Tirthankar Bhataacharjee

1021210374

Mechanical -E

SRM UniversityIndustrial Training

Mining

Index

1) Introduction2) About KFJ Steel JOST Group3) Acknowledgement4) Mining5) Surface6) Underground7) Machines8) Processing9) Mining Industry10) Safety11) Mining Industry of South Africa12) Mechanical Screening13) Feeders and Belts

Introduction

KFJ STEEL (PTY) LTD has the expertise and facilities to manufacture a comprehensive spectrum of machinery, vessels, tanks, fans, screens and kilns. We have been in operation since 1984. Our quality assurance: All our work is done in Accordance with ISO – 9002. Quality Manuals and Procedure Manuals may be viewed in our Quality Department.

About KFJ Steel JOST Group

Significant Customers:

Babcock Fabrication Humbolt Wedag

Custom Furnaces CMS Procurement Services

Metso Minerals FL Smidth

Krupp Polysius Air Blow Fans

 

Examples of Contracts for Customers:

● Furnace Plants for Ukor and other Heat Treatment Companies.

● Fan Housing up to 10m Diameter for the Mining Industry.

● Scissor Lifts for Material Handling.

● Various Conveyors in Mild and Stainless Steel for the Coal Industry.

● Chute Work with Liner Plate.

● Accessories for Crusher Plants.

● Stacker Re-claimers.

● Pelletiser Plants.

 

Staff:

Office: Workshop:

Managing Director 1 Foreman 1 Grinders 5

Directors 3 Foreman Assistant 1 Painter 1

Accounts/Administrator 1 Quality Inspectors 2 Operators 11

Receptionist 1 Storeman 1 Labourers 13

Draughtsman 1 Boilermakers 8 Dispatch Clerk 1

Tea Ladies 2 Assistant Boilermakers 8 Drivers 3

    Welders 5    

 

Acknowledgement

It is a pleasure to remind the people in the Brian Elgar KFJ STEEL JOST Group, for the sincere guidance we received to uphold our practical as well as theoretical skills in our field of study in engineering.

Mining 

Mining is the extraction of valuable minerals or other geological materials from the earth from an orebody, lode, vein, seam, or reef, which forms the mineralized package of economic interest to the miner.

Ores recovered by mining include metals, coal, oil shale, gemstones, limestone, dimension stone, rock salt, potash, gravel, and clay. Mining is required to obtain any material that cannot be grown through agricultural processes, or created artificially in a laboratory orfactory. Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or even water.

Mining of stone and metal has been done since pre-historic times. Modern mining processes involve prospecting for ore bodies, analysis of the profit potential of a proposed mine, extraction of the desired materials, and final reclamation of the land after the mine is closed.

The nature of mining processes creates a potential negative impact on the environment both during the mining operations and for years after the mine is closed. This impact has led most of the world's nations to adopt regulations designed to moderate the negative effects of mining operations. Safety has long been a concern as well, and modern practices have improved safety in mines significantly.

Mining techniques

It can be divided into two common excavation types: surface mining and sub-surface (underground) mining. Today, surface mining is much more common, and produces, for example, 85% of minerals (excluding petroleum and natural gas) in the United States, including 98% of metallic ores.

Targets are divided into two general categories of materials: placer deposits, consisting of valuable minerals contained within river gravels, beach sands, and other unconsolidated materials; and lode deposits, where valuable minerals are found in veins, in layers, or in mineral grains generally distributed throughout a mass of actual rock. Both types of ore deposit, placer or lode, are mined by both surface and underground methods.

Some mining, including much of the rare earth elements and uranium mining, is done by less-common methods, such as in-situ leaching: this technique involves digging neither at the surface nor underground. The extraction of target minerals by this technique requires that they be soluble, e.g., potash, potassium chloride, sodium chloride, sodium sulfate, which dissolve in water. Some minerals, such as copper minerals and uranium oxide, require acid or carbonate solutions to dissolve.

Surface mining

Surface mining is done by removing (stripping) surface vegetation, dirt, and, if necessary, layers of bedrock in order to reach buried ore deposits. Techniques of surface mining include: open-pit mining, which is the recovery of materials from an open pit in the ground, quarrying or gathering building materials from an open-pit mine[clarification needed]; strip mining, which consists of stripping surface layers off to reveal ore/seams underneath; and mountaintop removal, commonly associated with coal mining, which involves taking the top of a mountain off to reach ore deposits at depth. Most (but not all) placer deposits, because of their shallowly buried nature, are mined by surface methods. Finally, landfill mining involves sites where landfills are excavated and processed.

Underground mining

Sub-surface mining consists of digging tunnels or shafts into the earth to reach buried ore deposits. Ore, for processing, and waste rock, for disposal, are brought to the surface through the tunnels and shafts. Sub-surface mining can be classified by the type of access shafts used, the extraction method or the technique used to reach the mineral deposit. Drift mining utilizes horizontal access tunnels, slope mininguses diagonally sloping access shafts, and shaft mining utilizes vertical access shafts. Mining in hard and soft rock formations require different techniques.

Other methods include shrinkage stope mining, which is mining upward, creating a sloping underground room, long wall mining, which is grinding a long ore surface underground, and room and pillar mining, which is removing ore from rooms while leaving pillars in place to support the roof of the room. Room and pillar mining often leads to retreat mining, in which supporting pillars are removed as miners retreat, allowing the room to cave in, thereby loosening more ore. Additional sub-surface mining methods include hard rock mining, which is mining of hard materials, bore hole mining, drift and fill mining, long hole slope mining, sub level caving, and block caving.

