McNally Sayaji Engineering Limited,

Kumardhubi, Dhanbad, Jharkhand

DESIGNE PROJECT REPORT

BY

MR. OSCAR JAMUAR

UNDER GUIDANCE OF

MR. PINTU SADHU

AKNOWLEDGEMENT

I sincerely thank all the staffs of McNally Sayaji Engineering Kumardhubi who were related to training program. I want to express my warm and sincere regards to Mr Pintu Sadhu, for his consistent able and expert guidance throughout the training.

I would also like to extend my sincere thanks to Mr Tapas Kundu for his consistent involvement and Conscious Guidance and also to S.N Haque Sir for allowing me to use all the resource during the training period.

2 | P a g e

Submitted By:-Oscar JamuarB.E MechanicalShree Ramchandra College of Engineering,Pune

INDEXSR. NO Topic Page

No.1. Introduction 4

2. Conveyors 6

3. Feeders 8

4. Screens 11

5. Crusher 15

6. Mill 22

7. Washing Equipment 23

3 | P a g e

McNally Sayaji

TITLE:- Report on Design study of Coal Refining Equipment

INTRODUCTION:-

McNally Sayaji is one of the oldest companies in creating refining product for

the coal refining process. It has already created some remarkable projects in the

field of the coal extracting process. Getting trained in such great company and

learning the design and working of various machinery was really resourceful

and knowledge gaining experience.

By getting trained here I learned about various coal refining process. All the

various processes are required to increase the efficiency and decrease the final

size of the equipment where it will be used and the product size respectively.

The coal beneficiation process consists of various stages, i.e. primary crushing,

Screening process, secondary crushing and Milling. Passing through each stage

the final product size of material get reduced in each stage and at the last the

milling process help it to achieve the product size ranging from 5 to 100

microns.

The rest of the detail regarding the working of every equipment I studied here is given in the report.

4 | P a g e

The equipment which I studied can be classified into the following stage wise;

a) Conveyorsb) Feedersc) Screensd) Crusherse) Mills

Conveyors can be explained as the equipment which carries the material which is needed to be processed from one stage to another stage. In this it is not necessary to carry and feed the material in equal proportion.

Feeder can be explained as the equipment which is used to feed the material in the machine in equal amount with proper distribution. This proper distribution is required so that the feeding load on the processing machine is equally distributed all over the feeding area.

Screen can be explained as the equipment which is use to separate the required size of material grains from the crushed material lot and the material which do not pass the screen face will be carried to next machining process for further reduction of its grain size.

Crusher can be explained as the machine which breaks the material into smaller size according to its capacity of its size reduction power. The crusher is further classified based on its size reduction capacity, known as Primary crusher and Secondary crusher. The products of the primary crusher are usually large in size as compared to secondary crusher.

Mills can be explained as the equipment which takes the feed from the crusher and reduce the size of it into much finer size. There are two types of mills, Rod Mill and Ball Mill. The size reduction ratio of the Rod mill is up to 1:15 to 1:20, whereas in the ball mill the reduction ratio can be set up to 1:600. This gives you the feed in the range of 45 to 50 microns

5 | P a g e

1. CONVEYORS

Bucket Elevator

Bucket Elevator is used when the setup requires the material to be fed at a particular height and in vertical direction. The drive pulley is situated at the top which get its drive through a motor which is connected through a Fluid coupling and a 3 stage gear box. The belt speed can range from 1.8 to 2.5 meter per second. This speed is required so the material which is fed from a height just doesn’t drop directly downward on the bucket elevator system but it should be thrown away from it to a collector and so it requires a particular high speed.

The bucket is bolted on the elevator belt through a rubber strip. So that it don’t damage the belt of the elevator and if required to replace the bucket and rubber strip can be replaced without damaging the elevator belt.

The material which is needed to be carried by the elevator is placed in the Boot casing. The level of material fed in the boot casing is maintained so that it don’t get flooded and the operation remain smooth. The buckets collect the material from the boot casing while passing by the tail pulley assembly.

