(Balochistan University of Information Technology,Engineering & Management Science, Quetta)ASSIGNMENT No # 01 (Features of Mine-Machines)

SUBMITTED TO: Engg. Fawad-ul-HassanSUBMITTED BY: Ghulam MehdiSUBJECT: Mine Power ,Drainage & Material HandlingCMS ID: 23101DEPT: BS Mining Engg. 6th , (Fall-12)DATE: 15-04- 2015 Buitems,Quetta

Features of MachinesContinuous Operation: The machines combine the breakage and handling functions, cutting, drilling and blasting are eliminated, and extraction and loading are performed in a single function (excavation).Cyclic Operation: The machines performed the two principal operations loading and haulage, with hoisting an optional third when essentially vertical transport is required.Surface EquipmentContinuous Operation: Bucket Wheel Excavator (BWE)Thebucket wheel excavator(BWE) is a machine that digs andexcavatesdirt continuously with the help ofbuckets, chutes, and a conveyor apparatus. BWEs are used forcross-pit miningand largeconstructionprojects.BWEs Advancements includingmountingthem on crawler and wheeler bases to allow them to move forward for continuousexcavationdeveloped through time. The power and complexity of BWEs mean that they can take as much as five years to build but in return they are capable ofminingmore than 313,908cubic yards(240,000 m3) of earth per day.BWEs are typically some of the largest machines on earth, weighing as much as 11,000 tons and standing hundreds of feet tall.Features:The first BWEs were powered by steam and mounted on railway tracks. Traditionally, the buckets would empty dirt into carts that could be driven on the railroads. Eventually they became electric and were driven with hydraulics and oil engines.In their early days, BWEs consisted of booms that were raised and lowered by cables pulled by men. Eventually, manpower was replaced bywinchesthat raised the cables of theexcavator.To excavate materials continuously, the BWE uses a rotating wheel that is positioned at the rear of the boom. The wheel consists ofbackets, also known as buckets. It can have any number of buckets, depending on the project and model. The rotating wheel penetrates the face while the boom swings from both sides and the bucket collects the dirt. As the material falls onto the conveyor belts, it is transported to further conveyors until it reaches a discharge point. The conveyors used are usually connected so they can be dismantled when the BWE needs to be transported.Advantages Continuous operation; no swinging necessary. Long discharge range. Can be operated on a highwall bench or on the coal seam. Can easily handle spoil with poor stacking characteristic and poor stability. Can extend range of shovel or dragline when operated in tandem. Can facilitate land reclamation as it dumps surface material back on top of the spoil pile.

(Diagrammatic BWE Sketch)

Disadvantages Will not dig hard materials. Some surface preparation required. Lower availability. Large maintenance crew required. High capital cost compared with output. Can be susceptible to spoil slides and flooding. Can cause coal damage with resulting lower coal recovery. Poor mobility.

(Actual BWE)Cyclic Operation: Power ShovelSince its creation, theshovelhas evolved into many forms. Beginning as a steam-powered device, inventors and manufacturers continued its development for the two centuries after its birth.The result is a long line of machinery, many of which have crossed industries and become multi-functional and crucial to a majority of applications. The steam shovel, a simple device used to lift dirt, has branched off first ascable excavators, and then ashydraulic excavators. The wide variety of excavators is evidence of the impact shovels have had on the industry.The shovel has also served as the basic prototype for other equipment, stripping shovels,draglines, andbucket excavators, all of which have play important parts in how dirt is extracted from the earth.Features:The earliest shovel was rail mounted but later versions could be wheeled or mounted on crawlers for more mobility. Changes also included evolving from steam-powered to oil or gas-powered. Many of the features of the first shovel have merely been improved upon, such as the slew. The first machine was limited in its swing, but since manufacturers have devised a way to make the arm capable of a 360 degree swing. Thebucketcan also be altered to lift a certain weight of materials, usually measured incubic yards.Thearmof the shovel, also known as theboom, is controlled by switches andgears. This can be done by hydraulics, pneumatics, or in as in the cable excavator, by cable wires. The bucket strikes the earth and scoops the material. In some situations, there is a dump truck or other vehicle for the purpose of dumping. In stripping shovels, the shovel is capable of breaking through hard rock for the purpose of uncovering raw materials or minerals.Types:The way shovels have evolved since Otiss invention can be seen in the dozens of varieties have materialized over the course of two centuries. They have taken many forms, but the most important are listed below.Cable ExcavatorThe firstcable excavatororiginated in the form of the shovel but evolved when the mining industry required heavy-duty equipment. Cable excavators extract dirt by the pulling of wire ropes or cables. TheBucyrus 120-B, produced in the 1920s, answered the demands of mining quarries with its capabilities. The cable excavator was made almost obsolete and suffered a steady decline when excavators were madehydraulic. Manufacturers such asBucyrusandP&Hstill produce cable excavators and they are used mostly within theminingindustry; however, they are no match for thestripping shovelorwalking dragline.Hydraulic ExcavatorThehydraulic excavatorovertook the cable excavator because it was cheaper, faster and more productive. Usinghydraulicoil to function thearmandbucket, the hydraulic excavator is one of the most popular machines. The earliest record of a hydraulic shovel appeared in 1882, by a British Company calledSir W.G. Armstrong & Co.Stripping ShovelStripping shovelsare used to strip away hard materials and rock to uncover materials. They differ from thecable excavatorin its height and capability. More suited to extract hard materials in heavy-duty operations, mainly mining, it is embraced for its size and power. It is also more advanced in that it moves forward on the excavated surface to continually extract materials. Stripping shovels, such as the 15,000-tonCaptain shovel, are among the largest in the world.Advantages Lower capital cost per yd3 (m3) of bucket capacity, although when boom length or machine weight is considered, the capital costs are roughly equivalent. Digs poor blasts and tougher materials better. Can handle partings well.

