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These are all mineral processing laboratory assignments which are so much helpful to the students of mining engineering at graduation level.
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Assignments Mineral Processing Laboratory
1
USMAN UMAR TABASSUM 2008-MIN-36
LAYOUT OF THE HEAVEY MACHINARY MINERAL PROCESSING LAB
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LAYOUT OF THE HEAVEY MACHINARY MINERAL PROCESSING LAB
NAMES OF HEAVY MACHINES
1. DENVER JAW CRUSHER
2. SECONDARY CRUSHER
3. DISC MILL OR PULVARIZER
4. IMPACT CRUSHER
5. HIGH INTENSITY MAGNETAIC SEPERATOR
6. RO-TAP SIEVE SHAKER
7. LOW INTENSITY MAGNETIC SEPARATOR
8. MINERAL JIG (OLD)
9. CENTRIFUGAL HYDROCLASSIFIER
10. SHAKING TABLE
11. ELECTRICAL MINERAL JIG
12. DYNO CONE MACHINE
13. CENTRIFUGAL HYDRO CLASSIFIER (INDUSTRIAL SCALE)
14. AIR CLASSIFIER
15. BALL MILL
16. DENVER DILLON VIBRATING SCREEN
17. HUMPHERY’S SPIRAL CONCENTRATOR FOR COAL
18. HUMPHERY’S SPIRAL CONCENTRATOR FOR METAL
19. GYRATORY SCREEN SHAKER
20. ELECTROMAGNETIC VIBRATING SCREEN (SINGLE DECK)
21. DAVIES DISC MAGNETIC SEPARATOR
22. DRUM FILTER STATION
23. BOWL TYPE OR RAKE TYPE CLASSIFIER
24. RO-TAP SIEVE SHAKER
DOOR MACHINES
STAIRS
NUMBER
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LAYOUT OF HEAVEY MACHINARY MINERAL PROCESSING LAB
PRIMARY CRUSHERS
Primary crushers reduces the large pieces to a size which can be handled by the downstream
machinery.
JAW CRUSHER
A Jaw Crusher is one of the main types of primary crushers in a
mine or ore processing plant. The size of a jaw crusher is
designated by the rectangular or square opening at the top of the
jaws (feed opening). A Jaw Crusher reduces large size rocks or ore
by placing the rock into compression. A fixed jaw, mounted in a
"V" alignment is the stationary breaking surface, while the
movable jaw exerts force on the rock by forcing it against the
stationary plate. The space at the bottom of the "V" aligned jaw
plates is the crusher product size gap, or the size of the crushed
product from the jaw crusher. The rock remains in the jaws until it is small enough to pass
through the gap at the bottom of the jaws.
There are two basic types of jaw crushers, the overhead eccentric style and the double-toggle
style. Which style will work best for a given operation depends upon several factors.
SECONDARY CRUSHERS
It take primary crushed material then work essentially on finer
material and yield more new surface than would a primary
crusher for an equal reduction ratio.
These are basically of two types
1. Impact crushers
2. Roll crushers
3. Cone crushers
DISC MILL
A disc mill, is a type of crusher that can be used to grind, cut,
shear, shred, fiberize, pulverize, granulate, crack, rub, curl, fluff,
twist, hull, blend, or refine. It works in a similar manner to the
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ancient Buhrstone mill in that the feedstock is fed between opposing discs or plates. The discs
may be grooved, serrated, or spiked.
HAMMER MILL OR IMPACT CRUSHER
Impact crushers are used as primary and secondary crushers, depending on the nature of the material in the application. Impact crushers operate by feeding the material into an inner chamber, where it is beat on by large hammers. The material stays inside the chamber until it's at the proper size to fit through the discharge outlet. It is widely used in cement industry and such material is not allowed to be enter in the crusher which consist of more than 15% silica.
HIGH INTENSITY MAGNETIC SEPARATOR Wet-type permanent magnetic separator mainly consists of such four parts as cylinder, magnetic system, cell and transmission parts.
The magnetic separator is applicable for wet mineral separation of such materials as magnetite, pyrrhotine, roasted ore and ilmenite, etc. and it is also applicable for iron removal working of such materials as coal, nonmetal and building materials, etc
RO-TAP SIEVE SHAKERS
Rotap sieve shakers are used for laboratory testing of particle size and size distribution in samples of solid materials. Used for soils, geological materials, alloys, and a host of other solid sample types that have individual particle sizes of from over 5" down to 20 microns.
LOW INTENSITY MEGNATIC SEPARATOR low intensity magnetic separators for recovery of ferro magnetic ores to produce pre- concentrates or concentrates are available with three different tank designs, (concurrent, counter-current and counter-rotation) using a common magnetic drum assembly. When minerals are placed in a magnetic field, there are three reactions which may occur. First, they are attracted to the magnetic field. Second, they are repulsed by the magnetic field. And third, no noticeable reaction to the magnetic field occurs.
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MINERAL JIG (OLD) A jig is a simple mineral processing device using water and the force of
gravity to separate a raw ore stream by density. In many applications this
permits a low grade ore stream to be upgraded in quality sufficient for
sale: Gangue of different density to the valuable component is rejected
into a waste stream, leaving a higher percentage of the valuable
component in the product stream compared to the feed. The
distinguishing characteristic that separates a jig from other gravity and
water based mineral processing devices is the action of a pulsing water
current on a bed of ore to alternately fluidize and compact the bed,
allowing the denser minerals to settle to the bottom of the bed for subsequent splitting into a
product and reject stream.
CENTRIFUGAL HYDRO CLASSIFIER These classifiers use centrifugal forces, similar to cyclones, to separate particles at cut points between 15 and 100 microns. The feed material is carried into the classifier by the primary inlet flow stream. Internal baffles apply drag forces to the coarse particles while allowing air to pass through them for separation of the fines. The heaviest particles drop to the bottom of the classifier and are discharged through a valve.
SHAKING TABLE
Shaking Table is a kind of mineral processing equipment of fine materials according to weight. It is widely used for distilling tungsten, tin, molybdenum, aluminum, zinc, other rare metal and noble metal ore, and it is also applicable for distilling iron, manganese and coal. The rocking bed has the advantages of high enrichment grade, high separation efficiency, easy operation, convenient adjustment, and it can distill the final concentrate and gangue in one step, etc. Concentrating Tables are designed to wet gravity-based separation of minerals and other granular materials.
ELECTRICAL MINERAL JIG (NEW)
A jig is a simple mineral processing device and the force of gravity to separate a raw ore stream by density. Electro-hydraulically operates proportionally control the opening and closing of a refuse gate of a jig.
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The system provides for immediate adjustment of the specific gravity setting which triggers refuse discharge. This allows complete removal of the built-up refuse yet minimizes inadvertent coal losses with the refuse.
DYNO CONE MACHINE It is used for gravity separation. The heavier settles down while the
lighter floats up.
CENTRIFUGAL HYDRO CLASSIFIER (INDUSTRIAL SCALE) These classifiers use centrifugal forces, similar to cyclones, to separate particles at cutpoints between 15 and 100 microns. The feed material is carried into the classifier by the primary inlet flow stream. Internal baffles apply drag forces to the coarse particles while allowing air to pass through them for separation of the fines. The heaviest particles drop to the bottom of the classifier and are discharged through a valve. It is used on industrial scale.
AIR CLASSIFIER Air classification is a process used to separate material according to its
particle equivalent diameter (controlled by its density, volume and
surface characteristics) using a flow of air. It is an approximate sizing
process ordinarily used to separate coarser from finer material; This is
an alternative to screening which is the standard means of sizing
material; however it is inefficient below 250 micron, especially for dry
material. In the mineral industry, it is used for sizing powders with cut
points in the range 5 to 100 micron mineral industry commodities
processed using air classification include calcium carbonate, cement, diatomite, feldspar,
gypsum, kaolin, lime, mica, perlite, phosphates, silica sand and talc.
BALL MILL
A ball mill is a type of grinder used to grind materials into extremely fine
powder for use in mineral dressing processes, paints, pyrotechnics, and
ceramics. Ball mills rotate around a horizontal axis, partially filled with
the material to be ground plus the grinding medium. Different materials
are used as media, including ceramic balls, flint pebbles and stainless
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steel balls. . The ball mill is a key piece of equipment for grinding crushed materials, and it is
widely used in production lines for powders such as including cement, silicates, refractory
material, fertilizer, glass ceramics, etc. as well as for ore dressing of both ferrous non-ferrous
metals.
DENVER DILLON VIBRATING SCREEN
Vibrating screen is the major sieving equipment for all kinds of
crushing plants. The vibrating screen is suitable for sieving basalt,
granite, limestone, dolomite, feldspar, iron ore, gold ore, copper,
bauxite and so on. It is widely used for grading and screening materials
in the following fields: minerals, quarry, ,coal dressing, metallurgy,
mine, and so on. They are efficient screening machines for the
classification of bulk material such as coal, minerals.
HUMPHREY’S SPIRAL CONCENTRATOR FOR COAL
Spiral concentrators are a gravity based concentrating device, that separates light density granular and sandy material from heavier density material. In order to have a good separation, there should be a difference in SG's of at least 1.0. Spiral design that allows coal to be re-washed in a second stage Spiral located immediately below the Primary Spiral. Spiral concentrators use differences in density to separate particles simply, efficiently, and cost effectively. Typical capacities for spirals run from 3-5 tons per hour for coal.
