VIBRASI LEVEL 2

Copyright 2004- PT. Putranata Adi Mandiri – sole agent Prüftechnik AG, Germany – PART 2 1

GearBlades

Rolling ElementBearings

ShaftRotatingSpeed

2x

3x

JournalBearingsinstability

1 KHz 3KHz 25KHz

FFT - How to select Freq. Ranges, lines, Averages


Frequency Range

30dB

2Hz

20

10

0

-10

10KHz

Rel

ativ

e Se

nsiti

vity

Consider…Sensor…Instrument…Cables…Sensor Coupling

Useful Frequency Range10% limit -0.3f0 3dB limit -0.5f0

-20

-30

-40

Frequency [xf0]

Frequency Response of Sensor


Sensitivity vs Frequency Range

Sens

itivi

ty

Frequency


Vibration Pickups

GearBlades

Rolling ElementBearings

ShaftRotatingSpeed

2x3x

JournalBearingsinstability

1 KHz 3KHz 25KHzNon Contact Displacement

Velocity Probe

Accelerometer


Threaded & bonded stud

VIB 8.660

VIB 8.680 SET

Threaded & bonded transducer

VIB 6.10X

VIB 8.685 SET

Hand held probe

VIB 8.606

VIB 6.140

Magnetic holdercurved surfaces

VIB 6.140

VIB 8.736

2 20k 36k Hz

v

1510 10k 36k

Hz

v

10 1k 2k 36k Hz

v

22 15k Hz

v

VIB 6.12X

Coupling vs Frequency Range


Machine Signal Types

Stationary Signals

Non - Stationary Signals

- Vibration from rotating machines

- Vibration from reciprocating machines (short term)

- Vibration from run-ups and coast-down


Informasi penting tentang mesin

Amplitudovibrasi

frekuensi

Apa saja yang mungkin menyebabkan vibrasi ?


Analisa Amplitudo, Frekuensi dan Fase - 1

KETERANGANFASEFREKUENSIAMPLITUDOPENYEBAB GAMBAR SPECTRUM

Kondisi seringditemui

Single reference mark

1 x rpmSebanding dgnketidak balance, dominan pd radial (2x aksial)

1. Unbalance A

f1x

Pengukuran getaran :

Ha = 4

Aa = 3

Va = 4

Hb = 5

Vb = 3 Vc = 4

Ae = 7

Hc = 3Hd = 2 Vd = 4

Ad = 5

Ab = 4 Ac = 5

He = 15

Ve = 13 Vf = 13

Af = 8

Hf = 15






Ha = 5

Aa = 7

Va = 4

Hb = 10

Vb = 10 Vc = 10

Ae = 4

Hc = 10Hd = 5 Vd = 4

Ad = 7

Ab = 15 Ac = 15

He = 4

Ve = 3 Vf = 4

Af = 5

Hf = 3

Ditandai timbulnya vibrasiaksial. Gunakan alat laser-alignment. Apabila mesinbaru dipasang terjadivibrasi, maka kemungkinanbesar karena misalignment.

Singledoubletriple

Sering 1 x & 2 x rpm. Kadang 3 x rpm

Dominan pd aksial, 50% atau lebih dariarah radial

2. Misalignment kopling atauporos bengkok

A

f1x 2x




Vibrasi akan timbulapabila bearing sdhparah. Gunakanvibrotip / shockpulse u deteksi awal

Tdk tentu,Berubah-rubah

Sangat tinggi, beberapa kaliRpm, 1x, 2x, 3x,4x … 10x…..

