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www.gjaet.com Page | 308
Global Journal of Advanced Engineering Technologies Volume 5, Issue 3- 2016
ISSN (Online): 2277-6370 & ISSN (Print):2394-0921
TESTING AND VALIDATION FOR VIBRATION
REDUCTION OF A CENTRIFUGAL PUMP Suhas Sangle1, A. N. Surde2
1,2Mechanical Engineering Department, Walchand Institute of Technology, Solapur
Abstract: Centrifugal pump plays an important role in
industries and it requires continuous monitoring to
increase the availability of the pump. The pumps are
the key elements in food industry, waste water
treatment plants, agriculture, oil and gas industry,
paper and pulp industry, etc.
It is necessary to be interested in vibration in
centrifugal pumps because it has a major effect on the
performance. Generally, increasing vibration levels
indicate a premature failure, which always means that
the equipment has started to destroy itself. It is so
because excessive vibrations are the outcome of some
system malfunction. It is expected that all pumps will
vibrate due to response from excitation forces, such as
residual rotor unbalance, turbulent liquid flow,
pressure pulsations, cavitations, and/or pump wear.
The magnitude of the vibration will be amplified if the
vibration frequency approaches the resonant
frequency of a major pump, foundation and/or piping
component. Generally higher vibration levels
(amplitudes) are indicative of faults developing in
mechanical equipment.
Harmonic analysis performed to correlate physical
test results through FEA. All 3 directions are
physically tested and correlated for system without
isolators. Results plotted initially without isolators are
validated with FEA and then in FEA different shapes
were tried like round, groove and tapers to find the
best isolator mount for specific centrifugal pump
application to reduce vibrations in Vertical Direction.
Key Words: Isolators, Centrifugal Pump, Vibration
Amplitude, FEA
I. INTRODUCTION
To ensure the safety of pump and associated plant
components, the vibration and noise must be kept
within safer limits. Higher vibrations ultimately results
in decreased component’s life due to cyclic loads, lower
bearing life, distortion to foundation, frequent seal
failures etc. Higher vibrations ultimately results in
decreased component life due to cyclic loads, lower
bearing life, distortion to foundation, frequent seal
failures etc. Similarly noise has got huge impact on
working environment and comfort conditions of an
individual. Exact diagnosis of vibration and noise
sources is very difficult in centrifugal pumps as this
may be generated due to system or the equipment itself.
[2]. Vibrations basically are the displacement of a mass
back and forth from its static position. The major
challenge in diagnosis of vibrations and noise in
centrifugal pumps is service of the centrifugal pump
itself. In centrifugal pumps the root of vibrations and
noise may lie in mechanical or hydraulic aspects. It is
very easy to trace the mechanical causes but it becomes
very difficult to trace hydraulic causes. This makes
pumps vibration and noise diagnostic very complex. A) Sources of Vibrations in Centrifugal Pumps
The sources of vibration in centrifugal pumps can be
categorized into three types as below:
Mechanical causes
Hydraulic causes
Peripheral causes
B) Diagnosis of Vibrations in Centrifugal Pump:
Vibration measurement:
Mechanical vibrations are most often measured using
accelerometers, but displacement probes and velocity
sensors are also used. Generally, a portable vibration
analyzer is preferred. The analyzer provides the
amplification of the sensor signal, it does the analogue
to digital conversion, filtering, and conditioning of the
signal. Many analyzers also offer advanced processing
of the collocated signals as well as storage and display
of the data.
II. EXPERIMENTAL SETUP Assumptions:
The force that will cause the vibration, must overcome
the structure’s mass, stiffness and damping properties.
Structure’s mass, stiffness and damping properties are
inherent to the structure and will depend on the
materials and design of the machine.
As discussed in introduction, vibrations basically are
the displacement of a mass back and forth from its
static position. A force will cause a vibration, and that
vibration can be described in terms of acceleration,
velocity or displacement.
It is necessary to be interested in vibration in
centrifugal pumps because it has a major effect on the
performance. Generally, increasing vibration levels
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Global Journal of Advanced Engineering Technologies Volume 5, Issue 3- 2016
ISSN (Online): 2277-6370 & ISSN (Print):2394-0921
indicate a premature failure, which always means that
the equipment has started to destroy itself. It is so
because excessive vibrations are the outcome of some
system malfunction. It is expected that all pumps will
vibrate due to response from excitation forces, such as
residual rotor unbalance, turbulent liquid flow, pressure
pulsations, cavitation and/or pump wear. The
magnitude of the vibration will be amplified if the
vibration frequency approaches the resonant frequency
of a major pump, foundation and/or piping component.