Machines

Heavy machinery is used in mining to explore and develop sites, to remove and stockpile overburden, to break and remove rocks of various hardness and toughness, to process the ore, and to carry out reclamation projects after the mine is closed. Bulldozers, drills, explosives and trucks are all necessary for excavating the land. In the case of placer mining, unconsolidated gravel, or alluvium, is fed into machinery consisting of a hopper and a shaking screen or trommel which frees the desired minerals from the waste gravel. The minerals are then concentrated using sluices or jigs.

Large drills are used to sink shafts, excavate stopes, and obtain samples for analysis. Trams are used to transport miners, minerals and waste. Lifts carry miners into and

out of mines, and move rock and ore out, and machinery in and out, of underground mines. Huge trucks, shovels and cranes are employed in surface mining to move large quantities of overburden and ore. Processing plants utilize large crushers, mills, reactors, roasters and other equipment to consolidate the mineral-rich material and extract the desired compounds and metals from the ore.

Processing

Once the mineral is extracted, it is often then processed. The science of extractive metallurgy is a specialized area in the science of metallurgy that studies the extraction of valuable metals from their ores, especially through chemical or mechanical means.

Mineral processing (or mineral dressing) is a specialized area in the science of metallurgy that studies the mechanical means of crushing, grinding, and washing that enable the separation (extractive metallurgy) of valuable metals or minerals from their gangue (waste material). Processing of placer ore material consists of gravity-dependent methods of separation, such as sluice boxes. Only minor shaking or washing may be necessary to disaggregate (unclump) the sands or gravels before processing. Processing of ore from a lode mine, whether it is a surface or subsurface mine, requires that the rock ore be crushed and pulverized before extraction of the valuable minerals begins. After lode ore is crushed, recovery of the valuable minerals is done by one, or a combination of several, mechanical and chemical techniques.

Since most metals are present in ores as oxides or sulfides, the metal needs to be reduced to its metallic form. This can be accomplished through chemical means such assmelting or through electrolytic reduction, as in the case of aluminium. Geometallurgy combines the geologic sciences with extractive metallurgy and mining.

Mining industry

Mining exists in many countries. London is known as the capital of global "mining houses" such as Rio Tinto Group, BHP Billiton, and Anglo American PLC. The US mining industry is also large, but it is dominated by the coal and other nonmetal minerals (e.g., rock and sand), and various regulations have worked to reduce the significance of mining in the United States.In 2007 the total market capitalization of mining companies was reported at US$962 billion, which compares to a total global market cap of publicly traded companies of about US$50 trillion in 2007. In 2002, Chile and Peru were reportedly the major mining countries of South America.[41] The mineral industry of Africa includes the mining of various minerals; it produces relatively little of the industrial metals copper, lead, and zinc, but according to one estimate has as a percent of world reserves 40% of gold, 60% of cobalt, and 90% of the world's platinum group metals.Mining in India is a significant part of that country's economy. In the developed world, mining in Australia, with BHP Billiton founded and headquartered in the country, and mining in Canada are particularly significant. For rare earth minerals mining, China reportedly controlled 95% of production in 2013.

The Bingham Canyon Mine of Rio Tinto's subsidiary, Kennecott Utah Copper.

While exploration and mining can be conducted by individual entrepreneurs or small businesses, most modern-day mines are large enterprises requiring large amounts of capital to establish. Consequently, the mining sector of the industry is dominated by large, often multinational, companies, most of them publicly listed. It can be argued that what is referred to as the 'mining industry' is actually two sectors, one specializing in exploration for new resources and the other in mining those resources. The exploration sector is typically made up of individuals and small mineral resource companies, called "juniors", which are dependent on venture capital. The mining sector is made up of large multinational companies that are sustained by production from their mining operations. Various other industries such as equipment manufacture, environmental testing, and metallurgy analysis rely on, and support, the mining industry throughout the world. Canadian stock exchanges have a particular focus on mining companies, particularly junior exploration companies through Toronto'sTSX Venture Exchange; Canadian companies raise capital on these exchanges and then invest the money in exploration globally.] Some have argued that below juniors there exists a substantial sector of illegitimate companies primarily focused on manipulating stock prices.

Mining operations can be grouped into five major categories in terms of their respective resources. These are oil and gas extraction, coal mining, metal ore mining, nonmetallic mineral mining and quarrying, and mining support activities.Of all of these categories, oil and gas extraction remains one of the largest in terms of its global economic importance. Prospecting potential mining sites, a vital area of concern for the mining industry, is now done using sophisticated new technologies such as seismic prospecting and remote-sensing satellites. Mining is heavily affected by the prices of the commodity minerals, which are often volatile. The 2000s commodities boom ("commodities supercycle") increased the prices of commodities, driving aggressive mining. In addition, the price of gold increased dramatically in the 2000s, which increased gold mining; for example, one study found that conversion of forest in the Amazon increased six-fold from the period 2003–2006 (292 ha/yr) to the period 2006–2009 (1,915 ha/yr), largely due to artisanal mining.

Safety

Safety has long been a concern in the mining business especially in sub-surface mining. The Courrières mine disaster, Europe's worstmining accident, involved the death of 1,099 miners in Northern France on March 10, 1906. This disaster was surpassed only by theBenxihu Colliery accident in China on April 26, 1942, which killed 1,549 miners While mining today is substantially safer than it was in previous decades, mining accidents still occur. Government figures indicate that 5,000 Chinese miners die in accidents each year, while other reports have suggested a figure as high as 20,000. Mining accidents continue worldwide, including accidents causing dozens of fatalities at a time such as the 2007 Ulyanovskaya Mine disaster in Russia, the 2009 Heilongjiang mine explosion in China, and the 2010Upper Big Branch Mine disaster in the United States.

