TRF

11
“A Detailed Study of Screens
at TRF Limited.”
Submitted To::Mr. Diwakar jha
Head Production & planningTRF LTD.,JAMSHEDPUR
Submitted By::Mr. Abinash sahu.
Bengal College Of Engg. & Tech.,Durgapur,WB.

“A Detailed Study of Screens at TRF Limited.” TRF.
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CERTIFICATE
This is to certify that Mr. Abinash sahu, B.Tech student of Bengal
College Of Engg. & Tech.,Durgapur has undergone a summer
Training at TRF Ltd during the period 12-06-2013 to 13-07-2013.
During this training he has successfully completed a project on “A
DETAILED STUDY ON VIBRATING SCREEN” under my
guidance.
MR. DIWAKAR JHA
HEAD PRODUCTION & PLANNING
TRF LTD.(JAMSHEDPUR)

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PREFACE
This report is a sincere effort to reveal the expression of my
experience, observation and study apart from my regular
academic curriculum .This industrial training at TRF Ltd.
Jamshedpur in the Department of WORKS was the first time real
experience that has helped me to gain practical knowledge of
engineering and learn the discipline and safety of working in
industries.
I was mainly focussed on one equipment that
TRF produces in abundance “The Vibrating Screens” or “The
Screening Machine”. Although I tried to get an overview of
complete working of the company in this short time.

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ACKNOWLEDGEMENT
I take this opportunity to thank several persons who were a great help in making
this project a success.
I am grateful to Mr. Diwakar jha for his excellent guidance and co-operation
during my summer training. He gave me sufficient time between his tight
schedules and helped me wherever I needed. I would have never succeeded
without his friendly but disciplined attitude.
I would like to thank Mr. P. Sharma, Mr. D. K. Paul, Mr. S. N. Mishra and all
those employees of TRF Ltd. whose friendly behaviour never let me feel an
outsider in the industry throughout the whole period.
Finally, I would like to pay my sincere thanks to Mr. Bhola Sahu for his
sincere co-operation. Because of their good relationship with every department in
the organisation, they brought me in contact with several important people in the
organization that helped me a lot.

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ABOUT THE COMPANY
TRF Limited
The Tata Group, founded in the last quarter of the 19th century, at a time when
India had just embarked on the road to independence, is committed to aligning its
business opportunities with nation building activities.
TRF Limited, established in 1962, is part of the Tata Group of Companies which
consists of more than 90 enterprises operating in seven business sectors, in over
80 countries. .
The combined competencies of three companies, the erstwhile Tata Robins
Fraser (established in 1962), Tata Material Handling Systems (formerly Tata
Man. Ghh., established in 1978), and Tata Techno dyne (established in 1996),
resulted in the formation of TRF Ltd
The company has evolved into one of the most comprehensive sources of
engineering equipment, systems and services. It manufactures bulk material
handling and processing equipment, bulk material handling systems, coke oven
equipment, coal dust injection systems for blast furnaces, coal beneficiation
systems, and port and yard equipment. It's Port and Yard Division is also
equipped with the technology; EPC and EPCM services for mini blast furnace
technology. TRF Ltd caters to diverse industries including power, metallurgy,
chemical, mining and cement.
Over the last five decades, TRF has emerged as a pioneer in solutions for
material handling equipment and processing systems required in the
infrastructure development. In quest of rapid growth, TRF has also diversified
into automotive applications business. It envisages growing five times in five
years and becoming a Rs 2500 Crores Company by 2013 by enhancing focus on
material handling business and auto applications business.

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TRF Group Companies
The Company’s subsidiary, York Transport Equipment (Asia) Pvt Limited,
Singapore is engaged in the business of trailer under gear, which includes axles,
suspension and other components, with market presence in 27 countries. York
Transport Equipment (Asia) Pte Ltd has manufacturing facilities in Singapore,
Australia, China and India. TRF has also set up Adithya Automotive
Applications Limited, an automotive applications unit for a fixed body truck
application in India. The objective of this venture is to engage in automotive
applications and provide end-to-end solutions through fabrication and machining
for tippers, load bodies, refrigerated bodies, etc. TRF acquired the Dutch Lanka
Trailer (DLT) Manufacturers Limited, Sri Lanka. DLT is a world class trailer
manufacturing company and has manufacturing facilities in Sri Lanka, Oman and
India. It exports trailers to as many as 30 countries. More recently TRF has
acquired Hewitt Robins International Ltd (HRIL) London which has a world
class reputation in bulk material handling and processing equipment. Hewitt
Robins is engaged in design, manufacture of Mobile Crushing plants and
Screens, and related products in the quarrying, mining, recycling, iron and steel
industries. It's proven screen and crusher brands, including the ‘Container
Classic' and the ‘Super Jaw', are all setting standards by which competitors'
equipment is judged.

