Fluke VIBXPERT II User manual

VIBXPERT®II
Operating Instructions
Balancing

'Balancing'
Operating Instructions
VIBXPERT® II
Dual channel
FFT data collector
and signal analyzer
Edition: December 2019
Order no.: LIT 53.202.EN
Translation of the german manual
Series: VIB 5.310
Firmware version: 3.2x

LEGAL NOTES
Copyright
Both this manual and the product it describes are copyrighted. All rights belong to the
publisher. The manual may not be copied, reproduced, translated or made accessible to
a third party in any form, neither in its entirety nor as an excerpt.
Disclaimer
No liability may be claimed against the publisher regarding the product described in
this manual. The publisher assumes no liability for accuracy of the manual contents.
Furthermore, under no circumstances may the publisher be held liable for direct or in-
direct damage of any kind resulting from use of the product or the manual, even if the
publisher has expressly indicated the potential for occurrence of such damage.
The publisher assumes no liability for any product defects. This warranty and liability
limitation applies to all distributors and sales partners as well.
Trademarks
The trademarks mentioned in this manual are generally noted as such and are the prop-
erty of their owners. Lack of such designation does not imply, however, that names are
not protected by trademark laws.
© Fluke Corporation, all rights reserved

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VIBXPERT II Balancing 12.2019
Foreword
Foreword
Congratulations! And thank you for choosing the dynamic balancing
option in one or two planes to expand your VIBXPERT II FFT data col-
lector and signal analyzer*.
The balancing module is based on the well-known "influencing coef-
ficients method" and is distinguished by its efficiency and ease of use.
The measurement process implemented in the instrument has been
optimized by a new knowledge-based algorithm. Perfectly matched
measurement settings save time-intensive preparation and also en-
able the automation of recurrent tasks. Simple operation is guaran-
teed by intuitive graphic guidance which leads the user through the
balancing procedure step by step. A number of methods are available
to compensate rotor imbalance: free balancing, fixed weight, fixed
location or tape measure balancing. If necessary, VIBXPERT can com-
bine all mounted weights into a single new weight. If you do not wish
to attach a balancing weight to the rotor, VIBXPERT will calculate the
mass that should be milled from the rotor.
And just think! VIBXPERT even grows to meet your future require-
ments. The latest analysis and diagnostic functions are added on a
regular basis and made available as an update. This ensures that you
are always have the most modern equipment.
For further information visit us on the Internet at:
http://www.pruftechnik.com
And if you are ever faced with an unsolvable task, our specialists from
the PRÜFTECHNIK Service and Diagnostic Center (SDIC) will be glad
to assist you. Just send an e-mail:
[email protected]
* Also called 'VIBXPERT' and 'measure-
ment instrument' in this manual.
About this manual
This manual describes the operation of the measurement device in
the optional "Balancing" mode. The description of the measurement
device and operation in the "Multimode" and "Route" modes appears
in the VIBXPERT operating instructions (LIT 53.201.EN).
If you do not have immediate access to this manual, direct help is con-
tained in the device and can be opened with the HELP key.
This manual is valid for firmware version 3.2x.