Tidak stabil, ukur percepatan, gunakanacceleration probe

3. Anti friction bearing buruk

A

f1x 2x 3x 4x


Ha = 3

Aa = 4

Va = 2

Hb = 3

Vb = 4 Vc = 5-10

Ae = 4

Hc = 5-10Hd = 4 Vd = 3

Ad = 5

Ab = 3 Ac = 10-15

He = 4

Ve = 5 Vf = 3

Af = 2

Hf = 4



KETERANGANFREKUENSIAMPLITUDOPENYEBAB GAMBAR SPECTRUM

Excessive Clearance normally accompanied by FTP modulating other frequencies; can also sifnificantly affect balance sensitivity

Excessive Internal clearances

Sangat tinggi, beberapa kaliRpm, 1x, 2x, 3x,4x,5 x,6x



A

f1x 2x 3x 4x


Frequency 3X or greater is the predominant multiple

Bearing turning on shaft

Sangat tinggi, beberapa kaliRpm, 3xor greater



A

f1x 2x 3x 4x


Frequency 3X or greater is the predominant multiple

Bearing turning on shaft

Sangat tinggi, beberapa kaliRpm, 3xor greater



A

f1x 2x 3x 4x




Seringbersamaan dgnunbalance / misalignment

2 referensiagak kacau

2 x rpmTinggi padaaksial

7. Mechanical looseness (Housing bearing aus)

A

f2x


• Frequency Defect Remarks• 1-6X Excessive internal

Clearance


Why shock pulses for rolling bearing noise ?

Machine vibration Shock pulse range rolling bearingMaterial crackplastical / elasticaldeformation

1 000 10 000 100 00036 000 flog / Hz

velocity acceleration shock pulses ultra sound emission

Natural frequencies rolling bearing pieces

l = n ⋅ mf ≈ x ⋅ 1 / 1 mfnat ≈ x ⋅ 30 Hz

Example

d = n ⋅ 1 mmf ≈ x ⋅ 1/1 000 mfnat ≈ x ⋅ 30 000 Hz

a = n ⋅ μmf ≈ x ⋅ 1 / 1 00 000 mfnat ≈ x ⋅ 300 000 Hz

d a

fnat,O fnat, Ι fnat,B

l

fnat =x

cm

( ∼ , , )1m

1l

1d

1a m = Mass

c = stiffness

1

2

1 2


Pengukuran vibrasi dan jarak frekuensi

Component & Machine Vibration Frictional Vibration (Sliding, Rolling, Shock, Rubbing Vibrations)

Size of machine component Speed /Rolling speed

Acceleration Velocity

ShockPulses




pd rodagigi vibrasi segarisdengan pusat kontak. pd motor/gen vibrasi hilangbila mesin dimatikan. pd pompa/blower kemungkinan unbalance

Single1 x rpm, seolah-olah sepertiunbalance

Tidak besar, aksiallebih tinggi

4. Sleeve, metal, Jurnal bearing (friction bearing) / eksentrik

A

f1x


Ha = 3

Aa = 7

Va = 4

Hb = 8

Vb = 7 Vc = 3

Ae = 4

Hc = 5Hd = 3 Vd = 5

Ad = 4

Ab = 15 Ac = 4

He = 4

Ve = 4 Vf = 4

Af = 5

Hf = 3


Alignment pada sleeve bearing

Posisi pada saatpekerjaan alignment

Posisi seharusnyapada saat setelahalignment

Sleeve bearing

Ball bearing





Ha = 3

Aa = 3

Va = 4

Hb = 2

Vb = 3 Vc = 7

Ae = 8

Hc = 7Hd = 7 Vd = 7

Ad = 9

Ab = 4 Ac = 8

He = 6

Ve = 7 Vf = 3

Af = 5

Hf = 4

Tdk tentuSangat tinggiJumlah gigi xrpm

Rendah, ukurkecepatan & percepatan, gunakanacceleration

5. Rodagigiburuk ataubersuara

A

f1x 2x 3x 4x

tooth

Awal rusakbersuara, semakinlama keras.Vibrasi biasanyadalam toleransi.





Ha = 3

Aa = 3

Va = 4

Hb = 2

Vb = 3 Vc = 7

Ae = 8

Hc = 7Hd = 7 Vd = 7

Ad = 9

Ab = 4 Ac = 8

He = 6

Ve = 7 Vf = 3

Af = 5

Hf = 4

tooth

Sering terjadipada saatpemasangan


Rendah, ukurkecepatan &percepatan, gunakan accel.