HUMPHREY’S SPIRAL CONCENTRATOR FOR METALS Spiral concentrators are a gravity based concentrating device, that separates light density granular and sandy material from heavier density material. Slurry is pumped to the top of the spiral and it enters a feed distributor that evenly distributes the feed to each spiral concentrator. The design and shape of the spiral make it work, when combined with gravitational acceleration. Typical capacities for spirals run from 1-3 tons per hour of feed for minerals.
GYRATORY SCREEN SHAKER This is suitable for heavy materials, powders or granules. It is run by 1/4 HP electric motor through a reduction gear. Gyratory action involves upward and downward movement of the table. Standard gyratory motion produce inclination from the vertical axis and the
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direction of inclination changes continuously in the clockwise direction. The sieve table rotates in 45-degree direction, which makes each square inch of the sieve analysis possible. The whole gear mechanism runs in oil bath made of stainless steel. It is necessary to pour machine oil no. 40 up to level mark.
ELECTROMAGNETIC VIBRATING SCREEN (SINGLE DECK) These are used in grading as well as sieving purposes. These screens are composed of a main frame, electric motor, screen web, eccentric bock, coupler and rubber spring. The different applications of vibrating screens include crushing plant, cement, lime minerals, clay, rubber industries and many more.
DAVIES DISC MAGNETIC SEPARATOR High intensity electromagnetic separator is designed for the continuous removal of ferrous/magnetic particles from liquid based applications. The separator is also capable of separating a high percentage of paramagnetic particles. To clean the separator, contaminates are washed down through the matrix with automatic cycle once the separator is de-energized.
DRUM FILTER STATION
Rotary drum filters offer great flexibility in meeting the needs of producers of many products requiring the separation of liquids from solids. Rotary Drum Vacuum Filter is applied to process and waste slurries for filtering, clarifying, cake washing and extraction, and dewatering. There are many factors affecting the operation of a filtration process. Among these are the need for chemical pretreatment; the need for precoat or filter aid; power, water, air, or other utilities; operator attention; cleaning requirements; and maintenance needs. All of these should be considered when selecting a filter.
BOWL TYPE OR RAKE TYPE CLASSIFIER It is a mechanical classifier utilising rakes. The rakes are actuated by an eccentric motion to dip into the settled material and move it up the incline for a short distance. The rakes are then withdrawn, and return to the starting-point, where the cycle is repeated; the settled material is thus slowly moved up the incline to the discharge. In the duplex type one set of rakes is moving up,while the other set returns.
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LAYOUT OF THE LIGHT MACHINARY MINERAL PROCESSING LAB
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LAYOUT OF THE LIGHT MACHINARY MINERAL PROCESSING LAB
1. INDUCED ROLL MAGNETIC SEPERATOR
2. ISODYNAMIC MAGNETIC SEPERATOR
3. VIBRATORY MILL
4. ULTRA SONIC SIEVE SHAKER
5. SAMPLE DIVIDER
6. SCALE PLATE FORM
7. DIGITAL BALANCE
8. DESICATOR
9. CURICIBLE
10. VOLAND BALANCE
11. HIGH TENSION ELECTRO STATIC SEPERATOR ( SCREEN TYPE)
12. HIGH TENSION ELECTRO STATIC SEPERATOR ( PLATE TYPE)
13. HIGH TENSION ELECTRO STATIC SEPERATOR ( DRUM TYPE)
14. CHEMICAL SHELF
15. DENVER FLOTATION MACHINE (NEW)
16. DENVER FLOTATION MACHINE (OLD)
17. LAB FISHER OVEN
18. LAB FISHER OVEN
19. LAB FISHER OVEN
20. LINDBERG LAB FURNACE
21. AGITATOR OR CONDITIONER
22. REYMOND MILL
23. HARD GROVE GRINDIBILITY TESTING MACHINE
24. RING MILL
25. JAW MILL
26. CYLANDRO CONICAL BALL MILL
27. ROD MILL
28. VIBRO SIEVE SHAKER ( NEW)
29. SAMPLING / SIEVING PLAT FORM
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LAYOUT OF THE LIGHT MACHINERY MINERAL
PROCESSING LAB
INDUCED ROLL MAGNETIC SEPARATOR
Induced roll magnetic separator is basically used for separation
and concentrating of minerals or other materials of low
magnetic susceptibility. Uses for extraction of iron or chromium
bearing minerals from silica sand, the concentration mineral
such as wolframite, the removal of such paramagnetic minerals
such as limonite, siderite etc, from valuable non-magnetic
minerals.
Induced roll magnetic separator is used to extract small magnetic particles from minerals to
produce mineral purification for a wide range of minerals. Material being treated is fed from
the top of the hopper on to a high magnetic roll.
ISODYNAMIC MAGNETIC SEPERATOR
A unique and outstanding research tool for the mineral
investigator. Separates dry granular materials according to their
magnetic susceptibilities. Used at geological and mineralogical
laboratories worldwide, having set the standard for such
separations.
The Isodynamic® Separator consists essentially of an
electromagnet having two long pole pieces shaped to a special contour with a long narrow air
gap between them. Materials to be separated are fed into one end of the magnetic field and
travel through its entire length. The more strongly paramagnetic particles are urged toward the
narrow side of the gap. The grains are intercepted by a dividing edge which directs the two
fractions into separate containers.
The Isodynamic Separator makes sensitive separations of minerals or other grains according to
susceptibility, even of materials not usually thought of as magnetic.
VIBRATORY MILLS
Vibratory mills are for continuous or batch grinding materials to
a very fine end product. Grinding cylinders is placed either
directly above or inclined at 30 degrees to perpendicular. Unique
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vibratory motion, coupled with the use of cylindrical media, allows a dense packing of the
media bed assuring maximum media surface contact and minimum void area when operated
under a low energy condition.
ULTRA SONIC SHIEVE SHAKER
Ultrasonic Sieve Cleaner is specially designed to provide a safe and
effective means for cleaning test sieves. The unit requires little, if
any, maintenance. The cleaner produces ultrasonic vibrations in a
cleaning fluid bath, which cause contaminants to become
dislodged from both the sieve frame and media. Vibrations up to
40,000 per second (40 kHz) are transmitted to the cleaning
solution. Cleaning times range from 5-15 minutes. The unit will clean one 8" (200 mm) diameter
full height test sieve at a time.
SAMPLE DIVIDER
It is used for dividing the sample being used in the lab.
PLATFORM SCALES
Platform scales are specially designed and produced in large
number to meet the requirements of measuring the weight of the
objects. They come in different models, sizes, prices and capacities
to satisfy the requirement. Its capacity is by 100 kg.
ANALYTICAL BALANCE
An analytical balance is used to measure mass to a very high degree of precision and accuracy. The measuring pan(s) of a high precision (0.1 mg or better) analytical balance are inside a transparent enclosure with doors so that dust does not collect and so any air currents in the room do not affect the balance's operation. The use of a vented balance safety enclosure, which has uniquely designed acrylic airfoils, allows a smooth turbulence-free airflow that prevents balance fluctuation and the measure of mass down to 1 μg without fluctuations or loss of product. Also, the sample must be at room temperature to prevent
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natural convection from forming air currents inside the enclosure, affecting the measure of mass.
DESICCATOR
A desiccators used to refer to a laboratory glassware where things to
be kept inside it are dry and away from the moisture in the air. It is
also known as the dry box due to it keep the thing inside dry, what
makes the thing dry simply the use of a desiccant, an agent to absorb
all moisture in the air of a closure environment.
CRUCIBLE
A crucible is a cup-shaped piece of laboratory equipment used to contain chemical compounds when heated to extremely high temperatures. Crucibles are available in several sizes and typically come with a correspondingly-sized crucible cover (or lid).
Crucible is a refractory container used for metal, glass, and pigment production as well as a number of modern laboratory processes, which can withstand temperatures high enough to melt or otherwise alter its contents
VOLANDBALANCE
The Voland balance is the most fundamental tool in the chemists
arsenal. It is used to determine the masses of, or in other words the
amount of stuff in, objects or samples. Voland Outfit A 004 Assay
Balance Closed | VOLAND & SONS PORTABLE OUTFIT A ASSAY
BALANCE - Voland & Sons Portable Outfit A complete with slant front
assay balance and folding pulp balance and locking French polished
mahogany carrying case 13 in W x 9 1/2 in D x 10 in H; very lightweight construction; equipped
with locking device for beam. It can weigh minimum upto 3 mg.
HIGH TENSION ELECTRO STATIC SEPARATOR (SCREEN TYPE)
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HIGH TENSION ELECTRO STATIC SEPARATOR (PLATE TYPE)
Electrostatic plate separators work by passing a stream of particles past a charged anode. The conductors loose electrons to the plate and are pulled away from the other particles due to the induced attraction to the anode. These separators are used for particles between 75 and 250 micron and for efficient separation to occur, the particles need to be dry, have a close size distribution and uniform in shape. Electrostatic plate separators are usually used for streams that have small conductors and coarse non-conductors. The high tension rollers are usually used for streams that have coarse conductors and fine non-conductors.