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VIBXPERT II Balancing 12.2019
Contents
Contents
Chapter 1: Introduction.............................................1-5
Safety ............................................................................................1-5
Symbols ..........................................................................................................1-5
Intended use..................................................................................................1-5
Conformity.....................................................................................................1-5
General safety................................................................................................1-6
Registration ..................................................................................1-7
Chapter 2: Balancing..................................................2-1
Balancing on machines with rotating masses..............................................2-3
Diagnosis.......................................................................................2-4
Preparatory activities ...................................................................2-5
Assembly ........................................................................................................2-5
Operation .....................................................................................2-9
Balancing in one plane ..............................................................2-11
Measuring the initial imbalance.................................................................2-12
Trial run........................................................................................................2-12
Trim run........................................................................................................ 2-13
Undoing balancing runs..............................................................................2-14
Balancing in two planes.............................................................2-15
Overview of the measurement procedure.................................................2-15
Determining the measurement plane & balancing plane A.....................2-15
Measuring the initial imbalance in plane A and plane B ......................... 2-15
Trial run........................................................................................................2-16
Trim run........................................................................................................ 2-16
Saving the result..........................................................................................2-16
Evaluation of the data...............................................................2-17
Options for balancing................................................................2-18
1. Combining balancing weights................................................................2-18
2. Changing the correction mode (Tools menu / Machine setup) ...........2-19
3. Removing the balancing weight (Tools menu/ Machine setup) ...........2-21
4. Check functions (Tools menu / Machine setup) ..................................... 2-21
5. Entering the balancing radius and rotor mass later (Tools) .................2-22
6. Speed for balance quality (Tools menu / Machine setup).....................2-22
7. Influence coefficient (Tools menu).........................................................2-22
Display setup ..............................................................................2-24
Printing the balancing report....................................................2-25
Setup parameters.......................................................................2-26
Machine setup .............................................................................................2-26
Measurement setup ....................................................................................2-29
Balancing with a control plane .................................................2-30
Balance calculator ......................................................................2-31
Operation of the balance calculator.......................................................... 2-32
Chapter 3: Appendix..................................................3-1
Balancing quality classes and groups of rigid balancing bodies ...............3-1
Messages during balancing .........................................................3-2
Emergency storage.......................................................................3-4
Index ...........................................................................3-5

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VIBXPERT II Balancing 12.2019
Introduction
Chapter 1: Introduction
Safety
You must carefully read and understand the safety instructions in the
VIBXPERT operating manual (LIT 53.201.EN) as well as the follow-
ing safety instructions for balancing before starting work with the
measurement device.
Symbols
Danger to life and limb.
Danger of improper operation which can cause
damage.
Tips on operation as well as information about bal-
ancing.
Intended use
VIBXPERT is intended for use as a portable balancing device for the
balancing of stationary machines equipped solely with rotating compo-
nents (rotors), e.g. turbine rotors, inductors, circulating pumps, cen-
trifugal compressors, fans, etc. This does not include machines with
oscillating components, e.g. all reciprocating machines.
VIBXPERT can be used without any restrictions for the balancing
of rigid rotors. Elastic (soft) rotors may only be balanced with VIB-
XPERT at the resonant frequency (±25%) by an experienced user. The
measurement instrument and its accessories may only be operated by
authorized personnel.
PRÜFTECHNIK Condition Monitoring assumes no responsibility for
any damage arising from improper use.
Conformity
The product complies with the relevant European directives. The dec-
laration of conformity is available as a PDF and may be downloaded
from the PRÜFTECHNIK homepage at:
www.pruftechnik.com/certificates

NOTE
ATTENTION
WARNING!

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VIBXPERT II Balancing 12.2019
Safety
General safety
• The applicable safety regulations must be observed when per-
forming measurements on running machines.
• When assembling measurement components, make sure that no
holders, cables, etc. project into the range of movement of rotat-
ing machine parts.
• The respective manufacturer's instructions must be followed
when mounting balancing weights.
Make sure that attachment points for balancing weights to be
welded on are clean; clamp the ground electrode of the welding
device onto the rotor and not onto the machine.
For balancing weights that need to be screwed on, the maximum
permitted RPM of the motor must be observed.
• The machine must be disconnected in order to work on the rotor
and must be secured against being switched on again in accor-
dance with the applicable regulations.
• Before the first measurement (initial run), it is important to
ensure that the preparatory activities have been carried out
correctly and completely. In addition to the assembly of mea-
surement components, particular attention must be paid to the
correct input of parameters in the machine setup. If an incorrect
rotor mass is entered, a trial weight that is too large may be
calculated as a result. This could have serious consequences for
personnel and machine!
• No one is allowed to remain in the radial vicinity of the ro-
tor during balancing runs. This area must be properly secured
against unauthorized entry. If the trial weight of the rotor on a
running machine detaches, there is a risk of fatal injury in this
area!
• If the rotor is in a protective housing, any gaps in the housing
must be closed before switching on the machine.
• The permitted switch-on frequency of the machine may not be
exceeded. Otherwise, the motor could be damaged.
• The cause of the imbalance must be determined before balanc-
ing, and must be corrected if necessary (e.g. remove any caking
on the rotor, weld any cracks on the impeller or replace the im-
peller).

