This work presents the dynamic response related to varying in indispensable parameters of pulley-belt system such as rotational speed, pulleys center distance, diameters ratios and type of belt (cross section). A pulley- belt system was manufactured, and the experimental results were obtained and analyzed accurately which reveal the effects of the above parameters on system working. Then, the pulley-belt system faults were studied using vibration analysis technique. A Selected faults were created like belts damage, belt resonance case, manipulation of initial tension in the belt, introducing belt slippage while running with the pulley by adding oil between the belt and the pulley, and catching the pulley damage then an experimental results were obtained and analyzed to find out how these types of faults appear in the manufactured system. Manufactured system was assembled from a heavy steel structure, variable speed DC motor, speed measurement tool (tachometer), two shafts of 25 mm diameter, four pillow block ball bearings, V-belts and pulleys with different diameters (10, 15, 20, 25) cm. The fabricated system presents good mechanical characteristics, like gradually changing in rotational speed (500 to 2000) rpm, diameters ratios (1 to 2.5) and center distance (27 to 120) cm. Vibration sensors ADXL335 (3-axis accelerometer) were mounted on bearing brackets of drive and driven shafts and connected to Arduino type mega 2560 (microcontroller), which sends the data of vibration to the laptop in order to display it in Sigview software in the time and frequency domain band by FFT (fast fourier transform). The results of FFT is used for the effect of each type of faults and dynamic response of changing parameters comparing with the healthy condition (FFT band) of the system.

1. BY : KHALID MOHSIN ALI
SUPERVISION BY: Dr. ALI RAAD HASSAN
UNIVERSITY OF TECHNOLOGY
MECHANICAL ENGINEERING DEPARTMENT
DIGANOSIS OF PULLEY-BELT SYSTEM
FAULTS USING VIBRATIONS ANALYSIS

2. INTRODUCTION .
Vibration is a result of dynamic forces in machines which have moving parts and
structures. Different parts of the machine will vibrate with various frequencies and amplitudes.
Vibration causes problems like wear and fatigue. It is often responsible for the ultimate
breakdown of the machine.
SO, high vibration means short life.
Most machines and equipment in our life contents parts like motors, engine, shafts,
bearings, gearbox, flywheel, fans, pulleys, belts, chains….etc. which are the main source of
vibration in each machine if they have fault.

3. VIBRATION ANALYSIS
Vibration can be used to detect and diagnose problems on rotating equipment ranging from electric
motors to large crushing machines used for mining and processing. FFT has important features to show
for each part its frequency because each part is in a case of motion has an individual frequency, also
frequency of faults which are unavoidable due to the errors and accuracy in manufacturing or it may
temporarily develop in the system due to the operating conditions.
Sources
of
vibration
Sensor
of
vibration
microprocessor software
Fourier transformation (FFT)
is an algorithm that samples a signal over a period of time (or space) and divides it into its
frequency components. These components are single sinusoidal oscillations at distinct frequencies
each with their own amplitude and phase.

5. THE MOST COMMON FAULTS
Machine faults divided into three main types :
1- manufacturing faults 2- assembled faults 3- bad mechanical conditions

6. Pulley-belt system is widely uses in mechanical engineering fields and Production so it is
necessary to Improve its performance by diagnosing defects and treating them, also varying in
indispensable parameters of system such as rotational speed, pulleys center distance,
diameters ratios and type of belt (cross section) in order to give better performance, less
vibration and avoid dynamic stresses on the parts and thus prolong the life of the machine .
AIM OF PROJECT

7. Data :
V13-belt
𝜌 = 0.113 𝑘𝑔/𝑚 A=8.438 ∗ 10−5 m2 µ=0.3
case
i rpm C
cm
stress
exerted
MPa
Results Notes
1
1
1440 50
1.2886
Stress is directly
proportional
with reduce ratio ,as
shown in Fig.(3.6)
1.5 2.438
2 2.468
3 2.51
2 1
1440
50
1.2886
Stress is inversely
proportional with
running speed, as
shown in Fig.(3.7)
2000 0.927
2500 0.742
3000 0.624
3 1 1440
50 1.2886
No effect
60 1.2886
70 1.2886
80 1.2886
1.28
1.3
1.32
1.34
1.36
1.38
1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6
EXERTEDSTRESS,MPa
REDUCE RATIO (i)
CASE 1
0.4
0.6
0.8
1
1.2
1.4
1200 1700 2200 2700 3200
EXERTEDSTRESS,MPa
RPM
CASE 2
Relation between Stress exerted on belt and rpm, radius ratio and length of belt