6. Gear mesh buruk ataubersuara(pada saatstart / stop)

A

f1x 2x 3x 4x








A

f2x


Ha = 3

Aa = 3

Va = 4

Hb = 12

Vb = 12 Vc = 5

Ae = 4

Hc = 5Hd = 4 Vd = 5

Ad = 3

Ab = 15 Ac = 5

He = 4

Ve = 3 Vf = 3

Af = 4

Hf = 2




Kurang dari1 x rpm

Tinggi padavertikal

8. Mechanical Looseness (Pondasikendor – dudukanlemah/karatan –baut kendor)

A

f<1x


Ha = 2

Aa = 3

Va = 9

Hb = 4

Vb = 10 Vc = 5

Ae = 4

Hc = 2Hd = 4 Vd = 3

Ad = 2

Ab = 4 Ac = 2

He = 3

Ve = 3 Vf = 2

Af = 3

Hf = 4

Tdk tentu Kencangkan bautUntuk memastikan






2 x rpmTinggi padavertikal, horizontal & aksial

9. Mechanical looseness (Pondasimelengkung)

A

f2x


Ha = 13

Aa = 7

Va = 9

Hb = 14

Vb = 12 Vc = 5

Ae = 4

Hc = 5Hd = 4 Vd = 5

Ad = 3

Ab = 6 Ac = 5

He = 4

Ve = 3 Vf = 3

Af = 4

Hf = 2




1 atau 2 tergantungfrekuensi, tdk tetap

1,2,3 atau 4 x rpm belt

Tdktentu/berpulsa

10. Drive belt buruk

A

f1x 2x 3x 4x


Ha = 2

Aa = 2

Va = 3

Hb = 4

Vb = 2 Vc = 10

Ae = 8

Hc = 10Hd = 8 Vd = 10

Ad = 10

Ab = 3 Ac = 10

He = 7

Ve = 8 Vf = 4

Af = 3

Hf = 2

Belt

Biasanya terjadikarena belt tdk beradapada tempatnya secarasempurna.






Ha = 8

Aa = 6

Va = 7

Hb = 8

Vb = 6 Vc = 4

Ae = 3

Hc = 5Hd = 3 Vd = 3

Ad = 5

Ab = 7 Ac = 5

He = 3

Ve = 3 Vf = 2

Af = 3

Hf = 1

Vibrasi & suarahilang bilamesin dimatikan

Single/rotate double mark

2 x rpm lebihtinggi daripd1 x rpm.

Tidak tinggi, adasuaraberdengung, lebih terasa biladimatikan

11. Elektrikal A

f1x 2x






Ha = 2

Aa = 1

Va = 1

Hb = 2

Vb = 2 Vc = 4

Ae = 7

Hc = 3Hd = 4 Vd = 4

Ad = 3

Ab = 3 Ac = 5

He = 13

Ve = 14 Vf = 13

Af = 7

Hf = 14

Lebih terasa bilabeban tidakstabil.

1 x rpm ataujumlah suduatau fan atauimpeler x rpm

Tinggi padavertikal atauhorizontal

12. Gayaaerodinamik / hidrolik

A

f1x Jml x

Tdk tentu




Pada mesinreciprocating bisa gantidesain/isolasi

1 x,2 x rpm atau lebih

13. Gayareciprocating

A

f1x 2x


Ha = 8

Aa = 6

Va = 7

Hb = 7

Vb = 8 Vc = 3

Ae = 3

Hc = 2Hd = 4 Vd = 3

Ad = 4

Ab = 7 Ac = 4

He = 4

Ve = 2 Vf = 2

Af = 3

Hf = 2

Dominan aksial Single,double,triple


Ringkasan Analisa Amplitudo, Frekuensi dan Fase


Kondisi seringditemui

Single reference mark

1 x rpmSebanding dgnketidak balance, dominan pd radial (2x aksial)

1. Unbalance A

f1x

Ditandai timbulnya vibrasiaksial. Gunakan alat laser-alignment. Apabila mesinbaru dipasang terjadivibrasi, maka kemungkinanbesar karena misalignment.

