AERODYNAMIC DEVELOPMENT OF THE SEGURACING F1-R01 PROTOTYPE USING CFD
13mmcc23 akash
1. Design and Analysis of Vibrating Screen With
Vibromotor,Eliminating Bearings
By
Akash Vyas
13MMCC23
DEPARTMENT OF MECHANICAL ENGINEERING
INSTITUTE OF TECHNOLOGY
NIRMA UNIVERSITY
AHMEDABAD-382481
MAY-2015
2. Design and Analysis of Vibrating Screen With
Vibromotor,Eliminating Bearings
Major Project Report
Submitted in partial fulfillment of the requirements
for the Degree of
Master of Technology in Mechanical Engineering
(CAD/CAM)
By
Akash Vyas
(13MMCC23)
Guided By
Prof. Darshita Shah
DEPARTMENT OF MECHANICAL ENGINEERING
INSTITUTE OF TECHNOLOGY
NIRMA UNIVERSITY
AHMEDABAD-382481
MAY-2015
3. Declaration
This is to certify that
1. The thesis comprises of my original work towards the degree of Master of Tech-
nology in Mechanical Engineering (CAD/CAM) at Nirma University and has not
been submitted elsewhere for a degree.
2. Due acknowledgment has been made in the text to all other material used.
Akash Vyas
(13MMCC23)
ii
4. Undertaking for Originality of the Work
I, Akash Vyas, Roll. No. 13MMCC23, give undertaking that the Major Project enti-
tled “Design and Analysis of Vibrating Screen With Vibromotor,Eliminating
Bearings” submitted by me, towards the partial fulfillment of the requirements for the
degree of Master of Technology in Mechanical Engineering (CAD/CAM) of Nirma
University, Ahmedabad, is the original work carried out by me and I give assurance that
no attempt of plagiarism has been made. I understand that in the event of any simi-
larity found subsequently with any published work or any dissertation work elsewhere;
it will result in severe disciplinary action.
__________________
Signature of Student
Endorsed by
(Signature of Guide)
Date: 13-05-2015
Place:Ahmedabad
iii
5. Certificate
This is to certify that the Major Project Report entitled “Design and Analysis of
Vibrating Screen With Vibromotor,Eliminating Bearings” submitted by Mr
Akash Vyas (13MMCC23), towards the partial fulfillment of the requirements for
the award of Degree of Master of Technology in Mechanical Engineering (CAD/CAM)
of Institute of Technology, Nirma University, Ahmedabad is the record of work carried
out by him under our supervision and guidance. In our opinion, the submitted work
has reached a level required for being accepted for examination. The result embodied
in this major project, to the best of our knowledge, has not been submitted to any
other University or Institution for award of any degree.
Prof. Darshita Shah
Guide, Assistant Professor,
Department of Mechanical Engineering,
Institute of Technology,
Nirma University,
Ahmedabad-382481
Dr R N Patel Dr K Kotecha
Head and Professor, Director,
Department of Mechanical Engineering, Institute of Technology,
Institute of Technology, Nirma University,
Nirma University, Ahmedabad-382481
Ahmedabad-382481
iv
6. Acknowledgments
I am using this opportunity to express my gratitude and respect to everyone who sup-
ported me throughout the course of my M.Tech project. I am thankful for their aspiring
guidance, invaluably constructive criticism and friendy advice during the project work.
I am sincerely grateful to them for sharing their truthful and illuminating views on a
number of issues related to the project.
I would like to begin by thanking my institute project guide Prof. Darshita Shah who
has been a source of postivity for me at every stage of the project and for providing
his continuous guidance for project,inspiring suggestions and encouragement. I am
sincerely thankful for his valuable guidance.
I would like to express my deep sense of gratitude to Mr.Anand Patel (Managing Direc-
tor) and Mr. Subhash Rawal (Manager), Ammann Apollo India (P) Ltd for giving me
an opportinity and support throughout the project work and for giving there valuable
time throughout the project work. Also would like to thank the entire team of Ammann
Apollo engineering department for their inputs.
I would also like to thank our PG co-ordinator Dr.K M Patel & Head of Department
Dr R N Patel for allowing me to carry out my project atAmmann Apollo India (P) Ltd.
I express my sincere thanks to all faculty members who helped me during my M.Tech
curriculum.
I would like to thank God Almighty, my parents, grand parents, all my colleagues ,
family members, friends and all the special persons for their love, support and excellent
co-operation to build my moral during the work.
v
7. Abstract
Vibrating screen is used for separating materials in different sizes for batching or con-
crete plant.The problem arises is the frequent failure of the spherical roller bearing
within two months of the installation which is required to reduce and to improve the
screening process effectively is the aim of the project work.
In order to achieve the required task,design calculation for bearing and shaft are carried
out.Which shows it’s a highly mixed-mode loaded condition.To improve life another
option is to go for new lubricant and compare properties of new lubricant tungsten
disulfide (WS2) with old one is carried out but that also not shows significant improve-
ment of life.Finally in order to achieve the task complete elimination of bearing and
introducing vibromotor into vibrating screen and redesign & analysis with vibromotor
is carried out.
To fulfill requirement of vibrating screen 50 Hz frequency vibromotor is selected.Maximum
amount of vibration is expected from vibrating screen. Hence, it is required that natu-
ral frequency of the vibrator screen should be as near as possible to vibromotor natural
frequency. Various iterations have been performed in design of vibrating screen to bring
its natural frequency close to 50 Hz. Then the design of vibrator screen has been final-
ized.The model analysis of design is carried out to check deformation & stress patterns
which shows deformation & stress are within the permissible limit. To improve damp-
ing property of base support, spring support is designed and analyzed. Analysis results
are within the permissible limits.Finally, fatigue analysis is done for whole screen and
support.Results of analysis shows that frequency, displacement and stresses are within
the limits.