8. Experimental work

9. PULLEYS MATERIAL AND DIAMETERS SELECTIONS
Pulleys were manufactured from plate of steel with
thickness 25 mm cut by plasma CNC machine in circle
shapes having a diameters (11, 16, 21, 26 mm) 4 pieces
of each diameter. The second stage was reducing these
diameters by turning to (10.5, 15.5, 20.5, 25.5 mm)
respectively.
Bearings
Stainless steel ball bearings units with a ductile cast iron
housing were used (Pillow block), the code name is
UCP205. This UCP has the following properties: Self-
alignment shaft, the outer surface of the ball bearing
and the inner surface of the housing are spherical, thus
this bearing unit has a self-aligning characteristic.
Belts
Standard Rubber reinforced belts are used into two types
according to pulleys manufactured. The standard V belts
used have 13 mm width and the flat belts have 15 mm width,
as shown Appendix, B2 .All belt used have the same type of
material and manufacturer (DONGIL SUPER STAR).
COMPANY)

10. DC MOTOR WITH CONTROL SPEED DEVICE AND SPEED DIGITAL TACHOMETER
• TREADMILL Motor was used has the properties
And also it is very quiet without noise and vibration is very
smooth.
Control speed device. speed digital tachometer

11. VIBRATION SENSORS (ACCELEROMETER)
Vibration sensors ADXL335 (3axis accelerometer)
has a sensitivity of 300 mv/g and supply current 3V,
this sensor can read a range of 0.5 Hz to 1600 Hz for
the X and Y axes, and a range of 0.5 Hz to 550 Hz for
the Z axis output. Axes of acceleration sensitivity
corresponding output Voltage increases when
accelerated along the sensitive axis.
To calibrate the accelerometer, axis offset and axis
sensitivity parameters are measured to transform the
analog voltage to acceleration signal. The sensitivity of
axis is evaluated via the location of the accelerometer,
as illustrated in the figure.

12. Microcontroller and Positions, Directions of accelerometers
Arduino Mega 2560 is a microcontroller board based on the ATmega2560. Sensor after calibration must
be at the nearest point to the source of vibration, thus they are fixed on pillow block (bearings), and the
directions of the two sensors must be the same. (X) is radial-horizontal, (Y) is axial with shafts, and (Z) is
radial-vertical

13. Balancing of pulleys
Before taking the results, it is necessary to balance the pulleys.
Some amount of material is removed at the high
mass portion by drilling. The amount of
unbalance of mass is unknown, but its location is
known. By trial and error, material is slightly
removed until no portions of excess mass on the
pulley favors the bottom.

14. RESULTS
DYNAMIC
RESPONSE
FAULTS
DAIGNOSIS
V-belt
Flat-belt
V-belt
Flat-belt

15. DYNAMIC RESPONSE
c
a
s
e
Case description
rpm Drive and driven
pulleys Diameters
cm
C
cm
Radius ratio
1 Rpm change
500
1000
1500
2000
10x10 37 1:1
2 Equal diameter of pulleys change 1500
10x10
15x15
20x20
25x25
37 1:1
3 Radius ratio change 1500
10x10
10x15
10x20
10x25
37
1:1
1:1.5
1:2
1:2.5
4 Center distance change 1500 10x10
37
47
57
67
1:1

16. 500 rpm
1000 rpm
1500 rpm
2000 rpm
RPM CHANGE, X-DIRECTION
m/s2
m/s2m/s2
m/s2
m/s2m/s2m/s2m/s2

