBBBBBBBBBB


6/10

3- Coupling Fatigue


The problem was initiated by the maintenance groupe. They noticed that

high vibration level was sensed by human sense. Vibration measurements

were carried out by condition monitoring engineer as he received the order.

Measuring procedures and used instrumentations :The condition monitoring engineer select the measuring point which is near

to the expected fault. An axial vibration data ware collected using

piezoelectric accelerometer mounted with magnet. The accelerometer havethe following characteristics ( natural frequency F= 200 order 0f the




Analysis:Coupling defect was detected in the 4th mode as indicated from the time

signal and FFT plot where it was presented at 8order and 1 order in the axial

direction in the radial direction according the coupling type where the

coupling have 8 jaws and it needs to be changed As Soon As possible. This

defect can be attributed to misalignment of coupling jaws causes edge

loading and overstressing of the coupling jaws and result in premature

fatigue. Coupling defect frequency exists with rotating speed modulation

due to coupling excessive wear. Action must be taken is to adjust the

alignment and change the coupling.

Follow Up:

After adjusting the alignment and changing the coupling . the problem wasdisappeared .


7/10

VWP - VERTICAL WATER PUMP

PUMP#B -P1V INPUT SHAFT INB.BRG.VER.

Label: Before changing the coupling

Route Spectrum29-Jan-03 14:17:35


0 400 800 1200 1600 2000

0

1

2

3

4

5

6

7

8

Frequency in Hz

PKVelocityinmm/Sec

Freq:Ordr:Spec:

198.368.0006.221

L=Coupling frq: 198.3

L L L L L L


PUMP#B -P1V INPUT SHAFT INB.BRG.VER.

Label: After changing the coupling

Route Spectrum05-Feb-03 11:45:27


0 400 800 1200 1600 2000

0

1

2

3

4

5

6

7

8

Frequency in Hz

PKVelocityinm

m/Sec

Freq:Ordr:

Spec:

199.118.000

.275

L=Coupling frq: 199.1

L L L L L L


8/10


9/10

4- Impeller Wear

Problem Initiation and definition :The problem was initiated by the operator and from the pump performance.

They noticed that high vibration level was sensed by human sense. Vibration

measurements were carried out by condition monitoring engineer as he

received the order.

Measuring procedures and used instrumentations :

The condition monitoring engineer select the measuring point which is nearto the expected fault. An radial vibration data ware collected using

piezoelectric accelerometer mounted with magnet. The accelerometer have





.

Analysis:The defect was detected in the 4th mode as indicated from the time signal

and FFT plot . It was presented at 1order in the radial direction and it needsto be changed As Soon As possible. This defect can be attributed to Severe

pitting on the pump impeller due to corrosion erosion and chemical water

effect. Action must be taken is to adjust the alignment and change the

coupling. Sub-synchronous vibrations due to impeller wear which exits

structure resonance. Change the pump impeller and recoat it with the

ceramic coating.

Follow Up:The lifetime of the impeller was extended and the Sub-synchronous

vibration was disappeared after changing the impeller.


10/10


PUMP#A -MOH AC MOTOR OUTB.BRG.HO .

Label: Before changing the impeller

Route Spectru m18-Oct-01 12:08:35


0 50 100 150 200 250 300 350 400

0

2

4

6

8

10

12

Frequency in Hz

PKVelocityinmm/Sec

Freq:Ordr:Spec:

25.001.0058.558

failure analysis case studies by using vibration analysis t~

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