Mining ventilation is a significant safety concern for many miners. Poor ventilation inside sub-surface mines causes exposure to harmful gases, heat, and dust, which can cause illness, injury, and death. The concentration of methane and other airborne contaminants underground can generally be controlled by dilution (ventilation), capture before entering the host air stream (methane drainage), or isolation (seals and stoppings Rock dusts, including coal dust and silicon dust, can cause long-term lung problems including silicosis,asbestosis, and pneumoconiosis (also known as miners lung or black lung disease). A ventilation system is set up to force a stream of air through the working areas of the mine. The air circulation necessary for effective ventilation of a mine is generated by one or more large mine fans, usually located above ground. Air flows in one direction only, making circuits through the mine such that each main work area constantly receives a supply of fresh air. Watering down in coal mines also helps to keep dust levels down: by spraying the machine with water and filtering the dust-laden water with a scrubber fan, miners can successfully trap the dust.

Gases in mines can poison the workers or displace the oxygen in the mine, causing asphyxiation.For this reason, the U.S. Mine Safety and Health Administration requires that groups of miners in the United States carry gas detection equipment that can detect common gases, such as CO, O2, H2S, CH4, as well as calculate % Lower Explosive Limit. Regulation requires that all production stop if there is a concentration of 1.4% of flammable gas present. Additionally, further regulation is being requested for more gas detection as newer technology such as nanotechnology is introduced.

Ignited methane gas is a common source of explosions in coal mines, which in turn can initiate more extensive coal dust explosions. For this reason, rock dusts such as limestone dust are spread throughout coal mines to diminish the chances of coal dust explosions as well as to limit the extent of potential explosions, in a process known as rock dusting. Coal dust explosions can also begin independently of methane gas explosions. Frictional heat and sparks generated by mining equipment can ignite both methane gas and coal dust. For this reason, water is often used to cool rock-cutting sites.

Miners utilize equipment strong enough to break through extremely hard layers of the Earth's crust. This equipment, combined with the closed work space in which underground miners work, can cause hearing loss. For example, a roof bolter (commonly used by mine roof bolter operators) can reach sound power levels of up to 115 dB.Combined with the reverberant effects of underground mines, a miner without proper hearing protection is at a high risk for hearing loss.] By age 50, nearly 90% of U.S. coal miners have some hearing loss, compared to only 10% among workers not exposed to loud noises. Roof bolters are among the loudest machines, but auger miners, bulldozers, continuous mining machines, front end loaders, and shuttle cars and trucks are also among those machines most responsible for excessive noise in mine work.

Since mining entails removing dirt and rock from its natural location, thereby creating large empty pits, rooms, and tunnels, cave-ins as well as ground and rock falls are a major concern within mines. Modern techniques for timbering and bracing walls and ceilings within sub-surface mines have reduced the number of fatalities due to cave-ins, but ground falls continue to represent up to 50% of mining fatalities.Even in cases where mine collapses are not instantly fatal, they can trap mine workers deep underground. Cases such as these often lead to high-profile rescue efforts, such as when 33 Chilean miners were trapped deep underground for 69 days in 2010.

High temperatures and humidity may result in heat-related illnesses, including heat stroke, which can be fatal. The presence of heavy equipment in confined spaces also poses a risk to miners. To improve the safety of mine workers, modern mines use automation and remote operation including, for example, such equipment as automated loaders and remotely operated rockbreakers. However, despite modern improvements to safety practices, mining remains a dangerous occupation throughout the world.

What are the minerals and metals used for?

Minerals and metals are very valuable commodities.  For example, manganese is a key component of low-cost stainless steel.  It is also used to de-color glass (removing greenish hues), but in higher concentrations, it actually makes lavender-colored glass.  Tantalum is used in cell phones, pagers, and lap-tops.  Cooper and tin are used to make pipes, cookware, etc.  And gold, silver, and diamonds are used to make jewelry. 

Large scale mining versus small scale mining:

Large scale mining usually involves a company with many employees.  The company mines at one or two large sites and usually stays until the mineral or metal is completely excavated.  An example of a large scale mine is the Serra Pelada mine in Brazil which yielded 29,000 tons of gold from 1980 to 1986 and employed 50,000 workers (Kricher, 1997).

Small scale mining usually involves a small group of nomadic men.  They travel together and look for sites which they think will yield gold or another valuable metal or mineral.  Small scale mining occurs in places such as Suriname, Guyana, Central Africa, and many other places around the world.  Some researchers believe that small scale mining is more harmful to the environment and causes more social problems than large scale mining.  This will become apparent later in the lesson. 

Mining Industry

The mining industry is involved with extracting coal, minerals, and precious metals from the earth. Before a mine is created, explorers may try to determine how much of a particular item is located in the area, which is known as prospecting. They may then determine whether to extract material from the surface, underground, or abandon their efforts because it may be unprofitable to continue. Developers can then plan how to create the mine and oversee workers at the facility when it is completed.Prospectors often visit locations where valuable minerals are thought to be located. They do this in order to make an assessment as to how much of an item the area contains. People who work in this segment of the mining industry may use special equipment to extract a sample from the ground. In some instances, this effort is conducted by hand using a shovel or pick.

Other members of the mining industry take information from prospectors and analyze the data. That way, they can determine if it would be a profitable venture to create a new mine. They can also try to decide the best mining method, as well as estimate how much the material might be worth once it is extracted.

Mining industry of South Africa

Premier Diamond Mine, Cullinan, Gauteng, South Africa

Mining in South Africa has been the main driving force behind the history and development of Africa's most advanced and richest economy. Large scale and profitable mining started with the discovery of a diamond on the banks of the Orange River in 1867 by Erasmus Jacobs and the subsequent discovery and exploitation of the Kimberley pipes a few years later. Gold rushes to Pilgrim's Restand Barberton were precursors to the biggest discovery of all, the Main Reef/Main Reef Leader on Gerhardus Oosthuizen's farm Langlaagte, Portion C, in 1886, the Witwatersrand Gold Rush and the subsequent rapid development of the gold field there, the biggest of them all.