Key words : Vibrating screen, Bearing life, Lubricants, FE analysis,Vibromotor
vi
13. Chapter 1
Introduction
1.1 Preamble
Batching or concrete plant is used to gain the proper mixture of materials for the con-
struction of the road. Many components are used in batch mix plant. Main component
is vibrating screen, which is used for classifying material as per size. In vibrating screen
shaft is located in the centre. Above and the below of the shaft different size of wire
mesh are provided for classifying material. At the both end of the shaft weight is pro-
vided. Between weights on both ends spherical roller bearing is provided, with which
motor is attached through belt. So vibration motion is created and materials classified
and fed to next component for the process. This bearing was getting failed in very
less time which is costly and time consuming maintenance process. Next phase of work
is to design the vibrating screen with vibromotor by eliminating bearings and shaft.
Springs are placed at the bottom and damping property is going to be calculated. At
last fatigue analysis is going to be carried out.Stress and deformation are must have to
be in a permissible limits for the new design of vibrating screen.
1.2 Research Objectives
Below are the main objectives for the project work.
• To find centrifugal forces due to shaft, unbalance mass.
• Calculate the bearing life considering different loading conditions.
1
14. • Design and analysis of vibrating screen using vibromotor.
• To check stress and deformation of new design.
• To check the damping property of spring support at the bottom.
• Fatigue analysis of the vibrating screen should be check.
1.3 Methodology
In this experimental and simulation investigation procedure described below has been
used to obtain the Research Objectives.
• Design calculation of the centrifugal force for the shaft and unbalance mass.
• Calculation of the bearing life by determining loads on bearing and centrifugal forces.
• By literatures suitability of new lubricant for system with molybdenum disulfide.
• Design and analysis of the vibrating screen as per the vibromotor which is going to
be used.
• Design of spring support at the bottom of vibrating screen for eliminating resonance
with optimum damping.
• Fatugue analysis of vibrating screen design for estimating service life.
1.4 Thesis Organization
The thesis constitutes of various chapters and the description as follow:-
Chapter 1 : In this chapter over all understanding of the thesis is shown.
Chapter 2 : In this chapter Introduction of batching plant, bearing failure conditions
and introduction of lubrications is present. Different literature reviews are highlighted.
Chapter 3 : In this chapter calculation of centrifugal force, bearing life calculation, life
of lubricant with temperature chart and calculation of lubricant required for bearing
are shown.
2
15. Chapter 4 : In this chapter design & analysis of vibrating screen with vibromotor, design
of spring for the base considering damping characteristics and fatigue analysis is done.
All the parameters like deformation,stress etc. are checked considering permissible
limits.
Chapter 5 : In this chapter result and discussion for the project work is shown.
Chapter 6 : In this chapter conclusion and scope of work in future is discussed.
References are listed at the end of the thesis.
3
16. Chapter 2
Literature Reviews
2.1 Background
2.1.1 About the industry
Amman Apollo India Pvt. Ltd. is a joint venture of Amman group and Apollo con-
struction equipment Ltd. They are one of the leading manufacturers of wide range of
world class equipment to serve road construction industry. They are a leading global
supplier of mixing plants, machines and services to the construction industry with core
expertise in road building. With the equipment technology refined through over forty
years of experience as part of Apollo’s continuous product improvement focus, large
manufacturing facilities producing hundreds of asphalt Plants and asphalt pavers per
year and other Auxiliary Equipment. Paver machines, asphalt plant, macadam plant
and other construction auxiliary equipments are the main product of the industry.
2.1.2 Problem faced by the industry
The asphalt plant is one of the services provided by the industry. The asphalt is a
sticky, black and highly viscous liquid or semi-solid form of petroleum. The primary
use of asphalt is in road construction, where it is used as the glue or binder mixed with
aggregate particles to create asphalt concrete. In the asphalt plant the hot aggregates
is fed in to the toppers and then it is screened in to numerous hot bins. After that it is
supplied to the mixers. Here for screening the aggregates vibrating screen is used which
4
17. screens them according to the required sizes. This is done by the vibrating motion of
the screen. Now here is the problem faced by the industry, the life of the bearing
(spherical roller type bearing) used in the vibrating screen is less.
2.2 Introduction to batching plant
Batching plant is defined as,
“An assemblage of bins, conveyers, and weighing equipment arranged for the purpose
of weighing the materials entering into a batch of concrete”
To prepare hot asphalt mix for- base and surface courses, both aggregate and bitumen
are heated and along with filler material they mix thoroughly in the hot mix plant.
Its functions are:
• Rough proportioning of the aggregate.
• Heating & Drying the aggregate.
• Heating the bitumen.
• Mixing the proportioned aggregates, bitumen to produce a homogeneous mix.
In a batch mix plant, front end loader will fed raw materials like gravel and sand in the
feed hoppers. Then, mixture is elevated into the mixing chamber high up in the plant
where the binder agent is added from a large silo. The term batch is used because only
specified quantity is mixed. Once the mix is ready it is deposited into a truck.
5
18. Figure 2.1: Batching plant [1]
2.3 Vibrating screen & its bearing
2.3.1 Vibrating screen
A vibrating screen is a large mechanical tool used to separate solids and powders.
Industries as diverse as mining operations and construction firms utilize these tools to
help sort and clean items. Using gravity, motion and mesh screens, these tools perform
the work of several people in a fraction of the time.
A vibrating screen separator is roughly the size of a metal garbage dumpster. It is
constructed many times of a solid metal such as steel and has two open sides so users
can visually monitor the progress of the screen.
Most vibrating screens have four or more levels of screens stacked on top of one an-
other. The screens are made of wire mesh and come in a variety of sizes in order to
accommodate different jobs.
Vibrating screen used in the construction industry operates by having the items that
are to be separated, such as marbles, aggregates and materials of different sizes, placed
on the screen on the top layer. The entire machine vibrates in a gentle motion to work
the material through the screens and separate any impurities. So the aggregates of
different sizes would slowly work their way down the many layers of screens, usually
having the largest openings at the top layer and getting smaller as the aggregates head
toward the bottom.