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VIBXPERT II Balancing 12.2019
Registration
Registration
The balancing software is already contained in the instrument and
must be activated by entering a password. Changes to the instrument
or the loading of additional software are not necessary.
Entering the password
The password is given on the certificate contained in the scope of de-
livery of the balancing module.
• Click on "Device Setup" in the start screen.
• Click on "Registration" in the "Device Setup" screen (see below).
• Click on the "Balancing" in the "Registration" screen and enter the
registration password in the text editor.
Registration is now complete and the new operating mode now ap-
pears on the start screen.
Device Setup - Registration
'Balancing' module is registered

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VIBXPERT II Balancing 12.2019
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2-1
VIBXPERT II Balancing 12.2019
Chapter 2: Balancing
Increased vibrations on machines are undesirable phenomena. They
impair product quality, place additional strain on components and,
last but not least, reduce operational safety. The most frequent cause
for these increased vibrations is imbalance. The high centrifugal forc-
es that result lead to premature wear of machine components such
as bearings and seals, for example. Thus, the objective of balancing
rotors is to limit bearing forces and shaft deformations to acceptable
values.
VIBXPERT enables imbalance to be reliably detected and quickly cor-
rected. The balancing results are automatically compared with the
evaluation yardsticks of DIN ISO 1940 for the balancing condition of
rotating rigid bodies.
Imbalance
If a rotor is correctly balanced and this rotor is placed on balancing
rollers, any additional mass placed on the rotor will cause this mass to
immediately move downwards. This process is called 'roll off'.
Introduction
If this rotor is now turned with the balancing RPM, a centrifugal force
is caused perpendicular to the rotational axis by the displacement of
the center of gravity.
A static imbalance has to be corrected using 1-plane balancing be-
cause the planes of imbalance and center of gravity coincide. Consid-
ered from the measurement plane, the imbalance is static at a single
location.
If two equally heavy masses are attached to a completely balanced
rotor so that they lie exactly opposite in two separately lying radial
planes, this is called a couple imbalance (or a dynamic imbalance).
The center of gravity of the rotor remains on the rotational axis. The
imbalances cause a centrifugal torque that gives rise to opposing
forces of the same size in the bearings. Such imbalances can only be
balanced using two-plane "dynamic" balancing - one-plane balancing
would not bring any improvement.
Couple (dynamic) imbalance
Rotational axis
Imbalance
Moment
inertia axis
Imbalance

2-2
VIBXPERT II Balancing 12.2019
Two-plane balancing under operat-
ing conditions using an optical trig-
ger and two vibration transducers.
Introduction
R
R
Clamped weight
Reference mark
Optical trigger
Vibration transducer
If an individual imbalance which does not lie on the center of grav-
ity is added to a completely balanced rotor in one plane, it is called a
quasi static imbalance. It corresponds to the combination of a static
imbalance and a couple imbalance and is usually compensated in two
planes.
Basically, the consideration of whether to carry out balancing in one
or two planes depends on the specific machine situation, i.e. on the
balancing behavior of the rotor and the vibration behavior of the
machine. Simultaneous balancing in two planes is quicker and more
precise than successive balancing measurements in each of two in-
dividual planes. Residual errors that are accumulated in sequential
balancing are therefore prevented. The distance/diameter ratio of the
balancing planes is normally an important decision criterion.