Disadvantages More coal damage can result in lower coal recovery. Susceptible to soil slides and pit flooding. Cannot easily handle spoil having poor stability. Cannot dig deep box cuts easily. Reduced cover depth capability compared with a dragline of comparable cost. Difficult to move.

Underground EquipmentContinuous Operation: ShearerAcoal sheareris an electrically driven hydraulic cutting machine also referred to as a power loader, stage loader or shear loader used in thelongwall miningofcoal. The average coal shearing machine is 15 meters long, weighs in excess of 90 tons and can travel up to speeds of 10 to 14 meters a minute.Other coal shearers such as those used in theTwenty mile Coal Minehas the ability to travel at speeds of 45 meters per minute. Coal shearers of different models are designed with varying dimensions and power output depending on the manufacturer. The parameters for selecting a coal shearer for a longwall mining operation is contingent on the type of shearer, dimensions of the shearer as well as the haulage speed and power output of the machine.

(Shearer)

Features:The shearer travels along the face of the coal seam, slicing large slabs of coal with a large drum or cutting head mounted on a large number of picks. The drums featured on shearers consist of two types. One type is the conventional pick-flushing drum that sprays water through spray jets mounted on top of the cutter drum vanes which varies from two to six vanes. Spray jets located in the front of the cutter pick are known as pick face flushing (PFF) and in the back as pick back flushing (PBF). Wet cutting allows for dust particles to become wet as soon as the picks on the drum impact the coal and cut it. The water gets mechanically mixed with the cut coal. With an extraction drum, water is mixed with the cut coal as it gets discharged from the drum.The shearers are designed to cut the coal seam in two different patterns: Bidirectional UnidirectionalUnidirectional cutting is the most common type of cutting pattern used in U.S. longwall mining in which the shearer travels tail entry to head entry. A leading drum is raised and cuts the coal while the trailing drum remains free from cutting or cuts the floor coal depending on the height of the coal seam. On the return trip back along the face the cleaning of any loose remaining is achieved. With bidirectional cutting, a web width of coal is cut in both directions of travel with each cutting trip requiring involving two-faced end operations to turn the machine around. The machine is usually operated by remote control from a safe working position inside the underground mine.Coal shearers also come equipped with self-haulage unit usually comprised of aconveyorbelt system that transports the coal away from the face after it is cut. The most common conveyor belt system, called an armored face conveyor, travels under the shearers collecting the coal as it is cut.When using a shearer in a longwall mining operation a temporary mechanicalhydraulicroof support system is needed to stabilize the mines roof. The roof supports, positioned behind the shearers, advance along the entire length of the coal seam face. As the coal shearer moves over the face, the roof supports are lowered and get push hydraulically up to the newly positioned shearer.

(Shearer)

Cyclic Operation: Loud-Haul-Dump (LHD)Aload haul dump truck(LHD), also known as ascoop tram, is a specialized loading machine manufactured for theunderground miningindustry. LHDs are used to scoop extracted ore, such as coal, with abucket, load it into the cart, and dump it in the bottom of the mine to undergo primary crushing before beinghoistedto the surface out of the mine. LHDs are used in more than 75 percent of underground mines throughout the world and are suitable for small and largetunnels, chambers, andstopes.

(LHD)LHDInternalThe standard for LHD is adiesel enginewithhorsepowerranging from 78 to 145, but smaller LHDs are outfitted withelectric motors. The engine of the LHD are cooled either by water or air and located on thechassisalong with emergency and parkingbrakes, andhydraulicfluid resistant to fire.Other internals of the LHD include a diesel exhaust treatment device that uses water, catalyctic fume diluter, or similar substances to spray or bathe the exhaust device with water. The LHD is also commonly equipped with a device that automatically shuts off the fuel supply to the engine in emergency situations such as exceeding temperatures of exhaust gases.A ventilation system is required for the LHD to counter the excessive exhaust fumes it creates inside a confined space. Ventilation systems are also incorporated into safety laws and regulations defined by many countries. To accomplish a healthy working environment, it is recommended that the velocity of air should be more than 98.4 feet (30 m) per minute.LHD ExternalThe externals of the LHD include thebucket, loading and dumping mechanisms and tires. Buckets can come in a variety of sizes, from 1.04 to 13.1cubic yards(0.8 to 10 m3) with payloads of 1.5 to 17 tons. The standard type ranges from two to five cubic yards (1.53 to 3.83 m3).The tires can be treaded or smooth and may be fitted with chains. Most mines tend to remove the chains if the LHD includes them because they can prove dangerous in some conditions. Tires account for 10 to 20 percent of the total operation cost because they have to be re-treaded or replaced every 75 to 1,000 hours when they wear down. Tire experience such wear and tear as a result of wet ground, too much wheel spin, and the unstable and sometimes ragged condition of the road they run on.