6
19. Following fig. 2.2 and fig.2.3 shows the vibrating screen and its schematic diagram
respectively.
Figure 2.2: Vibrating screen [1]
Figure 2.3: Schematic diagram of vibrating screen[1]
7
20. 2.3.2 Bearing in vibrating screen
The bearing used in the vibrating screen is spherical roller bearing. The bearing used in
the screen of the industry is FAG-22320. Following fig. 2.4 shows the spherical bearing
in the vibrating screen.
Figure 2.4: Bearing in vibrating screen [1]
2.4 Function of vibrating screen
Basic function of Vibrating Screen is to screening hot aggregates and feed to hot bin
unit of individual hot bins as per sieve size and over size aggregates come out from
vibrating screen through over size chute.
Vibrating screen has also it’s applications in the mining industries as it is used to clean
the minerals taken from the soil and it also helps to shaken of the impurities from the
minerals.
2.5 Rotating direction for vibrating screen
The standard rotating direction is as shown in Figure 2.5 on the Left, but sometimes, the
reverse direction may be more efficient depending on feed rate, gradation and specific
gravity of the material.
8
21. Figure 2.5: Rotating direction[1]
2.6 Operating conditions for bearing in vibrating
screen
Vibrating screens is used for classification of solid materials as per the grain size of
materials.The bearings used in this machine must have to sustain not only high loads
and high speeds but also accelerations and centrifugal forces.Many of these applications
involve adverse environmental conditions such as contamination and moisture. The
spherical roller bearings are matched to the operating conditions in vibratory machinery
and have proved highly successful in practical use beacause it can support dynamic
angular misalignments of up to 0° to 15°.
2.7 Applications of spherical roller bearing
Provided below are a few common applications for spherical roller bearings. The spher-
ical roller bearing is designed to handle very heavy loads, even under misalignment or
shaft deflection conditions. The spherical shape of the outer ring raceway allows the
inner ring to tilt slightly relative to the outer ring without significant loss in bearing
life. Spherical roller bearings can also handle axial loading in either direction or heavy
shock loads.
• Continuous Casters (Support Roll, Guide Roll, Pinch Roll, Table Roll) > Other
Metal Mill Equipment
9
22. • Shaker Screens and Other Vibratory Equipment > Paper Making Equipment (Cal-
endar Rolls, Dryer Rolls, Fourdriner)
• Mining Equipment (Drag Lines, Gyratory Crushers, Continuous Miners, Jaw Crush-
ers) > Blowers and Fans
• Rubber and Plastic Forming Equipment (Extruders, Granulators)
• Pumps and Compressors (Deep Well, Slurry)
• Gears, Drives and Reducers > Construction Equipment > Oil Field Equipment
(Pump Jacks, Compounders, Derricks, Hoists)
• Overhead Cranes, Crane Hooks, Hoists > Metal Forming Equipment > Railroad
Generators and Alternator
2.8 Failure of spherical roller bearing
When a bearing does fail, it is important to determine the exact cause so appropriate
adjustments can be made. Examination of the failure mode often reveals the true cause
of failure. This procedure is complicated by the fact that one failure mode may initiate
another.
For example, corrosion in a ball race leaves rust-an abrasive-which can cause wear,
resulting in loss of preload or an increase in radial clearance. The wear debris in a
grease-lubricated bearing can impede lubrication, resulting in lubrication failure and
subsequent overheating. So this chapter includes the study of the reasons of bearing fail-
ure and different aspects related to it like lubrication, temperature effect, misalignment
etc.
10
23. 2.9 Bearing failure chart
The following fig. 2.6 shows a pie chart for the main reasons of hearing failure.
Figure 2.6: Bearing failure chart [2]
2.10 Bearing lubrication
Spherical roller bearings in vibratory machinery are subjected to very high operating
loads and adverse environmental conditions. The lubricant type, lubrication method
and lubricant supply must be carefully selected and matched in order to fulfill the
requirements for functional suitability and service life of the Vibratory machinery bear-
ings. Depending on the operating conditions, bearing size and particular requirements
of the plant operator, lubrication using grease or oil can be selected.
2.10.1 Grease lubrication
In most vibratory machinery, the special spherical roller bearings are lubricated using
grease. Grease lubrication is normally used up to a speed parameter n.dm = 300 000
min-1.mm (n = operating speed, dm = mean bearing diameter). Only greases that
have been tested and proven should be used.
11
24. The main advantages of grease lubrication are:
• A very simple design.
• Grease enhances the sealing effect.
• Long service life with maintenance.
• Free lubrication and simple lubricating equipment.
• Low frictional moment.
Grease is typically applied in areas where a continuous supply of oil cannot be retained,
such as roller bearings or gears. Factors to be considered when selecting suitable grease
are operating temperatures, water resistance, oxidation stability etc. The second fac-
tors, not less important, are the grease’s characteristics, including viscosity and con-
sistency. Lubricating grease consists of base oil, performance additives and a thickener
which forms a matrix that retains the oil in a semisolid state. Most grease thickeners
are soaps, i.e. lithium, calcium, or aluminum soap. Grease is the most widely used
lubricant for roller bearings and low velocity applications, mainly because grease type
lubricants are relatively easy to handle and require only the simplest sealing devices.
Figure 2.7: Grease anatomy[3]
As a solid lubrication it will reduce the required design for the lubrication system. And
the lubrication methods will also be very easy as that can also be done by "grease
guns and motion guards". Grease pumps and regulators can also be used where the
requirement of lubricants is more.
The high viscosity results in less oil release rate which will reduce the refill rate. Here
thickeners will help to increase the amount of oil release so by this we can maintain a
12
25. suitable intermediate time for supply of lubrication and it will also increase its working
ability in the high temperature conditions. Additives are also there to improve its
properties.