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VIBXPERT II Balancing 12.2019
Introduction
Balancing on machines with rotating masses
The VIBXPERT balancing module is based on the well-known 'influ-
ence coefficients method':
First, VIBXPERT measures the vibration amplitude and phase angle
and the vibration caused by the imbalance or so-called 'initial imbal-
ance'. A defined trial weight* is then attached and the instrument
measures the resulting change in amplitude and phase. VIBXPERT
calculates the influence coefficients from the difference between both
vibrations according to magnitude and phase which precisely indi-
cates the location and magnitude of the balancing weight with regard
to the position and size of the trial weight. In the case of two-plane
balancing, the calculation of the influence of the mass is also taken
into account in the other plane. All so-called 'rigid' rotors are balanced
using this method.
A rigid rotor mainly exhibits proportional vibration behavior if the
balancing weight and angle change. In the case of fixed rotational
speed, weaknesses or resonances in the mounting have no influence
on the vibration behavior. If the machine rotates at a variable speed,
it frequently exhibits different vibration behavior for each revolution
and, therefore, has to be balanced several times over the range of low-
speed to high-speed running.
Soft rotors do not exhibit the expected proportional behavior with the
calculated balancing weight, and the coefficients method does not ap-
ply. Such rotors can normally only be balanced in balancing machines
using a force measuring procedure.
* VIBXPERT calculates the weight and
location for the required trial mass in
such a manner that it usually results in a
reduction in the existing imbalance and
in the associated vibration load. This has
the added advantage that the trial mass
does not have to be removed again but
can remain on the machine indefinitely.

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VIBXPERT II Balancing 12.2019
Diagnosis
Before beginning the balancing procedure, first make sure that the
cause for the adversely affected smooth running of the rotors is actu-
ally an imbalance. Furthermore, a vibration diagnosis indicates which
balancing method is the most suitable.
A series of coordinated measurement tasks are available for the diag-
nosis of an imbalance:
• Click on "Balancing" in the start screen and open the 'Diagnosis'
tab (see below):
Overall value - vibration velocity
Records the broadband vibration of the machine in order to docu-
ment the actual condition before and after balancing. This also makes
it possible to determine the measurement location with the highest
vibration values where the sensors should be mounted.
RPM
Measures the rotor RPM. If a machine setup is used for balancing, this
parameter is required in order to calculate the resulting centrifugal
forces.
Phase measurement - one / two planes
Records the amplitude and phase angle of the RPM-synchronous vi-
bration signal. This allows, for example, the type of imbalance (static
/ dynamic) to be determined.
Spectrum & Time waveform - vibration velocity
Measures the FFT spectrum and time waveform. If the 1st harmonic
dominates the spectrum, an imbalance is probably the cause for the
poor running.
Introduction
Left:
Diagnosis measurement
Right:
FFT spectrum for diagnosis
1st RPM harmonic
vibration dominates -> imbalance
'1st Harmonic'