Generally higher vibration levels (amplitudes) are
indicative of faults developing in mechanical
equipment.
It is also important to know the location to mount the
vibration mounts. We know that a force cause vibration.
If we know what types of forces are generating the
vibration, we will have a good idea how they will be
transmitted through the physical structure of the
machine and where they will cause vibrations. With
rotating machines, this point is almost always directly
on the machine’s bearings.
Figure 1: Radial locations of probe mounting
Figure 2: Axial locations of probe mounting
The reason for this is that the various dynamic forces
from a rotating machine must be transmitted to the
foundation through the bearings. As a rule of thumb,
vibration readings on rotating machines must be taken
in the horizontal, vertical and axial direction on each
bearing as shown in figures as mentioned.
Experimental Setup available at client location as
shown in schematic below:
Figure 3: Overall system schematic
Experimental Setup available at client location as
shown below:
(a) Probe at Horizontal (b) Probe at Horizontal direction
direction
Figure 4: Experimental setup at client’s location
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Global Journal of Advanced Engineering Technologies Volume 5, Issue 3- 2016
ISSN (Online): 2277-6370 & ISSN (Print):2394-0921
III. HARMONIC ANALYSIS
Harmonic analysis (HA) is a technique to determine the
response of a structure to sinusoidal (harmonic) loads of
known frequency.
Input: Harmonic loads (forces, pressures, and
imposed displacements) of known magnitude
and frequency. Loads may be multiple loads,
in-phase or out-of-phase, all at the same
frequency.
Output: Harmonic displacements at each
DOF, usually out of phase with the applied
loads and other derived quantities, such as
stresses and strains.
Harmonic analysis is used in the design of supports,
fixtures, and components of rotating equipment such as
compressors, engines, pumps, and turbo-machinery.
And structures subjected to vortex shedding (swirling
motion of fluids) such as turbine blades, airplane wings,
bridges, and towers. A harmonic analysis is used to
make sure that a given design can withstand sinus oidal
loads at different frequencies (e.g.: an engine running at
different speeds) and to detect resonant response and
avoid it if necessary (by using dampers, for example).
Assumptions and Restrictions of HA
Valid for structural, fluid, magnetic, and
electrical degrees of freedom (DOFs).
Thermal DOFs may be present in a coupled
field harmonic analysis using structural
DOFs.
The entire structure has constant or frequency-
dependent stiffness, damping, and mass effects.
All loads and displacements vary sinusoidally
at the same known frequency (although not
necessarily in phase).
Element loads are assumed to be real (in-
phase) only, except for current density and
pressures in SURF153, SURF154, SURF156,
and SURF159 elements
Following are locations of probes for which Response
of Pump will be measured.
Figure 5: Locations at Probe
FEA Validation with Physical Testing:
Harmonic Analysis performed to correlate Physical test
results through FEA. Which will reduce the
experimentation with different isolators and some finite
quantity of isolator can be chosen for physical test.
Different isolator models were tried in FEA from which
4 best isolator models were taken for physical testing.
Below are correlation graphs for FEA and Physical
Testing without Isolator.
Graphs shows better correlation of FEA results and
Physical Test results considering the excitation
frequency and amplitude of vibration.
Frequency domain:
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0 200 400 600 800
A1-Axial-Freq Vs Acceleration
comparative Test and FEA
0
5
10
15
0 200 400 600 800
A1-Vertical-Freq Vs Acceleration
comparative Test and FEA
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Global Journal of Advanced Engineering Technologies Volume 5, Issue 3- 2016
ISSN (Online): 2277-6370 & ISSN (Print):2394-0921
With Isolators:
Isolator Dampers are used to minimize the
vibration levels. Different types of isolators are chosen
to get minimum vibration acceleration and vibration
displacement levels.
Circular type isolators are used with different
shapes to investigate the required stiffness and optimum
stiffness for mounting purpose. Different shapes of
isolators such as Round (Circular) diameter 2.5”, round
isolator diameter 1.5”, Circular with grooves, Tapered,
were chosen for experiment.
2.5” diameter Circular Isolator:
Fig. 6 2.5” diameter circular Isolator
While experimenting, 2.5” diameter circular
isolators (as shown in figure 6) are used as dampers to
minimize the vibration levels. Using these isolators,
vibration acceleration and vibration displacement
readings were taken.