In this specific case Molybdenum Disulfide (MoS2) is being used as an additive in grease
for lubrication of spherical roller bearing.
2.10.2 Molybdenum Disulfide (MOS2) as an Additive
Molybdenum disulfide is an inorganic compound with the formula MoS2. It is widely
used as a solid lubricant because of its low friction properties and robustness. In general
greases contain 1 to 2% of MoS2 with critical parameters being surface roughness, load
and speed.
Following are the properties of Molybdenum Disulfide (MoS2):-
Figure 2.8: Properties of MoS2 [3]
2.10.3 Disadvantages of Molybdenum Disulfide (MoS2)
Main disadvantages are as stated below,
• Molybdenum disulfide in grease decreases the wear resistant properties of the grease.
• Molybdenum disulfide has a lamellar structure, of which the layers can easily slide
along each other. Molybdenum disulfide has a black color. These lamellar can cause,
extra wear of the bearing material.
• MoS2 doesn’t function very well in a wet environment.
13
26. • Molybdenum disulfide in grease increases the corrosion caused by the grease. This is
caused through the formation of corrosive chemical elements by hydrolysis and galvanic
corrosion between Molybdenum disulfide and metals.
In only dry environment, at higher temperatures and under vacuum it works extremely
well. At a concentrated oxygen environment, oxidation possibly will arise.
2.10.4 Types of additive used in grease
As mentioned earlier, there are certain disadvantages of using Molybdenum disulfide
as an additive in grease. So, it is required to find a better substitute of Molybdenum
disulfide in order to overcome these difficulties. There are many additives are available
in the market which can be used for grease.
Figure 2.9: Types of additives [3]
Tungsten Disulfide (WS2) can be used as an additive in the grease for the lubrication
of spherical roller bearing in Extreme pressure and High Temperature conditions, so it
can be used as a substitute of Molybdenum Disulfide (MoS2).
14
27. 2.10.5 Properties of tungsten disulfide (WS2)
Figure 2.10: Properties of WS2[3]
2.10.6 Oil lubrication
Oil lubrication is recommended if adjacent machine components are supplied with oil
as well or if heat must be dissipated by the lubricant. Heat dissipation can be necessary
if high speeds and/or high loads are involved or if the bearing is exposed to extraneous
heat. Oil lubrication systems with small quantities of oil (throwaway lubrication),
designed as drip feed lubrication, oil mist lubrication or oil-air lubrication systems,
permit an exact metering of the oil rate required.
15
28. This offers the advantage that churning of the oil is avoided and the friction in the
bearing is low. If the oil is carried by air, it can be fed directly to a specific area; the
air current has a sealing effect. With oil jet or injection lubrication, a larger amount of
oil can be used for a direct supply of all contact areas of bearings running at very high
speeds; it provides for efficient cooling.
2.10.7 Selection of lubricant system
For the selection of a lubricating - system the following points should be taken into
account:
• Operating conditions for the rolling bearings.
• Requirements on running, noise, friction and temperature behavior of the bearings.
• Requirements on safety of operation, i.e. safety against premature failure due to wear,
fatigue, corrosion, and against damage caused by foreign matter having penetrated into
the bearing (e.g. water, sand).
• Cost of installation and maintenance of a lubricating system.
2.11 Failure due to over lubrication
At many industrial facilities, the task of equipment lubrication is often assigned to a
newly hired maintenance technician or mechanic with little or no lubrication training
that is just learning the ins and outs of the plant. Often times these mechanics are
handed a grease gun and told to lubricate the points on a particular line or maybe the
entire plant. To the maintenance supervisor, this seems like a good way to familiarize
the new mechanic with the plant’s equipment. To the new mechanic, he is performing an
important task that is helping to increase bearing life. Both the maintenance supervisor
and mechanic are right but they are also wrong.
Certainly, assigning a new mechanic the task of equipment lubrication will help famil-
iarize him with the plant’s equipment, but at what cost? The new mechanic is correct in
believing that he is performing an important task, but is the way he performs the task
actually increasing bearing life? The answer depends upon how well the new mechanic
has been trained. More than 35% of bearing failures can be attributed to improper
lubrication. An enthusiastic but untrained lube tech with a grease gun is more than
16
29. likely to cause premature bearing failures due to over greasing than he is due to under
greasing.
Over greasing a bearing will cause the rollers or balls to slide along the race instead
of turning, and the grease will actually churn. This churning action will eventually
bleed the base oil from the grease and all that will be left to lubricate the bearing is
a thickener system with little or no lubricating properties. The heat generated from
the churning and insufficient lubricating oil will begin to harden the grease. This will
prevent any new grease added to the bearing from reaching the rolling elements. The
end result is bearing failure and equipment downtime
Over lubricating the bearings in an electric motor causes an additional problem that
will negatively affect the efficiency of the motor resulting in higher operating costs and
cause excessive heat within the motor.
The key to preventing the over lubrication of bearings is to ensure that all maintenance
personnel are trained on proper lubrication techniques including how to determine the
correct amount of grease to pump into a bearing. Establishing a sound overall mainte-
nance program that includes lubrication intervals for each asset in your facility or even
condition monitoring using ultrasonic technology will not only decrease maintenance
costs; it will decrease downtime as well.
Formula in calculate appropriate grease quantity
G = 0.114 ∗ D ∗ B [4]
G=correct amount of grease in ounces
D=outside diameter in inches
B= the bearing width in inches
2.12 Literature review of published study
Zhao Yue-min. Liu Chu-sheng, He Xiao-mei, Zhang Cheng-yong, Wang Yi-
bin And Ren Zitling.[5] shows the finite element method is an important method
and necessary process in the dynamic design process of vibrating screen. Using FEM to
analyze structural characteristic can help the designers realize dynamic characteristic
of vibrating screen and make dynamic modification of the structure.