To maintain the required tension in the belt during operation the tail pulley assembly is placed on the guide frame. This guide frame is used to compensate the tension which is loosed during operation due to belt expansion at early stage when it is newly installed. During summer when the frame structure expand the tension in the belt can increase so to avoid this situation the guide frame is provided with a rack and pinion assembly which travel when the structure expand and reduce the tension in belt.

Belt travelling Tripper

It is used when discharge is needed at intermediate points on conveyor belts. Each tripper consists of two pulleys around which the belt is looped. Material falls from the discharge pulley into the chute which discharges material to either side of belt or reloads back onto the belt depending on the layout.

Travelling trippers are provided with a number of non-driven wheel shaft assemblies and one or two drive wheel shaft assembly for moving on rails. It has special drive arrangement to provide the power required to move the tripper

6 | P a g e

forward and in reverse direction along its course. Power is supplied to the tripper through Cable Reeling Drum.

To minimize dust nuisance, bunker sealing belts are provided to cover the bunker opening in the areas where material discharge is not taking place. Rail cleaners are provided at both ends of tripper for clearing small stray pieces, dust etc. which might be lying on the rails. To avoid over travel, limit switches are provided at both ends of tripper. Spring loaded buffers at both ends of trippers and buffer stops on rails at two extremities of travel are provided to combat emergency situation arising out of non-functioning of limit switches, rail clamp and brake, which is a rare possibility.

The feed size to this system is kept under 40 mm and it is made for continuous duty purpose.

7 | P a g e

2. FEEDERS

Apron Feeder

This equipment is used to transfer the unloaded material to the required machinery; it is placed directly below the wagon tippler.

The main frame assembly consist of the following parts which is designed to take sever impact. The pan chain assembly is made of 12mm thick Sailma 350HI, which are of overlapping type and are fixed with chain.

The Tail shaft assembly carries two traction wheels mounted on a stepped shaft. The tail shaft assembly is floating type and mounted on a take up block which can be moved forward or backward with the help of take up screw.

Return roller are placed at a spacing of about 1 meters to prevent excessive sagging of pans during return run. The number of carrying idler is always greater than the number of return idler

Vibrating grizzly feeder

It is also known as linear motion screen, because other than feeding process and transferring the material to other machining process it also separates the required size of granules from the regularly flowing material. This system consists of a vibrator assembly on the top of the main frame assembly. The mechanism consists of two unbalanced shafts rotating in opposite direction. One shaft is extended out to mount the driven sheave either directly or through Cardan Shaft and jack Shaft. A special double seal assembly is provided on this extended shaft to prevent the oil leakage.

The combination of eccentric setting of the mechanism and its internal unbalanced masses result in an approximate elliptical motion curve. Thermal expansion of the shaft is taken care by having one side of the shaft fixed whereas the other end is left free.

The main frame assembly comprises of two side frames soild deck and grizzly deck assembly. The solid deck is provided to take the initial impact of the feed, the screening area depends upon various factors like material to be handled, separation required, feed sieve analysis etc. a feed hopper is provided at the feeding area to utilize the maximum screening area. The whole assembly is

8 | P a g e

supported on heavy duty coil springs. The screen is normally inclined in the at the angle of 10º, the amplitude and frequency of whole screen is 6mm and 750 rpm respectively. The drive is provided with the help of V-belt assembly through jack shaft & Cardian shaft

(Note: - the construction and working of electro mechanical vibrating feeder is also same)

Reciprocating Feeder

Reciprocating feeder is used when the material is used to be fed equally and evenly through the whole width of the running bed. This assembly works same like the reciprocating engine the Feeder bed can be consider as the piston head placed between the cylinder walls, but here the cylinder walls are replaced by the turnnions. The turnnions are placed at the starting and at end of the feeding bed. This turnnions guide the bed and maintain it to move only in horizontally linear motion. The linear reciprocating movement of the bed helps the material to move in forward direction and get fed into the feeding chamber. As the bed is moved forward the feeding side of the bed get vacant and is filled by the material getting fed on the bed and as the bed moves backward, the material at the end have no room left for the movement and so it falls in the feeding chamber. The reciprocating motion of the beds help the material to get distributed through the whole width as it moves forwards.

