IJSRED-V2I3P38

International Journal of Scientific Research and Engineering Development-– Volume 2 Issue 3, May –June 2019
Available at www.ijsred.com
ISSN : 2581-7175 ©IJSRED:All Rights are Reserved Page 355
Investigation of Machinery Health Analysing Characteristics of
Vibration Using Comprehensive Experimental Setup
Arifur Rahman*, Md. Emdadul Hoque**, Shaikh Sumit Noor***
(Department of Mechanical Engineering, Rajshahi University of Engineering & Technology, Rajshahi, Bangladesh)
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Abstract:
The goal of this paper is to interpret the condition of a machine by investigating the experimental data
obtained using CSI 2140 machinery health analyzer from a multi-functioning arrangement. The multi-
functioning arrangement consists of pulleys, shafts, ball-bearings, overhung impeller and an electric motor
as a power source. These elements generate different forms of vibrational complications. These
complications are measured in terms of frequency, amplitude and phase angle and compared with the ISO
standard to determine machinery health. The Analyzer helps for the exact determination of the
characteristics of the vibration. An experimental setup has been designed and fabricated to create and
solve the vibrational complexities. In this research, mass imbalance has been detected and figured out the
proper measures such as the polar plot analysis to reduce the severity of vibration and attain the desired
level of the vibration according to ISO standard.
Keywords —Vibration analysis, Mass imbalance, Machinery health, Condition monitoring.
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I. INTRODUCTION
Condition monitoring (CM)is the process of
investigating and analysing the various parameters
concerning operational components of a system to
identify the pending breakdown [1]-[4]. It is widely
known as a predictive or condition-based
maintenance technique. Vibration measurement and
analysis is considered as one of the key components
of the condition monitoring technique. Each
component of industrial machinery performs in a
certain manner and consumes a certain amount of
energy. These components tend to vibrate at
specific frequencies [5]-[7]. The measurement of
these vibrations in terms of amplitudes and phase
angles ascertain numerous aspects of the condition
of the system. The analytical data reflect the
performance of the components and the entire
system which potentially indicates the possibilities
of a breakdown or sustainability under the given
condition [8], [9]. This paper concerns the
fabrication of an arrangement which consists of
different elements which are widely used in
industrial purposes. These are often subjected to
vibrations, the identification and measurement of
such vibrations in terms of amplitude and phase
angle [10], [11]. By analysing the obtained data to
detect the potential fault present in the system,
comparing the data to the ISO levels and ultimately
mitigating the intensity of vibration by using
dampers to achieve satisfactory levels of vibration
to ensure a better operational condition of the
system [12].
II. THEORETICAL DESCRIPTIONS
The characteristics of vibration data and the form
of the spectral value indicates certain faults present
in a system. Each of the faults present in the system
generates a certain trend of displayed spectral data
which is highly useful to detect the problem and
take necessary measurements to reduce the
generated vibration.
RESEARCH ARTICLE OPEN ACCESS