HIGH TENSION ELECTRO STATIC SEPARATOR (DRUM TYPE)
This high tension electrostatic drum separator is capable of producing
high grade concentrators with fast recovery of valuables owing to three
-step re-cleaning and facility for heating materials. Besides these
feature, it also consumes little electric power and is environment-
friendly. It is uses for Beneficiation of ferrous, non -ferrous and rare
metal ones, Recovery of metals from industrial wastes (electronic or
electrical engineering scrap, cables etc, Recovery of dielectric materials (e. g. plastics) for
recycling, Purification of metal and non -metal powders.
CHEMICAL SHELF
Is used for the storage of the chemicals in the laboratory.
DENVER FLOTAION MACHINE (NEW)
Denver Laboratory Flotation Machine by Metso with suspended type
mechanism, including totally enclosed anti- friction spindle bearing,
stainless tell shaft, stainless steel standpipe with air control valve,
two removable DENVER Urethane diffuser type hoods, and two
removable DENVER Urethane open type impellers of different sizes
or closed type impellor for use in tank. Mechanism is supported on a
spring-balanced movable arm that is raised or lowered on a column
by a hand crank through rack and pinion bearing and can be locked at
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any desired height.
DENVER FLOTAION MACHINE (OLD)
It also has the same description as mention above but this is old.
LAB FISHER OVEN ( SMALL)
A drying oven is a device for applying low heat over a long time to a variety of objects for a variety of purposes. Another use of the drying oven is sterilization and drying for laboratory equipment, such as glassware. A closed chamber for drying an object by heating at relatively low temperatures. This oven is manufactured by FISHER Company and it can use by 220°C.
LAB FISHER OVEN (LARGE)
This oven is also manufactured by FISHER Company and it can use by
250°C.
LINBERG LAB FURNACE
Lindberg furnaces provide fast, efficient, and economical heat-treating. Temperature range to 1400°C. The heat treat furnace system offers a variety of temperature to meet a broad range or process requirements.
AGITATOR
An agitator is a device or mechanism to put something into motion
by shaking or stirring. There are several types of agitators with the
most common are the "straight-vane" and "dual-action." Sonic's
superior performance Typhoon Propeller Mixers and Agitators are
used for mixing and agitating liquids and dissolving and suspending
solids within liquids.
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REYMOND MILL
The Raymond Mill is mainly applied to the powder processing of
mineral products in industries. The Raymond mill can produce
powder from more than 280 kinds of non-flammable and non-
explosive mineral materials with Mohs hardness below 7 and
humidity below 6%. The final size of the Raymond mill is between
613 micron and 440 micron (0.613mm—0.044mm).
HARD GROVE GRINDABILITY TESTING MACHINE
Preiser Scientific’s Grindability Tester is a compact precision built instrument designed specifically for the determination of the relative “hardness” or abrasive potential of coal. Unit is constructed in strict accordance with ASTM Designation D-409 and conforms to procedures proposed by ISO for the determination of the Hardgrove Grindability index of coal and coke.
RING MILL
It is used for pulverising rocks, soil, coal, cement, glass, limestone, bricks, wood, plant material, slags, concrete, etc… for subsequent analysis by instrumental methods or wet chemistry. The noise level is less than 85dB. It provides fast and dust free grinding, homogeneity grinding, very low contamination of samples, easy to clean, low capital cost, long life and maintenance free. Horizontal mills add some additional expense, much of it in using
a vertical output shaft gearbox for the main work roll drive.
JAW MILL ( DODGE TYPE)
A Jaw Crusher is one of the main types of primary crushers in a
mine or ore processing plant. The size of a jaw crusher is designated
by the rectangular or square opening at the top of the jaws (feed
opening). A Jaw Crusher reduces large size rocks or ore by placing
the rock into compression.
CYLINDRO CONICAL BALL MILL
The Conical Mill is most efficient when the maximum feed size is less than 2" and iron contamination is not a factor. A sphere has the greatest volume for a given surface area of any solid. In a typical
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cylindrical mill, it has been proven that most of the work is accomplished in only a portion of the mill cylinder length and the end corners are ineffective.
ROD MILL
These are very similar to ball mills, except they use long rods for
grinding media. The rods grind the ore by tumbling within the mill,
similar to the grinding balls in a ball mill. There are three main types
of rod mill, overflow, end peripheral discharge, and center
peripheral discharge but only the overflow mill is in common
usage. The rod mill performs best when making products having a
top size of 4 mesh to 16 mesh operating in open circuit, or as fine
as 35 mesh operating in closed circuit with a screen or other sizing device.
VIBRO SIEVE SHAKER (NEW)
This is suitable for heavy materials, powders or granules. It is run by
1/4 HP electric motor through a reduction gear. The sieve table
rotates in 45-degree direction, which makes each square inch of the
sieve analysis possible.
SIEVING PLATE FORM/ SAMPLING PLATE FORM
This table is used for preparing the samples which are to be
analyzed.
REFRENCES:
http://www.lindbergmph.com
http://www.outotec.com
http://www.grindermachine.org
http://www.socachim.com
http://www.wkipedia.org http://www.answers.com. http://www.google.com
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INTRODUCTION OF THE JAW CRUSHER
Jaw crusher are primary crushing machines operation almost always dry and are very suitable
for crushing all types of rocks and ores, except where the material is wet and sticky or
malleable. A jaw or toggle crusher consists of a set of vertical jaws, one jaw being fixed and the other
being moved back and forth relative to it by a cam or pitman mechanism.
CLASSIFICATIONS OF JAW CRUSHERS
Jaw crusher are classified by the method of pivoting the swing jaw as describes below:
Blake type
Dodge type
Universal type
BLAKE TYPE JAW CRUSHER
In the Blake type jaw crusher, the jaw is pivoted at the top and thus has the fixed receiving area
and variable discharge opening.
The Blake crusher was patented by W.E. BLAKE in 1858 and variation in detail on basic form are
found in most of the jaw crusher used today.
DODGE TYPE JAW CRUSHER
In the dodge type jaw crusher jaw is pivoted at the bottom, giving it a variable feed area but
fixed delivery area. This is restricted to laboratory use where close sizing is required.
UNIVERSAL TYPE JAW CRUSHER
The universal type jaw crusher is pivoted in an intermediate position and thus have variable
delivery and receiving area.
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But here we concerned with only Blake type jaw crusher because in laboratory we used Blake
type jaw crusher for crushing test of the given sample.
BLAKE TYPE JAW CRUSHER
In the Blake type jaw crusher, the jaw is pivoted at the top and thus has the fixed receiving area
and variable discharge opening.
KINDS OF THE BLAKE TYPE JAW CRUSHER
Basically there are two types of the Blake type jaw crushers:
Double Toggle Jaw Crusher
Single Toggle jaw Crusher
DOUBLE TOGGLE BLAKE TYPE JAW CRUSHER
The oscillation movement is of the swinging jaw is effected by vertical movement of the
pitman. This moves up and down under the influence of the eccentric. The back toggle plate
causes the pitman to move sideways as it pushed upward. The motion is transferred to the
front toggle plate and this in turn cause the swing jaw to close on the fixed jaw. Similarly,
downward movement of the pitman allows the swing jaw to open.
SINGLE TOGGLE BLAKE TYPE JAW CRUSHER
In this type of jaw crusher, the swing jaw is suspended on the eccentric shaft, which allows a
lighter, more compact design than with the double toggle machine. In this machine swing jaw
not only move towards the fixed jaw , under the action of the toggle plate, but it also move
vertically as the eccentric rotates. This elliptical jaw motion assists the in pushing rock through
the crushing chamber. Single toggle machine has double capacity then double toggle of the
same gape.
CONSTRUCTION OF THE SINGLE TOGGLE BLAKE TYPE JAW CRUSHER
Jaw crushers are extremely heavy duty machines and hence must be robustly constructed.
1. MAIN FRAME
The main frame is often made from cast iron or steel, connected
with tie-bolts. It is often made in sections so that it can be
transported underground for installation. Fully stress relieved after
fabrication.
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2. JAWS
The jaws are usually constructed from cast steel and are fitted
with replaceable manganese steel liners, which are bolted in
sections on to the jaws so that they can be removed easily
and reversed periodically to equalize wear. The jaw plate are
smooth themselves, but are often corrugated, being
preferred for hard, abrasive materials.
3. CHEEK PLATES
These are fitted to the sides of the crushing chamber to
protect the side main frame from wear. These are also made
from manganese steel and have the similar life to the jaw
plates.
4. FLY WHEEL
Rotational energy is fed into the jaw crusher eccentric shaft
by means of a sheave pulley which usually has multiple V-
belt grooves. Heavy fly wheel attached to the drive which is
necessary to store energy on the idling half of the stroke and
deliver it on the crushing half.
5. ECCENTRIC SHAFT
Jaw holder is put in motion by the oscillation of an eccentric
lobe on a shaft that goes through the pitman's entire
length. This movement might total only 1 1/2" but produces
substantial force to crush material. This force is also put on
the shaft itself so they are constructed with large dimensions
and of hardened steel.