The reciprocating can have a stroke length of 150mm/ 200mm/ 250mm. the bed is reciprocated by a bar connected to its starting base which gets drive by a chain and sprocket arrangement. Which is driven by motor which is connected through a cone ring flexible coupling and a reducer of a ratio of 35:1 and the sprocket have the ratio of 2:1. So the final drive achieved is of 22 rpm from 1500 rpm.

Disc Feeder

Disc feeder is used in low capacity, where feed is also needed to be regulated according to need. The material is fed at the centre of the revolving disc which lead to cone formation of material deposition. A small amount of amount of material is collected from the circumference of cone by a hand and level arrangement. It can move in 60º angle and collect the material only till 45º span

9 | P a g e

angle which cover the disc surface. The rest of the 15º angle is the ideal angle and used when no material is needed to be collected.

There are various positions for the lever which cover certain amount of rotating disc radius, shown in below table:

Angle setting from extreme 0º 10º 20º 30º 40º 50º 60º

% percentage opening in disc radius

0 0 13.2 32 50 66.8 82

The disk is mounted on the Reducer gear box directly which is getting driven by V belt pulley which is connected to a motor of 1500 rpm of 2.2 KW. The disk rotate in clockwise direction with 6 Rpm. It can be fed with the material till size up to 18mm

10 | P a g e

3. SCREENS

Inclined Vibrating screen (Circular Motion)

This system is used to separate the required size of grains i.e. is (-20mm) from the material fed to the equipment. It screens the material by vibrating the screen panels near amplitude of 4.5mm at a frequency of 850 rpm. The vibrating of system is created by the vibrating assembly.

This vibrating assembly is attached to the main frame support. This assembly consist of one eccentric shaft rotating at the 850 rpm. As there is only one eccentric shaft in the system it create a centrifugal force acting on the frame and cause it to move in the oval shape formation.

The whole screen deck is inclined at the angle of 10º to 20º. The combination of vibration and such inclination cause the material to move on screen and the grains which are less in size as compared to the opening of the screens passes from the screen and rest of the material is transferred to another system for further breakdown.

The whole system is floating type which is mounted on the spring support. This spring supports helps in avoiding the transfer of vibration from the main system to the support of the whole system and causes any kind of damage to it.

Linear Motion Screen (Single Exciter)

The linear vibration screen is a screen with linear vibration, created by an out of balance drive. The drive consist of only concentric shaft which gets it drive from a Cardan shaft and is extended on both side with adjustable flyweight. This flyweight can be adjusted at various angles to change the amplitude of the system and reduce or increase the G force acting on the system.

The screen frame is situated on parallel soring in such a manner as to allow it to vibrate freely.

Linear motion vibration screens have a V-belt direct drive with power transformation and can be fitted with units for accessing the machines according to size

11 | P a g e

This equipment is used to separate the grains ranging in the size of (-8mm), it vibrates with the amplitude of 4mm with a frequency of 960 RPM

Linear Motion Screen (Double Exciter)

Almost this system is equipment is mostly similar to the construction of Linear Motion Screen (Single Exciter), there is only one thing not similar in the construction and that is in the vibrating assembly. In Single exciter the single shafts use to consist of 2 flyweights on each side which were adjustable.

Just like single exciter it also consist of flyweight to create unbalanced vibrating motion in system but here you will find two shaft instead of one which are rotating in opposite direction with having two fly weight on each side on each shaft.