ISSN : 2581-7175 ©IJSRED: All Rights are Reserved Page 356
Mechanical systems, especially rotating
machinery are widely subjected to mechanical
imbalance. The vibration is generated when the
centre of mass of the rotating element is not turning
on the same axis as the rotating assembly. The
amplitude will increase with an increase in speed up
to the first critical speed of the rotating element.
The spectra generated will display a single
frequency vibration whose amplitude is the same in
all radial directions. In a pure imbalance, it will be a
perfect sinusoidal vibration at the machine running
speed. In case of an overhung rotor, an axial
component is observed.A vibration analysis system
usually consists of four basic parts: a transducer, a
signal analyser, analysis software and computer for
data analysis and storage. These basic parts can be
configured to form a continuous online system, a
periodic analysis system using portable equipment
that samples a series of transducers at
predetermined time intervals.
Mechanical vibration is the measurement of a
periodic process of oscillations with respect to an
equilibrium point. The vibration amplitude is
commonly expressed in one of three units of
measure – displacement (mils or microns), velocity
(inches per second (ips) or mm/s), and acceleration
(ips2
or mm/s2
). Each type of measurement is used
for a specific purpose.The difference between the
signal average and the maximum absolute value is
called peak value.The root means squares value
(RMS)is an indication for the power contained in
the signal, or in other words, the effective value.
Therefore, it is commonly used in vibration level
detection. In case of a set of n values{X1, X2,.....Xn},
=
1
+ … … … … . . +
Time waveform is simply displaying the signal in
the same manner as the oscilloscope plot. It is the
amplitude-time plot. The most common use of time
waveform data is to compare the waveform pattern
of one machine with another obtained from a
machine with similar defects. If necessary, the
frequency components of the major events in the
waveform pattern can be calculated.
Fourier theorem states that any time waveform
can be reconstructed from several harmonically
related sine and cosine frequency components.
Fourier transform is found to be a very efficient and
useful tool to analyse vibration signals and to detect
most of the common vibration problems. Fourier
spectrum is simply the amplitude-frequency plot
and can be done through different techniques.The
polar or Nyquist plot is also a representation of the
same three variables as considered in a Bode plot.
The variables are plotted on a single circular chart
instead of Cartesian axes. The overhung rotor is the
dominant source of the mass imbalance generated
in the system due to its non-uniform geometry. For
unbalance of overhung rotors, the FFT spectrum
displays a single 1X RPM peak, and the amplitude
again varies proportionally to the square of the shaft
speed. It may cause high axial and radial vibrations.
The axial phase on the bearings will seem to be in
phase whereas the radial phase tends to be unsteady.
Overhung rotors can have both static and couple
unbalance and must be tested and fixed using
analysers or balancing equipment.
III. EXPERIMENTAL SETUP
The representation of the schematic diagram of
the experimental setup is shown in Fig.1.The
experimental setup consists of a single-phase
induction motor of 0.25hpwith RPM of 1400 works
as the power source of the experimental setup. The
motor shaft is connected to a set of pulleys with 100
mm and 75 mm diameters respectively with a V-
belt of 16 mm of width and 560 mm length. A mild
steel shaft of 17mm diameter is connected to the
upper pulley whose axis is at a height of 165 mm
from the axis of the motor shaft. Two bearings
housings which house ball bearings and support the
shaft at a distance of 143 mm. The bearing houses
are bolted onto a supporting block made of mild
steel with a width of 222 mm and length of 254 mm.
The shaft extends to a length of 156 mm from the
outermost bearing housing. At the end of the shaft,
an overhung impeller is attached. The impeller is of

©IJSRED: All Rights are Reserved Page 357
127 mm diameter and 8 mm thickness with
equidistant 8 holes residing 51 mm from the
centre.The representation of close-up view with
transducer of experimental setup is shown in Fig. 2
A: Electric motor, B: V belt, C: Pulley, D: Bearing
housing, E: Shaft, F: Bearing housing, G: Over hung
impeller, H: Supporting block
Fig. 1 Schematic diagram of experimental setup
Fig. 2 Close-up view with transducer of experimental setup
IV. METHODOLOGY
The three transducers labelled as A, B and C of
the CSI 2140 machinery health analyser were
obtained for vertical, horizontal and axial directions
respectively. The configuration of the analyser was
shown in Table I.
TABLE I
THE CONFIGURATION OF THE ANALYSER
Parameter Specifications
Settings Spectra Parameters
Maximum Frequency 10 X actual CPM
Maximum Frequency 0
Lines 800
Resolution Default
Windows Hanning
Sensitivity 100mV/G
Sensor setup Single axis accel.
The portions of the setup, which were subjected
to the vibration measurement, are motor outboard,
motor inboard, first bearing and second bearing.
After mounting the transducers on each of the
locations with a separation of 90 degree with each
other, the power switch of the motor was turned on.
The spectral and waveform data were displayed on
the analyser for each of the components. The peak
and phase plot also obtained for the second bearing
via the tachometer provided with the device. Then,
the obtained values were compared with the ISO
standard for different levels of vibrations, as
provided in the Fig. 3. The trend of the spectral plot
indicated the problem that existed in the system.
Afterwards, the problem was detected as mass
unbalance and measures were taken accordingly.
The reduced vibration data were obtained in the
same procedure by the device and compared again
with the ISO standards for measuring the level of
vibration that obtained. After attaining the suitable
level, the system apparently generated a far lesser
degree of vibration in all three directions.
Fig. 3 ISO standard chart
V. EXPERIMENTAL DATA ANALYSIS
At first, the transducers were attached to the
specific locations of the second bearing to measure

