FACULTY MECHANICAL, MARITIME AND MATERIALS ENGINEERING Delft University of Technology Department Maritime and Transport Technology
Mekelweg 2 2628 CD Delft the Netherlands Phone +31 (0)15-2782889 Fax +31 (0)15-2781397 www.mtt.tudelft.nl
Specialization: Transport Engineering and Logistics
Report number: 2016.TEL.8042
Title: Application of Conveyors in Mining Industry
Author: M.C. van Etten
Title (in Dutch) De toepassing van transportbanden in de mijnbouw.
Assignment: Literature assignment
Confidential: no
Supervisor: Dr.ir. Y. Pang
Date: March 31, 2017
This report consists of 39 pages. It may only be reproduced literally and as a whole. For commercial purposes only with written authorization of Delft University of Technology. Requests for consult are only taken into consideration under the condition that the applicant denies all legal rights on liabilities concerning the contents of the advice.
FACULTY OF MECHANICAL, MARITIME AND TUDelft MATERIALS ENGINEERING Delft University of Technology Department of Marine and Transport Teclinology
Mel Student: M. C. van Etten Assignment type: Literature Assignment Supervisor: Dr. ir. Y. Pang Report number: 2016.TEL.8042 Specialization: TEL Confidential: No Creditpoints (EC): 10 Subject: Applications of Conveyors in Mining Industry In mining industry different types of conveying systems perform the transportation cf large volume of bulk solid material such as coal or iron ore. The applications of diverse conveying equipment and conveyors can be found in both underground mines and surface mining. This assignment is to provide an state of the art survey with respect to the applications and development of different conveyors in mining industry. Based on a fundamental understanding of the mining processes and the principles and functions of conveyors, for both underground and surface mining, the survey of this literature assignment should cover the following: • to describe the mining methods and conveying processes in mines « to survey the different types of conveyors applied in mining and material transport e to categorized the types of conveyors in different applications and to summarize the trend of the development of mining conveyors s to investigate the new solutions or technologies to improve the sustainability in mining industry with respect conveying systems. This report should be arranged in such a way that all data is structurally presented in graphs, tables, and lists with belonging descriptions and explanations in text. The report should comply with the guidelines of the section. Details can be found on the website. Dr. ir. Y. Pang Summary This literature assignment is the result of an investigation on the use, function and trend of conveyors in the mining industry. Conveyors using a drive pulley to be driven, are investigated for the underground and surface mining industry. The conveyors have a transportation function in the process of mining. In terms of bulk handling, this means a constant speed of moving the material. For handling raw material with a wide grading and high capacities, the chain conveyors is most often used in both industries. Also, the impact on the chain conveyors, especially the apron feeders, can be seen in both industries. In order to switch in conveyor type during the transportation process, to convey more efficiently, the material need to be prepared to work optimally for that type of conveyor. Therefore, equipment such as crushers are often installed at transfer points. The pouched, pipe, pocked and the most used troughed belt conveyor are applicable in both the underground and surface mining industries. These are examples of conveyors installed after such transfer point. During the assignment, it became clear that the capacity for lifting the material using different types of conveyors decreases. Pocket, sandwich, snake, cleated and other conveyors could be used for high angle conveying but with a decrease in capacity. These are most often found in open pit mines, due to high angle operations. Conveyors can vary in terms of for example maximum inclination, capacity, length, lump size, radius, weight and lump size. Each solution in the mining industry is a one of a kind. Lifting of the material can also be done in underground mines. Lifts of 1.2 km and 1.5 km using multiple flights, up to 500 vertical meters per flight, of conveyors are installed in both surface and underground mining. New solutions and research can be found in increasing the systems efficiency, especially the rolling friction of conveyor. CARIAT, cable, rope and rail conveyors use the low rolling resistance of wheels on rail instead of idlers. Using rail and creating a closed system is a trend that can be seen to improve the sustainability in term of power reduction, dust generation and noise generation. Unfortunately, these systems can not be found inside the mines yet and only in transportation systems outside the mine. Something to look forward to. i ii Contents Summary ...... i 1 Introduction...... 1 Background of mining ...... 1 1.1.1 History of mining ...... 1 1.1.2 Methods of mining ...... 2 1.1.3 History of conveyors ...... 3 1.1.4 Market ...... 4 1.1.5 Use of conveyors in mining ...... 4 1.1.6 Function of conveyors in mining ...... 5 1.1.7 Principles of conveyors...... 5 Scope of this work ...... 5 Goal of this work ...... 6 Outline of the report ...... 6 2 Underground mining methods ...... 7 Methods ...... 8 Hauling underground ...... 8 3 Underground conveyors ...... 11 Chain conveyors ...... 11 3.1.1 Armoured Face Conveyor ...... 12 3.1.2 Continuous miners ...... 13 3.1.3 Feeder breaker ...... 14 3.1.4 Two parallel chain conveyor ...... 14 Belt conveyor ...... 15 Pouched conveyor ...... 17 Pipe conveyor ...... 18 3.4.1 Pipe conveyors ...... 18 3.4.2 Coaxial pipe conveyor ...... 19 3.4.3 Extendable belt system ...... 19 Troughed belt conveyor ...... 19 Pocket conveyor ...... 20 Summary underground mining conveyors ...... 21 4 Surface mining methods ...... 23 Methods ...... 23 Transport in surface mining ...... 24 iii 5 Surface conveyors ...... 25 Apron feeder ...... 25 High angle hauling conveyors ...... 26 5.2.1 Sandwich conveyors ...... 26 5.2.2 Snake conveyor ...... 27 5.2.3 Pocket conveyor ...... 27 5.2.4 Cleated conveyor ...... 28 Troughed belt conveyor ...... 28 Summary surface mining conveyors ...... 29 6 Development ...... 31 Conveyor trends ...... 31 6.1.1 Rope conveyor ...... 31 6.1.2 Cable conveyor ...... 32 6.1.3 Rail conveyor ...... 34 6.1.4 CARIAT conveyor ...... 35 6.1.5 Material ...... 35 Sustainability ...... 36 7 Conclusion...... 39 8 References ...... 41 iv Introduction 1 Introduction Background of mining To get a full understanding of the use of conveyors in mining, more background information is needed. This is done by having a look at the history and methods of mining and conveying. After this is done the work can be placed into the right context. Furthermore, it is important to know the use of conveying before the scope and tasks will be introduced. 1.1.1 History of mining The Stone Age, the Bronze Age, the Iron Age, the Steel Age and the Nuclear Age. Various periods of time in the history of civilization are named after the widely-used minerals or their derivatives by the humankind. Parallel to the use of these materials is the history of the mining of the corresponding material. Therefore, the history of mining goes far back to the prehistory. Since flint implements have been found together with bones of humans living in the Old Stone Age, scientists say that surface mining started 450,000 years ago. This primitive form of mining was used to create tools and weapons by chipping the flint from loose masses [1]. Evidence of the other way of mining was found years and years later. The oldest underground mine known is located in Swaziland at the Lion Cavern site in the Ngwenya Mountains. This first underground mine was the source for the ores ‘hematite’ and ‘specularite’ which were used as cosmetic and rituals. Carbon-14 dating studies estimated that the extraction took place 43,000 B.C. to 41,000 B.C. [2]. Studies also found that in the pre-dynastic period around 4,400 B.C. to 3,000 B.C. copper, gold and silver mines were used in Ancient Egypt [3], while in China coal was extracted from the surface as a source of energy [4]. This period of time was an innovative one in human history. Both copper and tin were mined a lot and melting those ores together created bronze, the Bronze Age [5]. During the 7th Century B.C. in Ancient Greek ores like silver, gold, copper, bronze, tin, iron and marble were extracted for the use of payment and weapons [6]. During the first century, the Romans were the first to use surface mining on a large scale and once the open cast mining using the hydraulic mining was no longer feasible, they followed the ore veins underground creating shafts and galleries into the ground [6]. This was the beginning of the underground mining with the use of shafts. In the period of Medieval Europe, the demand for armour and weapons grew bigger and bigger. This caused the exploration to expand the open-pit mines and to reach deeper into the ground. The invention of new techniques to dewater the shafts and to go further underground was needed and found [5]. More and more mining operations were created all over the world and the knowledge and number of innovations was increasing. The German Bauer, also known as Georgius Agricola, published a book in 1556 about the mining methods, refining and smelting or metals. This book “De Re Metallica” was centuries long the most important and influential work in mining [7]. M.C. van Etten 1 Literature Assignment: Application of Conveyors in Mining Industry Figure 1. Wood cut in De Re Metallica [8] During the Modern period, several gold and silver rushes happened mainly in America and Australia, which also stimulated the mining for coal, copper, lead and iron [9] [10]. Especially during the end of the Modern Period around 1800, the newest techniques were introduced due to the start of the Industrial Revolution. Newest techniques in mining made it possible to mine deeper, more efficient, safer and more profitable. Although some of the mining techniques were already mentioned, the following subsection will introduce the most common mining techniques used nowadays. 1.1.2 Methods of mining The life of a mine knows five different stages: prospecting, exploration, development, exploitation and reclamation [11]. Before the actual production of the mine starts and the desired material is coming out of the mine, years of work has to be done. During the first three years, the prospecting, the exploitation methods are determined. The two common categories for exploitation methods are surface or underground mining. Marine and alluvial are two other categories of mining but these types will be left out in this work, since they are not known as the classic mining industry. In Figure 2, the different types of mining for coal are shown. Figure 2. Coal mining methods [12] 2 Introduction The types of underground mines can be categories in the way the material will be reached. In case of the drift mine, there is no vertical difference between the opening of the mine and the location of the material extraction. In case the coal or mineral beds are below the entrance level, a shaft mine using a slope or a vertical shaft can be used to get to the material. In chapter 2, the underground mining methods will be discussed. The types of surface mines are also shown in Figure 2. Coal mining methods Mountain tops, the contour on a lower level, holes from the side, and whole areas can be mined in surface mining. The first and last option are known of their high-volume mining, and therefore more interesting for this work since the use of conveyors is more applicable. The surface and open-pit mining will be introduced in chapter 4. 