Acceleration: Vertical
Graph 1 Vertical position: Acceleration Vs Frequency
Acceleration is measured with Vertical
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
48 Hz is lowest frequency with 3.5 m/s^2 amplitude
whereas without isolator it was 10.28 m/s^2 at 278.4
Hz.
Acceleration: Transverse
Graph 2 Transverse position: Acceleration Vs Frequency
0
2
4
6
8
10
12
14
16
0 200 400 600 800
A1-Transverse-Freq Vs Acceleration
comparative Test and FEA
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Global Journal of Advanced Engineering Technologies Volume 5, Issue 3- 2016
ISSN (Online): 2277-6370 & ISSN (Print):2394-0921
Acceleration is measured with Transverse
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
48 Hz is lowest frequency with 1.67 m/s^2 amplitude
whereas without isolator it was 12.5 m/s^2 at 277 Hz.
Acceleration: Axial
Graph 3 Axial position: Acceleration Vs Frequency
Acceleration is measured with Axial
accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
863 Hz is lowest frequency with 1.04 m/s^2 amplitude
whereas without isolator it was 0.43 m/s^2 at 425 Hz.
Displacement: Vertical
Graph 4 Vertical position: Displacement Vs Frequency
Displacement is measured with vertical
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
it reaches 17 Hz is lowest frequency with 0.274µm
amplitude.
Displacement: Transverse
Graph 5 Transverse position: Displacement Vs
Frequency
Displacement is measured with Transverse
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
15 Hz is lowest frequency with 0.49 µm.
Displacement: Axial
Graph 6 Axial direction: Displacement Vs Frequency
Displacement is measured with Axial
Accelerometer setting to get Frequency and Amplitudes
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Global Journal of Advanced Engineering Technologies Volume 5, Issue 3- 2016
ISSN (Online): 2277-6370 & ISSN (Print):2394-0921
respectively. From Above graph it can be observed that
11 Hz is lowest frequency with 0.229 µm amplitude.
NOTE: For the other isolators, only values of
acceleration amplitudes and displacement amplitudes
are discussed without graphs.
Grooved Isolator:
Fig.7 Grooved Isolator
While experimenting, grooved isolators (as shown in
figure 7) are used as dampers to minimize the vibration
levels. Using these isolators, vibration acceleration and
vibration displacement readings were taken.
Acceleration: Vertical
Acceleration is measured with Vertical
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
48 Hz is lowest frequency with 4.48 m/s^2 amplitude
whereas without isolator it was 10.28 m/s^2 at 278.4
Hz.
Acceleration: Transverse
Acceleration is measured with Transverse
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
48 Hz is lowest frequency with 1.58 m/s^2 amplitude
whereas without isolator it was 12.5 m/s^2 at 277 Hz.
Acceleration: Axial
Acceleration is measured with Axial
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
48 Hz is lowest frequency with 7.33 m/s^2 amplitude
whereas without isolator it was 0.43 m/s^2 at 425 Hz.
Displacement: Vertical
Displacement is measured with Vertical
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
16 Hz is lowest frequency with 0.347 µm amplitude.
Displacement: Transverse
Displacement is measured with Transverse
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
14 Hz is lowest frequency with 0.423 µm amplitude.
Displacement: Axial
Displacement is measured with Axial
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
13 Hz is lowest frequency with 0.557 µm amplitude.
Tapered Isolator:
Fig.8 Tapered Isolator
While experimenting, tapered isolators (as
shown in figure 8) are used as dampers to minimize the
vibration levels. Using these isolators, vibration
acceleration and vibration displacement readings were
taken.
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Global Journal of Advanced Engineering Technologies Volume 5, Issue 3- 2016
ISSN (Online): 2277-6370 & ISSN (Print):2394-0921
Acceleration: Vertical
Acceleration is measured with Vertical
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
48 Hz is lowest frequency with 17.8 m/s^2 amplitude
whereas without isolator it was 10.28 m/s^2 at 278.4
Hz.
Acceleration: Transverse
Acceleration is measured with Transverse
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
48 Hz is lowest frequency with 6.56 m/s^2 amplitude
whereas without isolator it was 12.5 m/s^2 at 277 Hz.
Acceleration: Axial
Acceleration is measured with Axial
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
241 Hz is lowest frequency with 3.56 m/s^2 amplitude
whereas without isolator it was 0.43 m/s^2 at 425 Hz.
