305573823-VIBRASI-Level-1.pdf

Copyright 2004- PT. Putranata Adi Mandiri – sole agent Prüftechnik AG, Germany 1
Condition Monitoring
& Vibration Fundamentals

Kenapa perlu condition monitoring ?
Biaya maintenance setelah pengenalan condition monitoring

Penyebab dari breakdown mesin

Apakah itu, Condition Monitoring ?
Suara !
Apa lagi ?
Temperature Pressure
Output Speed
Phase Vibration
Motor Current Oil Quality & Condition
Casing Expansion Differential Expansion
Eccentricity Rotor position
Valve position
Monitoring Parameters

Belt
vibrations
Unbalance
Mis-
alignment
Lubrication
Oil contam
Blade
defects
Stator
defect
Component
resonance
Rotor-
defect
Gear mesh
defect
Bearing
defect
Tipe Monitoring
Suara
X X X X X X X X
Oil Analysis
X X X X X X X
Vibration

Temperature
X X X X X X X X
Kerusakan pada mesin – Penyebab utama kerusakan

Pengukuran vibrasi

Kondisi bearing : lokasi persiapan

Pengukuran kavitasi

Pengukuran RPM

Pengukuran temperatur

Contoh alat - 1

Contoh alat - 2

Contoh alat - 3

Apakah ‘vibrasi’ itu ?
Vibration is a mechanical oscillation around a reference position.
In a machine, vibration is the result of internal dynamic forces created
by the rotating elements.
Reference : Introduction to Machinery Analysis and Monitoring – Second Edition - by John S. Mitchell

Parameter-parameter vibrasi
Harmonic motion is the simplest form of vibration, when plotted as a
function of time, it is represented by a sinusoidal curve.
A = Amplitudo, T = Perioda waktu, f = 1/T = frekuensi
φ = Phase

Frekuensi rotasi

Parameter umum pengukur vibrasi
∫
∫
=
=
T
rms
T
m
dt
t
x
T
x
dt
t
x
T
x
0
2
0
)
(
1
)
(
1
T
f
f
t
x
t
x p
1
2
sin
)
(
=
⋅
=
⋅
=
π
ω
ω
mean
rms
factor
Form
rms
peak
factor
K
rms
peak
factor
Crest
=
×
=
=
Rms = Root Mean Square
M = mean (rata-rata)
P = Peak (puncak)

Faktor-faktor konversi untuk gelombang sinus
Conversion ke :
Dari :
Faktor
Peak-to-Peak
value
Peak value Mean value Effective / RMS
value
0.32 = 1/π 0.35 = 1/2√2
0.71 =1/√2
1.11 = π/2√2
1
0.64 = 2/π
1
0.90 = 2√2/π
0.5
1
1.57 = ½ π
1.41 = √2
1
2
3.14 = π
2.83 = 2√2
Peak-to-Peak value
Peak value
Median value
Effective/RMS value

Nilai Peak dan RMS

Layar VIBROTIP®

Lokasi penempatan transducer yang cocok

Typical Uses of Vibration Transducers
Radial Casing
Vibration
Radial Shaft
Vibration Position
Axial Shaft
Vibration Position

Contoh alat - 1

Displacement, velocity acceleration
( )
p
p
p
p
p
p
pp
p
p
p
p
p
p
x
f
x
f
a
x
f
x
f
v
x
x
t
a
t
x
t
a
t
v
t
x
t
v
t
x
t
x
⋅
⋅
=
⋅
⋅
=
⋅
⋅
=
⋅
⋅
=
⋅
=
+
⋅
=
⋅
−
=
⎟
⎠
⎞
⎜
⎝
⎛
+
⋅
=
⋅
⋅
=
⋅
=
2
2
2
2
47
.
39
4
28
.
6
2
2
1
sin
sin
)
(
2
sin
cos
)
(
sin
)
(
π
π
π
ω
ω
ω
π
ω
ω
ω
ω

Bagaimana mengukur amplitudo vibrasi ?
( )
π
ω
ω
ω
π
ω
ω
ω
ω
+
⋅
=
⋅
−
=
⎟
⎠
⎞
⎜
⎝
⎛
+
⋅
=
⋅
⋅
=
⋅
=
t
a
t
x
t
a
t
v
t
x
t
v
t
x
t
x
p
p
p
p
p
sin
sin
)
(
2
sin
cos
)
(
sin
)
(
2

Transducer Vibrasi
Sensor…Transducer…Probe…Apakah ini ?
….Pada dasarnya peralatan ini merubah vibrasi
mekanis ke signal electric
Accelerometer
Charge Type
Line Drive
Constant Voltage
Constant Current
Velocity
Transducer
Displacement
Shaft Riders
Proximity Probes
(Eddy Current Probes)