Singledoubletriple

Sering 1 x & 2 x rpm. Kadang 3 x rpm

Dominan pd aksial, 50% atau lebih dariarah radial

2. Misalignment kopling atauporos bengkok

A

f1x 2x

Vibrasi akan timbulapabila bearing sdhparah. Gunakanenveloping & shockpulse

Tdk tentu,Berubah-rubah

Sangat tinggi, beberapa kaliRpm, 1x, 2x, 3x,4x … 10x… x

Tidak stabil, ukur acceleration untuk freq. tinggi


A

f1x 2x 3x 4x

pd rodagigi vibrasi segarisdengan pusat kontak. pd motor/gen vibrasi hilangbila mesin dimatikan. pd pompa/blower kemungkinan unbalance

Single1 x rpm, seolah-olah sepertiunbalance

Tidak besar, aksiallebih tinggi

4. Sleeve, metal, Jurnal bearing (friction bearing)

A

f1x


Rendah, ukurkecepatan & percepatan, gunakan accel.

5. Rodagigiburuk ataubersuara

A

f1x 2x 3x 4x

Awal rusak bersuara, semakin lama keras.Vibrasi biasanyadalam toleransi.

tooth




Sering terjadipada saatpemasangan

Tdktentu

Sangat tinggiJumlah gigi xrpm

Rendah, ukurkecepatan &percepatan, gunakan accel.

6. Gear mesh buruk ataubersuara padasaat start/stop

A

1xf

2x 3x 4x





A

f2x

Kurang dari1 x rpm

Tinggi padavertikal

8. Mechanical Looseness (Pondasikendor – dudukanlemah/karatan –baut kendor)

A

f<1x

Tdk tentu Kencangkan bautUntuk memastikan



2 x rpmTinggi padavertikal, horizontal & aksial

9. Mechanical looseness (Pondasimelengkung)

A

f2x

1 atau 2 tergantungfrekuensi, tdk tetap

1,2,3 atau 4 x rpm belt

Tdktentu/berpulsa

10. Drive belt buruk

A

f1x 2x 3x 4x

Biasanya terjadikarena belt tdk beradapada tempatnya secarasempurna.




Vibrasi & suarahilang bilamesin dimatikan

Single/rotate double mark

2 x rpm lebihtinggi daripd1 x rpm.

Tidak tinggi, adasuara dengung, lbh terasa biladimatikan

11. Elektrikal A

f1x

Lebih terasa bilabeban tidakstabil.

1 x rpm / jmlsudu / fan atau impelerx rpm

Tinggi padavertikal atauhorizontal

12. Gayaaerodinamik / hidrolik

A

f1x Jml x

Pada mesinreciprocating bisa gantidesain/isolasi

1 x,2 x rpm atau lebih

13. Gayareciprocating

A

f1x 2x

Tdk tentu

Single,double,triple

Dominan aksial

2x


Latihan - 1

PICKUP LOCATION Peak (mm/s)

FREQ(cpm)

Peak(mm/s)

FREQ(cpm)

Peak(mm/s)

FREQ(cpm)

Peak(mm/s)

FREQ(cpm)

0.080.07

-

-0.4

0.45

0.250.300.42

Variable 37500Variable 37500

-

-14001400

140014001400

600060006000

600060006000

75007500

-

75007500

-

0.050.050.01

0.050.050.01

0.050.4-

0.40.05

-

300030003000

300030003000

30003000

-

30003000

-

0.30.5

0.09

0.40.7

0.15

0.20.15

-

0.20.09

-

150015001500

150015001500

150015001500

150015001500

1.72.41.2

2.1

3.21.9

1.11.31.2

1.31.11.5

VertikalHorizontal

Aksial

VertikalHorizontal

Aksial

VertikalHorizontal

Aksial

VertikalHorizontal

Aksial

A

B

C

D

Single phasemotor

Coupling

5 bladeimpeller

Sleevebearing

Rollerbearing

A B C D


PERTANYAAN : LATIHAN-1

(a) Kemungkinan penyebab apa yang mengakibatkan terjadinyavibrasi 1500 cpm pada bearing A dan B ?

(b) Bila kemungkinan penyebabnya lebih dari satu, bagaimana caraAnda untuk menemukan penyebab yang sesungguhnya ?