1.1.3 History of conveyors As mentioned in the history of mining, new manufacturing processes were invented during the Industrial Revolution. The conveyor was one of the many inventive tools that made its introduction. The first conveyor system was introduced in 1795 as a tool to move grains over a short distance. It was in 1830 when the first use of belt conveyors for moving bulk loads to move away refuse from milling operations was documented [13]. The well-known Henry Ford introduced the application of the conveyor belt for unit load as the assembly line in his car manufactory in 1913. Since then, it is impossible to imagine industrial systems without the use of conveyors [14]. The first conveying system for the transport of mined material was a belt conveyor invented by Thomas Robins. In 1891, he invented the first heavy-duty belt conveyor for carrying coal and ore [15]. Only 14 years later, the British mining engineer Richard Sutcliffe created the first conveyor belt for the underground mining for coal [16]. Over the years, more and more types of conveyors were invented, each with their specific used to increase productivity and safety of the mine. An example of one of the inventions used in mining is the inventions of Joseph Joy, shown in Figure 3. The left patented machine from 1919 conveys the material after it is grabbed by the front arms. The right side shows a mobile conveyor machine from 1959, using chains to convey the material. Figure 3. Chain conveyor invented by Joseph Joy [17] [18] M.C. van Etten 3 Literature Assignment: Application of Conveyors in Mining Industry Conveyors in the mining industry are these days used in almost every step of the process. Beginning the mining process with the extraction and moving of the material away from the source. Followed by further transport after preparation and ending the process with washing, screening and stacking the product. Within each of these steps conveyors can be applied. The conveyors vary from chain conveyors to rail conveyors and from pipe conveyors to sandwich conveyors. 1.1.4 Market In a period of time where the major mining companies see sharply lower operating results and where the mining companies see major drops in net income, changes have to be made in order to survive the big hit. The performance in the metals and mining industry was on a big decline over a couple of years as shown in Figure 4. In 2015 some companies had a net loss of almost five billion dollars and left the minerals in the ground. A reaction of cutting investments and operations was the result. In these difficult times a critical eye on its own operations and productions is unavoidable for the companies to keep up and to limit the damage [19]. Figure 4. S&P Metals & Mining select industry index [20] The focus of every mining company will be on increasing productivity efficiency and containing costs. Since labour costs has a share of 40% to 50% in the mine costs, innovation in the supply chain and logistics during the operation is appealing [21]. Therefore for example, the comparison of the way of hauling in an open-pit mine between the use of haul trucks and conveyors for example, is done more often. With innovations in the whole process of mining, the productivity, efficiency and safety of the mine could be increased. 1.1.5 Use of conveyors in mining The market shows that mining companies are forced to cut costs and that labour costs is a big part of that. The use of conveyors can help decreasing the operation costs and therefore to mine the minerals cheaper. If financially the use of a hauling truck is compared with the use of a pocket conveyor in an open pit mine, the following is found. In terms of energy consumption, the pocket belt conveyor spends $450 per hour, against a $5,180 per hour for a haul truck. Furthermore, the initial capital investment of a pocket belt conveyor would cost around $500,000, while the price of only one small dump truck starts at $150,000 and reaches up to $5 million. For the initial capital investment and the energy consumption the truck hauling is ten times the conveyor’s [22]. Furthermore, the use of truck hauling in underground mining knows its limitations. An economic changeover point between the use of truck hauling and the use of hoisting in a vertical shaft is at 350- meter depth. When bigger sized 50 ton trucks are used, a depth of 450 meters can be reached while being economically positive. For deeper mines the use of conveying or hoisting is used [23]. Other advantages of using a conveyor, and in particular a belt conveyor, over truck hauling are as followed. Lower emission by the engines, the operation of a belt conveyor generates less dust and less noise 4 Introduction generation. The down side is though that a conveyor is often on a fixed position, unlike the haul trucks and other equipment on tires used in the mines. 1.1.6 Function of conveyors in mining Bulk handling can be divided into a number of functions which are: storage, transhipment, transfer and transportation. These functions of bulk handling can be categorised by the velocity of the bulk. For storage, the bulk will not be in motion and therefore it has a velocity of zero. Transhipment makes the bulk move from or to its storage. It will accelerate from or to zero. In case the bulk flow needs to change direction or speed, the transfer function is applied. The bulk has a velocity but not a constant acceleration. The last function, and in this assignment the most important one, is the transport function. In this situation, the velocity of the bulk is constant, carrying the bulk over great distance. Bulk is handled by transhipment and often transferred before it reaches the transportation phase. Bucket wheel excavators or constant miners have the function of transhipment equipment and a hopper and chute can function as the transfer. For the transport function, the conveyors are an ideal piece of equipment in bulk handling. Conveyors can be used for transporting almost everything. The extracted raw mineral, mining equipment, worker’s goods and even the miners themselves [24]. It can be used on an inclination up to vertical, decline or horizontal level. As said before, the use of a conveyor in the mining industry is to transport the extracted minerals. But for the conveyor to work properly the material conveyed has to be prepared, to meet the preferable production properties and limit for example wear and tear. The operation of conveying must be controlled and therefore the material must be crushed. Big lumps and pieces of material are harder to control during transport. Therefore, a crusher is installed in front of the conveyor. After the first preparation stop, the mineral can be moved to another conveyor till it reaches the panel conveyor. The panel conveyor transports the material over the biggest horizontal distance through the main gate to the point of haulage. There, it will be lifted out of the mine by hauling using trucks, hoisting trough an inclined or vertical shaft, or conveying [25]. 1.1.7 Principles of conveyors The principles of the transportation function of conveyors can vary. Some conveyors use an endless loop driven by a drive pulley to transport the material. Within this principle, a difference can be made in supporting the material or pulling and pushing the material. Supporting the material and using an endless loop is the principle of for example the troughed belt conveyor. Pulling while using an endless loop can be found in a type of chain conveyor. These two principles of support and pulling can also be found not using an endless loop. An example for the supported principle is a vibratory feeder. For the pulling principle without an endless loop this is for example a screw conveyor. Scope of this work Over the years, new solutions and new ways of transporting bulk in the mining industry have been introduced in order to make the system of mining more productive, more efficient and safer. This work gives an overview of the conveyors used in the mining industry. This gives a good insight of the used application for each type of operation and fully understanding of the working principle and function of conveyors in the mining industry. There are all sorts of conveyor system in the mining industry available. In this work the conveyor systems only used in the underground and surface mining are investigated. The type of conveyors investigated in this report are the conveyors which use the principle of an endless loop driven by one or more drive pulleys to move the bulk material. Therefore, the investigation excludes the use of individual cars or carriage, vibratory feeders, grizzly conveyors, and some others. Also, the material conveyed is the extracted material in the mine itself and no other goods like equipment or workers. M.C. van Etten 5 Literature Assignment: Application of Conveyors in Mining Industry Goal of this work In order to get a complete insight of the conveyor systems used in the mining industry, several tasks of this survey are described. The following tasks are set. The survey overviews the conveying processes in mining industry. The survey describes the functions of the conveyors applied in mining transport. And finally, the survey investigates the operational control principles of mining conveyors with respect to system sustainability and system reliability. Outline of the report The report is divided in three parts. The first part will introduce the underground mining, the second part will be about surface mining and the last part of the report will discuss the developments on the conveyor trends. The underground mining and surface mining will both be introduced by their principles and methods and in the chapter after that the applied conveyors will be discussed. Therefore, the structure of this work will be as follows. In chapter 2, the underground mining methods will be discussed, followed by the used conveyor systems in chapter 3. Later on, in chapter 4, the mining methods for surface mining are shown, with the applied conveyor systems in the following chapter 5. The developments in conveyor systems and the trend in the mining conveyors are discussed in chapter 6. Finally, the conclusions of this assignment will be introduced in chapter 7. Before the survey ends the references used during this assignment are shown in chapter 8. 