Ye Hengl And Ling Xiaocong.[6] shows temperature of the vibrating screen affects
17
30. the overall performance of the screen and by keeping it in the limit we can maintain
the equipments.
Haifeng Chi, Xiaoqiu Luo, Zhbngchao Ma, Chungiio Lhi And Yi Wang[7]
by increasing the performance of lubricating property we can increase the life of the
bearing and the vibrating screen which affects the overall performance of the screen.
Wenying Li and Shibo Xion [8] suggested Kinds of failure in large vibrating screen
consist of the faults of cross members, the side plates and the discharge chute. In order
to obtain satisfactory results from experimental mode analysis, using impact hammer
by means of multiple random exciting enhance the insufficient impact energy or using
proper shaker excitation.
Cheng Zhang, Zhang Youngsheng, Li Suozhu , Zhao Shuyan [9] shows that by
providing proper cooling we can improve greatly the life span of the bearing, prolongs
the cycle of the supplement of the lubricating lipid, prevents the malfunction caused by
the damaged bearing due to shortage of oil, and improves the reliability on long- term
running of the vibration screen.
Tohru Ueda, Koji Ueda and Nobnaki Mitamnra [10] investigated the Due to high
surface pressure, excessive sliding and roughness of the rolling element, the tangential
force acting between the raceways and a rolling element also becomes high and results
in surface originated failure, which is unique to spherical roller bearings.
Diiienhoefer Thomas [11] shown that the possible high oil flow is provided by which
large heat dissipation is achieved on the inner ring and therefore oil in the lubricating
gap retains a high viscosity, this ensures a long service life of the bearing.
Byung Ckul Kim, Dong Chang Park, Hak Sung Kim, Dai Gil Lee [12] are
worked that composite spherical bearing (CSB) was developed using carbon-phenolic
woven composite to solve the seizure of the conventional metal—metal spherical bearing
and also we can say that the composite spherical bearing was a good solution not only
to prevent the seizure but also to improve the high precision and high speed targeting
control of elevation driving mechanism.
18
31. Chapter 3
Vibrating screen with shaft and
bearing
3.1 Specification of vibrating screen
Figure 3.1: Specification of vibrating screen[13]
3.2 Bearing specification [13]
Specifications for bearing which used is as below
• Spherical roller bearing = FAG – 22320
• Bore dia. = 100 mm
• Outside Diameter = 215 mm
19
32. • Width = 73 mm
• Weight = 13 kg
3.3 Centrifugal force calculation
Centrifugal force of vibrating shaft Shaft RPM N = 960 RPM
Radius of eccentric weight r = 80 mm = 0.08 meter
Weight of eccentric part m = 64 kg
Linear velocity,
V = Π∗D∗N
60
∴V = 8 m/s
Now, angular velocity,
ω = V
r
∴ω= 100 rad/sec
Centrifugal force due to eccentric weight of shaft,
F = m ∗ r ∗ ω2
∴ F1 = 51200 N
Now, there is a unbalance mass hanged on both side of shaft. Whose terms are as
below.
Weight = 33 kg,
Quantity= 2 ,
Radius=180 mm=0.180 meter
Linear velocity,
20
33. V = Π∗D∗N
60
∴ V = 18 m/s
Now, angular velocity,
ω = V
r
∴ ω= 100 rad/sec
Centrifugal force due to eccentric weight of shaft,
F = m ∗ r ∗ ω2
∴ F = 59400 N
There are two weight.
∴F = 59400 * 2 = 118800 N
∴F2= 118800 N
Now, there is extra unbalance mass hanged on both side of shaft Whose terms are as
below.
Weight = 4 kg,
Quantity = 4
Radius = 180 mm = 0.180 meter
Linear velocity,
V = Π∗D∗N
60
∴ V = 18 m/s
now, angular velocity,
ω = V
r
21
34. ∴ω= 100 rad/sec
Centrifugal force due to eccentric weight of shaft,
F = m ∗ r ∗ ω2
∴ F = 7200 N
There are four weight.
∴ F = 7200 * 4 = 28800 N
∴ F3= 28800 N
Now, there are two bearings are also attached on shaft. So we need to take centrifugal
force due bearing’s mass hanged on both side of shaft. Terms for the bearings are as
below.
Weight = 13 kg,
Quantity = 2 ,
Radius = 215
2
mm =0.1075 meter
Linear velocity,
V = Π∗D∗N
60
∴ V = 10.807 m/s
now, angular velocity,
ω = V
r
∴ω= 100.5 rad/sec
Centrifugal force due to eccentric weight of shaft,
F = m ∗ r ∗ ω2
∴F = 14115.0991 N
22
35. There are two bearings.
∴ F = 14115.0991*2 = 28230.19875 N
∴ F4= 28230.19875 N
Therefore, Total Centrifugal Force,
F = F1 + F2 + F3 + F4
∴ F =51200 + 118800 + 28800 + 28230.19875
∴F =227030.1988 N = 227.0302 KN (A)
Figure 3.2: Centrifugal forces on eccentric shaft
3.4 Bearing Life Calculation
The equation of spherical roller bearing
L = (
C
P
)
10
3 (3.1)
[14]
For the existing bearing design parameters are as below :
Bore diameter=100 mm
Outside diameter=215 mm
Width=73 mm
Dynamic load rating c=810 KN
23
36. P = X ∗ V ∗ Fr + Y ∗ Fa[14] (B)
Here,
P=equivalent load
Fr=applied constant radial load
Fa= applied constant thrust load
V= rotational factor = 1.2
X= radial factor
Y = thrust factor
Figure 3.3: Open belt drive
Here for this open belt drive,
r1 =outer radius of bearing= 107.5 mm
r2 =radius of pulley attached with the motor= 45 mm
x = distance between centre of pulley and bearing =580 mm
Power transmitted by belt,
P = (T1 − T2) ∗ V [14]
Where,
T1& T2 =tension in tight side & slack side of belt respectively in N
P = 2.5 kW = 2.5 × 103 W
Now, V = Π∗D∗N
60
24
37. where,
D= diameter of pulley attached with motor = 90 mm
N= rpm of motor = 1440 rpm
∴2.5 ∗ 103
= (T1−T2)∗Π∗0.09∗1440
60
T1 − T2 = 368.414N (3.2)
But, ratio for driving tension is,
T1
T2
= eµ∗θ
(3.3)
[14]
Where,
θ=angle of contact for open belt drive
θ = (180 − 2α) ∗ π
180
radian [14]
sinα = r1−r2
x
[14]
