typical steps of field balancing illustration with model 907 e-mail: sales@sendig.com,...

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Typical Steps of field Balancing

Illustration with model 907

E-mail: sales@sendig.com, sendigbj@yahoo.com.cn 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.