Diamond and gold production may now be well down from their peaks, though South Africa is still no. 5 in gold[1] but South Africa remains a cornucopia of mineral riches. It is the world's largest producer[2] of chrome, manganese, platinum, vanadium andvermiculite. It is the second largest producer[3] of ilmenite, palladium, rutile and zirconium. It is also the world's third largest coal exporter.[4] South Africa is also a huge producer of iron ore; in 2012, it overtook India to become the world third biggest iron ore supplier to China, who are the world’s largest consumers of iron ore.[5]

Due to a history of corruption and maladministration in the South African mining sector, ANC secretary-general Gwede Mantasheannounced at the beginning of 2013 that mining companies misrepresenting their intentions could have their licences revoked.[6]

Coal

South Africa Coal production (red) and exports (black)

South Africa is the world's third largest coal exporter, and much of the country's coal is used for power production. (about ~40%)[4]

Gold

South Africa mined gold production, 1940-2011

South Africa accounted for 15% of the world's gold production in 2002[10] and 12% in 2005, though the nation had produced as much as 30% of world output as recently as 1993. Despite declining production, South Africa's gold exports were valued at $3.8 billion USD in 2005.[11] Almost 50% of the world's gold reserves are found in South Africa.[10]

Among the nation's gold mines are two of the deepest mines in the world. The East Rand Mine, in Boksburg, extends to a depth of 3,585 metres (11,762 ft). A 4-metre (13 ft) shallower mine is located at TauTona in Carletonville, though plans are in place to begin work on an extension to the TauTona mine, bringing the total depth to over 3,900 metres (12,800 ft) and breaking the current record by 127 feet (39 m).[12] At these depths the temperature of the rocks are 140 °F (60 °C).[13]

The gold in the Witwatersrand Basin area was deposited in ancient river deltas, having been washed down from surrounding gold-richgreenstone belts to the north and west. Rhenium-osmium isotope studies indicates that the gold in those mineral deposits came from unusual three billion year old mantle sourced intrusions known as komatiites present in the greenstone belts.[14] The Vredefort Domeimpact which lies within the basin and the nearby Bushveld Igneous Complex are both about a billion years younger than the interpreted age of the gold.[14]

Diamonds

Ever since the Kimberley diamond strike of 1868, South Africa has been a world leader in diamond production. The primary South African sources of diamonds, including seven large diamond mines around the country, are controlled by the De Beers Consolidated Mines Company. In 2003, De Beers operations accounted for 94% of the nation's total diamond output of 11,900,000 carats (2.38 t). This figure includes both gem stones and industrial diamonds.[15] Diamond production rose in 2005 to over 15,800,000 carats (3.16 t).[11]

Platinum and palladiumSouth Africa produces more platinum and similar metals than any other nation.[9] In 2005, 78% of the world's platinum was produced in South Africa, along with 39% of the world'spalladium. Over 163,000 kilograms (5,200,000 ozt) of platinum was produced in 2010, generating export revenues of $3.82 billion USD.[11]

Chromium

Chromium is another leading product of South Africa's mining industry. The metal, used in stainless steel and for a variety of industrial applications, is mined at 10 sites around the country. South Africa's production of chromium accounted for 100% of the world's total production in 2005, and consisted of 7,490,000 metric tons (7,370,000 long tons; 8,260,000 short tons) of material.[11]

Mechanical screeningMechanical screening, often just called screening, is the practice of taking granulated ore material and separating it into multiple grades by particle size.

This practice occurs in a variety of industries such as mining and mineral processing, agriculture, pharmaceutical, food, plastics, and recycling.

General categoriesScreening fall under two general categories: dry screening and wet screening. From these categories, screening separates a flow of material into grades, these grades are then either further processed to an intermediary product or a finished product. Additionally the machines can be categorised into moving screen and static screen machines, as well as by whether the screens are horizontal or inclined.

ApplicationsThe mining and mineral processing industry uses screening for a variety of processing applications. For example, after mining the minerals, the material is transported to a primary crusher. Before crushing large boulder are scalped on a shaker with 0.25 in (6.4 mm) thick shielding screening. Further down stream after crushing the material can pass through screens with openings or slots that continue to become smaller. Finally, screening is used to make a final separation to produce saleable products based on a grade or a size range.

Process

Model of Screening Process

A screening machine consist of a drive that induces vibration, a screen media that causes particle separation, and a deck which holds the screen media and the drive and is the mode of transport for the vibration.

There are physical factors that makes screening practical. For example, vibration, g force, bed density, and material shape all facilitate the rate or cut. Electrostatic forces can also hinder screening efficiency in way of water attraction causing sticking or plugging, or very dry material generate a charge that causes it to attract to the screen itself.

As with any industrial process there is a group of terms that identify and define what screening is. Terms like blinding, contamination, frequency, amplitude, and others describe the basic characteristics of screening, and those characteristics in turn shape the overall method of dry or wet screening.

In addition, the way a deck is vibrated differentiates screens. Different types of motion have their advantages and disadvantages. In addition media types also have their different properties that lead to advantages and disadvantages.

Finally, there are issues and problems associated with screening. Screen tearing, contamination, blinding, and dampening all affect screening efficiency.

Physical principles

Vibration - either sinusoidal vibration or gyratory vibration.

Sinusoidal Vibration occurs at an angled plane relative to the horizontal. The vibration is in a wave pattern determined by frequency and amplitude.

Gyratory Vibration occurs at near level plane at low angles in a reciprocating side to side motion.

Gravity - This physical interaction is after material is thrown from the screen causing it to fall to a lower level. Gravity also pulls the particles through the screen media.

Density - The density of the material relates to material stratification. Electrostatic Force - This force applies to screening when particles are extremely dry or is

wet.

