【畢業(yè)設(shè)計(jì)】裝載機(jī)設(shè)計(jì)資料

【畢業(yè)設(shè)計(jì)】裝載機(jī)設(shè)計(jì)資料,畢業(yè)設(shè)計(jì),裝載,設(shè)計(jì),資料 WHEEL LOADERSCoal International January/February 2001Copyright 2001. All right reserved.16WHEEL LOADERSWorkhorses of the industry，with larger units adding flexibility to surface coal mining operations and smaller machines invaluable in stock-pile work，rehandling and other tasks The primary choices today for open pit coal and overburden excavation and loading are between electric cable shovels，hydraulic excavators and wheel loadersWheel loaders carry 18-21% of their operating weight as payload，compared with 5-7% for electric cable shovels and 8- 11%for hydraulic face shovelsBy fitting the bucket close to the carrier，designers of wheel loaders create a very favorable payload-to-operating weight ratio，allowing mobility around a mineWith comparably sized buckets，an electric shovel will weigh something like four times as much as a wheel loader，while a hydraulic face shovel，might weigh about twice as much as a wheel loader for the equivalent bucket capacityElectric shovels can be expected to routinely achieve economic lives of 75,000-100,000 hours，with documented long-term operating costs in the range of $ 0060-0095/tonneHydraulic shovels and wheel loaders are generally considered to have economic lives in the 30,000-60,000 hour range They work in a wide range of conditions so their long-term operating costs are in a broader range of $ 00080-0140/tonneIt should be noted that these long-term comparisons assume that costs are spread over the entire economic lives of the machinesIt should also be remembered that the purchase of wheel loaders and hydraulic shovels could generally be considered to be reversible decisionsAt almost any point in their working lives，they can be fairly easily resold and moved without a severe cost penaltyThe same is unlikely to be true of electric shovelsIn practice，it is unlikely that a mines choice would be between a wheel loader and an electric shovelA more likely decision would be to make the choice between hydraulic excavators and wheel loadersChoosing between these two options can have significant effects on truck maintenance costsFor example，controlled dumping of material into the truck has a great influenceDumping heavy boulders into an empty truck can cause damageHowever ，a hydraulic excavator WHEEL LOADERSCoal International January/February 2001Copyright 2001. All right reserved.17equipped with a bottom dump bucket can ensure a certain amount of dampening of the fall of the material into the truck by opening the bucket only slightly so as to allow smaller rocks to fall first and form a buffer for the larger，heavier bouldersReach and dump heights also play a considerable role in truck repair costsA machine with a long reach greatly reduces and even eliminates the risk damage to tyre walls Furthermore the better suited the dump height of the loading tool is to the truck， the lower the risk of damage to the trucks side wallIn the case of the wheel loader， the use of high lift versions can compensate somewhat for thisHowever ，a wheel loader will always，essentially ，be nearer to the truck during the dump phaseVersatility and mobility are other important considerationsIn one minute a cable shovel will travel about 21 meters， a hydraulic shovel about 37 meters and a wheel loader about 370 metersMobility is a key factor in choosing wheel loaders，especially with large new models capable of producing in the 3,000-3,500 tonne/hour，range，and moreBlending，multiple faces and shove1 backup are all functions that can be performed well due to the wheel loaders mobilityHowever，a drawback to the mobility advantage of the wheel loader is its need for relatively smooth，flat floors，to prolong tyre life and provide machine stabilityHowever ，those smooth，flat floors in the loading area are needed anyway，unless the mine is prepared to pay severely for damage to expensive truck tyres as they roll onto the loading areaThe method of digging is different for all three machinesBecause the cutting edge does not change angle on an electric cable shovel bucket，loading is accomplished by raking the face in a long sweeping arc rather than biting into it by combining boom，stick and bucket forces (as with hydraulic excavators)，or by combining power train，bucket crowd and rack back forces (as with wheel loaders)A hydraulic shovel is considered a selective excavating tool and a wheel loader is considered a loading toolThis is because，due to geometry，a hydraulic excavator can apply its breakout force over its reach of the face，while a wheel loaders best digging occurs low-from the toe of the face to about the height of the loaders bucketWheel loaders can get the best bucket fill factors in production rock face conditions，if used properlyBoth they