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TRF Business Units
The Company has five business units which cater to the material handling
requirements of customers in the core infrastructure sectors of the economy. TRF
Limited undertakes turnkey projects for infrastructure development industries
such as power and steel plants, cement, ports, fertilisers and mining. TRF's
material handling products and systems are well known in the market, in India
and overseas, for their reliability, productivity and longevity. The Company been
constantly upgrading and developing new products and systems with the help of
internationally reputed enterprises having cutting edge technical expertise.
 BMHE
 BMHS
 PORT & YARD
 O & MS
 BOP

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BMHE:-
The Bulk Material Handling Equipment Division specialises in the design and
manufacture of a wide range of material handling equipment used in the
infrastructure industries, such as wagon tipplers, stacker reclaimers, ship loaders
and unloaders, travelling wagon loaders, etc.

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BMHS:-
The Bulk Material Handling Systems Division offers a complete package of
material handling and allied systems and services on a turnkey basis.
PORT & YARD:-
The Port and Yard Equipment Division focuses on the design, supply, erection
and the commissioning of material handling equipment for ports and stockyards
including level luffing cranes, ship loaders and unloaders, container cranes,
stacker-reclaimers and special purpose cranes for power and metallurgical plants.

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O & MS:-
TRF Ltd. has set-up the Operations and Maintenance Services (O&MS) division
to serve the end customer for an operational plant. This service is aims to lower
total cost of maintenance and asset upkeep for the customer.
Apart from direct financial benefits, O&MS strives to provide
customer with a safe and green plant, guarantee performance levels and develop
trust amongst the customer of the service provided.
BOP:-
TRF is exploring various possibilities to diversify into new areas of growth and
BoP business is one of such opportunity. With this intent TRF has launched a
new strategic business unit as BoP Division at Kolkata. This Strategic Business
Unit undertakes complete execution of BoP facilities for power generation
projects on turnkey basis. TRF has many strategic advantages which have made
it a frontrunner in this arena.
The BoP or Balance of Plant system comprises of all the system and utilities
which are required to run thermal power plants starting from raw material input
to waste output apart from the power island which includes the generator, turbine
and boiler with its auxiliaries

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MANAGEMENT
Mr. Sudhir Deoras
Managing Director
Mr. H.C. Kharkhar
Chief Operating Officer
Mr. P.K. Tibdewal
Vice President (Product Business)
Mr. Ranjit Sanyal
Chief (Projects)
Mr. Ashis Banerjee
Chief Technology Officer
TRF JAMSHEDPUR
The TRF Works at Jamshedpur spreads over nearly 22 acres with and this
includes six covered manufacturing bays on nearly 21,250 square metres. TRF’s
skilled manpower meets the expectation of its customers by continuously
adapting new technology, upgrading skills and serving its customers on time.
They also use several process improvement tools and techniques like TOC-
CCPM, quality circles, cross functional teams, etc to attain the highest level of
productivity.
TRF, with the help of advanced design and analysis software, constantly
innovates, enhances efficiency and improves reliability of its products and
systems which enable it to maintain leadership in the market.

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NAME OF THE CUSTOMERS
The companies whose orders are continuously bagged by TRF Ltd. are:
 Tata Steel Limited
 National Thermal Power Corporation Limited
 Bharat Heavy Electricals Limited
 Steel Authority of India Limited
 Bihar State Electricity Board
 Damodar Valley Corporation Limited
 Tata Projects Limited
 Tata Power Limited
 Bhushan Power and Steel Limited
 Indian Iron and Steel Company Limited
 Shaheed Iron and Steel Limited
 South Thermal Power Corporation Limited
 Rajasthan Rajya Utpadan Nigam Limited
 Calcutta Port Trust Limited
and many more…………….

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NAME OF COMPETITORS
Those companies which are producing the same products as TRF Ltd.
and are giving healthy competition in the world market are:-
 THYSSEN KRUPP
 BEEKAY ENGG
 LARSEN AND TOUBRO
 ELECON
 MCNALLY BHARAT
 MECON
 HEC
 PROMAC
 TECPRO