so, α = sin−1
(107.5−45
580
) = 6.186ř
so, θ = 2.93 radian
µ = 0.23
so,from equation (3.2) and (3.3),T2 = 384.165N & T1 = 752.579N
Figure 3.4: Maximum angle of shaft for tilt
Hence,for radial force,
25
38. Fr = T1 + T2 + C.F.
∴Fr = 752.579 + 384.165 + 227030.1988 (C.F.from (A))
∴Fr = 228166.9428 N
Now,shaft can be tilt for maximum angle of 20°. So, calculation for axial force,
Fa = Fr cos70
∴Fa = 78037.6905 N
Now, for equation (B),
X = 1,
Y = 0.4 ∗ cotα [14]
∴Y= 0.4 cot 30
∴ Y = 0.7275
P = X ∗ V ∗ Fr + Y ∗ Fa
From this equation,
P= 330572.7512 N
∴ P =330.5728 KN
Now from equation (3.1),
L = (C
P
)
10
3
∴ L = ( 810
3305728
)
10
3
26
39. ∴ L = 19.8332 million revolution
Now, for the rated bearing life in hour,
L10h = L10∗106
60∗N
[14]
Here,
L10h = rated bearing life in hour
N = speed of rotation in rpm = 960 rpm
L10 = rated bearing life in million revolution = 19.8332 million revolution
∴ L10h = 19.8332∗106
60∗960
∴ L10h= 344.3264 hours
3.5 Bearing failure due to lubrication
3.5.1 Effect of temperature on lubricant
Temperature is very important parameter in case of vibrating screen because Vibrating
screen separates Aggregates at temperature about 160 - 200 °C. So, it is highly essential
that the bearings, screens, lubricants like grease and other component can sustain such
a high temperature. For this temperature control effective lubricant is required. So, it
is required to add 25 grams grease per day for the lubrication of bearing in vibrating
screen.
27
40. The following fig 3.5 shows the grease life in the bearing for different temperature.
Figure 3.5: Grease life [1]
For this data graph for the temperature Vs. drease life is created as shown in fig. 3.6.
Figure 3.6: Graph for temperature Vs. life of lubricant
28
41. 3.5.2 Effects of lubrication
A very high percentage of all bearing damages can be attributed by inadequate lubrica-
tion. Grease lubricants aid in protecting bearing surfaces from corrosion and reducing
friction. Although a very broad term, inadequate lubrication can be classified into eight
basic categories:
• Overfilling
• Under filling
• Incorrect grease
• Mixing greases
• Incorrect lubrication systems and intervals
• Worn-out grease
• Water contamination
• Debris contamination
Probably the major cause of premature bearing failure is the contamination of the
bearing lubrication by moisture and solids. As little as 0.002 % water in the lubricant
can reduce bearing life by 48 % and 0.006 % water can reduce bearing life by 83 %.
29
42. 3.6 Comparision of technical & physical properties
of Tungsten Disulfide & Molybdenum Disulfide
Figure 3.7: Comparison of properties of WS2 and MoS2
3.7 Advantages of Tungsten Disulfide (WS2) over
Molybdenum Disulfide (MoS2)
• Tungsten Disulfide (WS2) is one of the most lubricous materials known to science.
With Coefficient of Friction at 0.03, it offers excellent dry lubricity unmatched to any
other substance. It can also be used in high temperature and high pressure applications.
It offers temperature resistance from -450°F (-270 °C) to 1200°F (650 °C) in normal
atmosphere and from -305°F (-188 °C) to 2400°F (1316 °C) in Vacuum. Load bearing
property of coated film is extremely high at 300,000 psi.
30
43. • Tungsten Disulfide (WS2) can be used instead of Molybdenum Disulfide (MoS2) and
Graphite in almost all applications, and even more.
• Molybdenum and Tungsten are from same chemical family.
• Tungsten is heavier and more stable then Molybdenum Disulfide(MoS2)
• Molybdenum Disulfide (Also known as Moly Disulfide) till now has been extremely
popular due to cheaper price, easier availability.
• Tungsten Disulfide is not new chemical and has been around as long as Molybdenum
disulfide and is used extensively by NASA, military, aerospace and automotive industry.
• Till few years ago, price of Tungsten Disulfide was almost 10 times that of Molyb-
denum Disulfide. But since then price of Molybdenum Disulfide has doubled every six
months. Now the prices of both chemicals are within comparable range. Now, it makes
more economic sense to use superior dry lubricant (Tungsten Disulfide) to improve the
quality and competitiveness of final product.
• Tungsten Disulfide offers excellent lubrication under extreme conditions of Load,
Vacuum and Temperature. The Tungsten Disulfide offers excellent thermal stability
and oxidation resistance at higher temperatures. Coefficient of Friction of WS2 actually
reduces at higher loads.
• Tungsten Disulfide has very less effect of moisture and water particles as compared
with Molybdenum Disulfide.
• Tungsten Disulfide possesses characteristics to work in bad weather conditions.
3.8 Calculation for quantity of grease required
We have the equation to calculate the quantity of grease required as
G = 0.114 × D × B [4]
where,
G =correct amount of grease in ounces
D =outside diameter in inches =215 mm = 8.4646 inch
B= the bearing width in inches = 73 mm = 2.874 inch
∴G = 2.773302 ounces .