and hydraulic backhoes should achieve 100% (more with some wheel loaders)，compared with 90-100% for electric shovels and 80-85% for hydraulic face shovelsWHEEL LOADERSCoal International January/February 2001Copyright 2001. All right reserved.18A survey in the 1990s undertaken by Caterpillar of midsize wheel loaders provided an interesting insight into the factors involved in machine purchase decisionsThe considerations brought into play，in descending order of priority were: Performs tasks well Can trust to run Easy to operate Easy to maintain Lasts long time Operator comfort Competitive price Repair cost low Versatility Good resale value Fuel consumption Easily transported Design appearance Today，with fuel costs rising，we might expect to see fuel consumption having a higher priority The operating conditions that favor the selection of wheel loaders include Mobility Versatility Low pile profile Smooth floorWHEEL LOADERSCoal International January/February 2001Copyright 2001. All right reserved.19 Level floor Load-and-carry Shop maintenanceWhy wheel loaders？In summary then，if wheel loaders have been selected as the primary loading tools， each unit should be capable of loading a truck in three to four passesThe cycle time per pass should be between 30 and 35 secondsThe loader should also achieve a 75-85% bucket fill factor in a single pass when loading blasted rock and 100% or more in rock-dirt mixturesThe ability of the chosen machine to achieve these performance criteria will be influenced by the loaders performance features and it is important to check that the machine has a high full-turn static top load capability，a high breakout force and fast hydraulic cycle timesThe dump height clearance and forward reach of the loader should be compared with the truck side board height and body widthWheel loaders are very mobile and are ideally suited to applications that demand selective mining and require the loader and haul trucks to move between various loading sitesIt should，however ，be borne in mind that the loader tyres can become a high cost item and care should be taken to protect these as far as possibleHowever ，wheel loaders can provide their own clean-up support in the loading area，where requiredThe big onesHigh capacity wheel loaders are not new to the industry，LeTourneau has pioneered such machines for many yearsAs far back as 1982，at the Las Vegas American Mining Congress，Marathon launched its L-1000 diesel-powered and TCL-1000 training cable wheel loaders; both equipped with 13 cubic meter buckets as standard Clark Michigan，now part of the Volvo Construction Equipment group， also offered a large capacity wheel loader many years agoMore recently，both Caterpillar and Komatsu have launched monster unitsLeTourneau is the specialist，offering all-wheel; electric drive wheel loaders based on concepts initially explored by founder RGLeTourneau back in 1923The technology has been proven since 1950 and refinements since have included traction proportioning WHEEL LOADERSCoal International January/February 2001Copyright 2001. All right reserved.20that minimizes wheel slip and tyre wear by allocating power to the wheels that gripThe company claims still to be the only manufacturer of wheel loaders offering all-wheel drive，which，LeTourneau reports， “improves stability and increases operator comfort”If LeTourneau has long been the major proponent of the large wheel loader，it was perhaps a Caterpillar development that got such machines widely acceptedA major milestone and a catalyst that led to much more widespread use of large wheel loaders was Caterpillars launch of the 994 back in late 1990That was also a significant milestone in Cats programme of development of large mining machines which has seen the company take the mining world by storm，particularly in large trucksCaterpillar has certainly proved that the mining industry is interested in large wheel loadersIts first 994 went into operation at the Cyprus Sierrita open-pit copper mine in Arizona in November 1992，over 50 such units had been sold，and the first 12 had logged over 100000 operating hoursAnnouncing this at the Las Vegas American Mining Congress in1992，the manager of Caterpillars Mining Vehicle center，Don Hopkins，admitted that this volume of sales was higher than expectedThat first 994 was a high-lift model equipped with a 16 cubic meters bucket，though buckets up to 31 cubic meters wear available depending on application The 994 was then the largest mechanical drive wheel loader available in the worldThe largest electric drive machine was a LeTourneau，as it is todayBut today，the largest mechanical drive honor goes to Komatsu with the WA1200-3Traditionally the much greater mobility of wheel loaders allows their use in secondary loading applications in very large open pitsThey are also widely used