the amplitude of vibration in all three directions
while the system remained unbalanced. The values
obtained for the second bearing in Fig. 5
extensively exceeded the ISO standards specified to
good or satisfactory levels of performance. This
was observed by comparing the highlighted data of
the amplitudes obtained from the resonant
frequencies in the plots with the ISO standard chart.
Moreover, the peak and phase value of the second
bearing from Fig. 7 depicts that the highest peak
RMS value is found at 52.20
phase angle in input B
(vertical direction). This critical RMS value is
responsible for generating the vibration due to mass
imbalance. This peak value should be minimized
through adding mass.
A. Experimental Data for Unbalanced System
The representation of Frequency and amplitude
for input A is shown in Fig. 4, Frequency and
amplitude for input B is shown in Fig. 5, Frequency
and amplitude for input C is shown in Fig. 6 and
Peak and phase Data for the second bearing is
shown in Fig. 7 for unbalance condition.
B. Comparison of obtained values with ISO standards and
Detection of fault
The motor power which was used in this
experiment is 180 W. As per ISO standard table,
this should be acceptable for Class I cause of its
power is less than 15 KW. To attain the satisfactory
level, the RMS value should not cross 1.80 mm/s.
Now experimental data will be compared ISO
standard. It is seemed that RMS value of transducer
input B is 7.3686 mm/s that should be satisfactory
level of ISO standard. Moreover, the behaviourof
data referred to mass imbalance. This was detected
as the displayed plot had a form of 1X which is an
indication of mass imbalance. The mass imbalance
had to occur in the overhung impeller due to design
faults and its centre of gravity not being on the axis
of rotation. It is clear that mass unbalancing issue is
responsible for this peak point.
Fig. 4 Frequency and amplitude for input A
Fig. 5 Frequency and amplitude for input B
Fig. 6 Frequency and amplitude for input C
C. Reduction of Flaws of the Arrangement
As the problem was detected as mass imbalance
in the overhung impeller, by the polar plot analysis
a corrected mass was used to balance the rotor and
reduce the intensity of vibration to a satisfactory
level. So, this value is primarily taken to consider
the issue and polar graph paper is used to reveal the
unbalance issue.
Input: B
Input: C