31
44. If the grease gun dispenses 0.0502 per shot , then 2.7733 is divided by 0.05.
∴G=2.7733/0.05 = 55.466 ≈ 56
Thus, grease gun in rounded to 56 shots.
Figure 3.8: Grease gun calibration [4]
3.9 Calculations for different types of bearings
Like the same procedure we have follow for FAG-22320 bearing , in that same way life
of bearing, which have different design parameters is calculated . So we can come to
the result that which bearing can give more life than the bearing which is presently
used.
Figure 3.9: Calculations for different types of bearings
32
45. Figure 3.10: Comparison of life For different bearings
So, from this fig. 3.10 we can conclude that bearing FAG-22330 can give approximately
three times the life of existing one. But still overall life is less so we have to redesign
the design which can give screening process without any disturbance like changing of
bearing in short time.
33
46. Chapter 4
Design and analysis of vibrating
screen with vibromotor
4.1 Overview of vibrating screen with vibromotor
There is a new advancement in the vibrating screen in which the old unbalanced load
vibration and the shaft assembly is replaced by a single motor called Vibromotor. In
this, vibrating screen takes the vibrating motion from the vibrating motor. We have
selected vibromotor of 50 Hz of german based company named “Fredrick”.Maximum
amount of vibration is expected from vibrating screen. Hence it is required that natural
frequency of the vibrating screen should be as near as possible to vibromotor natural
frequency. Various iterations have been performed in design of vibrating screen to
bring its natural frequency close to 50 Hz. Following design of vibrating screen has
been finalized.
4.2 Design of vibrating screen
Design of the model vibrating screen is created in ansys workbench 14.0 as shown in
below figure.
34
47. Figure 4.1: CAD model of vibrating screen
4.3 Details of FE analysis
4.3.1 Material properties
Material properties of Stainless steel is as follows , which is used in vibrating screen.
Figure 4.2: Material properties of stainless steel
35
48. 4.3.2 Meshing model
After selection of material properties , meshing of model is done which is as shown in
below figure.
Figure 4.3: Mesh model of vibrating screen
In this meshing model , Total nodes are 322270. Total elements are 87417 and type of
element is Solid 186 Hex element .
4.3.3 Boundary condition
Now applyinng boundary condition for designed model by self-weight of the structure
and fix support at base.as shown in below figures.
• Self-weight of the structure: Applied by standard earth gravity
• Fix support: Fix support has been applied at bottom surface as below.
36
49. Figure 4.4: Self-weight of the structure
Figure 4.5: Fixed support at bottom
4.3.4 Results
Natural frquency of vibrating screen 30 Hz is obtained when thickness of both side plates
was 10 mm.Same way natural frequency of vibrating screen in direction of vibration is
58.55 Hz is obtained by keeping 20 mm thickness of both the side plates as follows,
If vibrating spring is directly connected to ground, supports may get damaged due to
vibration. Hence it is necessary to isolate vibration generated from vibrator screen to
ground. This can be achieved by using spring supports. Also since vibration is taking
place near to natural frequency of vibrating screen, to avoid chances of failure due to
resonance of vibrating screen, spring supports are required.
37
50. Figure 4.6: Deformation of model vibrating screen
4.4 Vibrating screen with vibromotor
Now, vibromotor is attached at the top of vibrating scrren between two plates. So,
torque is applied on vibrating screen by vibromotor. So, we need to calculate it.
Power of motor, P = 4 kW = 4000 W,
Freuency = 50 Hz
So RPM, N = 50 x 60 = 3000 rpm
Now, we have the equation for motor power,
P = 2ΠNT
60
∴ T = P∗60
2ΠN
From about equation and values,we get Torque T = 12.73 N.meter
38
51. Torsional moment has been applied on vibrator screen as follows,
Figure 4.7: Torsional moment applied on both plates
• Total deformation:
Figure 4.8: Total deformation due to torsional moment
39
52. • Equivalent (Von-Mises) Stress:
Figure 4.9: Equivallent stress due to torsional moment
Since material of construction of vibrator screen is ductile material, von-mises theory
has been applied.
4.5 Design of spring at bottom of vibrating screen
If vibrator spring is directly connected to ground, supports may get damaged due to
vibration. Hence it is necessary to isolate vibration generated from vibrator screen to
ground. This can be achieved by using spring supports. Also since vibration is taking
place near to natural frequency of vibrator screen, to avoid chances of failure due to
resonance of vibrator screen, spring supports are required.Isolation of vibration by using
springs can be analysed by harmonic analysis.
Now, according to hook’s law,F = K ∗ X, [15]
stiffness of spring as 4000 N/mm has been selected based on minimum deformation due
to pre compression.Since mass of vibrator screen is 4000 kg, pre compression of spring
will be 9.81 mm.
40
53. Total load on spring = 4000 kg
Acceleration on mass can be calculated as follows,
a = (2Πf)2
∗ x [15]
Where, f = Applied frequency = 50 Hz
x = Displacement = 0.69 mm = 0.00069 meter (from fig. 4.6)
∴ a = 68 m/s2
= 6.94g ≈ 7g
∴ Load on spring = 4000 x 7g = 274680 N
Here,material of spring is Stainless steel
Modulus of rigidity of spring G = 84000 MPa
From spring design calculations following parameters are finalized,
• No. of springs = 40
• Spring diameter D = 80 mm
• Spring wire diameter d = 21 mm
• No. of active coils n = 20
• Pitch of coils p = 26 mm
• Stiffness of spring k = 4000 N/mm
• Weight on each spring w = 274680
40
= 6867 N
From above parameters shear stress on spring material can be observed by equation
τ = 8∗w∗D
Π∗d3 [15]
so, τ = 151.056 MPa
Allowable shear stress in stainless steel material = 160 MPa
Since shear stress in spring material is less than allowable limit, spring design is safe
from shear stress point of view.