Screening terminology

Like any mechanical and physical entity there are scientific, industrial, and layman terminology. The following is a partial list of terms that are associated with mechanical screening.

Amplitude - This is a measurement of the screen cloth as it vertically peaks to its tallest height and troughs to its lowest point. Measured in multiples of the acceleration constant g (g-force).

Acceleration - Applied Acceleration to the screen mesh in order to overcome the van der waal forces

Blinding - When material plugs into the open slots of the screen cloth and inhibits overflowing material from falling through.[1]

Brushing - This procedure is performed by an operator who uses a brush to brush over the screen cloth to dislodged blinded opening.

Contamination - This is unwanted material in a given grade. This occurs when there is oversize or fine size material relative to the cut or grade. Another type of contamination is foreign body contamination. Oversize contamination occurs when there is a hole in the screen such that the hole is

larger than the mesh size of the screen. Other instances where oversize occurs is material overflow falling into the grade from overhead, or there is the wrong mesh size screen in place.

Fines contamination is when large sections of the screen cloth is blinded over, and material flowing over the screen does not fall through. The fines are then retained in the grade.

Foreign body contamination is unwanted material that differs from the virgin material going over and through the screen. It can be anything ranging from tree twigs, grass, metal slag to other mineral types and composition. This contamination occurs when there is a hole in the scalping screen or a foreign material's mineralogy or chemical composition differs from the virgin material.

Deck - a deck is frame or apparatus that holds the screen cloth in place. It also contains the screening drive. It can contain multiple sections as the material travels from the feed end to the discharge end. Multiple decks are screen decks placed in a configuration where there are a series of decks attached vertically and lean at the same angle as it preceding and exceeding decks. Multiple decks are often referred to as single deck, double deck, triple deck, etc.

Frequency - Measured in hertz (Hz) or revolutions per minute (RPM). Frequency is the number of times the screen cloth sinusoidally peaks and troughs within a second. As for a gyratory screening motion it is the number of revolutions the screens or screen deck takes in a time interval, such as revolution per minute (RPM).

Gradation, grading - Also called "cut" or "cutting." Given a feed material in an initial state, the material can be defined to a have a particle size distribution. Grading is removing the maximum size material and minimum size material by way of mesh selection.[2]

Screen Media (Screen cloth) - it is the material defined by mesh size, which can be made of any type of material such steel, stainless steel, rubber compounds, polyurethane, brass, etc.[3]

Shaker - A generic term that refers to the whole assembly of any type mechanical screening machine.

Stratification - This phenomenon occurs as vibration is passed through a bed of material. This causes coarse (larger) material to rise and finer (smaller) material to descend within the bed. The material in contact with screen cloth either falls through a slot or blinds the slot or contacts the cloth material and is thrown from the cloth to fall to the next lower level.[4]

Mesh - Mesh refers to the number of open slots per linear inch. Mesh is arranged in multiple configuration. Mesh can be a square pattern, long-slotted rectangular pattern, circular pattern, or diamond pattern.[5]

Scalp, scalping - this is the very first cut of the incoming material with the sum of all its grades. Scalping refers to removing the largest size particles. This includes enormously large particles relative to the other particle's sizes. Scalping also cleans the incoming material from foreign body contamination such as twigs, trash, glass, or other unwanted oversize material.

Types of mechanical screening

There are a number of types of mechanical screening equipment that cause segregation. These types are based on the motion of the machine through its motor drive.

Circle-throw vibrating equipment - This type of equipment has an eccentric shaft that causes the frame of the shaker to lurch at a given angle. This lurching action literally throws the material forward and up. As the machine returns to its base state the material falls by gravity to physically lower level. This type of screening is used also in mining operations for large material with sizes that range from six inches to +20 mesh.[6]

High frequency vibrating equipment - This type of equipment drives the screen cloth only. Unlike above the frame of the equipment is fixed and only the screen vibrates. However, this equipment is similar to the above such that it still throws material off of it and allows the particles to cascade down the screen cloth. These screens are for sizes smaller than 1/8 of an inch to +150 mesh.[7]

Gyratory equipment - This type of equipment differs from the above two such that the machine gyrates in a circular motion at a near level plane at low angles. The drive is an eccentric gear box or eccentric weights.[8][9]

Chemical Tumbler Screener

Trommel screens - Does not require vibrations, instead, material is fed into a horizontal rotating drum with screen panels around the diameter of the drum.

Tumbler screening technique

An improvement on vibration, vibratory, and linear screeners, a tumbler screener uses elliptical action which aids in screening of even very fine material. As like panning for gold, the fine particles tend to stay towards the center and the larger go to the outside. It allows for segregation and unloads the screen surface so that it can effectively do its job. With the addition of multiple decks and ball cleaning decks, even difficult products can be screened at high capacity to very fine separations.[10]

Circle-throw vibrating equipmentMain article:

Circle-Throw Vibrating Equipment is a shaker or a series of shakers as to where the drive causes the whole structure to move. The structure extends to a maximum throw or length and then contracts to a base state. A pattern of springs are situated below the structure to where there is vibration and shock absorption as the structure returns to the base state.

This type of equipment is used for very large particles, sizes that range from pebble size on up to boulder size material. It is also designed for high volume output. As a scalper, this shaker will allow oversize material to pass over and fall into a crusher such a cone crusher, jaw crusher, or hammer mill. The material that passes the screen by-passes the crusher and is conveyed and combined with the crush material.

Also this equipment is used in washing processes, as material passes under spray bars, finer material and foreign material is washed through the screen. This is one example of wet screening.

High frequency vibrating equipment

High frequency vibrating equipment is a shaker whose frame is fixed and the drive vibrates only the screen cloth. High frequency vibration equipment is for particles that are in this particle size range of an 1/8 in (3 mm) down to a +150 mesh.

These shakers usually make a secondary cut for further processing or make a finished product cut.