Fig. 7Peak and phase Data for the second bearing (Unbalanced condition)
Figure 8 shows the polar plot for reducing mass
imbalance where outer numbers of the circle are
considered as the shaft rotates counter clock wise
direction. Phase angle increases against rotation of
the shaft as well the outer ring of polar graph. The
radial distance from centre to outer ring is
considered as 10 unit. The peak RMS value found
from the Fig. 7 is 7.37 at 52.20
phase angle in
vertical direction is labelled in polar graph as vector
1.A trial weight of 4.1 gram is added at 180 degree
of polar graph paper. After adding a trial weight at
1800
, it is shown that the peak RMS value got
decreased in three direction. However, still then the
value in vertical direction is high and exceeds the
desired range. The peak RMS value found from the
Fig. 9 is 4.75 at 27.10
phase angle in vertical
direction is labelled in polar graph as vector 2. A
new vector is drawn from head of vector 1 to head
of vector 2 and labelled it as vector 3. A vector 4 is
drawn starting at the origin of polar plot and
parallel to vector 3. The angle between the vector 4
and the extension of vector1 is measured and found
it as 390
. This is the same angle that the correct
weight goes with respect to trial weight. Therefore,
the correct weight location is fixed at 2190
of polar
graph. The correct weight is calculated using the
following formula.
Correct weight =
Length of vector 1 × Trial weight
Length of vector 3
Fig. 8Polar plot for reduction of mass imbalance
The length is measured with a fine scale ruler and
weight by a digital weighing scale. The
measurements are as follows-
The length of vector 1 is 6cm
The trial weight is 4.1gram
The length of vector 3 is 3 cm
So, the calculated correct weight required for
balancing is,
Correct weight =
6 cm × 4.1 gm
3 cm
= 8.2 , -
Fig. 9Peak and phase data for the second bearing (Trial).
D. Experimental Data for Balanced System
The representation of Peak and phase Data for the
second bearing (Balanced condition) is shown in

Fig. 10. The RMS values in all three directions are
decreased after placing the correct weight of 8.2
gram at 2190
. In this stage, the spectrum waveform
is taken from the experimental setup. The obtained
spectral plots depict that the amplitude of vibration
reduced in all directions, significantly in the vertical
direction as displayed in Fig. 5.By attaching the
correct weight at the calculated phase angle by the
polar plot analysis,the intensities of vibration are far
less than the ones obtained prior to balancing. The
representation of frequency and amplitude for input
A is shown in Fig.11. The representation of
frequency and amplitude for input B is shown in
Fig.12. The representation of frequency and
amplitude for input C is shown in Fig.13.
Fig. 10Peak and phase Data for the second bearing (Balanced condition)
VI. RESULTS AND DISCUSSION
This experiment was aimed to achieve a stable
system depending on ISO standard from an unstable
system. The main target was to keep the peak value
of the system below of 1.8 mm/s. Mass unbalancing
issue was detected after observing the
characteristics of vibration. Polar graph paper is
used here to balance the system with adding mass.
Finally, 8.2gram mass has been added at 2190
of
circular overhung impeller. It was found that the
system was stable within the satisfactory level of
ISO standard. The system can be more stable if
some changes in setup foundation would be done.
Hence the system is designed only for research only,
so permanent fixed foundation is not possible. The
mass balancing procedure has been experimented
by trial and error method.Two things are very
important in this experiment like precision and skill.
So precisely mass calculation and addition to exact
location were very critical issues. After several
attempts, finally more precision solution is
introduced in this experiment.
Fig. 11Frequency and amplitude for input A
Fig.12 Frequency and amplitude for input B
Fig.13 Frequency and amplitude for input C
Input: B
Input: A
Input: C

VII. CONCLUSIONS
Mechanical systems are widely subjected to
vibrations, especially in the industrial sectors. The
arrangement undertaken generated the similar form
of vibration in numerous mechanical machineries.
The dominant form of vibration in the system was
due to mass imbalance which was accurately
determined by the characteristics of the spectral plot
obtained from the machinery health analyser’s
display. The process of mitigation of this problem
required adequate steps to employ specific weight
at specific location of the element responsible for
the high amplitude of vibration. The spectral plots
along with the peak and phase values obtained from
the analyser provided the required value to facilitate
the balancing of the system by the polar plot
analysis procedure. This ultimately mitigated the
intensity of vibration to a satisfactory level
according to the standard ISO level chart. The
system was effectively balanced after the accurate
measurement, detection and reduction of the
vibration-oriented flaws that prevailed in it prior to
balancing the system to the desired level.
ACKNOWLEDGMENT
I would like to express my gratitude and heartiest
thanks to PranRfl Ltd. for their support. I also
grateful to Saj Engineering & Trading Company for
their restless technical support and guidance.
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