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VIBXPERT II Balancing 12.2019
Preparatory activities
Preparations include the mounting of the measurement components.
The machine must be...
... disconnected before carrying out any work on the machine.
... protected against being switched on again inadvertently!
Assembly
1. Find out the cause of the imbalance visually and fix it if possible,
e.g.: Remove any coatings from the impeller, fasten any loose bal-
ancing weights or tighten any loose screws on the foundation.
If the machine cannot be balanced in-situ, it must be firmly mounted
on a rigid foundation (directly on frames or on vibration isolators).
2. Determine the measurement and balancing planes (see figure on
next page). Mount the vibration transducer on the bearing hous-
ing at the measurement location with the highest vibration values.
Note that:
• The measurement plane should be in the middle of the bearing
and close to the balancing plane and the plane of the center of
gravity (e.g. impeller side, rotor).
• Vibrations are transferred via the outer ring of a bearing in a
radial direction. Thus, mount the transducer on the side (hori-
zontal) or on the top of the bearing (vertical).
• The transducer should be attached as close as possible to the
bearing. Prevent signal attenuation due to excessively long
transmission paths or bearing covers. The direction of mea-
surement must correspond to the main direction of vibration
(mostly horizontal). If the measurement direction is horizontal,
mount the transducer on the lower half of the bearing housing.
• Wherever possible, use transducers which are screwed onto the
machine or attach the transducer using a magnetic adapter (VIB
3.420). The transducer should not be attached to components
with intrinsic vibrations, e.g. covers.
• Hand-held probes are not suitable for balancing!
• Only for balancing in two planes: Determine the second plane
(B) in the same way.
3. Assess the machine smoothness.
• Measure the vibration velocity and record an FFT spectrum if
the measurement values are too high (see DIN ISO 10816-3). If
high vibration signals appear at the rotational frequency, there
is an imbalance that must be corrected by balancing.
• Save the measured values in order to be able to compare them
later with the values measured after the balancing procedure.
Preparations
WARNING!

Note

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VIBXPERT II Balancing 12.2019
Preparations
Typical assembly:
Measurement and balancing plane A &
B, reference marks, fixing angle φ
High axial amplitudes indicate a large imbalance of torque which
cannot be balanced using the methods described here.
4. Attach a reference mark on the shaft for the trigger sensor while
the machine is at a standstill.
• Use a light reinforcing (e.g. reflective tape VIB 3.306) or light
damping (black, high-contrast line on a bright surface) mark
and place this parallel to the shaft axis and perpendicular to the
direction of rotation.
TIP: Place the mark as close as possible to the groove of the
adjusting spring. The mark should be easy to find and the mea-
surement results can be reproduced more easily.
• Angle convention: the angular reference mark lies at 0°; the
fixing angle φfor the balancing weight is counted against the
direction of shaft rotation.
TIP: Number the blades corresponding to the counting direction
of the fixing angle. Blade no. 1 is taken as the 0° position.
• Active edge: Define whether the edge of the incoming trigger
mark or outgoing trigger mark on the shaft is to be used as the
reference signal. The setting can be made under 'Transducer/
Keyphaser' in the Device Setup. Observe the signal response for
the different types of reference marks (s. next page).
Balancing planes
Measurement plane
Trigger sensor Vibration transducer
on channel B
Reference mark
A
B
Measurement plane
φ
φ

Note
Vibration transducer
on channel A

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VIBXPERT II Balancing 12.2019
Preparations
R
R
R
F
E
S
C
M
E
N
U
H
E
L
P
Trigger Bracket
(VIB 6.632)
Vibration transducer on the
magnetic adapter
(VIB 6.142R + VIB 3.420)
Reflective tape
(VIB 3.306)
Laser Trigger Sensor
(VIB 6.631)
Trigger cable
(VIB 5.432-2.9)
5. Mount the laser trigger sensor (VIB 6.631) with the trigger bracket
(VIB 6.632) on the machine.
6. Connect the vibration transducer to the measurement instrument.
After completing the preparatory activities, ensure the following:
• The balancing RPM should lie as close as possible to the operat-
ing RPM. If this is not possible due to high vibration values, start
at a lower RPM and approach the operating RPM step-by-step in
several balancing runs.
Minimum balancing RPM: 30 cpm. (= 0,5 Hz)
• Pay attention to potential resonance points and, if there is any
doubt, perform a coast down measurement!
• The RPM must remain constant during a balancing run! Other-
wise, the balancing run must be restarted.
• The rotor must reach operating temperature during the measure-
ment (e.g. if the rotor works in a hot air stream).
• Often the static imbalance is dominant at vibration values above
10 mm/s. First, compensate this using 1-plane balancing before
proceeding with 2-plane balancing.
• Before starting the initial balancing run, check again that all mea-
surement components have been correctly installed.
• If a machine setup is used for the balancing procedure, check the
specified parameters. Incorrect rotor data may result in the calcu-
lation of excessive trial weights under certain circumstances!