Rest of working is totally similar to the single exciter system. The only difference is that, single exciter systems is used for light duty operation and double are used for heavy duty operation

High Particle Acceleration Screen (HPAS)

When the moisture content is too high in the material i.e.45% and there’s a need of separating fine material which can size below 6mm. As the need is of fine material and moisture content is high, it makes the whole feed sticky and adhesive to the screen, which can cause jamming of screen and will eventually reduce its efficiency.

So for screening of such feed very high speed is required to overcome the inertia of adherent grains and screen them. All this needs are satisfied by H.P.A system.

The H.P.A screening machine consists of an inner and an outer screen case. The screen case consists of two side walls each interconnected by cross beams. The screen panels which form the screen deck are mounted on the cross beam alternatingly. Both the screen case are interconnected by the guide springs. The inner case is mounted via rubber material springs on the support structure.

12 | P a g e

The outer screen case is driven by a crank shaft drive, which provides linear motion to the system. The shaft is of eccentric type which also creates the required force to create the required motion in the screens. The shaft rotates near to rpm and is selected according to the capacity and screening material concerned.

As the outer screen is driven by crank shaft it create a motion of case in such a way that they always moves in opposite direction to each other. As the screen mat is mounted on the casing beams. As the cross beams of both systems also carry out this motion and thus alternately tension and detention the mounted screen panels

This alternating tensioning and de-tensioning result in the trampoline-like motion of the screen panels installed transverse to the screening machine. The resilience and elasticity of these highly wear-resistant screen panels are fully utilized by application of the Flip-Flow principle for the screening process.

At low machine speeds of 500 to 60o rpm, the machine itself is subjected to only 3 to 4 G force. Due to dual drive system, the screen panel transmit, however a considerably higher acceleration. Depending on the pre-tensioning of the screen mats, this acceleration transmitted to the screening material can amount up to 50 G force and more. Pre Tensioning is adjustable within certain ranges.

High acceleration causes a through loosening and fast separation of the screening material. At the same time, a large amount of fines reaches the mesh opening, as compared with conventional screening machine. The result is a high specific passage capacity. The trampoline effect reduces the portion of adherent particles

Adhesion is prevented by the constant flexing action of the elastic screen panels. Elongation of the screen panels causes slight changes of the mesh opening in tensioning direction. This may be described as Breathing of the mesh openings, which is conjunction with the high acceleration forces, prevents blinding of the opening by near to mesh size particle.

13 | P a g e

Roller Screen

Such screen is made to filter material like Coal, slag, Gyps and coke at the size of (-) 50mm

Roller screens are generally described as screening machines where the screen surface consist of a number of screen rolls, which are driven in the same sense of rotation. For separating certain grain classes, the screen rolls are provided at corresponding distance with triangular disk and these disk are arranged staggered with respect to the disk of the next roll, forming square or rectangular screen opening together with them.

The material is separated in such a way that the smaller grains falls through the opening between the desk and adherent product is stripped of by adjustable scraper, which are mounted just below the screen rolls. The coarser product are transported by the triangular disk to the outlet of the roller screen and led to the post arranged machine.

Disc roll shafts are driven by a pair of bevel gear from longitudinal shaft. The longitudinal shafts are provided on either side of the screen and are driven by separate motors through fluid coupling, reducer and geared coupling. The longitudinal shafts are supported on roller bearings.

Banana Screen

When the required capacity of material separation is more and it is also needed to be washed at that time Banana Screen are used. It is mostly used for iron ores. Its capacity is around 400TPH and it vibrates with the amplitude of 4.5mm.This system vibrates linearly, which is created by an out of balance drive. The out of balance drive consists of one or more double out of balance drives with adjustable flyweight. The drives are usually mounted on a drive bridge above the screen frame. The screen frame is situated on a parallel springs in such a manner as to allow it to vibrate freely. The deck of banana screen is in curvature form just like banana which provided the material to stay more on the deck and give max opportunity for smaller size particle to take through aperture.

Decks are divided between 3 decks generally, but 1st two decks have high value of acceleration and subsequently sharp screening of finer size and by third deck the near size are separated.