(c) Apa penyebab terjadinya vibrasi 3000 cpm pd bearing A,B,C & D ?

(d) Apa penyebab terjadinya vibrasi 6000 cpm pd bearing A dan B ?

(e) Apa penyebab terjadinya vibrasi 37500 cpm pd bearing B ?

(f) Apa penyebab terjadinya vibrasi 7500 cpm pd bearing C dan D ?

(g) Apa penyebab terjadinya vibrasi 1400 cpm pd bearing C dan D ?

(h) Bagaimana Anda menentukan apakah penyebab vibrasi tersebutharus ditanggulangi ?


Latihan - 2

PICKUP LOCATION DISP FREQ DISP FREQ DISP FREQ DISP FREQ

1.21.3

4000040000

450045004500

450045004500

13001300

130013001300

1.31.10.9

1.21.21.0

2.02.1

2.12.22.0

300030003000

300030003000

1800018000

-

1800018000

-

1.21.21.3

1.21.40.9

0.91.1-

1.31.2-

150015001500

150015001500

150015001500

150015001500

2.72.81.3

1.81.91.2

1.21.11.1

1.21.31.1

VertikalHorizontal

Aksial

VertikalHorizontal

Aksial

VertikalHorizontal

Aksial

VertikalHorizontal

Aksial

A

B

C

D

Water turbine12 blades

CouplingGenerator

Rollerbearing

Sleevebearing

A B C D


PERTANYAAN : LATIHAN-2

aa) Kemungkinan penyebab apa yang mengakibatkan terjadinya vibrasi 1500 cpm padabearing A dan B ?

b) Bila kemungkinan penyebabnya lebih dari satu, bagaimana cara Anda untuk menemukanpenyebab yang sesungguhnya ?

(c) Apa penyebab terjadinya vibrasi 3000 cpm pada bearing A dan B ?(d) Apa penyebab terjadinya vibrasi 40000 cpm pada bearing A ?(e) Apa penyebab terjadinya vibrasi 4500 cpm pada bearing A dan B ?(f) Apa penyebab terjadinya vibrasi 18000 cpm pada bearing C dan D ?(g) Apa penyebab terjadinya vibrasi 1300 cpm pada bearing C dan D ?h) Bagaimana Anda menentukan apakah penyebab vibrasi tersebut harus ditanggulangi ?


Latihan - 3

5 blade impeller

Sleevebearing

C DSingle phase motor

Rollerbearing

A B1500 rpm

3000 rpm

PICKUP LOCATION AMPL FREQ AMPL FREQ AMPL FREQ AMPL FREQ

1.21.3

4000040000

450045004500450045004500130013001300130013001300

1.31.10.91.21.21.01.92.02.12.12.22.0

300030003000300030003000

360003600036000360003600036000

1.21.21.31.21.40.90.91.11.11.31.21.1

150015001500150015001500300030003000300030003000

2.82.92.44.04.14.94.54.44.83.83.93.3

VertikalHorizontal

AksialVertikal

HorizontalAksial

VertikalHorizontal

AksialVertikal

HorizontalAksial

A

B

C

D


Latihan - 4

PICKUP LOCATION AMPL FREQ AMPL FREQ AMPL FREQ AMPL FREQ

1.21.3

1.41.21.31.21.11.1

4000040000

240002400024000240002400024000

450045004500450045004500130013001300130013001300

1.31.10.91.21.21.01.92.02.12.12.22.0

300030003000300030003000

360003600036000360003600036000

1.21.21.31.21.40.90.91.11.11.31.21.1

150015001500150015001500300030003000300030003000

2.82.92.44.04.14.94.54.44.83.83.93.3

VertikalHorizontal

AksialVertikal

HorizontalAksial

VertikalHorizontal

AksialVertikal

HorizontalAksial

A

B

C

D

compressor

Sleevebearing

C DSingle phase motor

Rollerbearing

A B1500 rpm

3000 rpm

gearbox


Machine Signal Types

Pulsed• RE Bearing Wear• Rubs• Blade Damage, fouling• Surge, Cavitation, • Local Tooth Defects