Note

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VIBXPERT II Balancing 12.2019
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2-9
VIBXPERT II Balancing 12.2019
Operation
Operation
If you are not yet familiar with operation in balancing mode, please
note the following instructions:
Settings
All settings necessary for the measurement and evaluation of a bal-
ancing run are made in setup menus. The following setups can only
be changed before a balancing run is begun:
- Measurement setup: measurement settings (see p. 2-29)
- Transducer setup: parameters of the transducer in use
- Machine setup: data on rotor and balancing-related settings (see p.
2-26ff.)
The settings in the following two setup menus can also be changed
during a balancing run:
- Display setup: display settings (see p. 2-24).
- Tools: balancing-related settings and parameters that can be
changed during a balancing run (see p. 2-19ff.).
Display
In each balancing run, two main screens appear:
Data screen
The upper half of the screen shows the balancing weights and their
positions on the rotor. The lower half contains the measurement data
and balancing weights of all completed runs. If a machine setup is
used, it shows the balancing quality attained and the resulting cen-
trifugal force on the rotor.
Measurement screen
The measurement values (amplitude and phase angle) are displayed
and the imbalance pointer is shown in a polar diagram.
Left:
Data screen
Right:
Measurement screen
Balancing step Maximum display range

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VIBXPERT II Balancing 12.2019
Operation
The respective balancing step appears on the upper left of both
screens:
0. Initial imbalance
Measurement of the original imbalance; if the vibration values are
within the tolerance range, the rotor is balanced. Otherwise, the bal-
ancing weights must be placed on the rotor according to the following
balancing steps.
1st trial run
The influence of the attached trial weights is measured and the result-
ing balancing weight is calculated.
2. Trim to ..N. Trim
Trim runs for reduction of rotor imbalance.
The initial imbalance pointer represents the starting point of the
balancing procedure. The arrow direction indicates the path of the
balancing runs. A dashed pointer marks a balancing run in which the
weight was removed (see figure below).
Zoom
VIBXPERT automatically scales the display range with respect to the
last two balancing runs. To magnify the view, press the "+" button
repeatedly. If the initial imbalance moves out of the display range, the
maximum range is also given as a percentage of the initial imbalance.
Navigation
To scroll forwards and backwards, press the right or the left naviga-
tion key respectively.
Starting / stopping the measurement
Press the Enter key in the measurement screen.
Left:
Zooming the
measurement screen
Right:
Balancing runs in
the measurement screen
Starting/stopping the measurement:
<Start> / <Pause>
Initial run
Weight removedLatest run

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VIBXPERT II Balancing 12.2019
1-plane balancing
Balancing in one plane
On the basis of an example, the next section illustrates the steps that
are needed to balance in one plane:
Requirements
- In the following example, the machine setup is not used.
- The default settings in the 'Tools' menu item are not changed:
- Correction mode: free
- "Add" balancing weights
- Check that the functions are all active, except for the coefficients
calculation which is inactive.
- 'Use different radii' option: inactive
Activating the balancing mode
1. Switch on VIBXPERT.
2. Click on the "Balancing" icon in the start screen.
Selecting the task
1. Open the '1-plane' tab.
2. Highlight the rotor graphic which corresponds to the rotor type.
3. Optional: Check and change the current measurement task before-
hand if necessary. (MENU - Task Manager - Setup)
4. Click on the rotor graphic to open the measurement screen
Adjusting the trigger sensor
1. Connect the trigger sensor to VIBXPERT (see p. 2-7).
2. Press MENU, and click on "Power up keyphasor".
3. Adjust the trigger sensor to the reference mark on the shaft.
Left:
Selection screen
Right:
Start 'Initial' run
Keyphasor ON