17. 500 rpm
1000 rpm
1500 rpm
2000 rpm
RPM CHANGE, Y-DIRECTION
m/s2
m/s2m/s2
m/s2
m/s2m/s2m/s2m/s2

18. 500 rpm
1000 rpm
1500 rpm
2000 rpm
RPM CHANGE, X-DIRECTION
m/s2
m/s2m/s2
m/s2
m/s2m/s2m/s2m/s2

19. C=37 Cm
PULLEY SIZE INCREASEm/s2
m/s2m/s2
m/s2
m/s2m/s2m/s2m/s2

20. C=37 Cm
m/s2
m/s2m/s2
m/s2
m/s2m/s2m/s2m/s2

21. C=37 Cm
m/s2m/s2m/s2
m/s2
m/s2m/s2m/s2m/s2

22. C=37 Cm
RADUIS RATIO CHANGE

23. 37 cm
47 cm
57 cm
67 cm
CENTER DISTANCE INCREASEm/s2
m/s2m/s2
m/s2
m/s2m/s2m/s2m/s2

24. 37 cm
47 cm
57 cm
67 cm
m/s2
m/s2m/s2m/s2
m/s2m/s2m/s2m/s2

25. 37 cm
47 cm
57 cm
67 cm
m/s2
m/s2m/s2
m/s2
m/s2m/s2m/s2
m/s2

26. DAIGNOSIS FAULTS
Case Fault Description
1 Adding unbalance mass Add mass on pulley causes unbalance rotation (centrifugal
force)
2
Changing magnitude of the initial
belt tension
By reducing and increasing of initial tension over the optimum
installation tension of manufacturing company, the fault will
create and the results of FFT will show the effect of this
process
3
Making the belt slip over pulleys
Sometimes as a cause of poor friction between belt and pulley,
vibration increases and loss in power will be existed. This
process will be briefly done by adding some oil between belt
and pulley.
4 Catching the pulley damage By deformation of pulley-trench, pulley unbalance
5 Catching the belt damage This process is easy by cutting a piece of belt
6 Belt resonance Belt resonance depends on the center distance, rpm, initial
tension, and pulleys diameters

27. HEALTHY CONDITIONm/s2
m/s2m/s2
m/s2
m/s2m/s2m/s2
m/s2

28. UNBALANCE
FFT of unbalanced
pulleys operating
system, unbalance
masses cause
centrifugal force, and
in FFT spectrum
unbalance force cause
high peak at 1X
(16.7Hz) at the redial
directions. the
process of adding
magnetic pieces,
which generates
centrifugal force in
each pulleys.
1X
1X
1X 1X
2X
m/s2
m/s2m/s2
m/s2m/s2m/s2

29. HIGH INITIAL TNSION
FFT of high initial
tension (50N), with
conditions of: 1000 rpm
(1X=16.67 Hz), 25x25
cm pulleys diameters,
and center distance 50
cm. Because of high
tension, the belt will be
dive in the sheave as
shown in the below
figure. Also high peaks
of (1X & 2X) appeared in
the radial direction (x
and z).
1X 2X
1X
1X
1X
2X
2X
2X
2X2X
m/s2
m/s2m/s2
m/s2m/s2m/s2

30. LOW INITIAL TENSION
FFT of low tension
(15N), with conditions
of: 1000 rpm
(1X=16.67 Hz), 25x25
cm pulleys diameters,
and center distance
50 cm. Low tension
causes the elliptical
belt rotating shape, as
shown in the left
figure. Also, FFT
shows a high peak at
3X (50Hz).
1X
4X
4X
4X
4X
4X
4X

31. FFT of belt slip over
pulleys by oiled contact
place between them, as
shown on the below figure.
Operating conditions are
initial tension 30 N, 1000
rpm (1X=16.67 Hz), 25x25
cm pulleys diameters, and
center distance 50 cm.
FFT shows a high peak at
3X (50Hz).
4X
4X
4X
4X
4X
4X
Oiled pulley groove