Displacement: Vertical
Displacement is measured with Vertical
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
16 Hz is lowest frequency with 0.726 µm amplitude.
Displacement: Transverse
Displacement is measured with Transverse
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
12 Hz is lowest frequency with 0.595 µm amplitude.
Displacement: Axial
Displacement is measured with Axial
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
14 Hz is lowest frequency with 0.17 µm amplitude.
1.5” Diameter Circular Isolator
Fig.9 1.5” diameter circular Isolator
While experimenting, 1.5” diameter circular
isolators (as shown figure 9) are used as dampers to
minimize the vibration levels. Using these isolators,
vibration acceleration and vibration displacement
readings were taken.
Acceleration: Vertical
Acceleration is measured with Vertical
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
47 Hz is lowest frequency with 10.2 m/s^2 amplitude
whereas without isolator it was 10.28 m/s^2 at 278.4
Hz.
Acceleration: Transverse
Acceleration is measured with Transverse
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
48 Hz is lowest frequency with 3.67 m/s^2 amplitude
whereas without isolator it was 12.5 m/s^2 at 277 Hz.
Acceleration: Axial
Acceleration is measured with Axial
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
1044 Hz is lowest frequency with 0.88 m/s^2 amplitude
whereas without isolator it was 0.43 m/s^2 at 425 Hz.
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Global Journal of Advanced Engineering Technologies Volume 5, Issue 3- 2016
ISSN (Online): 2277-6370 & ISSN (Print):2394-0921
Displacement: Vertical
Displacement is measured with Vertical
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
10 Hz is lowest frequency with 1.91 µm amplitude.
Displacement: Transverse
Displacement is measured with Transverse
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
21 Hz is lowest frequency with 0.29 µm amplitude.
Displacement: Axial
Displacement is measured with Axial
Accelerometer setting to get Frequency and Amplitudes
respectively. From Above graph it can be observed that
10 Hz is lowest frequency with 0.947 µm amplitude.
IV.CONCLUS ION
Investigation lead results best for 2.5” diameter circular
Isolator in which the vibration levels are well below the
vibration levels when no isolator and are gives quite
good results compared to all other isolator. Grooved
isolator is used as baseline isolator which shows better
vibration results compared to tapered isolator and 1.5”
diameter circular isolator.
Below are the tables to understand vibration and
frequency levels.
REFERENCES
[1] Stefano, Marco, Giordano and Stojmenovic,
“Mobile ad-hoc networking- The cutting-edge
directions”, John-wiley, 2013.
[2] Wornell and Laneman, “An efficient protocol for
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[3] N.R. Sakthivel a, V. Sugumaran b, S. Babudeva
senapati a, “vibration based fault diagnosis of
monoblock centrifugal pump using decision tree”expert
systems with applications 37(2010),pages 4040-4049.
[4] A.A. Nasser, M.A.Nasser, E.H.T. El-Shirbeeny, and
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pump” undergoing research for ph.D research titled
"Dynamic Analysis and Control of lrrigation and
Drainage Pumping System in Egypt, Faculty of
witho
ut
2.5"
dia.
Circu
lar
Groov
e Taper
1.5"
dia.
Circul
ar
Freq.
(Hz) 278.4 48 48 48 47
Acc.
Amp.
(m/s2)
10.28 3.5 4.48 17.8 10.2
Vibr.
Red
(%)
- 65.95 56.42 -73.15 0.778
Freq.
(Hz) 425 863 48 241 1044
Acc.
Amp.
(m/s2)
0.43 1.04 7.33 3.56 0.88
Vibr.
Red
(%)
- -
141.8
-
1604.6 -727.9 -104.6
Freq.
(Hz) 277 48 48 48 48
Acc.
Amp.
(m/s2)
12.5 1.67 1.58 6.56 3.67
Vibr.
Red
(%)
- 86.64 87.36 47.52 70.64
Isolator
Vertical Axial Transverse
Freq
(Hz)
Disp.
Amp (µm)
Freq
(Hz)
Disp
Amp
(µm)
Freq
(Hz)
Disp.
Amp (µm)
2.5” dia Circular
17 0.274 11 0.229 15 0.49
Groove Round
16 0.347 13 0.557 14 0.423
Taper Round
16 0.726 14 0.17 12 0.595
1.5”
dia.
Circular
10 1.91 10 0.947 21 0.29
T
r
a
n
s
v
e
r
s
e
a
x
i
al
v
e
r
t
i
c
a
l
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Global Journal of Advanced Engineering Technologies Volume 5, Issue 3- 2016
ISSN (Online): 2277-6370 & ISSN (Print):2394-0921
Engineering, Shebin El-Kom, Menoufia University,
Egypt, pages 550-557.
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