Random•Lubrication Problems• Rolling Element (RE)Bearing Mounting defect• Flow Exited

Semi Static• Shaft Position

Modulated• Torsional Load• Tooth Fatigue• Eccentricity

1X 2X 200Hz

1X 5 kHz

1X 10 kHz

1X 10 kHz

Harmonic•Imbalance•Misalignment

Time Frequency


Penyebab vibrasi dan frekuensi karakteristiknyaPossible Dominant Direction Comments

cause FrequencyUnbalance 1x rotation frequency Radial for dyna- Amplitude proportional to unbalance and RPM;

mic imbalance, caused by displacement of rotation axis from masspossibly axial center of gravity

Misalignment; 1x rotation frequency Radial and Severe axial vibration and 2nd harmonic; bestbent shaft often 2x and higher axial realigned with ROTALIGN©, OPTALIGN© V or SYSTEM

multiples 2 TURBALIGN©

Bearing High frequency vibration, Radial and May be diagnosed from vibration only throughdamage Shock pulse vibration axial use of diagnostic functions, shock pulse analysis

or envelope curve analysis.Sleeve Subharmonic, exactly Radial Usually dependent upon RPM and operatingbearing play 1/2 or 1/3 of rotation temperature.

frequencyOil film whirl 40% - 50% of rotation Radial Occurs with high-speed machines; phaseor whip (sleeve frequency fluctuates.bearings)Hysteresis Critical shaft rotation Radial Vibrations are excited as machine climbs throughwhirl frequency critical RPM and remain at higher speeds. Remedy :

Rotor must be reworked (mounting improved).Gear tooth Tooth mesh frequency Radial and Sidebands occur from modulation of tooth meshdamage and multiples thereof axial vibration at rotation frequency; may be isolated using

with sidebands located envelope analysis.at multiples of rotationfrequency

Belt drive Rotation frequency and Radial Additionally recommended : combined RPM and beltdamage multiples thereof speed measurements to check for belt slippage.Turbulence; Blade/vane passing Radial and Additionaly recommended for pumps : shock pulsecavitation frequency axial measurement at the pump housing.Electrically Rotation frequency, Radial and Sidebands may also occur located at multiplesinduced 2x line frequency axial of the rotation frequency; vibration ceases when powervibration is cut off.Frequency Multiples of motor line Radial Disappears in direct line operation; proportionalalternator frequency to motor line frequency.signal


Contoh lapangan : Sifter


Spectra frekuensi dari Sifter


Contoh no. 2 : Turbocompressor

Tidak lama sebelumperbaikan total

Tidak lama setelahperbaikan total


Contoh no. 3 : Foundry Fan


Contoh no. 4 : Tunnel Furnace Fan


Contoh : Pompa centrifugal


• Evaluation criteria:ISO 10816-3

Symptom : High Amplitude at fn

Unbalance

Machine spectrum:

v [mm/s]

fn f [Hz]

• Fundamental Freq. Fn = RPM [Rev/min]60

fn f n

Misalignment

Machine spectrum:v

[mm/s]

fn 2xfn f [Hz]

Symptom : Increased amplitude visible at fn and/ or 2x

• First and Second order of rotor frequency

Radial : parallel misalignmentaxial : angular misalignment

•

Machine Vibration Example 1


Gear mesh faults

2xfz 3xfz 4xfz

Symptom : Harmonics of fzvisible

fn1

fn2

z1

z2

fz f (Hz)

Machine Spectrum:a

mm/s²

• Gear mesh frequency fz = fn1. Z1= fn2. Z2

• fn1 : rotational frequency driven shaft

•

Z, Z2 : number of gear teeth

Cracked / Broken Tooth

fn1fn2

z1 z2

fz 2xfz 3xfz f (Hz)

Machine Spectrum:amm/s²

Symptom : Side bands with fn• Side band distance fn is the fundamental frequency

of the defective gear (broken tooth)• many side bands around fz gear mesh with slowly

decreased amplitudes




Bad foundation

fn

nf f (Hz)