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COMPANY PRODUCTS
BULK MATERIAL HANDLING EQUIPMENTS:-
 VIBRATING SCREENING MACHINE
 FEEDERS(VIBRO FEEDERS, APRON FEEDERS, WOBBLER FEEDERS)
 BELT FEEDERS
 CONE, IMPACT AND JAW CRUSHERS
 HAMMER MILLS
 SINGLE AND DOUBLE ROLL CRUSHERS
 WAGON TIPPLERS
 SIDE DISCHARGE LOADERS
 SIDE ARM CHARGER
 PULLEY
 IDLER
BULK MATERIAL HANDLING SYSTEMS:-
 CROSS COUNTRY CONVEYORS
 COAL HANDLING SYSTEMS
 RAW MATERIAL BEDDING AND BLENDING SYSTEMS
 RAPID WAGON LOADING AND UNLOADING SYSTEMS
COAL BENEFICIATION SYSTEMS
STEEL PLANT SYSTEMS:-
 COAL DUST INJECTION SYSTEMS
PORT AND YARD EQUIPMENT:-
 PORT CRANES
 SPECIAL DUTY CRANES
 SHIP LOADERS AND UNLOADERS
 STACKER-RECLAIMERS

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PROCESS CHART
1. Planning :- Material
Instruction sheet
Process chart
Progress cum H/O sheet
2. Preparation:- Marking and cutting
3. Fabrication :- Drilling, Bending, Rolling, Straightening
4. Fitting
5. Welding
6. Assembly(Dressing, Cleaning, Painting)
7. Inspection
8. Cost centre

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INTRODUCTION
Screening is the separation of aggregate particles into various sizes. Types of
screens used are vibratory inclined, stationary inclined, vibrating grizzly,
vibrating horizontal and rotary.
The vibrating inclined screen is the most
popular of the screen types, it has proven to be the most reliable screen for
aggregate separation. The addition of extra counterweight allows the screen to
handle dense, coarse aggregate. When properly sized, the inclined vibrating
screen performs virtually maintenance free except for wear from the aggregate as
it is processed.
Horizontal screens are normally selected when
conserving headroom or there is a need to maintain a lower profile. Variation in
speed and stroke required for the separation.
All vibrating screens consist of four basic components:-
1. Vibrator: - This generates the force to move the vibrating frame.
2. Vibrating frame: - upon which the materials to be processed is passed over or
through.
3. Mounting parts: - which positions the machine in relation to the customers
feed and discharge points and isolates most of the vibration from its supporting
structure.
4. Drive parts: - which normally consists of an electric motor with sheave and V-
belts plus a motor base. This supplies the power to the vibrator.

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The
vibrating equipments can be classified according to their primary function:-
1. Screens which are used to separate product into specific granular or lump sizes
with a high efficiency.
2. Dewaterizers which are used basically for cleaning or washing of materials.
3. Scalpers or Grizzly which are used primarily to make a rough separation of
lump size to control the feed to the crusher.
4. Feeders which are used to transfer material from one place to another with a
control feed.
5. Shakeouts which are used to separate material from a restraining container or
separate sand from castings.
LIVE FRAME:- Live frame consists of 2 numbers side plates, 8 bucker up
frame, 2 cross struts, screening cloth panels, and skirt boards. Side plates are
made of steel plates stiffened with angle plates. The angle plates are bolted with
plates with hunk struts. Vibrator casing also adds to the stiffness of the live
frame.

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Bucker up frame is a fabricated structure with longitudinal members and cross
members. The longitudinal members located in each shape to give convex
surface to screen cloth and ensure even distribution of material over the entire
width of the screen.
Skirt boards give necessary tension to the screen cloth/panel. These are made in
segments and are assembled with the side plates.
High tension bolted connection are employed for fixing various replaceable
members to the live frame. Under the nuts and bolts heads hardened carburized
washers are provided to protect the main members of the live frame. These
fasteners are tightened with calibrated torque wrenches to ensure trouble free
operation of the screen for longer period. Other fixed members are HUCK
BOLTs.
VIBRATOR: - Vibrator comprises a medium carbon steel machined shaft
mounted on two self aligning screen duty spherical roller bearing. Two off centre
weight called counter weight one each side are keyed to the shaft to produce the
desired motion throw characteristics in the machine.

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One side
of the shaft is fixed (located) and the other side is free. The shaft is enclosed in a
steel casing. The casing coming below a deck is normally lagged on outside with
good quality rubber. The casing also serves as a stiffening device for the side
plates. The bearing are fitted with special core in the shop into the bearing
housing, and the bearing housing are bolted securely to the side plates on outside.
Only high tension fasteners are used. A bearing flange assembly provides
positive location of the shaft in the live frame.
Each bearing is protected by a suitable selected combination vibrator assembly.
No dust flinger is required in labyrinth type vibrator assembly. The bearing
housing can be dismounted from the screen for repairs etc. without disturbing the
shaft. At the drive end an eccentricity board specially, design vibrator sheave
(pulley for V-belt) is keyed when coupled with the drive motor sheave with
recommended V-belt set will seen the screen.