6. THE TOGGLE PLATE
It serves the purpose of allowing the bottom of the jaw
holder to move up and down with the motion of the
eccentric shaft as well as serve as a safety mechanism for
the entire jaw. It has one small toggle which rest on steel
bearings, at one end of back body of the movable jaw at the
other end on vertically slid able wedge block besides the
main frame.
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7. JAW-HOLDER & MAIN BEARING HOUSINGS
It Can be removed from the frame as an assembly. The jaw-holder is
a robust box construction with a fully machined face to support the
moving jaw.
BASIC TERMINOLOGIES ABOUT JAW CRUSHER
We are describing some basic terminologies in the below which help us to understand more
about the jaw crushers:
1. GAPE OF THE CRUSHER
The feed opening of the jaw crusher is called Gape. Which is the distance between the
jaws at the feed opening. Which is given as 5” × 6”.
2. SET OF THE CRUSHER
The maximum opening of the jaws at the discharge end is called set. The discharge size
of the material from the crusher is controlled by set. This can be adjusted by using
toggle plates of the required length.
3. THROW OF THE CRUSHER
The jaw is pivoted from above, it moves a minimum distance at the entry point and a
maximum distance at the delivery. This maximum distance is called the throw of the
crusher.
4. NIP ANGLE OF THE CRUSHER
The nip angle describes the angle the stationary jaw plate and the pitman make with each
other. The exact value of this angle isn't quoted or even determinable due to curvature in the
jaws themselves but what is important is how wide vs. narrow it is. Wide nip angles can tend to
expel material as the jaw closes as a large ball might squirt out from under a car tire. If the nip
angle is narrow, not much vertical upward force is generated and more consistent crushing
takes place.
5. FEED MATERIAL
Such a material which is introduced in the crusher for crushing purpose is called the
feed material. It should be 80% to 90% of the gape and it should also be a uniform size.
6. PRODUCT MATERIAL
Such material which is discharge from the set after crushing is called product. The size of
the product can be adjusted by adjusting the size of the set.
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CROSS SECTION OF SINGLE TOGGLE JAW CRUSHER
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MACHINE STUDY OF LABORTARY JAW CRUSHER AND TO PERFORM A
CRUSHING TEST ON THE GIVEN SAMPLE
APPARATUS/ EQUIPMENT
DENVER LABORTARY JAW CRUSHER
VERNIOR CALIPER
LUMP OF DOLOMITE AS ROCK SAMPLE
PROCEDURE:
1. WE studied the each part of the machine from instructor and draw their rough sketch
and label them.
2. We switched on the machine study the movement of the moving jaw and variation of
the set with motion.
3. We measure the sides of the gape and set.
4. we examine the feed as of dolomite and take the largest lump by taking measurements
with vernier caliper.
5. We introduce the lump in the machine and crushed the enire sample.
6. We examine the product and took the largest lump in the product and record its size.
7. Calculated the reduction-ratio of the machine.
OBSERVATIONS:
NAME DENVER JAW CRUSHER (BLAKE TYPE)
MOTOR HORSE POWER 5 HP
MOTOR R.P.M. 1440
CRUSHER R.P.M. 325-375
MOVABLE JAW DEPTH 14”
FIX JAW DEPTH 12”
WIDTH OF JAW PLATE 6”
CRUSHER CAPACITY 600 Lbs/Hr
FLYWHEEL DIAMETER 18”
FACE OF FLYWHEEL 3 ¼ “
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MAX: FEED SIZE (GAPE) 5”×6”
SIZE OF SET CLOSE ½ “ OPEN 1.25”
FEED DOLOMITE LUMPS
CALCULATIONS:
1. REDUCTION RATIO:
Reduction Ratio =
Reduction Ratio =
Reduction Ratio = 5.002
2. CAPACITY:
Capacity in tons/hour (approx.) from Targets formula =T = 0.6LS
Where,
S = Set I inches
L = Width of Jaw-plate in inches
Capacity = T = 0.6 LS
Capacity = 0.6 * 6 * 1.25
Capacity = 4.5 tons/hour
3. EXPRESS SIZE OF CRUSHER: Size of crusher = Width * Gape
Size of crusher = 5 * 6 inch²
REFRENCES:
MINERAL PROCESSING TECHNOLOGY BY B.A.WILLS
www.flsmidth.com. www.terexjaques.com .
www.westpromachinery.com
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INTRODUCTION TO ROLL CRUSHERS
Roll Crushers are compression type crushers, and were once widely used in mining. They have,
within the last 10 or so years, fallen into dis-favor among mining and processing companies but
these are still used in some mills, although they have been replaced in many installations by
cone crushers. They still have a useful application in handling friable, sticky, froze and less
abrasive feeds such as lime stone, coal, chalk, gypsum, phosphate and soft iron ores.
HISTORY OF ROLL CRUSHERS
Rolls were invented more than 100 years ago, recorded of their use in Cornwall going back to
1806. In Early machines, the rolls were mounted on the shafts revolving in open bearings
contained within cast iron side frames. One of the roll was driven positively and the other, or
idler, by friction. To assure rotation of the idler was pressed sideways against the live roll by
heavy weight hung from yoke.
MODERN STANDARD ROLL CRUSHERS
In a standard double roll crusher designs both rolls are positively driven, at much higher speeds,
and breakage is prevented by mounting the bearings of one roll shaft against coil springs while
the other connected to screw mechanism. Spring loading serve as a safety device against un
crushable lumps whereas the screw mechanism provides the set adjustment for different
product sizes.
TYPES OF ROLL CRUSHERS
Roll crushers are also manufactured with only one rotating cylinder while the others are three,
four, or six cylinders. Types of roll crushers are dependent on roll diameters.
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SINGLE ROLL CRUSHERS
a single roll crusher uses one wheel to grind up mining material, such as coal, salt, ore, chalk and slag. These crushers come with crushing rings, ledges, teeth or shells made of high quality steel. A single roll crusher produces medium particles. The crushing plate has a replaceable comb plate in case of wear and tear.
THREE ROLL CRUSHERS
Three roll crushers perform primary and secondary crushing, reducing material to medium and fine particles. Equipped with three turning wheels, crushing rings or ledges to execute crushing, three roll crushers have equipment that keeps dust from penetrating the machine and interfering with the rollers' performance. The rollers have rotating V-belts that are powered by electrical and gear motors. Three roll crushers accommodate a high capacity and constant flow of material for high volume crushing.
FOUR ROLL CRUSHERS
Four roll crushers grind material into medium particles by the primary crushing process and fine particles by the secondary crushing process. Four roll crushers are mainly used in the fertilizer and chemical industries, and with power plant technology. These crushers have a low dust output, with adjustable roll diameters that control the sizes of particles. Overload protection guards the machine against foreign material destroying the machine.
OPERATION OF THE ROLL CRUSHER
The material is fed at the top through a screen hopper and due to presence of the co-efficient of friction between the rolls surface and ore lumps, a nipping action take place which pulls the lumps downwards. When the lumps passes through the rolls it is crushed to a size equal to or finer than the set. Since the residence time of an ore lump between the rolls is very short, a rolls crusher normally does not produce excessive fines. The machine has been based extensively for preparing feed for gravity separation operations.
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TYPES OF ROLLS
There are basically three types of rolls are used in roll crushers fir different purposes.
SMOOTH SURFACE ROOLS
These rolls are usually used for fine crushing. Wear on the roll surface is very high, and they often have manganese steel tyre, which can be replaced when worn.
SLUGGER ROLLS
coarse crushing is often performed in rolls having corrugated surfaces, or with stub teeth
arranged to present a chequered surface pattern.
HIGH PRESSUR GRINDING ROLLS
HPGR consists of a pair of counter rotating rolls, one fixed and the other floating. Material is fed between the rolls with the floating roll pressing against the material flow by means of hydraulic pressure in excess of 50 MPa. The resulting force causes the material to compact by interparticle breakage. Pressures and roll speeds are adjusted to obtain optimum grinding conditions. The roll faces are typically studded because of improved wear characteristics.
PRINCIPLE OF THE ROLL CRUSHER
Consider a spherical particle, of radius r, being crushed by a pair of rolls, of radius R, the gap
between the rolls being 2a (fig.). If μ is the coefficient of friction between the rolls and the
particle, Ѳ is the angle formed by the tangent to the roll surfaces at their points of contact with
particle (the angle of nip), and C is the compressive force exerted by the rolls, acting from the
roll centers through particle center, then for particle to be just gripped by the rolls, equating
vertically,
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C sin Ѳ/2 = μC cos Ѳ/2
μ = tan Ѳ/2
The coefficient of friction between steel and the most ore particles is in the range 0.2-0.3, so that the val , otherwise the particle will slip.
The larger the angle of nip (i.e. the coarser the feed), the slower the peripheral speed needs to
be to allow the particle to be nipped. For smaller angle of nip (finer feed), the roll speed can be
increased, so increasing the capacity. Peripheral speeds vary between about 1 ms-1 for small
rolls, up to about 15 ms-1 for the largest size of 1800 mm diameter upwards.
The value of the coefficient of friction between a particle and moving rolls can be calculated
from the equation
μk = ( ) μ
Where μk is the kinetic coefficient of friction and v is the peripheral velocity of the rolls (ms-1).