Tipe transducer vibrasi

Fundamental Vibrasi
Seberapa besar vibrasi diijinkan ?
1. Gunakan Batas Vibrasi Absolut
- diberikan oleh pembuat mesin
- gunakan Standard Vibrasi
Internasional, misalnya ISO
2372, VDI 2056, BS 4675
(Canadian Government -
Vibration Limit for
Maintenance)
2. Gunakan Batas Vibrasi Relatif
- gunakan histori mesin
- gunakan batas dari
pengalaman sendiri
- lihat kondisi baru

Formula umur bearing
)
10
6.7753
Konst
:
menjadi
berubah
Konst
maka
lbs,
dalam
M
L,
C,
dan
inch/s
dalam
V
(Jika
(RPM)
speed
N
(mm/s)
vibrasi
V
(kg)
berat
M
10
2.6674
Konst
(kg)
service
-
in
bearing
beban
L
er)
manufactur
i
spesifikas
(dari
(kg)
bearing
kapasitas
C
(jam)
bearing
umur
H
N
16667
x
N
V
M
Konst
L
C
H
5
-
6
-
3
⋅
=
=
=
=
⋅
=
=
=
=
⎟
⎠
⎞
⎜
⎝
⎛
⎟
⎠
⎞
⎜
⎝
⎛
⋅
⋅
⋅
+
=

Contoh menggunakan formula umur bearing
(RPM)
1,800
speed
N
(mm/s)
15.24
vibrasi
V
(kg)
5,850
berat
M
10
2.6674
Konst
(kg)
450
service
-
in
bearing
beban
L
(kg)
9,000
bearing
kapasitas
C
(jam)
bearing
umur
H
tahun
1.13
365)
(24
9,971
jam
9,971
1,800
16667
x
1,800
15.24
5,850
10
2.6674
450
9,000
H
6
-
3
6
-
=
=
=
=
=
=
⋅
=
=
=
=
=
=
=
⋅
=
=
⎟
⎠
⎞
⎜
⎝
⎛
⎟
⎠
⎞
⎜
⎝
⎛
⋅
⋅
⋅
⋅
+
=

Ref
Batas
Peringatan
Batas
Bahaya
Ref
Batas
Peringatan
Batas
Bahaya
Monitoring Vibrasi
Mesin ‘A’ Mesin ‘B’
Mana mesin yang bagus ?

Waktu
Tingkat
Vibrasi
Mesin ‘A’
Batas Bahaya
Batas
Peringatan
Mesin ‘B’
Monitoring Vibrasi

Waktu
Tingkat
Vibrasi
Batas Bahaya
Batas
Peringatan
Mesin ‘B’
Mesin ‘A’
Monitoring Vibrasi

Overall Measurement
Time
Vibration
um
mils
mm/s
x x x
x x
x
x
x
x
x
x
x
x
Lead Time
Ref
Alert
Limit
Danger
Limit
Vibration
um
mils
mm/s

*
*
*
*
*
*
*
*
* *
*
*
* *
*
*
Poor Trend accuracy with no control
(Takes all data makes trend)
Danger Limit
Alert Limit
*
*
*
*
*
*
*
*
* *
*
*
* *
*
*
Improve Trend accuracy with Manual
Automatic Trending
(User define trend conditions)
Danger Limit
Alert Limit
Manual Automatic Trending
Vib Vib
Time Time
Trending with a Difference

Trending Vibration RMS velocity

Trending shock pulse method
5
/2
5
/9
8 6
/2
2
/9
8 7
/2
0
/9
8 8
/1
7
/9
8 9
/1
4
/9
8 1
0
/1
2
/9
8 1
1
/9
/9
8 1
2
/7
/9
8 1
/4
/9
9 2
/1
/9
9 3
/1
/9
9 3
/2
9
/9
9
d
a
te
-1
0
-5
0
5
1
0
1
5
2
0
2
5
3
0
3
5
4
0
4
5
5
0
S
h
o
c
k
P
u
ls
e
d
B
n
d
B
m
d
B
c
W
a
rn
in
g
C
a
rp
e
t
A
la
rm
C
a
rp
e
t
W
a
rn
in
g
M
a
x
A
la
rm
M
a
x
Path of Location : PT. CaltexWater PlantFresh Water
PumpCentrifugal PumpImpeller Sideshock pulse m. 120
Number of Meas. Values : 6
Meas. Task : Bearing
Meas. Type : Sum
Unit: dBn
SIM Date Time dBm dBc Ø (mm)
RPM dBia dBa
5/3/98 9:21:40 PM 9 1 80.00 -
20 0
6/2/98 8:46:42 PM 9 5 80.00 -
20 0
7/2/98 8:21:40 PM 11 3 80.00 -
20 0
8/8/98 6:03:53 PM 9 3 80.00
1500 20 0
9/18/98 1:18:12 AM 11 4 80.00
1500 20 0
3/23/99 11:48:27 PM -3 -10 80.00
1500 20 0