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DRIVE UNIT: - The vibrating screen is normally driven by an electric motor
and a V-belt transmission device. The sheaves are deep groove ones to prevent
belt jump off.
The drive motor is fixed on a hinged plate of a pivoted motor base sub
assembly. The details for motor foundation are shown on general arrangement
drawing fixing position for motor on the hinge plate is carefully designed to
maintain optimum tension in the bolts.
INCLINATION: - The vibrating screen is always installed with an inclination
angle with the horizontal. This feature gives more accurate rising and better
screening efficiency.
DIRECTION OF ROTATION: - A counter flow is preferred for high capacity
handling and better efficiency. In this configuration the vibrator rotates in the
direction opposed to the material flow.
HANDLING OF THE MACHINE: - The machine is designed as “left hand
drive” that is the drive unit is located on the left hand side of the machine while
looking from the feed end towards the discharge end.
SUPPORTING STRUCTURES (MOUNTING MEMBERS): - Correct design
of supporting structure is a prerequisite for proper performance of vibropulse
screen. The machine is isolated from its support by coil springs designed
appropriately to absorb nearly 95% of the dynamic forces caused.
BEAM FOR SUPPORT: - The beams should have a natural frequency greater
than 1.5 times the operating speed of the machine.

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The natural frequency condition is generally fulfilled if the ‘length to depth’ ratio
is less than 12.
CHUTE AND HOPPERS: - In constructing a hopper beneath the screen make
sure that the valley angles are steep enough so that the material flows freely and
will not back up contact breakage of the structural parts of the screen.
Design feed chute so as to get the best possible distribution of material across the
full width of the screen. Try to design the chute so that material will fall upon the
screen as gently as possible. Also employ the maximum length of the screen by
feeding close to the feed end. A properly designed feed chute will pay for itself
many times by reducing screen cloth wear and obtaining maximum efficiency.
SURROUNDING STRUCTURES: - When the vibrating screen starts or
stops it vibrates in the way of bouncing. It is known as ‘start/stop bounce’. So to
avoid accident due to vibration bouncing, minimum clearance of 75 mm is
provided with the machine.
The name of parts of screening machine:-
 Vibrator
 Vibrator assembly
 PM/CS bearing housing
 Bearing closure system
 Roller bearing system
 Closure gasket drawing
 Sleeve system
 Complete lubrication system
 Drive SFT collar
 Drive shaft
 CI-V groove vibration sheave
 Counter weight plate
 Live frame
 Side plate
 Spring Trunnion

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 Drive shaft casing
 Bucker-Up frame
 Counter weight housing system
 Counter weight housing cover system
 Shaft extension cover system
 Tension skirt board system
 Feed box
 Spring trunnion cross strut
 Discharge LIP
 Back plate ledge channel
 Screen cloth panel
GENERAL DESCRIPTION OF VIBRATING INCLINED
SCREEN
The vibrating inclined screen is the most popular of the screen types. Types of
vibrating screens include those with two or four bearing, high speed screen, and
screens which vibrate at the natural frequency of selected spring clusters. The
majority of aggregate producers utilize a two or three Deck inclined vibrating
screen with two bearing
 Sleeve system
 Complete lubrication system
 Drive SFT collar
 Drive shaft
 CI-V groove vibration sheave
 Counter weight plate
 Live frame
 Side plate
 Spring Trunnion
 Drive shaft casing

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 Bucker-Up frame
 Counter weight housing system
 Counter weight housing cover system
 Shaft extension cover system
 Tension skirt board system
 Feed box
 Spring trunnion cross strut
 Discharge LIP
 Back plate ledge channel
 Screen cloth panel
GENERAL DESCRIPTION OF VIBRATING INCLINED
SCREEN
The vibrating inclined screen is the most popular of the screen types. Types of
vibrating screens include those with two or four bearing, high speed screen, and
screens which vibrate at the natural frequency of selected spring clusters. The
majority of aggregate producers utilize a two or three Deck inclined vibrating
screen with two bearing as illustrated in figure. The two bearing, circle throw,
inclined screen utilizes a counter weight on a shaft to move the screen through
approximately a 3/8 inch displacement through, screen throw varies inversely
with the shaft speed which is ranges from 800 to 950 rpm. The screen is isolated
on spring and is customarily powered by an electric motor with a v-belt drive.
Screen slopes vary from 15 to 30 degree for dry separation to lightly flatter
slopes for wet sieving.
OPERATION:-
During operation of the machine pay attention to the following points to
ensure trouble free operation of the machine. Speed of the screen machine varies
only the plus minus 2% of the appreciable speed which is good for the machine.
Bearing housing is well lubricated. Bearing temperature doesn’t exceed 500
C
over the ambient temp. Springs should be kept free from foreign materials.
Belt should keep tighten condition it should not be lagging in any place otherwise