MAXIMUM SIZE OF ROCK
Following equation can be used to determine the maximum size of rock gripped in relation to
roll diameter and the reduction ratio (r/a) required. From figer
cos Ѳ/2 =
CAPACITY OF ROLL CRUSHER
The capacity of the rolls can be caldulated in terms of ribbon of material that will pass the space
between the rolls. Thus theoretical capacity is equal to
188.5 N D W sd kg h-1
Where
N is the speed of the rolls (rev min -1)
D is the roll diameter (m) W is the roll width (m) s is the specific gravity of the feed material (kg m-3)
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d is the distance between the rolls (m) In practice, allowing for voids between the particles, loss of speed in gripping the feed, etc., the
capacity is about 25% of the theoretical.
ADVANTAGES OF ROLL CRUSHERS
They produce very little dust or fines Rolls crushers are effectively used in minerals crushing where the ores are not too
abrasive. Coal plants will use roll crushers, either single roll or double roll, as primary crushers,
reducing the ROM coal.
DISADVANTAGE OF ROLL CRUSHER
The great disadvantage of roll crushers is that, in order for reasonable reduction ratios to be
achieved, very large rolls are required in relation to the size of the feed particles. They
therefore have the highest capital cost of all crushers.
REFRENCES
PRINCIPLE S OF MINERAL PROCESSING BY GAUDIN, A. M. MINERAL PROCESSING TECHNOLOGY BY B.A. WILLS
http://www.ehow.com/list_7643968_types-roll-crushers.html#ixzz1FvXVaWHN http://www.miningonlineexpo.com/content.php/9/50/mining_high_pressure_grinding_rolls.ht
ml
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MACHINE STUDY OF DENVER ROLL CRUSHER AND PERFORM A
CRUSHING TEST ON A GIVEN SAMPLE.
Apparatus
Laboratory roll crusher machine
Adjustable spanner wrench
A lump of dolomite
Feed sample
A set of sieve with shaker
Tachometer
Torsion –balance/ electric balance
Procedure
Identify each part of machine. Draw a sketch and label each part
Switch on the machine and study the working of each part. Note the RPM of machine
with tachometer.
Examine the feed for its size and record the average minimum size in the feed
Adjust the set of machine with the help of the lead lump and record it. Feed the
material slowly and note how each lump is nipped between the rolls.
Switch off the machine and recover the ground product.
Transfer the ground material to a sieve set and sieve for 20 minutes.
Switch off the sieve shaker and recover the retained weights of each sieve.
Calculate the reduction ratio of the machine for test performed.
Tabulate the sieve results and plot a graph.
OBSERVATIONS
Diameter of roll (D) 10 inches = 254 mm Length of rolls (L) 6 inches = 152.4 mm R.P.M of rolls 250 to 300 Set (S) 0.25 inches = 0.635 mm Horse power of motor 8 hp Maximum size in feed (-18.85+13.33) mm Maximum size in product (-6.680+3.327) mm Specific gravity of sample( G) 2.85
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CALCULATIONS
Reduction Ratio
Reduction Ratio =
= 18.85/6.628
= 2.82
CAPACITY
Capacity = 0.0034× N×D×W×S×G
= 0.0034 × R.P.M × Diameter × Length of the roll × Set × Specific
gravity of rock
(For maximum production we take value of R.P.M = 250)
= 0.0034×250×10×6×0.25×285
=36.3375 Ton/hour
CO-EFFICIENT OF FRICTION
Co-efficient of friction (Tan (n/2)) between the sample and rolls
Cos (n/2) = D+S/D+d
Where
n/2 = angle of nip D = diameter of roll in inch S = set = maximum size in product D = maximum size in feed Hence
Cos (n/2) = (254+6.35) / (254+18.85)
=0.95
So Angle of nip ( n/2) =17° 24’ 37" Tan (n/2) = Ø =0.3136
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0
20
40
60
80
100
120
140
160
180
200
-1 0 1 2 3 4 5 6 7 8
Dir
ect
wei
ght
reta
ined
e
Aperture size
Series1
Linear (Series1)
Mesh
no.
Aperture
size
Direct weight
retained(g)
%age
Direct
weight
retained
Comulative
wts.
Retained
(gm)
%age
Comulative
wts.
Retained
Comulative
wts. Finer
(gm)
%age
Comulative
wts. Finer
3 6.680 145 28.37 145 26.37 366 71.62
6 3.327 179 35.02 324 36.40 187 36.59
10 1.651 51 9.98 375 73.38 136 26.66
20 0.833 28 5.47 403 78.88 82 16.04
48 0.295 54 10.567 457 89.42 28 0.0547
-65 -0.208 54 100
Total
weight=511gm
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INTRODUCTION TO DISC MILL A disc mill is a mechanical device for the grinding of many different types of materials. Disc Mill can be used for secondary or fine crushing but its use is limited to special applications only because capacity is low and it is not suitable for all type of ores economically. For example, they are used to pulverize coal for combustion in the steam-generating furnaces of fossil fuel power plants also for glass, aluminum, concrete, plastic, coal, rock, resin, tires, and medical waste. Pulverizer machines come in a number of different forms.
CONSTRUCTION OF DISC MILL A disc mill consists of two saucer shaped discs with their surface having specially shaped grooves the depth of which reduced towards the circumference. The discs are face mounted vertically or horizontally and revolve at different speeds and in the opposite directions. In most designs of the disc is rather strongly fixed while the other flutters or gyrates during revolving. Our laboratory model has heat treated mechanical metal discs mounted vertically on revolving in a planetary manner always having a proper curvature with relation to the other which is stationary. Like other crushing machines a disc mill has not of the disc springs-loaded through a screw mechanism that helps in adjusting the set and also provides safety against un crushable lumps.
GRINDING CYCLE OF DISC MILL The material is fed through a hopper at the top and falls into the axial conic between the discs during revolving. Due to the centrifugal force the feed is pushed through the taper grooves towards the periphery and gets crushed progressively. The product is finally discharged peripherally and collected in a peripheral receptacle.
ADVANTAGES OF DISC MILL Users who need a higher level of strength and power than a hammer mill or ball milling machine can offer can use a disc mill grinder. This means they can handle harder or more durable materials like stone and steel, which may damage other types of milling equipment. They also have a relatively large capacity on average, and can accommodate large quantities of
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material in a single batch. Compared to hammer mill or ball mills, the disc mill is also relatively quiet, and less likely to cause hearing damage to nearby workers.
DISADVANTAGE OF DISC MILL Disc mills are relatively expensive to run and maintain however, and tend to require frequent maintenance. Discs may experience wear over time as they grind various materials, which can reduce performance. The machines also produce a large amount of dust, and must be carefully ventilated when used in an indoor workspace.
MACHINE STUDY OF A LABORATORY DISC MILL AND TO PERFORM A FINE
CRUSHING TEST ON THE GIVEN SAMPLE.
APPARATUS:
Laboratory disc mill Adjustable Spanner Wrench Feed Sample A set of sieve with shaker Torsion balance /electrical balance
PROCEDURE:
Identify each part of the machine. Draw a sketch and label each part. Switch on the machine and study the working of each part. Note the rpm of the machine
with a tachometer. Examine the feed for its size range and record the average maximum size in the feed.
Adjust the set for fine crushing. Feed the material slowly and check the size of the product. Make adjustments of the set
if necessary for fine crushing. Switch off the machine and recover the product. Transfer the ground material to a sieve set and sieve for 20 mins. Switch off the sieve shaker and recover the retained weights on each sieve. Record the retained weights for each sieve. Calculate the reduction ratio of the machine for the test performed. Tabulate the sieve test and plot a graph on a suitable graph paper.
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OBSERVATIONS
Motor power 5 hp
Motor r.p.m 1800 r.p.m
Disc r.p.m 275 r.p.m
Size of Disc 9 ½ inch (241.3 mm)
Max: feed size ¼ inch (6.35 mm)
Capacity 2 lbs/min
Sample dolomite
Feed size -2+8 mesh
Aperture size -6.680+2.362 mm
Max: product Size 6.680 mm
Weight of feed 600 gram
No. of grooves on moving disc 6
No. of grooves on stationary disc 5
RESULTS/CALCULATIONS:
A. Reduction Ratio: Max. size in the feed Max. Size in the product
= 6.35/0.208 = 30.53 B. Size analysis of the product
Mesh No.
Aperture Size (mm)
Direct wt. retained
(gm)
% Direct Wt.
retained
Cumulative Wt. retained
% Cumulative
Wt. retained
Cumulative Wt. finer
% Cumulative
Wt. finer
65 0.208 149 27.04 149 27.04 402 72.95 80 0.177 40 7.25 189 34.30 322 58.43 100 0.149 37 6.71 226 41.01 285 51.72 115 0.125 29 5.26 255 46.27 256 46.46 70 0.088 84 16.43 339 61.52 172 31.21 200 0.074 55 9.98 394 71.50 117 32.12 -200 0.074 175 28.49
Total=551
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AN INTRODUCTION TO HAMMER MILL In these machines comminution is by impact rather than compression, by sharp blows applied at high speed to free falling rock. The moving parts are beater which transfer some of their K.E. to the ore particles are often large enough to cause them to shatter. These are increased by causing the particles to impact upon an anvil or breaker plate. Reduction ratio of the hammer mill is high as 40:1 for non abrasive material and hammer mill should not be used on ores containing over 15% silica.