6 Underground mining methods 2 Underground mining methods One way to categorise mines is by its production rate. For underground hard rock mines this is done in classes of Large, Bulk and Super [26]. A large underground hard rock mine can have a production of 4 up to 6 megaton per year, also Mtpa. The bulk mines are known to have a production of 10 to 20 megaton of material per year, while the super mines reach up to 25 and even 45 megaton per year. An overview on the production rate against the mine depth can be seen in Figure 5 below. The super mines go as deep as 2,000 meter depth. As normally associated with these depths and production rates, the material can be hauled to the surface by the use of multiple hoist through the vertical shaft in a batch process, but this is not the only way. Multiple options and combinations are possible for a conveyor system used in an underground or open mine. This hauling process is discussed in section 2.2. For the option of lifting the material out of the mine by using a conveying system, multiple flight conveyors are used. By using a conveyor system with multiple flights, lifting the material around 500 meters in a single flight, the material can be hauled to the surface from a great depth. Figure 5. Production rate and mine depth [26] Underground mining methods are differentiated by many parameters such as: the type of the hardness of the surrounding material, the characteristics of the ore, and much more parameters. All these parameters are involved in the decision making of the mining method. Supported, unsupported and caving are types of underground mining. The two most common mining methods using conveyors are shown in Figure 6 and will be discussed in further detail in the next section. M.C. van Etten 7 Literature Assignment: Application of Conveyors in Mining Industry Figure 6. Left: Room-and-pillar method, Right: Longwall mining method [27] Methods The methods in underground mining can be categorised in supported roof methods, unsupported roof methods and caving methods. For the supported mining method, the most common method for supported mining is the cut-and-fill method and is often used for vein deposits. However, for this assignment the focus is on an unsupported method and a caving method. The most used unsupported method of mining is the room-and-pillar method. By mining the hard ore and surrounding rock in a systematic pattern, rooms and natural pillars are created with the pillars as support of the roof. Supporting the roof is necessary when soft but high-grade ore is mined. Longwall mining and block caving are widely-used caving methods. These methods know a high productivity up to 8 million ton per annum, Mtpa [28]. As the roof of the mine is supported, the ore is mined. During the process of longwall mining, a longwall mining system is placed in a gate road facing the wall to be mined. The shearer or plough can move with 20 to 30 meters per minute over a several hundred meters long track, cutting the material by rotation while the roof is supported by hydraulic chocks. The extracted material falls into the chain conveyor while the shearer keeps cutting more material by moving to one side [31]. Since the whole system moves forward through the mine after each slice of wall, the unsupported roof at the back of the mining equipment drops. This can cause surface ground above the mine to drop up to five meters [11] [29]. The depth of the mines depends on the value of the mined ore. While the deepest mines are gold mines and those can reach a depth of 3.9 km [30], coal mines for example do not go that deep. The deepest coal mine is about 1.5 km deep. Hauling underground The first phase is completed and the material is mined. Now, further transport is needed. There are two types of hauling. The haulage of the material from the position where it is extracted to the panel or section conveyor is called gate road hauling. The other type of hauling is the way of transporting the material to the surface, out of the mine. During the transport through the mine, conveyors are used in different ways at different stages. In the first stage when ore is extracted it’s often loaded on a conveyor transporting the ore to a crusher to prepare the ore for further transport. Since the material is raw and has a wide grading including almost dust to big lumps, the equipment is designed to handle that. But since other conveyor systems are more efficient and cheaper, it is preferable to switch to that conveyor system as soon as possible. That is why crushers and other equipment are installed to prepare the material for the way to the panel conveyor at the gate road. After the transport to the gate road, the material is ready for the long journey out of the mine. This hauling process can be all the way up to the surface or towards a hoisting system in an inclined or vertical shaft. When a conveyor does the hauling in a slope or drift mine, the material is transported from the crusher where the material is loaded to the entrance of the mine. Using conveyors on a slope has its break-even 8 Underground mining methods depth in the 300 to 400-meter range. Using a conveying system to a lower point often result in a higher overall cost and multiple conveyor flights. This is why the use of slopes is limited to the shallow mines. In order to reach to a certain depth, the required linear distance for this slope is approximately 4 times bigger. The skips and cages in shaft conveyances are used in hoisting the material in a steep inclined or vertical shaft. [31]. M.C. van Etten 9 Literature Assignment: Application of Conveyors in Mining Industry 10 Underground conveyors 3 Underground conveyors The gate road hauling directly after extraction and towards the panel conveyor, is the first part of transport in the mine. There are many design requirements and regulations in underground mining that has an effect on the design of the equipment used. Besides all the safety restrictions the size of the tools is limited. This makes designing of equipment used in underground mines more challenging. When conveyors are chosen to transport the material in an underground mine, the chain conveyor and the well-known troughed belt conveyor are used. Both applications are shown in Figure 7 and introduced in this chapter. Each type of conveyor is designed to handle material within certain limits, in terms of rock size and capacity. To meet these restrictions, often a station is placed to prepare the material for the next type conveyor system. For example, a crusher is installed in front of a troughed belt conveyor to avoid spillage during its transport due to bigger particles within the grading and therefore to get its maximum performance. Therefore, the conveyors in the first phase of conveying transport are designed to handle that type of raw material. In this chapter, the conveyors applied in mining will be introduced. Starting with systems handling the raw material and finishing with the systems used for more homogenous flows of more homogenous material. Figure 7. Schematic view on a chain and belt conveyor [32] Chain conveyors During the very first process of longwall mining, the material is extracted by using the rotating shearer cutting the material by rotation, while the roof is supported by hydraulic chocks. The extracted material falls into the chain conveyor while the shearer keeps cutting more material by moving to one side. Its function is to extract the material, transfer and transport the material. The extracted material, usually known as coal, has a wide particle grading of soft rock. Chain conveyors can also be applied in other systems such as the continuous miner and the feeder breaker. A side view on the shearer, the conveyor and the support chocks is shown in Figure 8. M.C. van Etten 11 Literature Assignment: Application of Conveyors in Mining Industry Figure 8. Longwall mining system with hydraulic chocks (left), AFC (lower middle), shearer (right) [33] 3.1.1 Armoured Face Conveyor The chain conveyors used at longwall mining are armoured face conveyors, also known as AFC. This type of conveyor needs to transport the very raw material to its first processing point. The AFC uses the pulling principle of conveying the material. After the soft rock has been extracted it falls down between the chains and the beams on the flat armoured face, over which the rock will be scraped. At both ends of the conveyor, the chain is locked and driven by rotating sprockets. The sprockets function as the pulleys rotating the chain and keeping tension on the chain. This piece of equipment in the process of longwall mining can have a width up to 1,342 mm and can reach a capacity of 6,000 ton per hour [33] The number of chains and their positions have varied over the years: The twin out-board chains, the single in-board chain and the twin in-board chain. With the correct tension on the chains created by tensionable tail drive, and locking the chain in the correct way, the AFC is a reliable system. In Figure 9, the rotation point at the end of the conveyor can be seen. The shear strength varies between 3,000 kN and 7,000 kN depending on the size of the operation. The sprockets holding the chain at the end of the conveyor and causing the rotation are located in the drive modules. These modules can suit power requirements, up to twice 1800 kW per drive. Figure 9. Left: Sprocket, right: Armoured face conveyor chains [34] 12 Underground conveyors The beams or flights of the AFC can reach a velocity up to 1.6 meter per second transporting the raw material on the stage loader via the cross frame. The cross frame is shown in Figure 10. A stage loader uses the same principle as the AFC to move the raw material on its first belt conveyor for further transport. Figure 10. Left: AFC, right: Cross frame to change direction [34] 3.1.2 Continuous miner In mining methods other than longwall mining, conveyor systems can also be used. For the unsupported room-and-pillar mining, the extracted material can be loaded on a conveyor system in the hauling drift by load-haul-dump machines. This way of mining is a batch haulage method. To avoid the use of haul trucks and make the process continuous, there are some products available. These products create a continuous system starting at the extraction of the material and finishing at the transfer of the material on the belt conveyor in the main gate. The use of a continuous miner machine and a flexible conveyor train can improve the productivity of the room-and-pillar mining method up to 2.5 megaton per year. Other equipment using conveyors like a feeder breaker system will be investigated later on. The function of the conveying system used directly after extracting the material is to be reliable in transporting the raw material. The continuous miner machine as shown in Figure 11 can be used in the room-and-pillar mining method. This machine is at the extraction of the material, the very begin of a chain of multiple machines. At the rear of this machine a haul truck or a conveyor system will collect and convey the material coming of the continuous miner’s conveyor. Figure 11. Left: Continuous miner, right: chain conveyor [35] At the inlet of the machine, below the cutting head, the gathering heads are located. These rotating arms, based on Joy’s idea back in 1919, feed the conveyor with the extracted material. The capacity of this machine and its conveyor is relatively slow. The conveyor has a loading rate between 540 ton per hour and 1,860 ton per hour. The conveyor used in these type of machines is a dual sprocket chain. This means that two sprockets lock the outside pins of one single chain. This reduces the noise exposure of the machine to the operator by 27.4% [36]. The design difference between the single and the dual sprocket can be seen in Figure 12. M.C. van Etten 13 Literature Assignment: Application of Conveyors in Mining Industry Figure 12. Left: single sprocket, right: Dual sprocket used by JOY