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it can produce problem at the working period.
Before operating the clearance factor should be checked all around.
Also check the direction of rotation.
FUNCTIONING:-
The working of whole screening machine depends on the vibration of the
machine. And that vibration is achieved by the counterweight which is attached
to the shaft. The shaft is also attached with the drive pulley which is connected
with the motor via V-belt. When the motor starts then the shaft which is
connected with motor via V-belt also starts to move and then and then counter
weight which is attached act such as the whole axis of shaft and centre of the axis
of counter weight is not in same line and so it starts producing vibration in
machine. The machine is placed with some appropriate inclination. The trunnion
which is connected with the cross-strut is placed upon the frame which gives the
support to the vibration of machine. And this vibration is used to screen the raw
material of appropriate size. Raw materials are feed from the end side and the
screened materials are taken out from discharged side. The diameter of screen
cloth is 10 mm for both top Decker and Bottom Decker. Square of Top Decker is
45 mm and square of Bottom Decker is 27 mm.
TYPES OF SCREENS
VIBROPULSE SCREEN
TRUFLO SCREEN
GYROPULSE SCREEN
ROLLER SCREEN
BIVITEC SCREENING MACHINE
ULTRAFLO SCREEN
DESCRIPTION OF SCREENS
 VIBROPULSE SCREEN:-

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 VIBROPULSE SCREEN:-
TECHNICAL SPECIFICATION:-

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CONSTRUCTION & OPERATION:-
This type of vibrator uses a shaft supported by one pair of bearings. The entire
assembly is attached in vibrating frame. A mass called the counterweights
fastened to or fabricated as part of the shaft.
This counterweight produces the unbalance in the system and causes the
vibrating frame to move or vibrate; much like an unbalanced tire on auto
produces in the auto body or chassis.
In a screen the movement of the vibrating frame will be 180 opposite the
position of the counterweight. Therefore with the counterweight down the motion
is upward and so the left of the motion is right and vice versa. The amount of this
motion is in direct solution with the force produced by the counterweight and the
weight of the entire vibrating frame plus the weight of the vibrator. The force
produced by the counterweight is called WR and is expressed in kg.m. Centre of
rotation of the shaft.
DRAWING OF TM-13 SCREEN:-

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Main Features
The vibrating frame has been specially designed to ensure maximum ruggedness
and rigidity.
 Two side plates of heavy duty design.
 Shaft casing ensure dual function-protecting shaft and serve as structural
member of the live frame.
 Tension skirt board serves two purposes-
I. To hold screen cloth in proper tension.
II. To make screen cloth replacement easier and simple.
ADVANTAGES
foot of
the screen.
Service
applications.
It enable to adjust to maintain proper tension in the v-belts while running.

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TABLE FOR THE DIFFERENT PARTS OF THE DOUBLE
DECKER VIBROPULSE SCREENING MACHINE:-
S Serial no. DDescription of the part Quantity
1 Dust hood 1
2 Spring pivot 4
3 v-belt guard 1
4 Pivoted motor base 1
5 v-belt 1
6 Motor sheave 1
7 Motor 1
8 Spring pedestal 4
9 Springs 8
10 Screen cloth(BD) 3
11 Screen cloth(TD) 3
12 Back plate 1
13 Tension skirt board 16
14 Feed box with liner 1
15 Bucker up frame(BD) 4
16 Bucker up frame (TD) 4
17 Side plates 2
18 Live frame assembly 1
19 Vibrator sheave 1
20 Vibrator assembly 1

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 TRUFLO SCREEN
TECHNICAL SPECIFICATION

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CONSTRUCTION & OPERATION
This type of vibrator uses two shafts supported by one pair of bearings each. This
exciting forces generated by this vibrator is supplied by two counterweight
shafts, rotating in opposite directions. The centrifugal forces of each separate
shaft are thus combined into an alternating force, which gives the driven machine
an elliptical
motion. This vibrator is basically a crank shaft. The shaft will have two pairs of
bearing journals, the centre pair being radially eccentric to the outer pair. The
amount of this eccentricity will be half of the desired stroke. The outer set of
bearings (called main bearings) will be attached to the supporting base and rotate
normal to it. Attached to it and rotating with this same shaft and located on both
sides between vibrating frame and main bearing is an arm and adjusted weight.
The drawings call them counter weights but they are in reality counterbalances.
These counterbalances should have a moment equal to the vibrated weight times
the eccentricity in the shaft. This would produce static balance. When properly
balanced there should be no vibration transmitted to the supporting structure.
In the large and heavy units it will be found that that complete isolation cannot be
achieved. In these cases the base is mounted on springs to isolate the remaining
motion from the structure.
Main features
Features that makes truflo vibrators extra reliable:-
 Self-counter weighted shafts machined from steel forgings.