in smaller operations such as eastern US coal mines and medium to smaller gold minesBut the large wheel loader has really taken off and a growing number of these machines are being put to heavy-duty loading requirements，especially in North America，Australia and selective markets in Latin America and elsewhereThe smaller units with bucket capacities of 10 to15 cubic meters are used only with the smaller truck sizes，but Komataus WA1200， Cats 994 and the bigger LeTourneaus can be matched with all but the very largest trucksThere are still only a few big mines that rely on these bigger wheel loaders completely However，several hundred such machines are now working alongside，or in place of ， electric and hydraulic shovelsWHEEL LOADERSCoal International January/February 2001Copyright 2001. All right reserved.21By the time Caterpillar had achieved sales of well over 220 994s around the world， representing around 60% of all large wheel loader sales，it released the 994DSignificant among the technology updates were Cats Steering and Transmission Integrated Control (STIC) system that combines gear selection and steering into one control lever that requires less effort and makes shifting smootherCaterpillar reports that this allows up to 10% greater productivityA number of older machines were retrofitted before the 994 launch and displayed anything from 7 to 12% greater productivity in field trialsRetrofits are available for all 994s already operatingThe rim pull control with new left-pedal operation also is importantThis allows the operator to match rim pull to conditions for improved tyre life，loadability and increased controlOperator comfort is becoming more and more importantIn the 994D，the new seven-way Contour Series air-suspension seat lets the operator adjust his or her seat to precisely the right position，optimizing movements and experiencing less fatigue over the shiftThe 994Ds payload has been increased to 345 tonne for standard models and 31 tonne for the high-lift arrangementBucket capacities can be 14 to 31 cubic meters The 994D should load 2800-3000 tonnes per hour and achieve a tyre life of 5000-6000 hoursLeTourneaus monsters LeTourneaus designers have been busy recentlyFirst the company announced the L-1350 loader in 1999，with deliveries beginning in 2000，and then at MINExpo in Las Vegas last October，LeTourneau exhibited the monster L-2350The 1120KW L-1350 has a 20cubic meter bucket capacity，66 meter lift height，and 29 meter reachIt rides on 49/75-51 tyres and has been specifically designed to minimize loading costs for 136 to 181 tonne capacity trucks and has the capability to load many of the 218 tonne capacity unitsMany of the major components incorporated on the loader have already been field proven on the other LeTourneau loader modelsAt the time of its launch，LeTourneau said the introduction of the L-1350 would strengthen its position “as the market leader in high-performance，cost effective front-end loaders ”The new 1715 kW LeTourneau L-2350 wheel loader，with a standard 405 cubic meter bucket capacity，a 73 meter lift height and 38 meter reach，is now，clearly ，the worlds largest wheel loaderThe L-2350，like the L-1350，is WHEEL LOADERSCoal International January/February 2001Copyright 2001. All right reserved.22controlled and monitored by the LeTourneau Integrated Network Control System (LINCS)，which provides the most intelligent computerization available，LeTouneau claimsThe information it provides includes bucket weights，cycle times，preventative maintenance data，self-diagnostics and moreLINCS manages all loader systems (including hydraulics，electrics，traction drive and engine) through the interactions of the Master System Manager (MCM) and multiple Remote Control Modules (RCMs)The MCM combines ruggedised industrial hardware with a Pentium class microprocessor to direct the entire system from the cabThe RCMs are distributed around the machine providing the MCM with the hands and eyes needed to control and monitor the machineThe MCM is located in the cab of the loaderIt has more than 350 input/output points and the ability to store more than a months worth of operating and production dataThe RCMs use a high-speed 30-bit processor and connect directly to sensors，drive outputs and operator controlsThey are housed in environmentally sealed enclosures，designed to withstand high-pressure hot water washes and drenching in any vehicle fluidsOther features include reliable gold-to-gold connections and short circuit and reverse polarity immunityThese EMC tested modules automatically programme themselves to the needs of the locationThus they operate on a quick pull-out/plug-in procedureAmong the advances is that the second reduction gear is centre-hung between two bearings with a splined interface between this gear and the middle pinionThis design change