Global [36] 3.1.3 Feeder breaker Another application of the chain conveyor in the mining process and in the transportation function of the material is the feeder breaker. The principle of the feeder breaker, using the roller type conveyor chain and a crusher, can be used in a chain of conveyors preparing and moving the material. To convert the raw material onto a conveyor, a transfer point is needed. The feeder breaker machine is a piece of equipment preparing the material by breaking it and dumping it as a continuous flow onto a connected conveyor belt. The capacity of a feeder breaker can be varied up to 2,000 ton per hour. Compared to the AFC, the chains and sprockets are roller type conveyor chains and sprockets. These are more flexible and can rotate over sprockets with smaller diameter. The roller chain and sprockets are in a different configuration compared to the AFC. At the AFC, the chains and sprockets are located at the middle, where the feeder breaker has them located on the outside. The relatively flat beams are attached on and in between the chains. In Figure 13, a feeder breaker is shown. The inlet of the feeder breaker is on the flat right side of the machine. After the rotated breaker has fractured the raw material into a more easily handled size, the material is conveyed on the next piece of equipment [35]. Figure 13. Feeder breaker [35] 3.1.4 Two parallel chain conveyor The chain conveyor is also used in shuttle cars. Although it does not increase the continuity of the whole operation of mining, it decreases the offload time. To haul the material extracted by the continuous miner to the main belt conveyor there are multiple options. The haulage could be done by shuttle cars, driving back and forward to discharge the continuous miner unit and feeding the fixed belt conveyor. These shuttle cars can use a chain conveyor system aboard to discharge the material loaded on top of it. The conveying system is comparable to chain conveyor on the continuous miner unit or the longwall miner. 14 Underground conveyors On a shuttle car, a conveying system of two parallel chains and flights can be used instead of one main chain with attached flights. As can be seen in Figure 14, there are shuttle cars using two parallel chain conveyor systems and shuttle cars using a single chain conveyor system with two chains on the side and one flight in the middle comparable to the feeder breaker unit. Another application of the chain conveyor is the Apron Feeder. This conveyor can have its application in underground mining, but since it is more often used in surface mining it will be discussed later in section 5.1. Figure 14. Left: Shuttle car using two parallel chain conveyors. Right: single chain conveyor shuttle car [35] Belt conveyor To avoid the use of many feeder breaker or shuttle cars and to make the mining process more continuous in the room-and-pillar method, two types of belt conveyor can be used. 3.2.1 Flexible conveyor train The use of the shuttle cars behind the continuous miner unit is a batch process. There is an option to also make this hauling system towards the main fixed belt conveyor a continuous process. This can be done by the use of a flexible conveyor train, also known as a FCT. Since the route to the continuous miner unit in the room-and-pillar method commonly involves multiple 90 degrees turns, as shown on the left side of Figure 6, a conveyor system is not an obvious solution. But with the use of a FCT, there is a way to haul the material by a continuous process. The FCT, is a combination of a belt conveyor and a feeder breaker unit. The front of the FCT is located underneath the outlet chain conveyor of the continuous mining unit. When material is dropped on the front of the FCT, the material is reduced in lump size by the breaker and conveyed onto its belt conveyor part. This midsection of the FCT is a flexible belt conveyor. The belt speed can reach up to 3.6 meter per second in order to haul coal up to 1,470 ton per hour or for example salt up to 2,178 ton per hour [35]. The conveyor can have a length ranging from 38 meter to 152 meter and is able to follow the continuous miner by radio remote control. M.C. van Etten 15 Literature Assignment: Application of Conveyors in Mining Industry Figure 15. Flexible Conveyor Train [35] For unloading the FCT onto the panel conveyor or the maingate both the over-the-top and the sideway configuration can be installed. The sideway configuration is used when the fixed panel conveyor goes further into the mine than the FCT is operating. Both configurations are shown in Figure 16. This system is most often used in high production coal mines. Like other systems, this type of conveying can also be roof mounted although the floor mounted configuration is more often used. Figure 16. Left: Over-the-top loading, Right: Sideway loading [35] 3.2.1.1 Flexiveyor A similar conveyor train between the continuous miner unit and the panel conveyor is the flexiveyor. This type uses multiple small flight troughed conveyors. Each car is about 6 meters long and can cover a distance of 140 meter with a capacity of 1,100 ton per hour for transporting potash. Since each car in this conveyor can function as a pivot point, corners of 50 degrees per car can be made easily as they appear in the room-and-pillar method. In Figure 17, the flexibility of the multiple flights conveying system with its 1,200 mm wide belts is shown. Also, this conveying system can be attached on the continuous miner unit and follow it while extracting and dumping the material [37]. This system can be used for the transportation of all types of mineral, e.g. coal and salt onto the panel conveyor by sideway or over-the- top offloading. 16 Underground conveyors Figure 17. Left: Flexiveyor using multiple flights, Right: 50 degrees steering at each pivot point [37] Comparing this multi flight system with the flexible conveyor system gives some disadvantages. The capacity difference for conveying potash can get up to 1,000 ton per hours less compared to the FCT. Another disadvantage is that the chance on spillage using this conveyor is much bigger than comparable types of conveying. The third one is the dust generation, due to the transfer flight on each next segment. Because of safety and health regulation this can be a no-go for the multiple flight belt conveyor system. Pouched conveyor This type of rail mounted conveyor uses a belt in the shape of a teardrop and is classified as a closed conveyor. This is often called a pouched conveyor and the difference between some of them is the way the belt is supported. Cross sections of some types are shown in Figure 18. This system uses two thick profiles which are pushed together by the tilted support pulley. One of the advantages of close conveying systems is that it protects the environment surroundings for its dust generation. Also like other pouch and pipe conveyors this system is capable of making tight corners. This system is of most value over great distance including corners. Figure 18. F.l.t.r.: Cross-sections of the SICON conveyor, the ICS conveyor and the E-BS conveyor [38] [39] M.C. van Etten 17 Literature Assignment: Application of Conveyors in Mining Industry The maximum capacity of the SICON conveyor reaches up to 440 cubic meter per hour or 400 ton per hour conveying coal and having a belt speed up to 5 meter per second. The loading and discharging configuration of the conveyor system can be seen in Figure 19. Since this is a roof mounted monorail the minimum operating height is 2.2 meter and 3 meter wide. Figure 19. Loading, turning and discharging configuration of the SICON conveyor [38] The cross section in the middle of Figure 18 is the one corresponding to the innovative conveying system. Alike the other pouch conveyors in this chapter, this is a closed pouch and roof mounted conveying system. The support of this conveyor is done by tilted idlers and driven by the main pulley at the discharge end of the conveyor. [39] The Enerka-Becker conveyor system, also the E-BS, is another type of pouch and close conveying system. Comparing the E-BS to the previous pouch conveyors, no difference in performance or safety can be seen. The belt speed reaches up to 3 to 5 meter per second, conveying up to 400 ton per hour. The only difference between those two is the way of supporting and sealing the belt. Pipe conveyor Another but less popular way, to convey the raw material to the panel conveyor is by a pipe conveyor. The main advantages of the pipe conveyor are similar to the ones for the pouch conveyors: close systems preventing dust escaping the system and the possibility of making tight corners in comparison to the classis troughed belt conveyor. 3.4.1 Pipe conveyors Although the pipe conveyor is mostly implemented for long distances, it can be used in underground mining. Therefore, the principle and its limitations will be introduced in this chapter. These systems are capable to convey the material over 10 km and have an angle of inclination up to 30 degrees. The same main reasons to use the pipe conveyor underground appear for the transport over long distances away of the mine; dust free and protected transport. Furthermore, the small radii corners, steep inclination and high operational safety are some more advantages. The longest pipe conveyor is capable of conveying its material over a distance of 16.4 km with a difference in altitude of 164 meters. Especially the protection of the material for the outside environment and the other way around is of key value. For instance, hot ash with temperatures reaching 90 degrees Celsius is protected to a minus 45 degrees Celsius outside the belt. This is all done for a capacity of 2,200 ton per hour and a belt speed of 5.2 meter per second [40] [41]. The loading and unloading process of the pipe conveyor is shown on the left side of Figure 20 and a possible idler configuration on the right side. 18 Underground conveyors Figure 20. Left: Filling and unload process [42], right: Possible configuration of idlers [40] 3.4.2 Coaxial pipe conveyor Another type of pipe conveyor is the coaxial pipe conveyor. This system is invented to be able to adjust the end of the pipe. Therefore, it can move around and by trajectory flow stack material over a wide area without moving the whole system. However, this invention is not used that often and not a well-known system. Figure 21. Coaxial pipe conveyor intermediate drive frame details [43] 3.4.3 Extendable belt system Companies Sandvik Mining and BHP Billiton has entered into an agreement for the conceptual design and testing of an extendable belt system (EBS) for use at BHP Billiton’s Jansen project. The project is BHPB’s most advanced potash development project, located 100 km east of Saskatoon, Saskatchewan Canada. It will employ Sandvik Borer Miners for production with the EBS used for haulage to the panel belts. The Sandvik EBS designed and developed under this agreement will incorporate the latest technology available for enhancement of automation, production, life cycle costs and safety. Troughed belt conveyor The best-known conveyor is also used in the hauling process of underground mining after extraction and crushing of the material. Therefore, the troughed belt conveyor can be used as panel conveyor to convey the material over greater distance to the transfer point at the hoist shaft or to convey the raw