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 All splash lubrication system.
 Slip fit spherical roller bearings protected against contamination by grease-
purged.
 Double-lip seals & precision-cut, wide-face, helical gears.
 Truflo screen offer all benefits of horizontal mounting
Advantages
minimum
downtime and maintenance cost.
specialized type.

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three
way motion (horizontal, vertical & elliptical).
 GYROPULSE
1. Adjustment
Gyro pulse screens may be pivoted about the shaft centre and held in position at
any point between horizontal and 280 inclination in minutes. This adjustment
require no more than
loosening of the clamping nuts, changing the slope as desired and retightening
the nuts.
2.Screw adjusted counter balance weights-
It enables balance with no escaping vibration.
3.Main features
Its main features are same as vibropulse but as mentioned earliest that the
vibrator is basically a crank shaft and hence it has positive stroke- which means
ABILITY TO STAND UPTO OVERLOAD.
 ROLLER SCREEN

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TECHNICAL SPECIFICATION
 Higher capacity up to 1500 TPH running at low power compared to
conventional screens
 Less space required
 Higher screen efficiency
 Non clogging, smooth, non-vibrating and low noise while running
 Length and width of roller screens can be adjusted to suit customers'
requirement
DESCRIPTION
Roller screens consists of a rigid main frame and a series of
roller disc assemblies mounted on shafts and supported on
spherical roller bearings across the width of main frame. These
roller discs are elliptical in shape and arranged at a predetermined
distance in such a way that they form a square or
rectangular opening in the roller screen at several places. Over
sized materials are pushed forward by rotation of elliptical
discs and finally reach the crusher as feed, while undersized
material falls through the screen opening. The scrapper
provided below the elliptical discs ensures clog free screening.
CONSTRUCTION
The roller screens consist of a rigid frame on which a series of
roller shaft assemblies are mounted with anti-friction bearings.
These roller shaft assemblies are driven by chain and sprocket
arrangement. All roller shaft assemblies are connected
alternately with chain and sprocket and are driven in same
direction by two drive units. Drive is fully covered and operates
in a circulating oil bath.
DRIVE
Each roller screen has two drive units along with electric motor,
fluid coupling, gearbox and drive sprocket.
APPLICATION
TRF Roller screens are most suitable for separating coarse,
wet and sticky raw material. Roller screens are used in soft coal
and lignite handling plants for preliminary screening of ROM
coal. It acts as relief to crushers and ensures a clog free flow of

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wet and sticky materials. TRF roller screens are useful for
separation of undersized material ranging from (-) 20 mm. to (-)
60 mm. The roller screens can be placed horizontally or at
angle of maximum 10 degrees.
BIVITEC SCREENING MACHINE
DESCRIPTION
Development of the BIVETIC screening machines was based up on

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TECHNOLOGY
PERFORMANCE

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DESIGNS
DRIVE
APPLICATIONS

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The screening surface must be strong enough to support the weight of the
material, flexible enough to withstand the vibration, and provide enough open
area to allow the desired throughout of aggregate.
TYPE:
 Wire cloth
 Rubber
 Polyurethane perforated plate
 Rubber clad perforated plates
 Grizzly bars
 Piano wires
 Wire cloth: Woven wire cloth is most commonly used
and the versatile screening media in the aggregate industry. Aggregate
plants utilize the woven wire to scalp size and dewater.
Matching the open area against the wire diameter best suited for maximum life
permits selection of the optimum cloth. In practice, open area varied from 20% to
80% of the total screen area.
CONFIGURATION
 Square: Square openings are commonly used and provide the most
accurate separation.
 Rectangular:Rectangular openings provide better service under certain
operating conditions.
 Short slot : The short slot rectangular configuration has a length to width
ratio of approximately four and utilizes a larger wire diameter to increase
service life while maintaining the same percent of open deck area.

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Long slot:The long slot rectangular configuration utilizes cluster woven slot that
are 1 to 6 inch Long exceed four times their width. The long wire of the cluster
actually develop a secondary motion which helps alleviate plugging and sticking
the secondary motion is particular advantageous screening near size or most
aggregate.
 Other type of screening media: The grizzly bars and perforated plates are
of rugged construction and can
withstand great abuse when used in heavy scalping application.
Rubber and polyurethane are typically employed in high
wear areas to increase service life. It also help reduce noise and
decrease blinding by flexing the aperture which can be tapered outward
from the top.
Piano wire screening is used to separate
damp and fine aggregate.