These shakers are usually set at a steep angle relative to the horizontal level plane. Angles range from 25 to 45 degrees relative to the horizontal level plane.

Gyratory Screener

Gyratory equipment

This type of equipment has an eccentric drive or weights that causes the shaker to travel in an orbital path. The material rolls over the screen and falls with the induction of gravity and directional shifts. Rubber balls and trays provide an additional mechanical means to cause the material to fall through. The balls also provide a throwing action for the material to find an open slot to fall through.

The shaker is set a shallow angle relative to the horizontal level plane. Usually, no more than 2 to 5 degrees relative to the horizontal level plane.

These types of shakers are used for very clean cuts. Generally, a final material cut will not contain any oversize or any fines contamination.

These shakers are designed for the highest attainable quality at the cost of a reduced feed rate.

Trommel Screens

Trommel screens have a rotating drum with screen panels around the diameter of the drum and is on a shall angle. The feed material always sits at the bottom of the drum and as it rotates, always comes into contact with clean screen. The oversize travels to the end of the drum as it does not pass through the screen, while the undersize passes through the screen into a launder below.

Screen Media Attachment SystemsThere are many ways to install screen media into a screen box deck (shaker deck). Also, the type of attachment system has an influence on the dimensions of the media.

Tensioned screen media

Tensioned screen cloth is typically 4 feet by the width or the length of the screening machine depending on whether the deck is side or end tensioned. Screen cloth for tensioned decks are made with hooks and are attached with clamp rails bolted on both sides of the screen box. When the clamp rail bolts are tightened, the cloth is tensioned or even stretched in the case of some types of self-cleaning screen media. To ensure that the center of the cloth does not tap repeatedly on the deck due to the vibrating shaker and that the cloth stays tensioned, support bars are positioned at different heights on the deck to create a crown curve from hook to hook on the cloth.[11] Tensioned screen cloth is available in various materials: stainless steel, high carbon steel and oil tempered steel wires, as well as moulded rubber or polyurethane and hybrid screens (a self-cleaning screen cloth made of rubber or polyurethane and metal wires).

Modular screen media

Modular screen media is typically 1 foot large by 1 or 2 feet long [12] (4 feet long for ISEPREN WS 85 [13]) steel reinforced polyurethane or rubber panels. They are installed on a flat deck (no crown) that normally has a larger surface than a tensioned deck. This larger surface design compensates for the fact that rubber and polyurethane modular screen media offers less open area than wire cloth. Over the years, numerous ways have been developed to attach modular panels to the screen deck stringers (girders).[14] Some of these attachment systems have been or are currently patented.[15] Self-cleaning screen media is also available on this modular system.[16]

Types of Screen MediaThere are several types of screen media manufactured with different types of material that use the two common types of screen media attachment systems, tensioned and modular.

Woven Wire Cloth (Mesh

Traditionally, screen cloth was made with metal wires woven with a loom.[17][18][19] Today, woven cloth is still widely used primarily because they are less expensive than other types of screen media. Over the years, different weaving techniques have been developed; either to increase the open area percentage or add wear-life. Slotted opening woven cloth[20]is used where product shape is not a priority and where users need a higher open area percentage. Flat-top woven cloth[21] is used when the consumer wants to increase wear-life. On regular woven wire, the crimps (knuckles on woven wires) wear out faster than the rest of the cloth resulting in premature breakage. On flat-top woven wire, the cloth wears out equally until half of the wire diameter is worn, resulting in a longer wear life. Unfortunately flat-top woven wire cloth is not widely used because of the lack of crimps that causes a pronounced reduction of passing fines resulting in premature wear of con crushers.

Perforated & Punch PlateOn a crushing and screening plant, punch plates or perforated plates[22] are mostly used on scalper vibrating screens, after raw products pass on grizzly bars.[23] Most likely installed on a tensioned deck, punch plates offer excellent wear life for high-impact and high material flow applications.

Synthetic screen media Synthetic screen media is used where wear life is an issue. Large producers such as mines or huge quarries use them to reduce the frequency of having to stop the plant for screen deck maintenance. Rubber is also used as a very resistant high-impact screen media material used on the top deck of a scalper screen.[24] To compete with rubber screen media fabrication, polyurethane manufacturers developed screen media with lower Shore Hardness. To compete with self-cleaning screen media that is still primarily available in tensioned cloth, synthetic screen media manufacturers also developed membrane screen panels, slotted opening panels and diamond opening panels. Due to the 7-degree demoulding angle, polyurethane screen media users can experience granulometry changes of product during the wear life of the panel.[25]

Self-Cleaning Screen MediaSelf-cleaning screen media was initially engineered to resolve screen cloth blinding, clogging and pegging problems. The idea was to place crimped wires side-by-side on a flat surface, creating openings and then, in some way, holding them together over the support bars (crown bars or bucker bars). This would allow the wires to be free to vibratebetween the support bars, preventing blinding, clogging and pegging of the cloth. Initially, crimped longitudinal

wires on self-cleaning cloth were held together over support bars with woven wire.[26] In the 50s, some manufacturers started to cover the woven cross wires with caulking or rubber to prevent premature wear of the crimps (knuckles on woven wires). One of the pioneer products in this category was ONDAP GOMME made by the French manufacturer Giron.[27] During the mid 90s, Major Wire Industries Ltd., a Quebec manufacturer, developed a “hybrid” self-cleaning screen cloth called Flex-Mat, without woven cross wires.[28] In this product, the crimped longitudinal wires are held in place by polyurethane strips. Instead of locking (impeding) the vibration over the support bars with woven cross wires, the polyurethane strips lessens the vibration of the longitudinal wires over the support bars but does not stop it, consequently allowing vibration from hook to hook.[29] Major Wire quickly started to promote this product as a high-performance screen that helped producers screen more in-specification material for less cost and not simply a problem solver.[30] They claimed that the independent vibrating wires helped produce more product compared to a woven wire cloth with the same opening (aperture) and wire diameter. This higher throughput would be a direct result of the higher vibrationfrequency of each independent wire of the screen cloth (calculated in hertz) compared to the shaker vibration (calculated in RPM), accelerating the stratification of the material bed. Another benefit that helped the throughput increase is that hybrid self-cleaning screen media offered a better open area percentage than woven wire screen media. Due to its flat surface (no knuckles), hybrid self-cleaning screen media can use a smaller wire diameter for the same aperture than woven wire and still lasts as long, resulting in a greater opening percentage.