material by itself to the surface. In the last case, often a large difference in altitude has to be covered. To perform a lift of a couple of hundred meters, a strong belt is required to lift it over a maximum angle of 20 degrees. Conveyor belts lifting raw material 800 meter vertical and over 8,000 meters in a single flight, require a belt tensile strength of 8.200 N/mm [44]. The mass flow rate versus the vertical lift is M.C. van Etten 19 Literature Assignment: Application of Conveyors in Mining Industry shown in Figure 22. In this figure the light grey coloured lines starting from the left top of the figure, are representing the characteristic lines for hoisting. The more horizontal and darker lines, starting from a mass flow rate of at least 1,000 ton per hour, are the characteristic lines for mines using conveyor haulage. Figure 22. Mass flow rate versus the vertical lift for hoisting and conveying [26] The maximum common lift for the troughed belt conveyors in underground mining is around 500 meters per flight. Often multiple flights are applied to realize a lift much higher, for example in the Cadia East Bulk mine five flights are used to lift the material over 1,400 meters. Where mines were categorized by production capacity up to super, an even bigger operation will be realized. The ‘Beyond Super’ with a capacity of 10,000 ton per hour and a lift of 2,000 meter. For this project, two parallel belt conveyors with a width of two meters will lift the material using four flights, running at 6 meters per second. Research in high lift application as in tensile strength and splicing technology has made the high lift for the 45 megaton per year in the Chuquicamata mine successful. [26] Pocket conveyor As mines come in several types and designs, the way of transport is most of the time an one-of-solution. When material is extracted from a deep and shallow shaft inside the mine, the material needs to be lifted to the main level or surface. Besides the previous options, a solution for a steeper incline and small shaft is a pocket or bucket conveyor, conveying the material up to an angle of 90 degrees. This type of conveyor uses pockets up to 1.2 meter wide to lift material up to 800 meters per flight. The capacity of these conveyors can reach up to 1,815 ton per hour for coal. The belt driven by the pulleys has sections cut out where these pockets will be attached. A single pocket and the ‘open’ belt on the pulley side is shown in Figure 23. Using a pocket conveyor, the use of underground bunkers to store the material can be avoided [40]. 20 Underground conveyors Figure 23. Left: A single pocket, right: The belt with the open spaces for a pocket to be attached [40] Summary underground mining conveyors In this chapter the application of conveyors used in underground mining was investigated. Conveyors can cover the whole process of underground mining. By using a longwall mining AFC or continuous miner, the material is extracted and transferred to the next process station. These pieces of equipment use chain conveyors to handle all sizes of material. When the extraction and first transport to the first process station, often a crusher, other types of conveyors are used. Crushers make sure the desired lump size is created to make sure the next piece of equipment can perform on its best. The next function in the process after extraction and transferring is transportation. This means often transporting the extracted material to the main gate. Depending on the method and the distance, multiple solutions are known. In case of room-and-pillar mining, including the corners through the mine, a FCT or Flexivayor can be useful. In case of a batch process by cars, conveyors can also be found in the flat hauling trucks using chain conveyors to on and offload the material. When the transport to the main gate has been done, the main distance to a hoisting point or hauling the material straight out of the mine needs to be done. At this point the pouched, pipe and troughed belt conveyor are applicable. These conveyors can be used also to lift the material, but because of the limited inclination this is over a greater distance. In case of lifting the material using a steep incline, pocket or bucket conveyors can be used. Research is done to improve working conditions, the process performance, automation, reduction in wear and tear, to name but a few. This is all to make it a safer, efficient and productive process. In the next chapter the use of conveyors in surface and open pit mining will be investigated. Many conveyors introduced in this chapter are also applicable in the open pit or surface mining. The principles of these conveyors will be the same except for differences in capacity and performances. M.C. van Etten 21 Literature Assignment: Application of Conveyors in Mining Industry 22 Surface mining methods 4 Surface mining methods Strip, open pit, dredging, hydraulicking and placer-and-solution are examples of surface mining methods. In this work the focus will be at the exploitation of the near-surface deposit during open pit mining. The reason to choose for surface or underground mining is generally because of geology and topography manner. Roof conditions of the mine, vertical distance between ore seams and ore thickness are examples of variables to be considered choosing the type of mining. Comparing maximum production rates shows for underground mining a maximum of 26 Mtpa and 107 Mtpa for surface mining. As said before, the economics is a key consideration in mining. It does not mainly decide if it is going to be a surface or underground mine, but it does determine the mining method to be applied [45]. The world’s deepest open pit mine is located in the U.S. and is 4.5 km across and 1.2 km deep. The biggest mine is Germany’s Garzweiler mine with a total surface of 48 km2 using the famous bucket wheel excavator [46]. Methods Within the surface mining there are, as mentioned in the introduction, multiple ways of surface mining. The one shown on the left side in Figure 24 is the open pit mining and strip mining on the right side. For strip mining the main characteristic is that the material is relatively near the surface. Long strips are mined with the bucket wheel excavators. First a whole layer of soil is mined and transported to the other side of the mine. After that, a layer of for instance coal and other soft rock can be mined. For open pit mining the material needs to be close to the surface as well. Blasting is a well-known method to extract the material and to create the benches functioning as the stability, haul way for haul trucks and protection against falling rock. Material mined in open pit mines is classified as ‘hard rock’ for example: gold, copper, armour stone and aluminium. Figure 24. Left: Open pit mining, Right: Surface mining M.C. van Etten 23 Literature Assignment: Application of Conveyors in Mining Industry Transport in surface mining In the Garzweiler mine, the extraction of the different layers of soil and ore is done by a bucket wheel excavator and is dumbed on a system of belt conveyors. In these wide surface mines distances are big and slopes are small which makes it ideal for though belt conveyors. However, this is not the case in open pit mines since big slopes are unavoidable because of the greater depth. Hauling the material back out of the open-pit is often done by haul truck but they carry some disadvantages with them. Some of those are the high fuel consumption with a difference in fuel costs of 4,730 dollars per hour. Also, comparing to a pocket conveyor, the haul trucks carry higher capital investment and high emissions with them [47]. New solutions in conveying are found and will be introduced in the next chapters. 24 Surface conveyors 5 Surface conveyors Similar to the underground mining, extracted material often needs to be prepared for transport. Every type of transport and so conveyor system has its specifications in order to perform as wanted. When material is extracted it can include odd and large lumps due to the blasting. The capacity of the crusher and stacker in Figure 25 can reach up to 400 ton per hour, where the right side mobile belt conveyor can reach up to 2500 megaton per hour. Figure 25. Crusher and conveying unit using an apron feeder and belt conveyor [48] Apron feeder As mentioned earlier an apron feeder is often used to transport the raw material to its first transfer or preparation point. The hopper has the function of a buffer and the apron feeder can extract the material coming out of the hopper and transport it often to a crusher. In Figure 26 are two possible setup configurations shown involving the apron feeder in an underground and an open mine. The material dumped into the hopper above the apron feeder can be in all kind of conditions. This type of equipment can convey all types of raw material over a short distance. It can content abrasive, sticky, small and large pieces of material. To feed this material onto another piece of equipment such as a belt conveyor, crusher or train carriages, an apron feeder can be used. For underground mining, the range of capacity if from relatively small to 1400 ton per hour. For surface mining this is much more and can be 16,000 ton per hour [31] [49]. Figure 26. Possible configurations for the use of an apron feeder [50] M.C. van Etten 25 Literature Assignment: Application of Conveyors in Mining Industry The Apron feeder consist of series of pans, also called flights, driven by a roller chain on each end of the pans. These roller chains are driven by chain sprockets connected to a shaft and a powerful drive pulley, as can be seen in Figure 27. It can be seen as one of the members of the chain conveyors. The layout of the pans can vary in flat pans or with a small cleat included. Also, this piece of equipment has a belt conveyor inside. This transports the material dribbling out of the apron feeder. This is a so-called dribble conveyor. Figure 27. Left: The sprocket on each side of the conveyor attached to the shaft, Right: The dribble conveyor [51] An addition to the apron feeder can be a conveyor belt on top of the pans. This makes it a mixture of a belt and apron feeder. Doing this, the spillage through the pans is solved and makes a dribble conveyor unnecessary, making the whole system lower in comparison with the apron feeder. The capacity of this type of conveyor is between 1,200 to 4,500 cubic meter per hour [52]. Figure 28. The low profile feeder [52] High angle hauling conveyors Open pit mines or surface mines vary in width, depth, capacity, mined material and many more parameters. Every mine is different and solutions to a problem are most often one of a kind. The hauling process in surface mining is often by the use of conveyors. For open pit mines, which are usually deeper and the sides of the mine are steeper, the haul trucks are well known. But there are some unique solutions which are used more often. The sandwich conveyor and the pocket conveyor are some of those solutions. 5.2.1 Sandwich conveyors To lift the material over steep hills up to 90 degrees vertical, sandwich conveyors can be used. These conveyors are supported on the mines walls, on the steps with legs, or even with a boom supporting the conveyor from the top of the open pit mine [53]. As the name tells, the material conveyed will be sandwiched and so compressed with two belts as can be seen in Figure 29. 