results in more equal load share between the middle pinion and the three reduction counter-shaft gearsBetter load share results in lower shaft and gear stress at the third and fourth reductionsThe splined interface enables the middle pinion to be removed so that the loader can continue to run if a motor is disabledIn addition，the middle pinion can be replaced if the other driver gearing is in good conditionBoth operations can be accomplished without removing the driver from the machine LeTourneaus proven taper lock design and a unique timing method further ensure equal load shareThe driver ratio minimizes the required motor torque while simultaneously minimizing the shock loads at the counter-shaft pinionBefore the L-2350，LeTourneaus L-1800 was the largest wheel loader in the world， with a capacity of 454 tonne and able to centre-load trucks of 270 tonne capacity and largerThe L-1800 is offered with a 1342 or 1491 kW engine and，in WHEEL LOADERSCoal International January/February 2001Copyright 2001. All right reserved.23keeping with the trend to longer service intervals，its self-cleaning KLENZ air filtration system reduces maintenance costs and improves reliabilityIt can lift loads up to 50 tonneOther features include full helical gearing in the final drive units and a cab designed for better operator comfort and visibility，enhanced by the machines sloped design which provides a superior rear viewThere is an L-1800 at work at Triton Coals North Rochelle coal mine in Wyomings Powder River Basin (the proving ground for so many of todays largest earthmovers) in the early stages of North Rochelles development (opened in December 1998) Its narrow pits required manoeuvrability and this was ably supplied by the L-1800 with its 134 meter turning radius in high-lift configuration Mobility is one of the reasons the mine purchased this loaderThe other was capacity Bucket capacities can be up to 42 cubic meters for coal mining and North Rochelle chose a 34-cubic-meter combo bucket to load both coal and overburden Its 73-meter dump clearance allows it to load 218 tonne capacity trucks with easeThe worlds biggest mechanical drive loader today，Komatsus WA1200-3，is powered by Komatsus SDA16V160 electric-controlled engineIts standard 163 cubic meter bucket will load 216 tonne trucks in just six passesIts modulated clutch system offers adjustable travel speed，traction control and tyre specification settings for multiple applicationsThe Precise Dial Control of Travel Speed setting offers the operator variable travel speeds for tight V cycles decreasing cycle times and increasing digging capabilities and tyre lifeThe Traction Control setting features a traction power selection of 20 to 100% to accommodate various application conditionsThe Tire Saver setting controls tyre slip，preventing wear and prolonging tyre lifeThe WA1200-3 features the Remote Boom PositionerThis allows the operator to set maximum and minimum bucket positions， promoting smooth component movement and preventing spillageThe Variable Output Hydraulic System(VOHS) is a self-adjusting hydraulic system that reduces oil consumption and increases tractive effort and saves fuelIn addition，a new 65/65-67-62PR ultra-wide tyre with additional rubber on the ground and increased air volume is now availableAs any good earthmover today，the WA1200-3 is designed for easy maintenance and service To minimize maintenance and downtime the machine is equipped with a Vehicle Health Monitoring System (VHMS)，an integrated WHEEL LOADERSCoal International January/February 2001Copyright 2001. All right reserved.24maintenance system that employs self-contained diagnostics，a preventive maintenance scheduler and machine performance historyCaterpillar brought about a radical change in wheel loader design in 1997 when it launched the 992GThe 992 wheel loader has long been a workhorse of the mining industry，and widely used in stockpilingThe 992G began an innovative concept，the cast box section boom，the first major change in wheel loader design in about 20 yearsThis increases dump clearance， improves bucket visibility and requires no maintenance It also offers three times the tortional strength of a traditional design，according to CaterpillarCompared with previous models，Caterpillar reports a 15-20% increase in productivity from the 597 kw 992G，payload raised by 7%，and cycle times cut by 10% Cab sound levels have been reduced and daily service costs cut by about 20% This 91.8 toone unit can be equipped with 11.5 to 12.3-cubic-meter buckets and features a dump heignt of just over 4.6 meters and a reach of 2.3 metersIt will four-pass load a 90 toone payload 777D truck (around 2000 toones/hour) in the high reach versionCaterpillars testing of the machine showed that in truck loading it is 43% more productive than the 992C in coal operations