typical steps of field balancing illustration with model 907 e-mail: [email protected],...
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Typical Steps of field Balancing
Illustration with model 907
E-mail: [email protected], [email protected] Telephone: +8610 82895321
Fax: +8610 82895320http://www.sendig.com
Balancing Training Part 1
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1. Collecting Machine data
2. Preparing Instrument & Sensor
3. Balancing really required ?
4. Balancing possible ?
5. Procedure of balancing
An Overview of the Steps
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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
Sample: Machine to be balancedImpeller Parameter:
• Diameter: 1400mm
• Thickness: 500mm
• Blade Number: 12
• Material:Fiberglass-
Reinforced
Plastics
• RPM: 1825 r/min
• Bearing Model: ?
Motor Parameter:
• Power: 75kW
• RPM: 1500 r/min
Others:
• Belt transmission
• Spring base
• Manufacture: LG
Impeller
Bearing1 Bearing2
Motor
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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 connectingAttach
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
1) Switch to Analyzer
2) Use “Collector” to measure vibration
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6: Point: Motor-1-Side-2-XAlarm-mode: DisplacementFreq-Range: 500HzSensor:4.6………………………… New Data Old DataACC xxx / xxx m/s2
VEL 7.2 / 2.1 mm/sDISP 68 / 12 µm ENV xx / xx m/s2
Horizontal VELOCITY is the critical parameter
Comparison with ISO2372
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Overall Value Measurement
Acc. Vel. Disp. Envelope
Peak ms-2 RMS mm/s P_P um RMS ms-2
Hor. 88.81 9.95 101.5 5.268
Ver. 55.89 5.554 38.77 7.362
Sample
Measurement
9.95 mm/s
Not Permissible, Balancing really required !
Sample
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Step 4-1: Balancing possible? – “single peak spectrum” ?
Use 904/907 to measure vibration spectrum Only “single peak spectrum” can go for balancing
1) Switch to Analyzer
2) Use “Collector” to measure vibration
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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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
1) switch to balancer and use 2-planes balancing procedure
2) Page down to “Initial Measurement” to measure vibration phase at X & Y
3) See if “90o phase difference” exist?
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Phase Measurement:
Velocity Amplitude Phase
Vertical: 9.416 320
Horizontal: 3.08 116
Since phase difference is not 90o nor closer to 90o ,this means the problem with the fan is something else other than unbalance.
Phase difference
not 90o
SampleSample of “non-90o phase difference” –
You cannot reduce the vibration by Balancing
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1. Phase stable
2. Phase Measurement:
Velocity Amplitude Phase
Vertical: 0.693 73
Horizontal: 1.569 150
?
Phase difference is
77o
SampleSample of nearly “90o phase difference” –
You can reduce the vibration by Balancing
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Procedure of balancing
Balancing Training Part 2
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Different Kinds Of Imbalance
1-plane imbalance
2-plane imbalance
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Characteristics Of Imbalance
1. The vibration frequency is mainly composed of
RPM frequency. For each round the rotor turns, a v
ibration 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
Q
AA 01
0AP
amplitude phase RPM
A
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)
3 fix a trial mass Q on the plane, measure vibration A1
4 calculate influence coefficients:
5 calculate balancing mass P:
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Illustration of 1 Plane Balancing
A0A1
A1- A0
o
•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 :
Ko
QP
01
0
AA
AQP
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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 NOTICES DURING THE OPERATIONOPERATION
Confirm the dynamic balancing are needed according to spectrum and phase analysis.
Direction of phase: reverse to the direction of rotation
Reflecting slice
phase
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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
•The radius of loading trial mass is as same as loading the amended mass
•The turning speed is steady
before and after trial value difference<25% value difference>25%
phase difference<25° increase or move mass move trial mass
phase difference>25° ok ok
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1-PLANE BALANCING
Without influence coefficients
907
A
Tachosensor
Accelerometer
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Operation Basic
Prompt is displayed at the last line Press ‘∧’ and ‘∨’ key to move the curso
r up and down Press Enter to select iterm Press number keys to input digits To other MENU, press PgDn or PgUp
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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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CALCULATION
Cursor on 2nd line, press ENTER to calculate influence coefficients
The result is shown in 4th line
Cursor on 2nd line, press Enter to calculate balancing mass
The result is shown in 3rd line
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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
Pa
Pa1
Pa2
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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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Calculation, Decomposition & verification
calculate
balancing mass
Decomposition
and verification
are the same as
illustrated earlier
Pa
Pa1
Pa2
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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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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
earlier
Pa
Pa1
Pa2
Pb Pb1
Pb2
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2-PLANES BALANCING With influence coefficients
With influence coefficients, you do not need to add trial mass. You need only measure the initial vibration.