26 Surface conveyors After the material is loaded on the belt conveyor and right before the inclination starts, the second belt is pressed on top. Compressing the material will increase the shear stress of the material, this way vertical lifting is made possible. The belts in a sandwich conveyor can get up to around 3 meters wide, conveying 10,000 ton per hour. Figure 29. Sandwich conveyor for high angle conveying [54] 5.2.2 Snake conveyor A similar sandwich type conveyor is the snake conveyor. This conveyor makes slight curves over idlers which creates a radial pressure on the belt laying on top of the material as it moves over the curves. An invert part with idlers on the top belt creating another curve does the same for the other side. The result is tension on the belt pushing on the material as it is lifted upwards. The sandwich conveyor bending over the idlers and moving like a snake is shown in Figure 30. Figure 30. Idlers in the snake conveyor create a curve in the belt and causing pressure on the material [55] 5.2.3 Pocket conveyor As introduced in underground mining, for the high angle incline conveying a pocket conveyor is an option. The application of a pocket conveyor is also possible in an open pit mine. The same advantages like conveying the material over a steep incline in a continuous way are present in the open pit mining. These pocket conveyor and cleated conveyors have applications in open pit and underground mining. In figure 32, the pocket conveyor lift height and capacity are compared to the cleated conveyor. M.C. van Etten 27 Literature Assignment: Application of Conveyors in Mining Industry 5.2.4 Cleated conveyor The use of cleats and sidewalls makes it possible to lift the material on an angle up to 90 degrees. The advantage of this system is that the conveyor can move also in horizontal way. This makes it capable of conveying over a range of 0 to 90 degrees inclination in one single flight. The capacity of conveyors using cleats and sidewall can get higher than that of a pocket conveyor but on average cannot reach up that high. Over a lift of 276 meter a capacity of 2,000 ton per hour can be performed. Sidewalls and cleats of this type of conveyor get up to 630 and 600 mm. The higher the sidewalls and cleats the more it can carry and therefore, the system is capable of conveying material with a high capacity. Not only can the height of the cleat cause the possibility to lift the material, they also can have a slight curve, causing them to hold the material tight. In order to make a turn over a pulley the sidewalls of the conveyor have a wave profile. This can be seen on the left-hand side in Figure 31, as well as the different types of cleats on the right-hand side. [40] Figure 31. Left: Cleats and sidewalls conveyor, right: different types of cleats [56] Figure 32. Cleat conveyor (grey) vs pocket conveyors (yellow) [40] Troughed belt conveyor The application of troughed belt conveyors is the most common one in terms of conveying bulk. Belt conveyors used in surface mining are often designed to handle a high demand of material. This is because in surface mining, the minerals are often underneath one or more layers of ground. This layer is then moved by excavating and stacking that material somewhere else. This way the wanted minerals are exposed to the surface and ready to get mined by excavating. Transferring big pieces of land asks for conveyors with high capacities. For surface mining by excavating the material, the capacity can reach 28 Surface conveyors up to 40,000 ton per hour. This is the result of the biggest bucket wheel excavators in the world moving 240,000 cubic meter per day. Another record using a bucket wheel excavator is set in the surface mining. This is done by a 2,800 mm wide belt running at a record speed of 15 meters per second, mining lignite [44]. The use of troughed belt conveyors can have extreme dimensions, this is proven inside and outside the mines. The strongest conveyor belt is one with an effective breaking strength of 8,600 N/mm and it contains 13.2 mm diameter steel cords in the carcass. It is implemented in a triple flight 24 km long belt conveying system in Chile transporting copper ore. Another record of the troughed belt conveyor is the longest single flight conveyor belt worldwide, covering a distance of 27 km and transporting 2,400 ton per hour from a coal mine in South Africa [57]. The longest belt conveying system in the world covers a distance of 100 km [58]. Figure 33. Longest single flight conveyor in India and Bangladesh to the cement mine [59] Summary surface mining conveyors The mining process has its strict order for mining depending what type of equipment is used. This is similar for underground, surface and open pit mining. When conveyors are used in the process, the material has to be prepared in order to maximize the conveyor’s performance. Depending on which type of equipment or units, this can be done in a specific way. When truck hauling is used in open pit or surface mining, the material will not be prepared for that first transport or transfer process. But when a conveyor is installed, a crusher in combination with a feeder is installed in order to feed the conveyor with its desired capacity, lump size and speed. Applications as the sandwich, snake, pocket and cleated conveyors are solutions for high angle inclinations in open pit mines. These systems can be used to haul the material out of the mine instead of using multiple haul trucks. When material is hauled out of an open pit mine, the material is transported further often by the high efficient troughed belt conveyor. In surface mining the capacity of the extraction can be extreme high, due to the use of the bucket wheel excavators. Conveyors are adjusted to these capacities. In case of less homogenous material, apron feeders are often installed to transport the material from the offload point of dump trucks to crushers, resizing the raw material. After resizing the material, it is most often transported by troughed belt conveyors, capable of handling the large capacities of ore. M.C. van Etten 29 Literature Assignment: Application of Conveyors in Mining Industry 30 Development 6 Development The developments in conveyors used in the mining industry are discussed in this chapter. First the trends in new types of conveyors in overland conveyors will be discussed. The light weight conveyors will be introduces giving some interesting conveyor types. There are some types of conveyors which might be used in surface and underground mining in the future, but which have not been introduced yet. In the second part of this chapter the developments in sustainability of the conveyors will be briefly discussed. Conveyor trends Since the transport by conveying is often done over long distances the friction resistance is an important factor in the energy consumption. Therefore, various research is going on in order to eliminate the cause as much as possible. Although the advantage of the low rolling resistance using idlers and other rollers has made the conveyor as big as it is nowadays, research in this field of rolling resistance is still going on. Other recently research developments are done in the starting and stopping phase of the conveying process, since this is the primary cause of equipment failure. After the material is mined either in surface mining or underground mining, the material is prepared to be transfer to its next process station. This last step of transport before the material reaches a plant or storage, can also be done by conveyors. The conveyors are designed for a long journey with possible variation in circumstances. The constantly recurring design requirements per type of conveyor will tell if a type of conveyor is applicable for the job. Design and requirements priorities on capacity, lump size, dust generation and environmental conditions are key requirements that make the decision which type of conveyor will be used. A brief investigation on the trends in other types conveyors close to the mining process. These conveyor types are applicable in surface or underground mining after extraction is done, mostly applied over long distance and rough surface. 6.1.1 Rope conveyor A conveyor system for difficult terrain can be a cable or rope conveyor system. Often the belt is flat, has sidewalls and cleats and a beam on it attached. At the ends of each beam rollers are installed running over the rope located on each side of the flat belt. Since the ropes are the only support to the conveyor it is a light weight system, up to 30% lighter than a conventional system. Therefore, it is an ideal conveying system for conveying the material through the air and it is still capable to handle 25,000 ton per hour [60]. In Figure 34, the support of the rope on the rollers is shown and in Figure 35, a cross section compared with the conventional conveyor is shown. Furthermore, and according to Fruehstueck [61] the comparison in required drive power between the rope conveyor and the conventional conveyor, show a 50% difference. A loaded conventional belt conveyor transporting material over 1 km and up to 6 km needs the double amount of required drive power and this will increase for longer distances. Another advantage of the cable conveyor over a conventional conveyor is the generation of noise. The environment and workers around the conveyor will experience a noise emission three times lower compared to the conventional conveyors. M.C. van Etten 31 Literature Assignment: Application of Conveyors in Mining Industry Figure 34. Rope conveyor used in Mexico [62] Figure 35. Cross sections of a conventional and a RopeCon, the cable conveyor [63] This principle can also be executed by using a rail. Instead of a rope, the system uses a rail. A flat belt with sidewalls and possible cleats supported by rollers attached on a beam. Only the wheels on the rail conveyor roll over a mounted rail and not a cable. This makes the construction a lot heavier and not applicable to convey material through the air. An advantage is that it can handle much more material and so the possible capacity can reach up to 40,000 ton per hour. [60] 6.1.2 Cable conveyor The cable conveyor operates almost similar to the rope conveyor. Where the rope conveyor has rollers attached to the belt rolling over a static rope, the cable in the cable conveyor is attached to the belt and is running over fixed installed rollers. The capacity of this type of conveyor is about 6,000 ton per hour, much less than the 25,000 ton per hour for the rope conveyor. The cross-section of the cable conveyor is shown in Figure 36. 