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Working of Surface MinerThe milling drum ismechanically driven by thedirect drive system throughtransmission (V-belts)directly via a mechanicalclutch on the flywheel sideof the diesel engine.A Gear box provided inbetween Cutting drum andTransmission will suitablyreduce the RPM of thedrum.There is also a Power Take Off Gear / Split Gear connected to other end of the enginethrough universal joint which transmits power for driving four Hydraulic pumps oneeach for Advance drive, Rising & lowering of Cylinders, Conveyoroperation, Water/Fan pump.
Cutting Performance Properties of rock affecting the cutting performance are: • Uniaxial compressive strength [MPa] and tensile strength [MPa] • Abrasivity • Structure of the rock (i.e. number and distance and direction of fractures) Machine parameters affecting the cutting performance are: • Type of cutting tool • Type of cutting tool holder • Number of cutting tools on the drum (spacing) • Angle of attack of the tools • Rotation speed of cutting drum • Cutting depth • Advance speed of the machine
Operating ModeHarvesting mode – slice method In the harvesting mode, the Surface Miner operates on an even field and continuously cuts the material. The cutting process can thus be continued also during driving a curve with the machine. The mining area is developed by cutting slice by slice. For each slice the cutting depth only needs to be set once on the Surface Miner.
Operating Mode Block operation with ramp cuttingWhile cutting the block down to its planned level, the Surface Miner also cuts its ownramp. After completing the cut of the first block, the next block can be started adjacent tothe first one.Since turning on narrow benches is difficult and time consuming, two alternativeoperations can be recommended:a. Turning the machine on an appropriate area outside the rampb. Reverse the machine after finishing one cut and reposition the Surface Miner at theadjacent cut.
Operation of Surface MinerSurface miner is crawler-mounted machine having a cutting drum located b/w two setsof crawlers and positioned at the centre of the machine. The drum is lowered and raisedby hydraulic system with powerful hydraulic motors thereby varying the depth of cut.The material cut is loaded onto the primary and secondary discharge conveyors forloading the same onto the loading/transporting equipment.The depth is adjusted through electronically controlled depth regulator located at theside of the machine which is operated by the co-operator at the floor of the machine.The rear crawler travel at lower level then the front crawlers to adjust to the requireddepth.Dust suppression is ensured by means of water spray arranged on the cuttingdrum, which also serves the dual purpose of cooling of picks, thus prolonging theiruseful life.The operator in the cabin controls the speed, position of the belt conveyor for properloading into the tippers. The machine normally loads on to tippers directly by slewingthe belt conveyor. In case of failure of the mechanism of belt conveyor, the machine canproduce coal/mineral by windrowing operation.
Applicability Flat or gently inclined deposit Best suited for rock compressive strength up to 60 MPa. Less abrasive rock Non sticky material Thin seams or thin dirt bands Sized material production Environmentally sensitive areas where blasting is prohibited or restricted. In general surface miners are capable of cutting rocks of hardness b/w 10-80 MPa. Under certain circumstances (E.g. Highly fractured material) even harder material can be cut economically.
Various Loading Options LOADING OPTION DIRECT TRUCK INDIRECT LOADING LOADINGFRONT LOADING REAR LOADING SIDECASTING WINDROWING
Comparison of Loading Options ADVANTAGE DISADVANTAGEDirect Loading No re-handling of material Larger working area required for required truck manoeuvring Production affected by truck exchange time Belt wearSidecasting Blending of materials in mine. Restricted to 3-5 cuts wide on each Stockpile of material in the mine. side of the mine stockpile. No waiting for trucks. Belt wear. Material has to be re-handled independent operation Material prone to absorb water when lying on the groundWindrow No waiting for trucks Large working area required No belt wear / higher availability Material has to be re-handled Higher production rates than either by loader or scraper conveyor loading Material prone to absorb water Coarser material when lying on the ground Better selectivity on steep inclined seams
ProductivityThe productivity of a Surface Miner depends on the length of the available workingarea. Longer cuts will enhance the productivity, because only a smaller amount of timeis spent in manoeuvring from one cut to the next. The forward speed (and thereforetravel time for a given cutting length) furthermore depends from a number of factors:• cutting depth• material hardness and structure• type of machine and installed engine power
Benefits of Surface MinerMaterial exploitation without drilling & blasting Drilling and blasting is not necessary No vibrations No fly rock Reduced noise and dust development Production of small particle sizes directly during the mining process Primary crushing stage can be omitted Gentle loading of trucks due to size of the cut material The material can be conveyed without further crushing Surface Miner replaces equipment for drilling, blasting, loading and auxiliary works i.e. secondary blasting Selective mining Low investment costs in comparison to the range of equipment necessary for conventional mining Low operating costs due to less equipment and less personnel