CONSTRUCTION OF HAMMER MILL ROTOR The material to be reduced determines the rotor construction of the hammer mill. A series of tough armor plated steel disks or spacer plates is keyed to the extra heavily constructed shaft. Long bolts pass through their outer diameters. From these, sets of hammers are suspended. The rotor revolves within a substantial housing of exclusive cast design insuring maximum return on investment. The speed of rotor varies from 500 rpm to 3000 rpm. SHAFTS Shafts for hammer mills are made of forged alloy steel. Machined to very close tolerances from 50% to 100% oversize to prevent whipping and vibration. HAMMERS Important to consider when deciding whether to equip a machine with hammer or rings are material to be reduced, feed size, whether hard, soft, fibrous, tough, friable or abrasive, also equally important are finished product specifications. The type of the hammer selected depends also upon whether the sized product is to be uniform with a minimum of fines or pulverized with a maximum of fines. The hammers are made of high grade manganese or alloy steel, alloy steel parts being heat treated to resist abrasive wear. The hammers can weigh over 100 kg and can work on the feed size by 20 cm.
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GRATE BARS Heavy duty grate bars are furnished when sizing hard and abrasive material like limestone, brick bats, fertilizer tailing etc. these are of rapid discharge type. Opening between the bars from 1/16 inch to 4 inch are maintained by spacing blocks securely riveted to the bars. The bars are constructed that they can be shifted around in the machine distributing the wear and getting the maximum service from each set. When a complete set of bars is installed in the machined recesses on the housing sides or bar presses against the spacing blocks of the next bar. Maintains the proper spacing when the cover is lowered the grate bars are locked into position.
HOW DOES A HAMMER MILL WORK? Hammer mills work on the principle that most materials will crush, shatter, or pulverize upon impact using a simple four step operation:
1) Material is fed into the mill’s chamber typically by gravity. 2) The material is struck by ganged hammers (generally rectangular pieces of hardened
steel) which are attached to a shaft which rotates at a high speed inside the chamber. The material is crushed or shattered by the repeated hammer impacts, collisions with the walls of the grinding chamber as well as particle on particle impacts.
3) Bar grates covering the discharge opening of the mill retain coarse materials for further grinding while allowing properly sized materials to pass as finished product.
4) Hard, heavy materials such as glass, stone or metals exit the mill via gravity. Pneumatic suction us used to assist in the discharge of lighter materials such as wood, paper or other low bulk density products.
Varying the screen size, shaft speed or hammer configuration can dramatically alter the finished size of the product being ground. For example, faster speed, a smaller screen, and more hammers result in a finer end product. GRINDING PATH The fractures pieces which can pass between the clearances of the rotor and breaker plate entre a second chamber created by another breaker plate, where the clearance is smaller, and then into a third smaller chamber. This is the grinding path which is designed to reduce flakiness and gives very good cubic particles. CAPACITY OF HAMMER MILL Large impact crusher will reduce 1.5 m top size rum of mine ore to 20 cm, at capacities of around 1500 ton/hour, although crushers with capacities of 3000 ton/hour have been manufactured. USES OF HAMMER MILL Industrial uses for hammer mills include many types of recycling operations, including producing pulp for paper production, bio-fuel production, and stone crushing. Grinding grain for ethanol production or pulverizing fruit in juice production are other possible uses for a hammer mill.
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MACHINE STUDY OF HAMMER MILL AND PERFORM CRUSHING TEST ON GIVEN SAMPLE
APPARATUS:
Laboratory hammer mill Feed sample A set of sieves with shaker Torsion Balance/Electrical Balance
PROCEDURE: Identify each part of the machine. Draw a sketch and label each part. Switch on the machine and study the working of each part. Note the rpm of the
machine. Examine the feed for its size range and record the average maximum size in the feed. Feed the material slowly. Switch off the machine and recover the product and weight it. Transfer the product to a set of sieve And sieve for 20 minutes. Switch off the sieve shaker and recover the retained weight on each sieve. Recover the retained weight for each sieve. Calculate the reduction ratio of the machine for the test performed. Tabulate the sieve results and plot a graph on a suitable graph paper.
OBSERVATIONS Motor power 5 hp Motor r.p.m 1420 r.p.m Mill r.p.m 2130 r.p.m Motor pulley dia 18 cm Mill pulley dia 12 cm Grate opening 1 cm Full swing dia of shaft and hammer 35 cm No. of hammer 32 Capacity 200 ton/hour Sample dolomite Size of feed -18.85+13.33 mm Weight of feed 1 kg RESULTS/CALCULATIONS: Reduction Ratio: Max. size in the feed Max. Size in the product = 18.85/3.327= 5.66
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Size analysis of the product Mesh No.
Aperture Size
Direct wt. retained
% Direct
Wt. retained
Cumulative Wt.
retained
% Cumulative Wt. retained
Cumulative Wt. finer
% Cumulative
Wt. finer
6 3.327 34 4.26 34 4.26 763 95.73 10 1.651 122 15.30 156 19.57 641 80.42 20 0.833 211 26.47 367 46.14 430 53.95 28 0.589 111 13.92 478 59.97 319 40.25 48 0.259 185 23.21 663 83.18 134 16.81 65 0.210 44 5.52 707 88.70 90 11.29 -65 0.210 90 11.29
Total=797
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AN INTRODUCTIO TO ROD MILL
Grinding of materials in a tumbling mill with the presence of metallic balls or other media dates back to the late 1800’s. Historically, rod mills have been used as the first grinding stage after crushing in mineral beneficiation circuits. The rod mill product was further ground in ball mills before separation of valuable minerals from the host rock. Rod mills are similar to ball mills in appearance and in general principle. These may be defined as rotating cylindrical shells loaded with rods that grind the ore by tumbling within the shells. Rod mills are differ from ball mills in their grinding action in that the rods are kept a parted by the coarsest particles. This peculiar property of the rod mills recommends their selection where mills are used in connection with concentrating processes that fail on fine particles. Conversely, whenever flotation is to be used, ball mills are preferable. Scissoring action of the rods is an extra factor aiding to efficiency in a rod mill. They are capable of taking feed as larger as 50mm and product as fine as 300µm. its reduction ratio is 15-20:1. These are preferred to fine crushing machine when the ore is clayey or damp, thus tending to choke crusher.
Rod milling in the size range utilized is more efficient than ball milling in that the desired product is obtained at a lower cost per ton. This is due to several reasons:
1. Grinding rods do not require cascading as do ball charges, thus enabling rod mills to be operated at lower peripheral speeds than ball mills.
2. Less void spaces exist in a rod charge tan in a ball charge. Therefore, these is more grinding contact between metal an ore per surface are of media in a rod mill.
3. Lower steel consumption per ton of product occurs in a rod mill than in a ball mill due to better contact between steel and ore. The action within the rod mill causes the energy of rods to be directed to the largest sized pieces of ore. Often in a ball mill the balls grind on one another or against ore already ground fine enough.
4. Rods are more suited than balls to breaking larger pieces of ore due to their much higher weight. (Energy is equal to hall the product of the mass times the velocity squared). Larger media are capable of transmitting moiré energy per collision.
5. Grinding rods can be maintained in good working condition because broken and worn rods can be removed through the large open discharge end. Often broken pieces of rods will float out with the pulp thus avoiding entanglements.
CONSTRUCTION OF ROD MILL
SHELL
These are design to sustain impact and heavy loading, and constructed from rolled milled steel
plates and holes are drilled to take the bolts for holding the liners.
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MILL ENDS
The conical heads attached to the ends of the cylindrical shell section are provided with hollow
trunnions of large diameter and narrow width for supporting the shell in suitable bearings.
MILL FEEDER Feed is introduced through a feed chute or drum feeder attached to one of the hollow trunnions. The product is discharged through a suitable opening in the opposite trunnion or through ports in the periphery of the mill shell. The trunnion, end peripheral and center peripheral discharge arrangements. Bearings
Trunnions and trunnion bearings design receive special attention. Hydrodynamic oil lubrication is generally used for Rod Mills equipped with the trunnion bearings 40” diameter or smaller. Larger sizes are arranged for full hydrostatic oil lubrication.
LINERS
Among the cast materials used for linings are Ni-Hard, chrome-molybdenum steel, and manganese steel. Rolled alloy steel plate with lifter bars is available. Rod mill liners are
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subjected to severe impact. Premature breakage and scrap loss are reduced by correct selection of liners for the specific grinding duty.
Rod Mill Grinding Action
When the mill is rotated without feed or with very fine feed, the rods are in parallel alignment and in contact with one another for their full length. New feed entering at one end of the mill causes the rod charge to spread at that end. This produces a series of wedge shaped slots tapering toward the discharge end. The tumbling and rolling rods expend most of their crushing force on the coarse fractions of the feed material and only to a lesser degree on the finer material filling the interstices in the rod charge. The horizontal progression of material through the mill is not rapid compared to the movement of the rods and material resulting from rotation of the mill. The average particle is subjected to an action similar to many sets of rolls in series, before it is discharged.