32. Pulley damage fault at
conditions of: 30N initial
tension, 1000 rpm (16.67
Hz),25x25 cm pulleys
diameters, and center
distance 50 cm. Shape of
created fault is shown
(bump inside the sheave).
FFT shows many random
high peaks at (1X,2X,3X..)
because of severity.
4.9X
1X
2X
3.8X
1X
1X
1X
4.9X
4.9X
4.9X
4.9X
6.9X3.8X
PULLEY DAMAGE

33. BELT WORN
Belt damage fault
and FFT spectrum at
conditions of 30 N
initial tension, 1000
rpm (16.67 Hz),
25x25 cm pulleys
diameters, and
center distance 50
cm. Belt damaged is
shown by side-cut
out. FFT graph
shows the peaks at
(1fb, 2fb, 3fb….),
and peaks depend
on the shape of
damage
1X
1Fb
1X
1X1X
1Fb
1Fb
2Fb
2Fb

34. Belt damage fault and
FFT spectrum at
conditions of 30 N
initial tension, almost
1528 rpm (25.47Hz),
25x25 cm pulleys
diameters, and center
distance 50 cm. figure
of stroboscope
camera picture shows
the belt resonance
state .
BELT RESONANSE
1X 1X
1X 1X
m/s2
m/s2m/s2
m/s2
m/s2m/s2

35. Flat belt
1- Sub harmonic peaks at frequencies equal to
the belt rate (1fb, 2fb, 3fb…) as V-belt worn
although there were no faults in all system
parts. These peaks cause of a continuous and
irregular contact between vertical edges of
pulleys and the sides of flat belt, as shown in
figure.
2- If there was any fault created, it will appear
as a high peak with board base in all figures,
specially.
3- A wide range of resonance because of small
thickness (4 mm), this leads to generate a high
peak at 1X frequency.
4- Slipping will be more active when the initial
tension is reducing, this leads to decrease the
rotating speed of driven pulley and generate a
high peak at 3X as V-belt

36. CONCLUSIONS
1-Increasing in speed rotation leads to
increasing in vibration of machine but in the
same time reduce in stress exerted on belt.
2-Vibration reduces with increase of the size of
pulleys.
3-Vibration of pulley-belt system increases with
increase the center distance(belt length).
4-Unbalanced pulley (static) spectrum showed
high 1X in the radial directions and low in the
axial direction.
5-High initial tension will cause high peeks at
(1X and 2X) in FFT spectrum graph.
7-Oiled contact surface (oiled belt) causes a
high peek at 3X in FFT spectrum graph at all
directions and the output rotating speed will be
change able along the time of working.
8-Existence signs of pulley damage depend on the damage
strength and its form, usually FFT spectrum contains many
unnumbered of unknown behavior high peaks.
9-The sign of worn belt is a (sub-synchronous) and harmonic
peeks at frequency (1fb, 2fb, 3fb …) Hz in the radial directions,
where fb is the fundamental belt pass frequency.
10-The sign of resonance in the belt is a high peek at
frequency 1X in the radial direction, also this fault appears
clearly on the slag side of belt which is in case of fluttering, (It
can also be seen with the naked eye or stroboscope camera).
11-The same conclusions above agree with flat belt results
except: high range of resonance because of small thickness of
belt so the flat belt always needs to idlers to overcome flattering
in belts during work, faults appeared in FFT graphs as a high
peak with board base (mountain-shaped), flat belt has less
friction contact surface as compared with the same thickness
and diameter of pulley of V-sheave, and this leads to lose in
power and irregularity of driven pulley speed that appeared as
3X peek in FFT as Vbelt behavior.
6-Low initial tension will cause high peeks appearing
in FFT spectrum at (1Xand 3X), 3X will be the
highest.

37. RECOMMENDATIONS FUTURE WORKS
1- Experimental study of dynamic response due to parameters change
( rpm, center distance, radius ratio) and diagnosis faults on cross belts
drive.
2- Study of dynamic response and diagnosis faults of double and triple
pulley-belt sheaves.
3- Study of dynamic response of vibrations of a pulley-belt system with
a condition of high rotating speed (more than 3000 rpm).
4- Design an electronic system for vibration monitoring by Wi-Fi.

38. Thank u for attention