Machine spectrum:v mm/s

2xfn 3xfn 4xfn

Symptom : Harmonics of fn are visible

• Root Cause: Resonance or Instability

fundamental freq. fn =•RPM[Rev/min]

60

Turbulencess=9

fn

x=3(e.g. fixture for bearing)

f (Hz)

Machine spectrum:

fn fBPF x ∗ fBPF

v mm/s

Symptom : Blade pass frequency fBPF

• Blade pass frequency fBPF = fn . s•• s: number of blades• x: number of disturbance locations

Higher orders x*fBPF = fn . s . x



Resonance

a) Machine spectrumVmm/s

fn f (Hz)

c) Waterfall diagram velocityspectra in coast down

Resonance step-up

vmm/s

n (Rev/min)Natural frequency f (Hz)

nf 2xfn 3xfn

fn

2xfn 3xfn 4xfn 5xfn

Symptom : Harmonics of fn visiblepreferably uneven multiples

fundamental freq. fn =•RPM[Rev/min]

60

b) Bode diagram in coast down

ϕ(°)

Phase shift of 180°

nRes. n in Rev/min

vmm/s

nRes.

Resonance step-up

n in Rev/min


Productive Maintenance Technology

BEARING CONDITIONMEASUREMENT


Types of Bearings

Journal Bearings• Stationary Signals• Relative Low Frequency• Displacement transducer

Journal Bearings• Stationary Signals• Relative Low Frequency• Displacement transducer

Rolling Element Bearings• Modulated Random Noise• Pulsating signals• High Frequency• Accelerometers

Rolling Element Bearings• Modulated Random Noise• Pulsating signals• High Frequency• Accelerometers

Use Proximity probes

Use Accelerometers

Monitoring Techniques


VIR > VRE > VOR > VRC

fIR > fRE > fOR > fRC

bearing clearance

contact no air gap

breaking impulseroller enters load zone

load zone = measuring zone

v(fn)

V c

V b

Fcentrifugal, rolling element

Fdyn., rotor

Fstat, rotor

acceleration impulseroller leaves load zone

vibration

shaft

housing

Example:

bearing type 62222C3 = 0.05 mm

gap

C3

Hertzsurface pressure

Forces and Motions in Rolling Bearings


A Typical Bearing Life Cycle


Types of Rolling Bearing Damages (1)

Damages types/ Causes

- lifetime expired- overloading- assembly /

- greasing deficiencymanufacturing error

shock pulses

wear

wear

1 Wear

2 Damage torolling track

- lifetime expired- bearing overloaded- bearing under-loaded- greasing deficiency

damage

envelope

shock pulses

3 Contaminated lubricant

- Damaged rolling track- damaged sealing- contaminated

lubricant

high variation in shock pulse levels

and defect frequencies




4 Greasing deficiency

- greasing deficiencyUnder-loading-

temperature rises very late

5 Unround deformation of bearing race

- assembly error- manufacturing defect

in shaft or bearing housing

damagefrequenciesin envelope

shock pulsesair gap

dirt

6 Jammed loose bearing

- in bearing housing(sliding fit)

- mis-calculation of housing design

high vibrationincreasing bearing

temperature

fixed bearing loose bearing




7 ExcessiveGreasing

- maintenance error (quantity, interval)

- defective grease grease drain

Large temperature-Increase after greasing

8 Installed at anangle

- assembly errorWhistling

Bearing noise

clearance too small9 Rolling bearing

- assembly error at

-inner race diameter

- got hot by friction after greasing deficiency

bearing with taper sleeveshaft diameter to large to

Large temperatureincrease after greasing

deficiency


Types of Rolling Bearing Measurement Methods

k (t) Method Spike Energy ValueBCU Value Kurtosis FactorgSE - Factor

SEE Factor Acceleration Crest Factor

Shock pulse measurement

?

?