TYPES OF ROD MILL
Rod mills are classified according to their nature of discharge. There are three main types of rod
mill, overflow, end peripheral discharge, and center peripheral discharge only the overflow mill
is in common usage.
CENTER PERIPHERAL DISCHARGE
These are feed at both ends through the trunions and discharge the ground product through
circumferential ports at the centre of the shell. Short path and steep gradient gives acoarse
grind with minimum of fines, but the reduction ratio is limited.
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END PERIPHERAL DISCHARGE
Material is fed from one end and discharge ground product from 2nd end by means of several
peripheral apertures into a close fitting circumferential chute. This is used for dry and damp
grinding where moderately coarse products are involved.
OVERFLOW ROD MILL
This is most widely used rod mill in the mining industry, in which feed is introduced through one
trunions and discharge from other. This is only used for wet grinding. A flow gradient is
provided by making the overflow trunion diameter 10-20 cm larger than that of feed opening.
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MACHINE STUDY OF LABORATORY ROD MILL AND TO PERFORM A
GRINDING TEST ON THE GIVEN SAMPLE.
APPARATUS
Rod mill cylinder and rollers
Feed sample
Tachometer
A set of sieve
Sieve shaker
Torsion balance
PROCEDURE
Identify the each part of machine.Draw a stach and lable each part o f machine.
Switch on the machine and study each part of machine.
Note the RPM of machine with tachometer
Examine the feed for its size range and record the average size of largest lump in the
feed.note the total weight of feed.
Load the mill cylinder with its feed sample and its rod load.
Switch on and run the machine for 30 minutes and then recover the ground product.
Transfer the ground material to the set of seive by consulation and sieve for 20 minutes.
Switch off the sieve shaker and record the retained weight of each sieve.
Note the weights of the individual sieve and of the base pan.
Calculate the reduction of the machine for the test performed.
Tabulate the sieve test and plot a graph on a suitable graph sheet.
NOTE
Carefull record the weight ratio between the feed sample and rod load. portion of mill cylinder
filled and empty, keeping in view the theoretical specifications.
OBSERVATION
NAME Rod Mill R.P.M OF MILL 160 MOTER POWER ½ hp MOTOR R.P.M 710 CYLINDER DEPTH 12.25 inches ROD MATERIAL Hard carbon Steel WEIGHT OF EACH ROD 1220 grams
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SIZE OF ROD 12”×1” NO. OF RODS 3 SAMPLE Dolomite WEIGHT OF FEED 1830 grams FEED SIZE -13.33+9.423 GRINDING TIME 30 min SIEVING TIME 20 min
Mesh No.
Aperture Size
Direct wt. retained(g)
% Direct Wt.
retained
Cumulative Wt.
retained(g)
% Cumulative
Wt. retained
Cumulative Wt. finer(g)
% Cumulative
Wt. finer
4 4.699 513 28.2 513 28.1 1312 71.9
10 1.651 244 13.4 757 41.5 1068 58.5
20 0.833 158 8.7 915 50.2 910 49.8
48 0.297 247 13.534 11.62 63.7 663 36.3
60 0.250 113 6.2 1275 69.9 550 30.1
100 0.147 180 9.9 1455 79.7 37 20.3
-100 370 20.3
Total=1825
CALCULATION:
Reduction Ratio = Max. size in the feed = 13.33 = 2.84 Max. Size in the product 4.699
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AN INTRODUCTION TO BALL MILL
The final stage of comminution are performed in tumbling mills using steel balls as the grinding
medium and so designated ball mill. Ball s have greater surface area per unit weight than rods,
they having a length to diameter ratio of 1.5 to 1 and less.
Grinding balls are made of forged high carbon or alloy steel or cast steel and consumption
varies between 0.1 to as much as 1 kg/tone of new feed. Mill charge should be 40 to 50 % of
the internal volume of the mill. Ball mills are rated by power rather than capacity.
Efficiency of grinding depends upon the surface area of the grinding medium. The ball should
be as small as possible and charge should be graded such that the largest balls are just heavy
enough to grind the largest and hardest particles in the feed.
An internal cascading effect reduces the material to a fine powder. Industrial ball mills can
operate continuously, fed at one end and discharged at the other end. Large to medium-sized
ball mills are mechanically rotated on their axis, but small ones normally consist of a cylindrical
capped container that sits on two drive shafts (pulleys and belts are used to transmit rotary
motion).
CLASSIFICATION OF BALL MILL
Ball mills are classified by the nature of the discharge. These are
Trunion overflow mills
Grate discharge mills
GRATE DISCHARGE MILL
This m ill type embodies the principle of steep pulp gradient. Quick discharge operation. A grate
assembly at the discharge en d of the mill permits retention of a higher ball charge (up to 50%)
than is possible in an overflow mill which has a practical limit of around 40%. Behind the grates
is a lifting compartment which picks up the ground material as it passes through the grates and
transports it out of the mill. grate mill will draw more power and produce more product than its
overflow counterpart of the same dimensions.
This quick removal of ground material reduces overgrinding to a minimum. The fact that all
material leaving the mill must pass though the grates and in so doing must become enmeshed
in the ball charge minimizes the possibility of tramp oversize material passing though the mill
without being ground. In dry ball mill grinding, a grate mill should be used because dry material
will not overflow as well as wet material. Thus savings on power consumption are available by
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selecting the grate design. The grate mill by virtue of its steeper pulp gradient has a more rapid turnover
of material than its overflow counterpart.
TRUNION OVERFLOW BALL MILL
In this type of mill the balls are kept in the mill, by keeping the top of the ball charge below the
level of the trunnion opening. When operating an overflow mill with a higher charge escaping
balls are returned to the mill by a reverse spiral in the trunnion liner or are restrained by a ball
retaining grate.
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MACHINE STUDY OF DEN VER LABORATORY BALL MILL AND TO
PERFORM A GRINDING TEST ON THE GIVEN SAMPLE
APPARATUS
Denver ball mill
Feed sample
Tachometer
A set of sieve
Sieve shaker
Torsion balance
PROCEDURE
Identify the each part of machine. Draw a sketch and label each part o f machine.
Switch on the machine and study each part of machine.
Note the RPM of machine with tachometer
Examine the feed for its size range and record the average size of largest lump in the
feed. Note the total weight of feed.
Load the machine with a suitable ball rod and feed material.
Switch on and run the machine for 30 minutes and then recover the ground product.
Transfer the ground material to the set of sieve by consulation and sieve for 20 minutes.
Switch off the sieve shaker and record the retained weight of each sieve.
Note the weights of the individual sieve and of the base pan.
Calculate the reduction of the machine for the test performed.
Tabulate the sieve test and plot a graph on a suitable graph sheet.
NOTE :
Carefully record the weight ratio between the feed sample and rod load. Portion of mill cylinder
filled and empty, keeping in view the theoretical specifications.
OBSERVATION
NAME Ball Mill
R.P.M OF MILL 42
MOTER POWER ¼ hp (Gear Reducer)
MOTOR R.P.M 1425
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CAPACITY 4 kg/hr
MATERIAL OF BALL Alloy Steel
DRUM MATERIAL Cast Iron
TOTAL WEIGHT OF BALLS 3550 gram
SAMPLE Dolomite
WEIGHT OF FEED 1775 gram
FEED SIZE -13.33+9.423
GRINDING TIME 30 min
SIEVING TIME 20 min
No. of balls Size of ball(cm) Weight of each ball Total weight
2 5.5 685 1370 4 4 275 1100 8 2.5 75 600
16 1.9 30 480
Mesh No.
Aperture Size
Direct wt. retained(g)
% Direct Wt.
retained
Cumulative Wt.
retained(g)
% Cumulative
Wt. retained
Cumulative Wt. finer(g)
% Cumulative
Wt. finer
4 4.699 1069 60.4 1069 60.4 701 39.6
10 1.656 160 9.1 1229 69.5 541 30.5
28 0.589 99 5.6 1328 75.1 442 24.9
48 0.297 133 7.5 1461 82.6 309 17.4
60 0.250 49 2.8 1510 85.3 260 14.7
100 0.147 75 4.3 1585 89.5 185 10.5
-100 185 10.5
TOTAL=1770
CALCULATIONS:
Reduction Ratio = Max. size in the feed = 13.33 = 2.84 Max. Size in the product 4.699
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STANDARD SIEVE SERIES
Product sieving is now an essential requirement in nearly all industries. To obtain a quality-controlled end product not only required diligent ingredient choice but careful handling and processing. Removal of any substandard or unwanted matter is therefore a prime requirement.
For all laboratory sieve analysis standard sieve series are employed. Different sieve series different from one another in their actual mesh dimensions for the same mesh numbers. In the U.S.A American standard sieve series are Taylor standard sieve series are used. The British, French and German use their own standard sieve series while from Japan OGAWASEIKI standard sieve series are available. A mesh number is number of apertures per linear inch, e.g. a 100 # sieve has one hundred
apertures per linear inch. A square inch of the 100 # screen surface accordingly has 10000
apertures. Depending upon the size of the wire the actual size of the apertures for a varies
particular mesh number from one standard series to another, and generally this is the only
difference between different series. Total mesh numbers in a series may be upto 28 or more
and the series follows a Geon metrical progression with a ratio of 2 or its multiples starting a
200 # sieve.