32 Development Figure 36. Cross-section of the cable conveyor compared to a troughed idler conveyor [64] At the end of the conveyor the belt is turned by a pulley while the cable is guided underneath and away of the belt. When the belt leaves the pulley and is turned around, the cables are connected again. This time the cables support the belt on the outside. When the belt reaches the other end of the conveyor, the same happens. The cable leaves the belt as soon as the belt reached the pulley and connects the belt when it leaves the pulley. Now the belt is ready to get loaded again and is supported on the inner groove at the sides of the loaded materials surface, as shown in Figure 36. As can be seen in Figure 36 and Figure 37, the rollers supporting the cable belt on the outside can be installed under a certain angle to decrease the components used in a curving track at the troughed idler conveyor [64]. Figure 37. Using minimum components in a curve using inclined rollers [64] In a system where a rope is driven and the belt locks itself to the cable or rope, a system has been invented to lock and release the belt from the rope. In Figure 38, it can be seen that a grab can be opened when it moves through two small cylinders because of the press-on rollers and spreading the device. The belt with the locking system is then released [65]. This invention has the main goal to easily lock and release the belt with the cable or rope. M.C. van Etten 33 Literature Assignment: Application of Conveyors in Mining Industry Figure 38. Transporting device locking and releasing the rope [65] 6.1.3 Rail conveyor Transport over rail has proven its efficiency because of the low rolling resistance and is a method well known. The same principle has been applied on the Rail conveyor. This system has been invented by Dr. Craig Wheeler at TUNRA Bulk Solids. In this principle of bulk transport, a conveyor belt is supported by carriages. These carriages roll over a rail with a low rolling resistance, causing a high efficient conveying system. On the left side of Figure 39, it can be seen that a curved support beam attached to the carriages keeps the belt in its shape and position. On the right side, the drive and tension system is shown. The belt of the rail conveyor is driven by the drive belt technology and a drive pulley for the interconnecting rope make the system move. Before the belt reaches the head pulley where it offloads its material, the carriages are redirected over their return loop towards the point where the belt will meet the carriages again [66]. Figure 39. Left: Carriage with the belt on top, right: The drive and tensioning system [66] 34 Development 6.1.4 CARIAT conveyor Another recent developed conveyor with the use of rail and the principle of an endless loop is the CARIAT conveyor. The name CARIAT stand for continuous articulated rail in a tube. In this system multiple linked carriages travel through a tube over a rail. Traveling with loaded carriages between 5 and 15 meter per second makes it a fast-moving system in a closed environment [67]. Although it is not sticking to the definition of a conveyor since it is divined in this assignment, as it is not powered by a drive pulley at one of the conveyor systems end, it shows a trend. The trend seen is the development in conveyors using the rail for its efficiency and a closed system. Figure 40. Left: A single carriage in the tube, Right: Offloading principle of the CARIAT [67] 6.1.5 Material Not only the way of conveying and the way of moving the supporting surface is research, also the supporting material itself, the belt, is an important element. Multiple solutions to strengthen the belt are nowadays standards. Besides the use of steel cords in the conveyor belt to increase strength, the use of Kevlar was investigated. In a 1984 the company Du Pont implemented Kevlar cords in the belt in order to make the belt stronger. Since Kevlar is five times stronger the use of Kevlar cords in the belt improves the strength, the impact resistance and the wear of the belt. Therefore, less material needs to be used and a belt carcass of Kevlar can end up being 0.25 times the thickness of a belt carcass using steel cords. The use of Kevlar in the belt knows one very important down side. The use of Kevlar in the belt is very limited because of it costs. The material is several times more expensive comparing to the use of other material [68]. The search for other materials keeps on going. M.C. van Etten 35 Literature Assignment: Application of Conveyors in Mining Industry Sustainability Companies are looking for more sustainable ways of doing their business, since more proven technology is occurring and the change is ordered by government. Although sustainability is a wide concept a couple of subjects concerning sustainability will be briefly introduced. Energy At first, the reduction of input into the mining system to increase the sustainability of the mine will be discussed. Many research is done in reducing rolling friction in conveyor systems. In the first place, the low rolling resistance over rail is implemented in new conveyor systems as shown in chapter 6.1.3. The second part of reducing rolling friction and therefore reducing the energy consumption of existing systems, is for example the rolling friction within idlers which can take up to 20% of the total resistance in the belt conveyor system [69]. Not only the amount of energy needed is reduced also the source of the energy can be changed. The changeover can be made for example to renewable energy such as wind energy. This is done at the Diavik Diamond Mines where a windfarm is installed to generate and supply the mine with 17 gigawatt hour per year. This results in a reduction of diesel consumption by 10% and a reduction of the carbon footprint by 6% [70]. Water Another input of the mining process is water. In the process of mining, water is used for the needs of workers, mineral processing and controlling generated dust. The way of applying water to prevent dust generation has been topics of multiple research. Knowing the exact amount of water needed and finding better systems to apply it, can save a lot of water and therefore make it more sustainable. Also, the water can cause contamination of the ground since it contains concentrations of the material, which effects the environment around the mine [71]. Dust generation Due to transhipment, transfer and transportation of the bulk, dust can be generated. Fine particles smaller than a millimetre, can pollute the air which can cause not only serious damage to the workers and the environment, but it can also cause explosions. Therefore, dust needs to be controlled. This can be done by taken dust generation into account in the designing and the decision phase of the mining process. Less transfers means less dust. As mentioned earlier, dust generation is controlled by adding water. If for example the bulk is discharged to its storage, wind can spread the material over land undesirable. By adding moisture around the dust flow, the dust flow is limited and controlled. An example is shown in Figure 41. Figure 41. A ring of water nozzles keeps the dust flow limited and controlled [72] 36 Development Noise generation Another sustainability factor which involved worker’s health and the surroundings of an installation is noise generation. Similar to the dust generation, noise can be generated at transfer points where the material flow changes for instance direction. This also shows the performance factors for a design of a bulk handling system. One example of a redesign in the chain conveyor is shown in chapter 3.1.1. By redesigning the sprockets driving the chain, the noise could be reduced. In many other conveyor systems idlers are used. These rollers are one of the component which can not only cause resistance but also noise. Research on design and different type of material in components show a being on reduction of the noise up to 12 dB [73]. This makes a big difference knowing that the limit for exposure to the noise over a long period of time is maximum 85 dB [74]. Maintenance To keep a process running within a certain level of sustainability, the maintenance is also an important key factor. Replacing or repairing components because of for example wear and tear, will prevent a reduction in performance. The performance in terms of sustainability can be seen in the earlier introduced factors; resistance and therefore energy consumption, dust generation and noise generation. Automation As mentioned in the beginning of this assignment automation is also an important issue since the labour costs is a big cost for every company. More equipment can now be operated by one person and more accurate, this will be seen more often. When the accuracy of a process is increased, the sustainability of such is increased as well. Or even more extreme, the mine will be operated by a small team of operators in a cabin outside the mine. M.C. van Etten 37 Literature Assignment: Application of Conveyors in Mining Industry 38 Conclusion 7 Conclusion The conveyors have all the same bulk handling function: transportation. The material properties of the extracted raw material do not always meet with of the desired ones for the used conveyor systems. Each different type of conveyor has been designed with a different philosophy and requirements. Since in almost every way of mining different types of conveyors are used, the material properties need to be changed for a more efficient and productive operation. Only a view conveyor systems are designed for transporting the raw material extracted. These conveyors transporting the raw and excavated material are capable of conveyor a variety of lump sizes and capacities. A chain conveyor using flights or apron feeders are the right conveyors to do such thing. Often a crusher or other piece of equipment to prepare the material is installed at the transfer point. Belt conveyors, pipe conveyors, and cleated conveyors transporting the right sized material makes the system reliable, efficient and productive. This is applicable for underground, surface and open-pit mining. The right equipment for the job all depends on the mine configuration. The type of equipment depends on the material being mined, together with the rate and the environmental conditions and surroundings. For instance the use of a troughed belt conveyor: It has a maximum inclination of 20 degrees and a maximum length depending on the production rate and inclination. In case of maximum inclination and a production rate of 6000 ton per hour a maximum length of 800 meters was reached during underground mining. On the other hand, for a situation without inclination a troughed belt can handle 40.000 ton per hour during surface mining over a similar length. Also, the characteristics of a troughed belt conveyor and an apron feeder are similar on the maximum inclination and production rates. However, because of the robustness and material grading the apron feeder can handle, they vary a lot of each other. All the conveyors are one off a kind solutions. However, it can be seen that equipment using a chain conveyor principle often is used in the beginning of the mining process. Later on in the process where the material is more homogenous of size, the use of the troughed belt conveyor is more likely. For high angle conveying the solutions are varying in a small range. Snake, sandwich, cleated and pocket conveyors are capable of handling material across the high angle walls of open pit mines and therefore, replacing the haul trucks. Similar to the troughed belt conveyor example, the solutions can handle less capacity in case of a greater lift. Lifts can reach up to 1.5 km, using multiple flights of troughed belt conveyors or other conveyors in both underground and surface mining. Research and more solutions are focussed on the rolling resistance and some light weight conveyor types. This results in the rope, cable, rail conveyor and CARIAT being low power solutions in the transportation of bulk handling. However, these systems are not showing implementations in an inclined