A feeder is a piece of material handling equipment used to regulate the flow of a bulk material from a bin or hopper[1].  A feeder is essentially a conveyor used for short distances where a constant rate of dispersal is required.[2]  There are many types of feeders to suit many different industries; ranging from mining, to pharmaceuticals, to agriculture. Feeders are often used in conjunction with other types of material handling equipment, like conveyors, crushers, dryers, grinders, blenders, and mixers.[3]

Feeders can be loosely classified as either volumetric or gravimetric:[4]

Volumetric Feeder

Volumetric feeders achieve precise outputs through a process similar to using a measuring cup. First, fill the cup past the brim, then shake it to settle the contents, level-off any excess above the brim, and tap on the bottom to dislodge anything stuck to the sides of the cup.[5]

In a volumetric feeder, material is first fed into a hopper. Next, vibrations encourage the material to form a consistent density. Then, material is levelled off as it is forced through an adjustable gate at a constant speed. Lastly, the material is exposed to more vibrations as it exits the feeder, which dislodges any stuck material.  By maintaining a constant density, a constant speed, and a constant opening size, volumetric feeders are able to achieve a near constant output.[6]

Gravimetric Feeder

Gravimetric feeders, also known as loss-in-weight feeders, are used for applications which require extremely precise output, even more than a volumetric feeder. In a gravimetric feeder, the weight of the material being processed within the feeder is constantly monitored with the

goal of keeping a steady weight. If there is too little material in the feeder, then the rate of supply is increased. If there is too much material, then the rate is decreased.[7][8][9]

Feeders are further segmented according to their method of conveying: [10]

Apron Feeder

Apron feeders are typically used in the mining industry to handle bulky material coming directly from a jaw crusher. The “apron” is a conveyor made up of a series of steel pans fit snugly together. The apron is propelled by steel chains rotating around metal sprockets. The rate of discharge is controlled by adjusting the height of the gate or adjusting the speed at which the apron rotates.[11]

Belt Feeder

Belt feeders are used in lieu of apron feeders when material is of a fine composition. A belt feeder is simply a conveyor with a short belt. Typically belt feeders are less expensive than apron feeders, and operate at higher speeds. However, they not suited for heavy-duty applications.[12]

Chain Feeder

Chain feeders are used to control the release of a bulky material within a bin. Their design consists of several heavy chains, which drape over top of the bulky material on an incline. While resting, the chains hold the material in place. When the chains are moved, material slides down the incline.[13]

Roller Feeder

Roller feeders are used to handle dry granules and powders. Material is fed into a hopper at an uncontrolled rate where it is agitated by guiding vanes so it keeps a consistent density. These guiding vanes then direct the material towards the hopper’s outlet. The material passes between two steel rollers, which compresses the material into a thin uniform ribbon.[14]

Rotary-Vane Feeder

Rotary-vane feeders are used for low density powdered material. These units feature a rotating vane (a rotating cross with four separate quadrants). At the top of the vane rotation, each quadrant scoops up a load of material. At the bottom of the rotation, the load of material is discharge by gravity. The rate of discharge is determined by the speed at which the vane rotates.[15]

Revolving Disc Feeder

Revolving disc feeders, also known as a rotating table feeders, are able to process many types of material, including fine, bulky, and sticky. These units feature a hopper above a rotating table. As the table rotates, material falls from the hopper onto the table’s face at a constant rate by gravity. Then, the material is directed off of the table by stationary arms called skirt

boards. The rate of discharge is controlled by changing the speed at which the table rotates, or by adjusting the size of the opening where material exits the hopper.[16]

Screw Feeder

Screw feeders are used to transport fluids and fine granular materials. A rotating auger within a cylindrical encasing propels material. The rate of discharge is controlled by the speed of rotation.

Vibrating Grizzly Feeder (VGF)

Vibrating Grizzly Feeders are used in the mining and construction industries to separate large rocks from fine material.[17] Grizzly feeders are powered by an off-balance electric motor, which causes the unit’s vibrations.[18] They operate by conveying ore over a series of steel beams, which prevents large rocks from passing. The mixture that falls through is entirely fine.

Vibratory Feeder

Vibratory feeders are used for a wide variety of materials, including aggregate, coal, and chemicals.[19]  Essentially, a vibrating feeder is a ramp which vibrates to agitate material into falling down an incline. The vibrations spread the material evenly along the ramp, which results in a smooth discharge. [20]

Conveyor belt

This article is about industrial conveyor belts. For information on the global flow of sea currents, see Thermohaline circulation.

This article is about industrial conveyor belts. For the meteorological conceptual model, see Norwegian_cyclone_model#Conveyor_belt.

Point of contact between a power transmission belt and its pulley. A conveyor belt uses a wide belt and pulleys and is supported by rollers or a flat pan along its path.

These conveyor structures contain belts for moving bulk sulfur from railcars to storage piles and from the piles to ships.