14 | P a g e

4. CRUSHERS

Rotary Breaker

When products is initially extracted from there ores or mine. They are generally in large size of lumps which need to be break down into smaller size according to the further machine process requirement. So at this stage most of the time rotary breakers are used. Normally the feed size in the system is 300 mm and is converted into 100 mm size.

The capacity of this machine is normally between 1000 to 1200 TPH

Rotary breaker is designed to handle R.O.M coal. It employs a slowly revolving cylindrical body on turnnions, rotated by means of chain drive located at each end of the breaker synchronised to give even torque and smooth operation. The rotary breaker has a screen for the passage of coal and a discharge chute for refuse. Lifters on the inside raise the coal and let it fall to the bottom, using gravity as the breaking force. The undersize coal is immediately screened out and this minimizes the production of fines. The coarse refuse and tramp iron pass out through the reject chute

Ring Granulator

When the material is needed to break down from its ore directly to smaller size, than a sever and a tough operation is required to achieve this. This system can break down material ranging from (-) 250 mm to the size of (-) 20 mm.

It consists of multiple rows of ring hammers which crush material by a combination of impact and rolling compression. The ring hammers are suspended from suspension bars. The bars run the width of the crusher. The granulator has an adjustable cage equipped with breaker plates and perforated screen plates. The sizes of the perforation in the screen plates have been designed for the specific application. Product size is determined by the size of the perforation and to some extent by the amount of clearance between the cage and the path of the ring hammers.

A provision of tramp iron trap door is provided to remove tramp iron and other non-crushable material from the crushing zone.

15 | P a g e

The rear frame of top side is detachable and can be taken away from the main frame. This exposes the inside of the crusher for inspection and maintenance.

The main components of Ring Granulator are as follows:

1. Main frame

2. Rear frame

3. Cover frame

4. Rotor assembly

5. Cage assembly

6. Cage hinge shaft

7. Breaker plates

8. Screen plates

9. Screen plate clamp bar

10.Worm gear jack assembly

11.Kick off plates

12.Tramp iron deflector

13.Tramp iron tray

14.Set of liners

One Way Hammer Mills

The whole construction of hammer mill is same to the Ring Granulator. The only difference is that the liner placed inside the system. In the RG, slotted plates are place in the place of liner.

But in one way hammer mill, the breaker plates are placed in the place of liners. And rest all the construction is mostly similar

Toothed Double Roll Crusher

When the force required to crush the material is more and output is also needed in fine size that is at (-) 40 mm. this system consist of two toothed roller placed parallel two each other and rotating toward the centre of them. The crushing operation is done when the material passes through gap provided between the rollers.

On every toothed row there’s a tooth missing on each row but at different angle. It is provided so that the bigger lump getting into the feed which are larger than the gap between the rollers can be gripped into the crusher and can be converted into the required product.

The crusher is mounted on a rigid welded structural steel base. Both rolls are driven independently by electric motor through V-belts and gear box.

16 | P a g e

Protection against damage due to tramp metal in the feed has been provided by the use of plate spring which back up the sliding bearing of one of the rolls. This spring will compress and any hard material, which will not crush, will pass through the crusher.

This spring back action of one of the roller avoids the toothed rollers to get damaged.

Single Roller Crusher

Single roller crusher is used in place where the foundation place is not available and capacity of material handling is less. Just like the crushing effect created in TDRC, here also same effect is created but here only one impact roll crusher is used and material is fed in the gap created between the toothed roller and the breaker wall.

This break wall is supported by spring which helps in protection of toothed roller when some unbreakable gets in. At that time, the breaker walls will back off and create enough space for the unbreakable material to pass on.

Reversible hammer mill

When the materials fed into the crusher is too hard, hammer mills can be used to break such material with the help of impact force on the material. It is mostly used for iron ore crushing. The feed size can range from (-) 110 mm to (+) 10 mm and the product size is below (-) 10 mm.