A laboratory sieve with some variations generally measures about 8 inch in Dia and 205 inch
deep. The frame is rimmed at the top and screen cloth rigidly mounted at its bottom. The frame
is labeled with the particular # no. with notation of the standard sieve series. The actual
dimension of the aperture in mm or microns is also given on the label. The sieve can be
attacked together because they fit into one other very easily.
For a particular sieve test the required sieves are stacked together in a prope order so that the
coarsest is at the top and the finest at the bottom. A Pan is fitted below the finest sieve and a
lid at the top of the series and the set placed in sieve shaker. After filling the top sieve with the
sample to be tested. Shaking in allowed for a suitable time then the set is removed and opened
for weighing different size fractions.
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STUDY OF LABORATORY WOVEN WIRE STANDARD SIEVE SERIES AND TO
PERFORM A DETAILED SIEVE ANALYSIS TEST ON A BALL MILL PRODUCT SAMPLE.
EQUIPMENT /APPARATUS REQUIRED:
Laboratory standard sieve series set of 18 sieves or 12 sieves.
Ro-tap sieve shaker.
Torsion balance.
Set of brushes for cleaning the sieves.
Timer.
Sample to be analyzed.
Sample trays 19 Nos.
PROCEDURE:
Study the sieves for their size (dia. & depth), mode of construction, printed mesh numbers and
aperture size on individual sieves.
Record the mesh numbers and aperture sizes of all the sieves in the set in a decreasing size
order.
Study the construction and operation of the ro-tap sieve shaker.
Study the timer connected to the sieve shaker.
Transfer the weighed sample to the top sieve in a set of first 6 sieves. Fit the lid and the pan to
the sieves and loaded in the shaker. Adjust the timer for 20 minutes and the switch on the
shaker.
After 20 minutes switch of the shaker, remove the sieve set dismantle and weigh the retained
sample on each sieve and record the weights.
Transfer the contents of the pan to the next set of 6 sieves and repeat the process.
Transfer the pan contents of the second set to the third set of engaged of sieves and repeat the
process.
Record all the weights retained and the weight of the last under size in the series.
Clean the sieves with the help of bushes and put them back in the rack carefully. Take care not
to damage any screen cloth while handling and cleaning.
Tabulate the results properly and also draw a suitable graph of the results.
OBSERVATIONS:
DIAMETER OF THE SIEVES IN INCHES 8”
DEPTH OF THE SIEVES IN INCHES 2.5”
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NO. OF SIEVES FOR SIZING 6
WEIGHT OF FEED 1 KG
MOTOR POWER 0.25 HP
MOTOR SPEED 1425 RPM
RESULTS / CALCULATIONS:
Mesh no.
Aperture mm
Direct weights Cumulative weights retained
Cumulative weights passed
Actual weights (grams)
%age weights
Actual weights (grams)
%age weights
Actual weights (grams)
%age weights
65 0.208 48 4.93 48 4.93 926 95.07 80 0.177 45 4.62 93 9.55 881 90.45 100 0.149 147 15.09 240 24.64 734 75.36 115 0.125 79 8.11 319 32.75 655 67.25 170 0.088 208 21.35 527 54.11 447 45.89 200 0.074 123 12.63 650 66.73 324 33.27 -200 325 33.26
Total = 975
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AN INTRODUCTION TO STANDARD SCREEN
Screen is name which is given to a number of things, one of these things is any such a
vessel/utensil integrally consists of a perforated surface which is used for sifting to separate
particles of a desired size-grade from a multitude of sizes contained in a given material. In the
mineral dressing terminology, this act of sifting is called screening and the vessel is screen.
TYPES OF SCREEN SURFACES
Woven wire (square openings)
Punch plates (circular, square or slot like openings)
Parallel rods (slot like openings)
Screening is the most important method of sizing both industrially as well as in laboratory but
with varying limitations. The second most important method is classification, Elutriation and
sedimentation being a part of it.
In industry are employed larger and larger screening/classification plants for and more output,
where as in laboratory work standard screens called “ test sieves” and mini model classifiers for
more and more accuracy.
Material’s size range within which it’s considered an industrial scale screen is effective for
efficient sizing is from several inches to 1 mm generally and in special cases of materials
requiring the products must be dry, like talcum powder, Al powder, cement etc. down to 200
mesh.
TYPES OF SCREENING MACHINES
The machines called ‘automatic screens’ are of two basic kinds,
The Stationary Screens
Moving Screens.
STATIONARY SCREEN
A stationary screen has the screening surface in sloping position and idle on which the feed
material is moved by an automatically driven element from outside and gets the chances to
pass across the openings, whereas in the case of a moving screen, the screen surface itself
moves and causes the feed material pass across the openings.
Again moving machines are of several types including moving grizzlies, trammels, shaking
screens, and a modern type named vibrating screens. The vibrating screens for its extensive
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efficiency and use have bypassed all other types and attained the status of most of most useful
screens for all types of permeable materials.
VIBRATING SCREENS
Vibrating screens are the most important screening machines for mineral processing
applications. They handle material up to 25 cm in size down to 250 microns. Their main
application is in the crushing circuits where they are required to handle material ranging, in
general, 25 cm to 5 mm in size.
They can work at low slopes and little headroom. In multiple deck systems the feed is
introduced to the top coarse screen, the undersize falling through to the finer screens, thus
producing a range of sized fraction.
The vibrating screens are vibrated mechanically or electromagnetically and both give equally
good sizing results.
In our laboratory, we have one tiny model of mechanically vibrating industrial screen and one
of the electromagnetically vibrating screen. Mechanically vibrating screen has its trade name
“Denver Dillon” provided with 2 decks of different aperture sizes.
MECHANICALLY VIBRATING SCREENS
A mechanically vibrating screen may consist of a single deck
(screening surface) are more than 1 decks arranged one over the
other, with a base frame carrying through heavy coil springs and
screen frame or frames rigidly fastened to the vibrating mechanism.
The vibrating mechanism consists of a shaft fitted with an eccentric
and the motion is thus transmitted mechanically. The screens are
removable and any desired one’s can be fitted in the frame.
A single deck screen gives two products, oversize (coarser than the screen opening) and the
undersize passed through it. A double deck screen will give three products, oversize of the top
screen, undersize of the bottom screen, and middling product that has passed through the top
screen but retained on the bottom screen. Provisions are made for collecting the products
separately.
ELECTROMAGNETICALLY VIBRATING SCREENS
Electromagnetically vibrating screens are generally called hummer
screens and are truly electrically vibrated. Vibration is obtained from
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the action of electromagnet on an armature. The upstroke is suddenly interrupted when the
armature hits the striking block but the down stroke is not so interrupted. The differential
motion results in constant un blinding of the screen. It further simulates jigging and causes the
particles to stratify, the coarsest particle at the top and the finest next to the screen surface.
This helps in the discharge of coarser/oversize particles quickly off the screen surface and
allows more chances to the fine particles to pass through the screen.
The screen consists of a coarse backing screen over which the requisite fine screen is laid but
kept in tension by suitable tensioning devices. The fine screens can be easily replaced when
necessary.
A low frequency alternating current or a rectified current is normally used. For finer or damper
materials a relatively higher frequency current is used. Hummer can also be multi-deck screen.
Gyratory screens
This type of screen which imparts gyratory motion throughout the
whole screen cloth is becoming widely used for fine screening
applications, wet or dry, down to 40 microns. The basic components
consist of a nest of sieves supported on a table which is mounted on
springs on a base; suspended from beneath the table is a motor
with double shaft extensions, which derives eccentric weights and in
doing so effects horizontal gyratory motion. Vertical motion is
imparted by the bottom weights, which swing the mobile mass
about its center of gravity, producing a circular tipping motion to the screen, the top weights
producing the horizontal gyratory motion.
Ball trays may be fitted below a screen assembly to reduce blinding.
PROCEDURE:
Identify each part of each of the both machines. Draw sketches and label each part of the both.
Make two representative samples of the given feed by the method of ‘coning and quartering’ or the ‘Rifflers’
First feed 1 sample to the hummer screen, slowly, with the tilt suitably adjusted, so that the material gets sufficient time to pass through the screen cloths.
Switch off the machine and collect the oversize and the undersize products.
Weigh the products and calculate weight percentages.
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Secondly, feed the second part of the sample to the Denver Dillon vibrating screen (which has two screen decks of different mesh sizes and gives three products), and proceed as done in the 1st case.
OBSERVATIONS
FEED WEIGHT 500 G
FEED SIZE -4 + 48 #
APERTURE SIZE -4.699 + 0.295 MM
SAMPLE DOLOMITE
Characteristics Hummer screen (single deck)
Denver Dillon screen (double deck)
Size of the screen 22”*30” i. (12”*24”) ii. (12”*24”)
Mesh no. 10 # i. 10# ii. 20#
Frequency of vibration 3000 vib/min 1200 vib/min
RESULTS AND CALCULATIONS
SINGLE DECK
Oversize weight % weight of oversize Undersize weight % weight of undersize
214.5 42.9 293 58.6
DOUBLE DECK
Oversize weight % weight of oversize
Middle size weight
% weight of middle size
Undersize weight
% weight of undersize
109 21.8 136 27.2 170 34
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