A conveyor belt is the carrying medium of a belt conveyor system (often shortened to belt conveyor). A belt conveyor system is one of many types of conveyor systems. A belt conveyor system consists of two or more pulleys (sometimes referred to as drums), with an endless loop of carrying medium - the conveyor belt - that rotates about them. One or both of the pulleys are powered, moving the belt and the material on the belt forward. The powered pulley is called the drive pulley while the unpowered pulley is called the idler pulley. There are two main industrial classes of belt conveyors; Those in general material handling such as those moving boxes along inside a factory and bulk material handling such as those used to transport large volumes of resources and agricultural materials, such as grain, salt, coal, ore, sand, overburden and more.

Today there are different types of conveyor belts that have been created for conveying different kinds of material available in PVC and rubber materials.

The belt consists of one or more layers of material. Many belts in general material handling have two layers. An under layer of material to provide linear strength and shape called a carcass and an over layer called the cover. The carcass is often a woven fabric having a warp & weft. The most common carcass materials are polyester, nylon and cotton. The cover is often various rubber or plastic compounds specified by use of the belt. Covers can be made from more exotic materials for unusual applications such as silicone for heat or gum rubber when traction is essential.

Material flowing over the belt may be weighed in transit using a beltweigher. Belts with regularly spaced partitions, known as elevator belts, are used for transporting loose materials up steep inclines. Belt Conveyors are used in self-unloading bulk freighters and in live bottom trucks. Belt conveyor technology is also used in conveyor transport such as moving sidewalks or escalators, as well as on many manufacturing assembly lines. Stores often have conveyor belts at the check-out counter to move shopping items. Ski areas also use conveyor belts to transport skiers up the hill.

Belt conveyor systemsConveyors are durable and reliable components used in automated distribution and warehousing.[1] In combination with computer controlled pallet handling equipment this allows for more efficient retail, wholesale, and manufacturing distribution. It is considered a labor saving system that allows large volumes to move rapidly through a process, allowing companies to ship or receive higher volumes with smaller storage space and with less labor expense.

Rubber conveyor belts are commonly used to convey items with irregular bottom surfaces, small items that would fall in between rollers (e.g. a sushi conveyor bar), or bags of product that would sag between rollers. Belt conveyors are generally fairly similar in construction consisting of a metal frame with rollers at either end of a flat metal bed. The belt is looped

around each of the rollers and when one of the rollers is powered (by an electrical motor) the belting slides across the solid metal frame bed, moving the product. In heavy use applications the beds which the belting is pulled over are replaced with rollers. The rollers allow weight to be conveyed as they reduce the amount of friction generated from the heavier loading on the belting. Belt conveyors can now be manufactured with curved sections which use tapered rollers and curved belting to convey products around a corner. These conveyor systems are commonly used in postal sorting offices and airport baggage handling systems. A sandwich belt conveyor uses two conveyor belts, face-to-face, to firmly contain the item being carried, making steep incline and even vertical-lift runs achievable.

Belt conveyors are the most commonly used powered conveyors because they are the most versatile and the least expensive. Product is conveyed directly on the belt so both regular and irregular shaped objects, large or small, light and heavy, can be transported successfully. These conveyors should use only the highest quality premium belting products, which reduces belt stretch and results in less maintenance for tension adjustments. Belt conveyors can be used to transport product in a straight line or through changes in elevation or direction. In certain applications they can also be used for static accumulation or cartons.

Belt Conveyor systemsat a Packing Depot

 

Baggage Handling BeltConveyor systems

 

Rollgang for cartons and totes in a fashion distribution centre

Long belt conveyors

The longest belt conveyor system in the world is in Western Sahara. It is 98 km (61 mi) long, from the phosphate mines of Bu Craa to the coast south of El-Aaiun.[2]

The longest conveyor system in an airport is the Dubai International Airport baggage handling system at 63 km (39 mi). It was installed by Siemens and commissioned in 2008, and has a combination of traditional belt conveyors and tray conveyors.[3]

Boddington Bauxite Mine in Western Australia is officially recognised as having the world's longest and second-longest single belts with a 31-kilometre-long (19 mi) belt feeding a 20 km (12.5 miles) long belt. This system feeds bauxite through the difficult terrain of the Daring Ranges to the alumina refinery at Worsley. The longest single-belt international conveyor runs from Meghalaya in India to a cement factory at Chhatak Bangladesh.[4][5][6] It is about 17 km long and conveys limestone and shale at 960 tons/hour, from the quarry in India to the cement factory (7 km long in India and 10 km long in Bangladesh). The conveyor was engineered by AUMUND France and Larsen & Toubro. The conveyor is actuated by three synchronized drive units for a total power of about 1.8 MW supplied by ABB (two drives at the head end in Bangladesh and one drive at the tail end in India). The conveyor belt was manufactured in 300-meter lengths on the Indian side and 500-meter lengths on the Bangladesh side, and was installed on-site by NILOS India. The idlers, or rollers, of the system are unique[citation needed] in that they are designed to accommodate both horizontal and vertical curves along the terrain. Dedicated vehicles were designed for the maintenance of the conveyor, which is always at a minimum height of 5 metres (16 ft) above the ground to avoid being flooded during monsoon periods.

Belt conveyor safety system

Conveyors used in industrial settings include tripping mechanisms such as trip cords along the length of the conveyor. This allows for workers to immediately shut down the conveyor when a problem arises. Warning alarms are included to notify employees that a conveyor is about to turn on. In the United States, the Occupational Safety and Health Administration has issued regulations for conveyor safety, as OSHA 1926.555.

References

John DavisSenior DesignerKFJ STEEL JOST Group

Malcom MendyForemanKFJ STEEL JOST Group

Brian ElgarManager Human ResourcesKFJ STEEL JOST Group

ConclusionSo we can conclude by saying that the mining industry is one of the leading industries in the world. It will always be required and there is always room for environment. The processing and plant techniques will be always competitive. The market is very volatile and the process is simple and I would like to work further in this field due to the dealing with heavy machinery equipment’s.