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39
SCREEN PERFORMANCE: Screen performance is controlled by the
screen capacity and efficiency.
o Screen capacity: Screen capacity is defined as the number of tons per
hour of aggregate being fed to the screen. Capacity is directly
proportional to the screen width. Since increasing capacity usually
result in decreased efficiency, the two criteria should always be stated
together when referring to a screen.
o Screen efficiency: Screen efficiency is defined as the
percent of undersize which actually passes a screening deck. A screen
efficiency of 100% is not practical to attain. Screen efficiency if 90% to
95% is typical for sizing in aggregate industry.
For scalping and crusher, efficiency 75% to 85% is generally
accepted since the final sizing is performed later in the plant.
CALCULATION USE IN SCREEN SELECTION
 Screen bed depth: The screen bed depth at the discharge end should not
exceed 5 times the size of the opening in the media.
The theoretical bed depth is determined by the following formula:
DBD = (O*C)/(5*T*W)
Where:
DBD= Discharge End Bed Depth (in)
O = Oversize in short tons per hour
C = Volume of material per ton (ft^3/ton)
T = Rate of travel (fpm), Nominal 75 fpm for an inclined screen at a slope
of 18 degree to 20 degree with flow rotation and usually and 45 fpm for
horizontal screen. Counter flow rotation on an incline screen typically decrease
the rate of travel by 20 to 25 fpm.
W = Width of screening area (ft)

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40
 screening area :-A separate calculation is required for each deck of a
multiple deck screen.
The following formula is used in each calculation:
Screening Area(ft2)= U/(A*B*C*D*E*F*G*H*I)
Where:
U=Undersize factor
A=Basic capacity factor
B=Oversize factor (Actual percent of material feed to deck that is larger than a
specified aperture)
C=Half size factor (Actual percent of material in feed to deck that is one half of
the size of a specified aperture)
D=Deck location factor (Applies to multiple deck screens, this factor is
expressed in a percent of top deck effective areas.)
E= Wet screening factor(Applies when water is sprayed on the material as it
moves down the screening deck.)
F= Material weight factor.
G= Screen surface open area factor(Applies when open area of screening surface
is less than open area shown in factor “A” capacity chart.)
H=Shape of opening factor (Applies when rectangular openings are used.)
I= Efficiency factor(Applies when objective screening efficiency is less than
95%.)
SCREEN SELECTION
Screen selection utilizes:

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41
 Bed depth calculations to determine the width that maintains the
appropriate bed depth
 Screening area calculation to determine length and width which provides
the minimum total screening area necessary to maintain the required
efficiency.
The Vibrating Screen Manufacturer Association
Handbook and Boliden Allis publication entitle “Vibrating Screen Theory
and Selection” are excellent references for use in the selection of vibrating
screen.
Options offers by screen manufactures include screen bars, wear liners,
guards, feed box, cloth, sheaves, v-belts, additional room between decks,
ball tray decks, blank plate deck sections, dams electrically heated decks,
longitudinal dividers, step decks, troughs discharge lip extensions, tension
wedge fasteners, enclosures, motor bases and motors.
A bid specification package should be
prepared and presented to potential suppliers which reflect those option
desired.
DUTY CONDITION:-
Description Iron ore crushing
screen
Screen for coal
circuit
Screen for iron
ore circuit
Material Iron ore Coal Iron ore
Bulk density 2.28 T/m3 0.8 T/m3 2.2 T/m3
Capacity 250 TPH 100 TPH 100 TPH
Feed size 65 mm 20 mm 20 mm

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42
Handling Left hand Right hand Right hand
Problems involving application of vibrating screens:
1. Plugging: Near size particles which become lodged in
the openings block the openings.
2. Blinding :-Fine particles which stick to the surface
media due to moisture gradually blanking over the openings.

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43
3. Carry over or dirt material:- Excessive undersize particles
failing to pass through the openings.
METHODS OF IMPROVEMENT OF SCREEN
PERFORMANCE &EFFICIENCY
 BY SCREEN CLEANING METHODS:
Screen cleaning generally associated with Screen blinding which occurs when
the screen mesh openings are blocked or closed by the material which is being
screened. Near size particles become trapped or build up on the wires effectively
blocking the screen openings preventing further material from passing through
the screen.
.
Screen cleaning methods are used to upgrades its performance by
employing different types of screen cleaning devices.
 CLEANING BY SLIDERS
The most common self cleaning device is the “SLIDER”. Slider Rings are loose
rings which slide directly beneath the screen surface on a slider support surface,
normally a perforated metal plate. The rings are bounced vertically into the
screen mesh.