The crusher assembly consist of number of hammers placed in row. This hammer impact with the breaker plate so that the material placed in between the hammer and plates are crushed into the required size. The crusher is reversible; it may be operated in either clockwise or counter-clockwise rotation. If the crusher is made to rotate reversible at regular interval will help in increase the life of hammers.

Both breaker blocks assemblies are adjustable, which allows adjustment towards or away from the hammer circle to compensate for wear and to achieve desired product size. This adjustment is accomplished either adjusting its fulcrum or gap/ distance of its lower most point with the hammer circle.

17 | P a g e

OHE Jaw Crusher

When the capacity of system is required to be high and the size reduction ratio is between 5:1 than a system can use a Jaw crusher. In this system there are two heads one is fixed and other one is vibrating head. The vibrating head is fixed at some angle which creates a huge space near opening at the beginning and become smaller as we move towards the discharge ends.

The vibrating head is attached to an eccentric shaft which when rotates helps the head to vibrate in a linear motion. This linear motion cause opening and closing of the discharge end. These also cause the materials to impact with the head and get crushed due to that effect.

As the mechanism of this machine is same as compared to the chewing action of JAW of animals and humans. It is known as JAW Crusher.

To increase discharge opening:

1. Loosen the hex. Head lock nuts of the tension rods to return the tension springs to their free length position.

2. Start the hydraulic power pack.3. Operate the hand lever to shift the spool position of direction control

valve so that the piston rod extends out.4. Release the lever once a Gap is created between toggle seat and the

shims.5. Remove shims of desired thickness.6. Reverse the hand lever of direction control valve so that the piston rod

retracts leaving no gap between the toggle seat and the shim. Keep a watch on the Pressure gauge reading.

7. Reset the spring compressions. Run the crusher and check for a clattering noise between the toggle and toggle seats. If this noise is present, continue to tighten tension rods until this noise is eliminated. Do not over tighten the tension rods; this may cause tension rod breakage.

18 | P a g e

Dual Chain Mill

These types of mills are used to crush soft material. It takes feed below 75 mm and gives out the product below 6 mm. It is designed for bearing the capacity of 75 TPH. It consists of total 36 hammers in each rotor which rotates at the rpm of 1000 rpm.

A chain curtain is provided in between the feed so that the material which tends to fly out will get restricted by chain curtains and will be fed back to the crusher. The rotors are operated in clockwise and counter-clockwise direction toward the centre of the machine.

The hammers are suspended in the rotors by the means of chain attached to them.

Swing Hammer Reversible Impactor (SHRI)

When the materials fed into the crusher is too hard and output required size is very small that is (-) 25 mm to (+) 4 mm, at such places Swing Hammer Reversible mills can be used to break such material with the help of impact force on the material.

The crusher assembly of SHRI is mostly similar to reversible hammer mill; the only difference in the construction of mill is that the rotor of hammer diameter created here by the hammer head is small as compared to container height.

The crusher assembly consist of number of hammers placed in row. This hammer impact with the breaker plate so that the material placed in between the hammer and plates are crushed into the required size. The crusher is reversible; it may be operated in either clockwise or counter-clockwise rotation. If the crusher is made to rotate reversible at regular interval will help in increase the life of hammers.

Both breaker blocks assemblies are adjustable, which allows adjustment towards or away from the hammer circle to compensate for wear and to achieve desired product size. This adjustment is accomplished either adjusting its fulcrum or gap/ distance of its lower most point with the hammer circle.

19 | P a g e

Impact Crusher

All the parameter of feed and output of impact crusher are similar to SHRI. Here only difference is in the construction of rotor.

Instead of placing number of hammer head with each connecting rod in the rotor. A hammer installation disc is provided at an equal space with spacer in between and hammer for single bar shape is placed in the hammer disc. This helps in reducing the number of parts for maintenance purpose.