•••

NormalisingAlarm Levels Gradient of trend development is necessary for evaluation of rollingbearing condition


i

ideal measurement

dB

dB = normalised shock pulse value

dBi = initial value• Basic normalised shock pulse value• function of RPM and shaft diameter

n

dBi = (f(φ, rpm)

dBn = dBsv – dBi

-9

0

90dBsv

dBsv= absolute shock pulse value

dBia = (f(φ, rpm)

dBn = dBsv – dBia

dBia = dBi + dBa

Where dBa(dB) is the adjusting value

measurement location with signal damping

dBsv

0

90

-9

dBia

dBm

dBc

dBm

dBc

dBn

dBia = adjusted initial value• Actual measurement location

(not at load zone)• influencing factors like load condition

lubrication and bearing type

Normalising of Shock Values


Normalising of Shock Pulse Measurements


d

n - number of rolling elements in contact with damage

ba - extent of damage torolling bearing component

0 good

ac

at

1 very small- small material defects- several pitting- defect frequencies are visible

in envelope spectrum

2 small - slight material splintering- Max values of shock pulses begin to rise

when rolling element passes over defect

Extent of rolling bearing surface damage


3 medium - one roller drops into slight depression caused by damage to rolling track

- maximum values rise perceptibly

- one or more rollers drop into large depression by damage to rolling track

- maximum values rise dramaticallycarpet values rise continuously

4 large

- carpet values rise substantially- bearing approaching crash- componentsmay break- increasing machine vibrations- rotor drops into very large depression- several rollers drop into severe

5 very large

Extent of rolling bearing surface damage


Productive Maintenance Technology

ENVELOPE ANALYSIS


Envelope Analysis – Rolling Bearings Fault Detection

No rolling track defect:

Time signal:a

m/s2

t (s)

am/s2

t (s)

Rectification

Envelope

am/s2

t (s)

Enveloping

f (Hz)

am/s2

Envelope spectrum:


Rolling track defect:

Time signal:a

m/s2

t (s)

am/s2

t (s)

Rectification

am/s2

Envelope

t (s)

Enveloping Envelope spectrum:a

m/s2

fRPOF

2• 3• 4• f (Hz)

Defect frequency

fRPOF

fRPOF

fRPOF

(Hz)• fRPOF=

1TRPOF

Envelope Analysis – Rolling Bearings Fault Detection


Roller Bearing Race Track DefectsOuter Race Defect:

2fRPOF3fRPOF4fRPOF5fRPOF

Envelope Spectrum:a

m/s²

f (Hz)fRPOF

Rolling element pass outer race fRPOF and harmonics clearly visible• if only fRPOF appears, then it can also be an unround

deformation of the outer race track

• In the case of very big unbalance, side bands with interval

(in the load zone modulation with fn as the unbalance runsfn appear because of periodic load changes

periodically through the load zone)

Inner Race Defect:

f 2xfRPIFRPIF

Envelope Spectrum:a

m/s²

f (Hz)

Rolling element pass inner race frequency fRPIFand many side bands with interval fn

• Modulated with the fundamental frequency fn as the innerrace defect runs periodically through the load zone with fn

• Fundamental modulation frequency fn and harmonics are visible


Roller Bearing Defects – Part 3 Rolling element defect:

Rolling element pass frequency fRPFwith harmonicsAnd side bands with interval fCRF• fRPFcan be also visible because of too small bearing clearance

or insufficient lubrication• Modulation with cage rotational speed fCRF , as the rolling

element runs periodically through the load zone with fCRF• Sub-harmonics of fRPF exist always with the harmonics, because the

pulse on outer race gives a higher level as pulses on the inner race • Fundamental modulation frequency fCRFand harmonics are visible

Cage Defect:

2 fCRF CRF3 f 4 fCRF

Cage rotational frequency fCRF and harmonics

• fCRFcage rotational frequency is cage defect frequency

• coming out of the load zone: the rolling element is accelerated and slides on the cage defect

• or coming into the load zone: the rolling element is braked and slideson the cage defect

visible

f0.5 RPF RPF•f 1.5•fRPF RPF2•fRPF RPF3•f

Envelope Spectrum:a

m/s²

f (Hz)2.5 f•

Envelope Spectrum:a

m/s²

f (Hz)CRFf

Documents

VIBRASI LEVEL 2