Balancing Training
Part 1
Typical Steps of field Balancing
Illustration with model 907
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1
An Overview of the Steps
1.
Collecting Machine data
2.
Preparing Instrument & Sensor
3.
Balancing really required ?
4.
Balancing possible ?
5.
Procedure of balancing
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Step 1 - Collecting Machine data

Understand the machine to be balanced
as much as possible

Collect machine data

Take a photo of the machine
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Sample: Machine to be balanced
Impeller Parameter:
• Diameter: 1400mm
• Thickness: 500mm
Bearing1
Bearing2
• Blade Number: 12
• Material:Fiberglass-Reinforced
Impeller
Plastics
• RPM: 1825 r/min
• Bearing Model: ?
Motor Parameter:
• Power: 75kW
• RPM: 1500 r/min
Motor
Others:
• Belt transmission
• Spring base
• Manufacture: LG
Step 2 - Preparing Instrument & Sensors



Sendig-904/907 dual-channel data
collector/analyser/balancer
A notebook computer
Sendig-MCM3 Analysis Software
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Sensors & Cable connecting
Attach reflecting
paper on shaft
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Step 3 - Balancing really required ?


Use 904/907 to measure overall vibration values
Compare with ISO Standard
2) Use “Collector” to
measure vibration
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1) Switch
to Analyzer
7
Horizontal VELOCITY is the critical parameter
6: Point: Motor-1-Side-2-X
Alarm-mode: Displacement
Freq-Range: 500Hz
Sensor:4.6
…………………………
New Data Old Data
ACC xxx / xxx
m/s2
VEL 7.2 / 2.1
mm/s
DISP 68
/ 12
µm
ENV
xx
/ xx
m/s2
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Comparison with ISO2372
Sample
Overall Value Measurement
Acc.
Disp.
Envelope
RMS mm/s
P_P um
RMS ms-2
Hor. 88.81
9.95
101.5
Ver. 55.89
5.554
38.77
Peak ms-2
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Vel.
5.268
7.362
10
Sample
Not Permissible, Balancing really required
Measurement
9.95 mm/s
!
Step 4-1: Balancing possible?
– “single peak spectrum” ?


Use 904/907 to measure vibration spectrum
Only “single peak spectrum” can go for balancing
2) Use “Collector” to
measure vibration
1) Switch
to Analyzer
3) Use “C-Spect” to
see velocity spectrum
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Sample of non-single peak spectrum- not suitable for Balancing
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Sample of non-single peak spectrum- Better change bearing before balancing
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Sample of single peak spectrum –
You can reduce the vibration by Balancing
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15
Step 4-2: Balancing possible ?
– “90o phase difference” ?


Use 904/907 to measure vibration phase difference between
vertical and horizontal directions
Only “90o phase difference” can go for balancing
3) See if “90o phase difference” exist?
1) switch to balancer
and use 2-planes
balancing procedure
2) Page down to “Initial
Measurement” to measure
vibration phase at X & Y
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Sample
Sample of “non-90o phase difference” –
You cannot reduce the vibration by Balancing
Phase Measurement:
Velocity
Vertical:
Horizontal:
Amplitude
9.416
3.08
Phase
320
116
Phase
difference
not 90o
Since phase difference is not 90o nor closer to 90o ,this means the
problem with the fan is something else other than unbalance.
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17
Sample
Sample of nearly “90o phase difference” –
You can reduce the vibration by Balancing
1. Phase stable
2. Phase Measurement:
Velocity
Vertical:
Horizontal:
Amplitude
0.693
1.569
Phase
73
150
Phase
difference is
77o
?
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Balancing Training
Part 2
Procedure of balancing
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19
Different Kinds Of
Imbalance
1-plane
imbalance
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2-plane
imbalance
20
Characteristics Of
Imbalance
1. The vibration frequency is mainly composed of
RPM frequency. For each round the rotor turns, a
vibration is occurred.
2. The wave is an approximate sine wave.
3. There is a difference of 90o between the vertical
vibration phase and the horizontal one.
4. With RPM increasing, the vibration amplitude is
increased
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Basic Principle
Of 1 Plane Balancing
1 select a plane to fix trial mass and a
point to measure, draw scale of phase
and sign of 0o phase
2 measure initial vibration A0(phase
and amplitude)
A
3 fix a trial mass Q on the plane,
measure vibration A1
4 calculate influence coefficients:
A  A0
phase RPM
amplitude
  1
Q
P   A0
5 calculate balancing mass P:
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Illustration of 1 Plane Balancing

K
o

Q
P
A1- A0
A1  A0
o
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•draw A0 & A1, calculate A1- A0
•measure the angle  between A1- A0
and A0
•turn Q a  along the direction of  ,
gain the correct location of balancing
mass.
•the weight of balancing mass is as
the following :
A
P Q
0
A1  A0
23
Method of Influence
Coefficients