20 | P a g e

5. MILLS

Rod Mill

Rod mills are used when the required product should be less than 4mm and the feed material of rod mill should be (-50mm to +0.8mm). Its length can range from 1.4 to 1.6 meters. It consists of a cylindrical vessel which contains rods of various diameters. The rolling action of drum cause the rod to rise little higher and fall on to the material which is grounded in the shell, this cause the material to break into smaller size. The material is fed from the feed sleeve, it consist of spiral shape guide which guides the material into the shell and then the material is guide to discharge head automatically because of the material slope created in the drum towards the feed end.

The product size reduction ratio of the rod mill can range from 1:15 to 1:20 and Rods used in rod mills normally range from 65mm to 125mm.

The assembly of rod mill consist of shell, feed and discharge head, bearing pedestals, Hi-Lift Pump, turnnions and discharge hood assembly. The shell is connected to feed head and discharge head with the help of the flange. The flange also helps to connect the Driven gear on the discharge side. There are slots provided in the gear ring to form an assembly with the flange. The whole gear is divided into two parts and slots are provided at the end to connect both the gears. the gears are of helical types having a helix angle of 6º. The shell is driven by the pinions mounted at the side which is driven by the Main reducer gearbox having a ratio of 6.3:1. This is connected to motor through Coupling. The whole shell rotates at the rpm of 14 to 16, keeping in mind the critical speed of the drum. The shell diameter and length is obtained by the ratio of 1.6 times of diameter for rod mills. If the shell is much larger than it is divided into compartments but such shells are only used in ball mills.

This system is also provided with an auxiliary drive. This is only used for maintenance purpose only. This drive consist of a motor having a rating of 30KW/ 1500 rpm which is connected to auxiliary reducer, it have the ratio of 112:1 and this is connected to main reducer gearbox and to the pinion.

This auxiliary drive provides the shell to be controlled with very slow rpm. This is used to place the manhole in shell according to the accessibility and to rotate the shell at very slow rpm to replace shell liner by the person inside the shell.

21 | P a g e

The manholes have enough opening size that the liners can be transferred through them easily for the replacement.

The shell liners are made from Mn steel IS.276, GR-1 and are bolted to the shell. The bolts end are faced outward from the shell and the heads are faced inside.

Before starting the main drive motor, the Hi-Lift Pump are turned on so that enough lubrication oil is pump inside the bearing under pressure. This creates a positive lubrication by lifting the turnnions of shell by little space and allows avoiding contact with the bearing surface. This increases the life of turnnions and avoids frequent maintenance of it.

Ball Mill

The construction and working of ball mill is same as compared to rod mill, still are some difference in the product obtained by this operation. The milling operation is done with the help of metal balls in this process and the product size reduction can range from 20:1 to 600:1.

Ball mills are used when the size of the product is required in micrometre. Shells can be divided into compartment in such mills. For step by step processing of material grain size, at the end discharge sleeve is provide with the reverse spiral construction so that the balls of mill doesn’t flow out with material.

22 | P a g e

6. WASHING EQUIPMENTS

Rotary Drum Scrubber

Sometime the ores extracted from the mines are needed to be washed and the washing process should be of continues flow. For such application rotary drum scrubber is perfect equipment to wash the ores in a continuous flow. The feed size in the drum should be limited to (-) 40 mm.

The shell is lined and contains number of lifters to produce the necessary washing action and to discharge the washed material through discharge end assembly.

The scrubber is fitted with a plain tyre near the feed end and a thrust tyre near the discharge end. These tyres revolve on carrying rollers. Pair of carrying rollers, completely assembled with shafts and pillow blocks, are mounted on a base frame. The base frame is fabricated from structural steel and has machined bearing pads for mounting base blocks on which pillow blocks sit.

The scrubber drive arrangement consists of a split gear mounted on the scrubber shell. The driving pinion is directly mounted on output shaft of the reducer while the input shaft of reducer is connected to the drive motor by means of a gear coupling.

23 | P a g e