Trending bearing condition

Standar ISO 2372
Amplitudo
velocity
RMS
(mm/s)
Daya 15 kW
atau 20 HP
15 kW - 75 kW
atau 20 – 100 HP
Daya 75 kW
atau 100 HP
Turbomachinery
(Turbine/Comp dll)

Standar ISO 10816-3

Standard ISO 10816-3

Persiapan untuk pengukuran vibrasi

VIBCODE: pengenalan lokasi dengan cara otomatis

Sistem VIBCODE

Vibrasi dominan vertikal
POMPA/DN
MOTOR/DR
Penyebab Utama :
1. Pondasi (karatan, dudukan lemah, melengkung, baut kendor)

Vibrasi dominan horizontal
BLOWER
MOTOR
Penyebab Utama :
1. Unbalance
2. Housing bearing
3. Gaya aerodinamik

Vibrasi dominan aksial
BLOWER
MOTOR
Penyebab Utama :
1. Misalignment
2. Sleeve bearing
3. Housing bearing

Vibrasi dominan vertikal, horizontal, aksial
Penyebab Utama :
1. Antifriction bearing
2. Shaft bengkok
3. Pondasi melengkung
BLOWER
MOTOR

Fase

Contoh fase - 2

Contoh fase - 3

Vibrasi gabungan
1
2
1 + 2
Amplitudo(1) = 10, Amplitudo(2) = 5, Amplitudo(1+2) = ???

Vibrasi gabungan 1 frekuensi

Vibrasi gabungan 1 frekuensi beda fase

+ +
Time Signal
Machine Vibration Signal
S1 S2 S3
S1 + S2 + S3

Spectrum frekuensi dari gelombang sinus
Frekuensi = 1 / T

Time signal Spectrum frekuensi

Machine Vibration Signal Time Signal
Vibration Fundamentals
Hz
Freq. Spectrum

FFT Analysis
+ +
1X 5 kHz
FAST
FOURIER
TRANSFORMATION
Converting
time signal to
freq. spectrum
Eg.
1x = 1/T
T

Spectrum Analysis

Filtering
Window Function
Detectors
FFT
Sample 1
+ =
FFT Spectrum 1
Sample 2
Window Function
Detectors
FFT
Filtering
FFT Spectrum 2
Avg FFT Spectrum
FFT - Fast Fourier Transformation

Time Signal:
transient signals, repeat
frequencies, beats and sine
waveform good visible
→ but:
Individual Frequencies of the
Vibration Spectrum
almost not visible
Amplitude Spectrum:
good visibility of the dominant
frequencies of the vibration signal
→ but:
transient Signals, shocks with
repeat frequency and beat signals
almost not visible
FFT
Fast Fourier
Transformation
Time vs FFT

Spectrum frekuensi dari signal yang kompleks

Contoh : Pompa centrifugal

Spectra untuk bentuk gelombang yang standard

Displacement, velocity acceleration spectra

Fungsi window

Skala linear dan logaritmis
Logaritmis

Spectrum dengan alarmband
0 5 1
0 1
5 2
0 2
5 3
0 3
5 4
0 4
5 5
0 5
5 6
0 6
5 7
0 7
5 8
0 8
5 9
0 9
5 1
0
0
fH
z
0
.0
0
.5
1
.0
1
.5
2
.0
2
.5
3
.0
3
.5
4
.0
4
.5
5
.0
vm
m
/s
W
a
rn
in
g
A
la
rm
Location :PT. CaltexWater PlantFresh Water
PumpCentrifugal PumpImpeller Sidemach.
spectr. 600 including band alarm
# X Y
0 25.00 0.78
1 49.75 0.49
2 99.75 0.40
3 74.75 0.23
4 124.75 0.19
5 97.25 0.15
6 10.25 0.09
7 9.00 0.09
8 122.00 0.09
9 11.75 0.07

Vibrasi harmonis dan vibrasi resonan
Vibrasi
harmonis
Vibrasi
resonan

305573823-VIBRASI-Level-1.pdf

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