Since spring is subjected to dynamic loading at 50 Hz, it is necessary to ensure safety of
spring during surge. It is necessary that ratio of surge frequency and applied frequency
should be more than 20.[16]Surge frequency can be calculated as follows,
41
54. fsurge = d
2ΠD2n
∗ 6Gg
ρ
Now, putting all the value in above equation we get fsurge = 1836.02 Hz.
fsurge
fapplied
= 1836.02
50
= 36.72
Since ratio is more than 20, design of spring from dynamic loading point of view is safe.
Spring has been simulated as spring element in Ansys as follows,
Figure 4.10: Model of spring at bottom
Calculation for damping:
Purpose of springs attached at the base is to isolate vibrations coming from vibrator
screen. But at the same time it should provide optimum damping, i.e. damping should
not be too much which can cause failure of vibrator screen as well as it should not be
too less which causes large amount of response time for spring to become stable.
Now for damped free vibration, we have the homogenous equation as below,
md2x
dt2 + cv
dx
dt
+ kx = 0 [15]
Here we have input values as below,
• Mass on spring, m = 4000 kg,
• spring stiffness k = 4000 N/mm
• initial velocity v0 = 0 mm/s
• pre-compression x0 = 9.81
so,by solving above equation we get damping co-efficient
42
55. • cv=3000 N.s/mm
Natural angular frequency,
• ωn = k
m
= 4000
4000
= 1radian/sec.
Now, critical damping co-efficient,
• cc = 2mωn = 2 ∗ 4000 ∗ 1 = 8000 N.s/mm
Damping ratio,
• ξ = cv
cc
= 3000
8000
= 0.375 (here, ξ<1 so it is the underdamped vibration )
The frequency of damped oscillation is ,
• ωd = ωn
√
1 − ξ2 = 1 − (0.375)2 = 0.927radian/sec.
The solution to the underdamped system for the mass spring damper model is the
following :
x(t) = e−ξωnt
x0sin (ωdt) + v0+ξωnx0
ωd
sin (ωdt)
In above equation by putting all the values required and changing the value of time t,
we will get different values of amplitude,x(t). By plotting this values on graph x(t) vs.
t , we will get damping graph as below.
43
56. Figure 4.11: Graph of Amplitude Vs. time
So, response time of spring will be approx. between 10 to 15 seconds which is optimum.
44
57. 4.6 Stresses and deformation in vibrating screen
with spring
For vibrator screen, it is also required to check if stresses are within allowable limit
during static condition, as well as fatigue failure is not taking place.
Stresses are analysed for vibrator screen by applying static load along with self weight.
Result of which are as follows,
• Total deformation
Figure 4.12: Total deformation using spring support
• Equivalent Stress
45
58. Figure 4.13: Equivalent stresses using spring support
4.7 Fatigue analysis
For fatigue analysis constant amplitude load (fully reversed) is applied as follows,
Figure 4.14: Fully reversible constant applied load
46
59. For mean stress correction, Gerber mean stress theory has been applied since it is more
conservative and more accurate as follows,
Figure 4.15: Mean stress correction theory
From above inputs, following cycle of operation has been obtained,
Figure 4.16: Fatigue analysis result with spring
We have stress cycle graph as below,
47
60. Figure 4.17: Stress cycle data
Hence we get maximum stress 4.8239 MPa (fig.4.13).By plotting it in graph we get
maximum cycles for this design.So,selected design is optimum.Our fatigue analysis re-
sult is also showing this as shown in fig.4.16.So, it can be observed from results that
vibrating screen will have very long service life.
48
61. Chapter 5
Result and discussions
• Vibrating screen with shaft and bearing
In Batch mix plant for classifying materials,vibrating screen is used.For vibrating shaft
with shaft and bearing we have done calculations for bearing life which was around 345
hours for FAG 22320.Suggested new bearing was FAG 22330 whose life was three times
than the older one.But still life is less accordingly as shown in below figure.
Figure 5.1: comparison of life of different bearings
49
62. • Vibrating screen with vibromotor
In below figure, comparison is shown for the different type of analysis. Which shows
selected design is prefferable because it does not esceeds the allowable limit.
Figure 5.2: comparison of different results of analysis
50
63. Chapter 6
Conclusion and future scope
6.1 Conclusion
From above project work we can summaries some things like, by calculating the life
of bearing which is about 345 working hours for bearing FAG 22320.Suggested new
bearing is FAG 22330 whose life is three times than the older one. Still life is so short.
Batch mix plant works around temperature of 160° C to 200° C. In this range the
life of lubricant is 1.156 days to 1.73 hours,which is shown in fig.3.5.So it is the quite
time consuming and long maintenance process. From present study of vibrating screen
with vibromotor , it can be observed that design of vibrating screen provides maxi-
mum vibration with provided capacity of vibromotor. Also it can be observed that by
providing isolation at base location with spring prevents vibrations of vibrating screen
to pass at ground location hence prevents failure of vibrating screen from resonance.
Also damping of spring is calculated and time required for system to stable in shut
down condition is optimum for calculated damping. Calculation of spring and fatigue
calculation shows that vibrating screen will be having long service life with provided
vibrations and resultant stresses and deformations are in permissible limit . So, design
is safe.
6.2 Future scope
• There is the scope by using vibromotor with 60 Hz and 70 Hz frequency. New
design and analysis of vibrating screen can be done accordingly and suitability of
51
64. new design can be checked with new vibromotor.
• When vibrating screen is loaded with aggregate , in that condition dynamic anal-
ysis can be done with new selected vibromotor.
• In older design with shaft and bearing , new bearings and shaft assembly can be
design and can be analysed.
• New design can be done by placing wire meshes at different angles in vibrating
screen and suitability of new design can be analysed.
52
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53
66. [11] Dittenhoefer Thomas “Spherical roller bearing having two row of rollers”
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54