Method of influence coefficients is
widely used, its step as the following
(1 plane balancing as example):
1 measure initial vibration
2 fix a trial mass
3 measure the vibration with the trial mass
4 calculate the result of balancing mass
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IF THE INFLUENCE COEFFICIENTS ARE KNOWN, THE
STEP OF FIXING TRIAL MASS ARE IGNORED
The former steps are simplified as the following:
1) measure initial measurement
2) input influence coefficients
3) calculate the result of balancing mass
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NOTICES DURING THE OPERATION


Confirm the dynamic
balancing are needed
according to spectrum
and phase analysis.
Direction of phase:
reverse to the
direction of rotation
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phase
Reflecting slice
26
SELECTING PARAMETERS


Measure displacement or velocity for
middle or low speed machines
Measure velocity or acceleration for high
speed machines
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CONFIRM whether the trial is suitable
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•The radius of loading trial mass is as same as loading
the amended mass
•The turning speed is steady
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1-PLANE BALANCING
Tacho
sensor
Without
influence
coefficients
A
Accelerometer
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907
29
Operation Basic


Press ‘∧’ and ‘∨’ key to move the
cursor up and down

Press Enter to select iterm

Press number keys to input digits

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Prompt is displayed at the last line
To other MENU, press PgDn or
PgUp
30
Always make sure the “Setting”
is correct before the balancing
Enter a digit, select 1 set of data from 10
Enter a digit, select plan number
Change by “ENTER”,
use displacement or velocity
for most machines
Input sensitivity (from
accelerometer certificate)
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INITIAL MEASUREMENT



Press Enter to measure
rotation speed first
Press Enter for a moment
to measure vibration after
rotation speed become
steady
After phase and amplitude
become steady, press Enter
for a moment to end the
measurement
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TRIAL ESTIMATION



Input the 4
parameters
When cursor on 6th
line, press Enter to
calculate trial range
Stop the machine, fix
a trial mass according
to the range
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TRIAL MEASUREMENT




Input phase and weight of the
trial, confirm whether it will be
removed afterward, restart the
machine
Move cursor to 6th line, press
Enter to measure rotation speed
When RPM steady, press Enter a
moment to measure vibration
When amplitude and phase
steady, press Enter for a
moment to end the
measurement
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TRIAL RESULT



See what the 6th line
shows
If YES displayed, press
Pg Dn to go on
If NO displayed, stop
the machine, adjust
trial mass, return to the
early page of TRAIL
MEASUREMENT,
measure again
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35
CALCULATION


Cursor on 2nd line, press
ENTER to calculate influence
coefficients
The result is shown in 4th line
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

Cursor on 2nd line, press
Enter to calculate balancing
mass
The result is shown in 3rd line
36
Decomposing/Splitting



Input the 2 angles
Display the results
If nothing displayed at
right side, change the
order of the 2 angles
and re-enter
Pa2
Pa
Pa1
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VERIFICATION




Cursor on 2nd line, press Enter
to measure rotation speed
When RPM steady, press Enter
a moment to measure
vibration
When amplitude and phase
steady, press Enter for a
moment to end the
measurement
The last 2 lines displays the
results
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1-PLANE BALANCING
With influence coefficients,
you do not need to add trial
mass. You need only measure
the initial vibration
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SETTING PARAMETERS
Set “Yes” for the question
of “Have influence
Coefficient?”
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INITIAL MEASUREMENT



Press Enter to measure
rotation speed
Press Enter for a moment
to measure vibration after
rotation speed become
steady
When phase and amplitude
become steady, press Enter
for a moment to end the
measurement
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INPUT COEFFICIENTS


Move the cursor to the
4th line, input
amplitude and angle of
coefficient
Press Pg Dn to the next
page
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42
Calculation, Decomposition &
verification

calculate
balancing mass

Decomposition
and verification
are the same as
Pa2
illustrated earlier
Pa
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Pa1
43
2-PLANES BALANCING
Without influence coefficients
The main difference than 1-plane:
1.
Need to add trial mass one after
another at the 1st plane and 2nd
plane
2.
Need to use 2 vibration sensors
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Sensors & Cable connecting
Attach reflecting
paper on shaft
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SETTING PARAMETERS
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INITIAL MEASUREMENT & TRIAL
ESTIMATION
Get 2
lines of
reading
here
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47
TRIAL I MEASUREMENT

Input phase
and weight of
the trial on
plane 1,
decide if it will
be removed,
restart the
machine
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TRIAL II MEASUREMENT

Input phase
and weight of
the trial on
plane 2,
decide if it will
be removed,
restart the
machine
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Calculation, Decomposition &
Verification

calculate
balancing mass

Decomposition
and verification
are the same
as illustrated
Pa2
Pb2
earlier
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Pa
Pb
Pb1 50
2-PLANES BALANCING
With
influence coefficients
With influence coefficients,
you do not need to add trial
mass. You need only
measure the initial vibration.
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