configuration. Despite the fact that back in the days carriages using the low rolling friction of rail were used for transportation in underground mining. The trend of conveyors using rail does match with the sustainability topic: More efficient systems using less resources as power and water to perform equal or even better, including noise and dust generation. M.C. van Etten 39 Literature Assignment: Application of Conveyors in Mining Industry 40 References 8 References [1] C. G. Lewis R.S., Elements of mining, New York: J. Wiley, 1964. [2] G. C.E., A concise history of mining, Oxford: Pergamon Press., 1980. [3] I. Shaw, The Oxford History of Ancient Egypt, Oxford: Oxford University Press, 2003. [4] J. Dodson, X. Li and N. Sun, “Use of coal in the Bronze Age in China,” The Holocene, 2014. [5] R. Cowen, Exploiting the Earth, Johns Hopkins University Press, 1999. [6] C. Mundigler, “Ancient Mining Techniques,” 21 06 2016. [Online]. Available: http://uwlabyrinth.uwaterloo.ca/labyrinth_archives/ancient_mining_techniques.pdf. [7] E. H. Ash, Power, Knowledge, and Expertise in Elizabethan England, London: The Johns Hopkins University Press, 2004. [8] G. Agricola, 21 06 2016. [Online]. Available: http://ihm.nlm.nih.gov/images/A12175. [9] C. Miller, The Atlas of U.S. and Canadian Environmental History, New York: Routledge, 2003. [10] Commonweatlh of Australia, “History of Australia's Minerals Industry,” 21 06 2016. [Online]. Available: http://www.australianminesatlas.gov.au/history/index.html#1900. [11] M. J. Hartman H.L., Introductory Mining Engineering, Hoboken: John Wiley, 2002. [12] Kentucky Geological Survey, “uky coal mining,” [Online]. Available: http://www.uky.edu/KGS/coal/coal_mining.htm. [Accessed 09 07 2016]. [13] CEMA, Belt Conveyor of Bulk Materials, 2014. [14] T. M. Journal, “themhedajournal.org,” [Online]. Available: http://www.themhedajournal.org/2004/07/15/transport-of-bulk-materials-by-conveyor-dates-back- to-1795/. [Accessed 18 07 2016]. [15] “The Encyclopedia Americana,” [Online]. Available: https://en.wikisource.org/wiki/The_Encyclopedia_Americana_%281920%29/Robins,_Thomas. [Accessed 18 07 2016]. [16] Habasit, “Habatec.net,” 2011. [Online]. Available: http://www.habatec.net/HNet/HabaTEC.nsf/vwWebContent/B3AFDB9C92909C37C12578BE002 BB553?OpenDocument. [Accessed 18 07 2016]. [17] J. Joy, “Loading Machine”. United States of America Patent 1306064, 10 06 1919. [18] J. Joy, “Mobile conveyor apparatus for underground mines”. United States od America Patent 2879884, 31 03 1959. [19] S. Reed, “Glencore's Big Loss Reflects Hard Times for Mining Companies,” The New York Times, no. March 1, 2016. [20] S&P, “Us.spindices.com,” [Online]. Available: http://us.spindices.com/indices/equity/sp-metals- and-mining-select-industry-index. [Accessed 19 07 2016]. [21] Deloitte Touche Tohmatsu limited, “Top 10 issues mining companies will face in the coming year 2016,” Deloitte, 2016. [22] L. Else, “Built it big,” Newscientist, 19 06 2004. [Online]. Available: https://www.newscientist.com/article/mg18224526-300-build-it-big/. [Accessed 27 07 2016]. [23] S. Rupprecht, “Mine Development - access to deposit,” University of Johannesburg, Johannesburg, 2012. [24] Alberta, “OHS Code Explanation Guide,” 1 07 2009. [Online]. Available: http://work.alberta.ca/searchaarc/385.html. [Accessed 2 10 2016]. [25] P. Darling, SME Mining Engineering Handbook, Society for Mining Metallurgy and Exploration, Inc., 2011. [26] J. Spreadborough, “High-Lift belt conveyors for underground hard rock haulage,” Parsons Brinkerhoff, Brisbane. M.C. van Etten 41 Literature Assignment: Application of Conveyors in Mining Industry [27] Arch Coal Inc., “technology.infomine.com,” 09 2012. [Online]. Available: http://technology.infomine.com/reviews/UndergroundHaulage/welcome.asp?view=full. [Accessed 02 07 2016]. [28] N. Singh, “Design in Longwall Mining,” in Engineered Rock Structures in Mining and Civil Constructions, Wollongong, Taylor & Francis, 2006, p. 319. [29] B. Cubby, “Longwall mine plan a threat to water supply,” The Sydney Morning Herald, vol. June 10, 2009. [30] mining-technology, “www.mining-technology.com,” 11 09 2013. [Online]. Available: http://www.mining-technology.com/features/feature-top-ten-deepest-mines-world-south-africa/. [Accessed 29 06 2016]. [31] B. R. Hustrulid W.A., Underground Mining Methods, Littleton: Society for Mining, Metallurgy and Exploration, (SME), 2001. [32] R. Stefanko, Coal Mining Technology: Theory and Practice, SME, 1983. [33] JOY Global, “Longwall systems,” 2012. [Online]. Available: http://www.joyglobal.com/docs/default-source/product-documents/underground/longwall- systems/longwall-brochure.pdf?sfvrsn=24. [Accessed 27 07 2016]. [34] Caterpillar, “High-Capacity AFC System,” 2011. [Online]. Available: http://s7d2.scene7.com/is/content/Caterpillar/C741338. [Accessed 27 07 2016]. [35] JOY Global, “JOY Underground Equipment brochures,” 2015. [Online]. Available: http://www.joyglobal.com/docs/default-source/product-documents/underground. [Accessed 27 07 2016]. [36] P. G. Kovalchik, “A dual sprocket chain as a noise control for a continuous mining machine,” National Institute for Occupational Safety and Health, Pittsburg. [37] Prairie Machine & Parts, “Flexiveyor Brochure,” [Online]. Available: http://pmparts.com/wp/wp- content/uploads/Flexiveyor-Brochure_Web.pdf. [Accessed 29 07 2016]. [38] Continental, “ContiTech's SICON conveyor belt,” [Online]. Available: http://www.contitech.ru/pages/news/140530_ugol-sicon_en.html. [Accessed 04 08 2016]. [39] D. Hastie, “The current state and future requirements of continuous haulage systems for underground gateroad development,” in BELTCON17, Wollongong, 2013. [40] Continental, “Contitech.de,” [Online]. Available: http://www.contitech.de/pages/produkte/transportbaender/brochures. [Accessed 12 08 2016]. [41] Beumer group, “Pipe conveyor,” [Online]. Available: https://www.beumergroup.com/en/products/conveying-technology/pipe-conveyor. [Accessed 28 07 2016]. [42] Bridgestone, “Pipe conveyor belt,” [Online]. Available: http://www.bridgestone.com/products/diversified/conveyorbelt/products/pipe_conveyor_belt.html. [Accessed 28 07 2016]. [43] BOSMIN, “CoAxial Pipe Conveyor Detail Design,” [Online]. Available: http://www.bosmin.com/CAP/CAP_DesignDetail.pdf. [Accessed 04 08 2016]. [44] Phoenix conveyor belt systems gmbh, “World records,” 2015. [Online]. Available: http://krk.com.br/wp-content/uploads/2015/02/World-Records.pdf. [Accessed 21 07 2016]. [45] G. Kitts, “National Mining Association,” 21 Sep 2012. [Online]. Available: http://www.nma.org/pdf/fact_sheets/why_surface_mine.pdf. [Accessed 23 06 2016]. [46] “Tagebau Garzweiler,” RWE, [Online]. Available: view- source:http://www.rwe.com/web/cms/de/1140420/umsiedlung/tagebau-rekultivierung/tagebaue- genehmigte-abbaufelder/tagebau-garzweiler/. [Accessed 28 06 2016]. [47] S. Nekoufar, “Trucks vs. pocket belt conveyors,” Australian Bulk Handling Review, no. January/February, p. 68, 2014. [48] METSO, “Mobile belt conveyors,” [Online]. Available: http://www.metso.com/products/conveyors/lokolink-mobile-conveyor/. [Accessed 08 08 2016]. 42 References [49] Terex, “www.terex.com,” 2011. [Online]. Available: http://www.terex.com/minerals-processing- systems/en/cs/groups/webcontent/@web/@mps/documents/web_content/ucm03test_005084.pd f. [Accessed 24 07 2016]. [50] M. A. Yester, “www.nwsassn.org,” [Online]. Available: http://www.nwsassn.org/files/metsomineralsfeeder.pdf. [Accessed 27 07 2016]. [51] Merrick Industries, [Online]. Available: http://merrick-inc.com/model-450a. [Accessed 08 08 2016]. [52] Transmin, “Low Profile Feeder,” 2016. [Online]. Available: http://transmin.com.au/wp- content/uploads/2016/04/Brochure_Low-Profile-Feeder_English_Web_Rev0.pdf. [Accessed 28 08 2016]. [53] G. L. J. Imants Ozolins, “Mobile elevator conveyor”. USA Patent 4765461A, 23 August 1988. [54] Joy Global, “High Angle Conveyor,” 2016. [Online]. Available: http://www.joyglobal.com/docs/default-source/product-documents/surface/high-angle-conveyors- and-related-systems/xs-5182-1-en.pdf?sfvrsn=28. [Accessed 06 08 2016]. [55] J. D. Santos, “Qualifications in Sandwich Belt High Angle Conveyors,” 2016. [Online]. Available: http://www.dossantosintl.com/JDSRecord.php#DSI Snake-Sandwich High-Angle Conveyor. [Accessed 07 08 2016]. [56] DUNLOP, “Dunlop conveyor belting,” [Online]. Available: http://www.dunlopconveyorbelting.com/uploads/media/Sidewall_brochure_E_oct_01.pdf. [Accessed 12 08 2016]. [57] C. Wheeler, “An Overview of specialised belt conveyors,” TUNRA Bulk Solids ICCHPS, Newcastle, 2015. [58] G. Lodewijks, “Strategies for Automated Maintenance of Belt Conveyor Systems,” TUDelft, Delft, 2004. [59] J. Athialy, “www.flickr.com,” 2010. [Online]. Available: https://www.flickr.com/photos/joeathialy/4671395790. [Accessed 11 08 2016]. [60] Doppelmayr, “doppelmayr-mts,” [Online]. Available: www.doppelmayr-mts.com. [Accessed 06 08 2016]. [61] F. K. Hermann Fruehstueck, “Saimh.co.za,” [Online]. Available: http://www.saimh.co.za/beltcon/beltcon12/paper1210b.htm. [Accessed 12 08 2016]. [62] Doppelmayr, “Youtube,” mei 2016. [Online]. Available: https://www.youtube.com/watch?v=Chp2nOOdkIQ. [Accessed 07 08 2016]. [63] F. Kessler, “Recent developments in the field of bulk conveying,” 2006. [Online]. Available: http://www.mas.bg.ac.rs/_media/istrazivanje/fme/vol34/4/6._kessler_213-220.pdf. [Accessed 11 08 2016]. [64] Metso, “Metso mining and constructing,” [Online]. Available: http://www.metso.com/miningandconstruction/MaTobox7.nsf/DocsByID/D845D05614339D00422 56B640041A178/$File/CableBelt2010-Low-Res-Final.pdf. [Accessed 14 08 2016]. [65] K. Switzeny, “Transporting device with transporting belt”. USA Patent 7500552 B2, 10 March 2009. [66] C. A. Wheeler, “Rail conveyor system”. Australia NSw Patent US20130118371 A1, 16 May 2013. [67] Reynolds resources pty ltd, “Cariat Conveyor Mining and Bulk Haulage System,” 02 05 2014. [Online]. Available: https://www.youtube.com/watch?v=NbOQ2GvsMIE. [Accessed 21 09 2016]. [68] T. S. Mohammad E. Fayed, Mechanical Conveyors: Selection and Operation, Basel: Technomic, 1997. [69] R. K. Miroslav Bajda, “Experimental Tests of Selected Constituents of Moving resistance of the Belt Conveyors Used in Underground Mining,” Wroclaw University of Technology, Wroclaw, 2015. [70] L. v. Wyk, “Diavik Diamonds Mines Inc. Wind Farm Project,” 13 08 2015. [Online]. Available: http://www.pws.gov.nt.ca/pdf/EnergyCharrettePresentations/Diavik%20Wind%20Farm%20Proje ct%20-%20Liezl%20van%20Wyk.pdf. [Accessed 21 09 2016]. M.C. van Etten 43 Literature Assignment: Application of Conveyors in Mining Industry [71] Safe water (SDWF), “Mining and water pollution,” 31 08 2015. [Online]. Available: https://www.safewater.org/PDFS/resourcesknowthefacts/Mining+and+Water+Pollution.pdf. [Accessed 22 09 2016]. [72] Dust Boss technology, “Dust suppression ring designed for conveyor discharge points,” 7 03 2014. [Online]. Available: http://www.dustboss.com/dust-suppression-ring-designed-for- conveyor-discharge-points/. [Accessed 22 09 2016]. [73] S. Brown, “Conveyor noise specification and control,” in Acoustics, Gold Coast, Australia, 2004. [74] P. C. H. Hansen, “Engineering noise control,” University of Adelaide, Adelaide, 2006. [75] Joy Global, “Joy Global,” [Online]. Available: www.joyglobal.com. [Accessed 20 07 2016]. [76] Caterpillar, “CAT equipment,” 2016. [Online]. Available: http://www.cat.com/en_US/products/new/equipment. 44