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44
.
Sliders are especially good on fine mesh and it can be used in both wet and dry
screening applications. Sliders work by four different methods depending on the
material properties.
1- Vertical separator motion impacts the slider ring on the bottom of the mesh
dislodging trapped near size particles out of the screen mesh openings effectively
cleaning the screen and opening the mesh for the next particle to be screened.
2- The slider shears or breaks protruding hard or friable materials into smaller
pieces which flow through the screen clearing the openings.
3- If the material is soft and pliable, the sliders can help the material through the
screen openings.
4- If the material is fibrous, the sliders horizontal scrubbing motion across the
bottom of the screen will dislodge trapped fibers from the screen openings
improving throughput capacity.
Slider clusters work on essentially the same
principles as slider rings. The difference is the size is 4 to 8 times larger than a
slider ring. Slider clusters are normally used for large diameter machines for
easier for maintenance.
 CLEANING BY BALL TRAYS
Rubber balls are the second most utilized screen cleaning method, but can only
be used for dry screening. The rubber balls are generally 1-3/8” inch diameter
and are supported by a second coarser mesh two inches below the classifying
screen mesh.

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45
Self
cleaning kit balls bounce between a support screen and the classifying screen. The vertical
motion of the separator launches the balls and generates the screen cleaning action.
The larger vertical motion and higher weight balls impart more energy to each
impact as compared to sliders or clusters. As a result of the higher impact energy,
balls are generally used for coarse meshes which can withstand higher impact
energy from the balls.
Balls are very good at cleaning near size irregular or jagged shape particles
wedged in mesh openings.
The disadvantage of ball trays is that the balls spread
radially to the periphery of the screen. This generates excellent cleaning action at
the screen edge, but leaves the centre of the screen un-cleaned.
 CLEANING BY TOP SIDE SCREEN CLEANING DEVICES
The top side cleaning devices which reside on top of the classifying screen mesh.
These can be divided into three classifications: brushes, wipers and dams
o TOP SIDE ROTARY BRUSHES: The top side rotary brushes are exceptional
for clearing fibrous materials which tend to mat on top of the screen and
block the mesh openings.
The disadvantage to the top side brushes is the bristles which can be lost
into the product streams.

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46
o TOP SIDE NECKLACE RING DAMS: Top side necklace rings create a radial
edge dam to keep materials on the active screen longer. The longer some
materials are on the screen, the higher the capacity throughput. This can
increase the yield of smaller machines to match the capacity of larger
machines.
o TOP SIDE WIPER RING
Top side wiper rings provide the same radial edge dam as a necklace, but also
add a wiper which improves capacity with an additional shearing action.
The disadvantage to top side wipers is that they slow or impede material flow
through the machine. Materials which tend to ball up should never use a top side
wiper.
 CLEANING BY WATER SPRAYS
Water sprays clear screen mesh openings, help eject solids, and keep slurries
from drying out and building up inside separators. Another spray advantage is
there is no contamination from slider, ball, or brush materials.
The disadvantages of liquid sprays are cost and potential dilution
of products.

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47
 CLEANING BY ULTRASONIC METHOD
Ultrasonic screen cleaning uses vibrational energy generated by an ultrasonic
frequency transducer attached to the metal screen mesh to generate the screen
cleaning action. Ultrasonic assisted screening is good for high accuracy screening
where the particle size approaches that of the mesh opening. Ultrasonic energy
breaks down electrostatic
charges and surface tension which agglomerate particles and prevent efficient
screening.
.
Ultrasonic screen cleaning is the most expensive separation process, therefore it
is only used on high value materials and difficult screening operation which
cannot be accomplished efficiently by any other method.
 CLEANING BY ENERGIZER
The energizer is a pneumatic screen vibration generator which operates at
frequencies and amplitudes between ultrasonic motion and standard round
separator. The pneumatic screen energizer can be used on both synthetic and
metal screen meshes.

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48
.
The energizer adds the effectiveness of high frequency screen excitation at a
lower cost impact. Energizer system cost is 1/3 that of ultrasonic equipment and
the disposable screen cost is ¼ that of an Ultrasonic screen.
 BY PLUGGING SOLUTIONS
a) Increase stroke
b) Increase speed
c) Smaller wire diameter
d) Change hole shape (rectangular or slotted openings)
e) Different surface media
f) Adjust crusher setting
 BY BLINDING SOLUTIONS
a) Increase speed
b) Change stroke
c) Smaller wire diameter
d) Different surface media
e) Ball trays
f) Screen heating
g) Add water
BY CARRY SOLUTIONS
a) Change stroke

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49
b) Change speed
c) Reverse screen rotation
d) Change wire diameter or shape of opening to increase surface area
e) Change inclination
f) Feed centred or uniformly distributed
g) Control feed segregation
h) Change feed tonnage
BIBLIOGRAPHY:-
www.wikipedia.com/industrial_screen
www.trf.co.in

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