【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 loaders．Wheel loaders carry 18-21% of their operating weight as payload，compared with 5-7% for electric cable shovels and 8- 11%for hydraulic face shovels．By fitting the bucket close to the carrier，designers of wheel loaders create a very favorable payload-to-operating weight ratio，allowing mobility around a mine．With 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 capacity．Electric 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 $ 0．060-0．095/tonne．Hydraulic 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 $ 0．0080-0．140/tonne．It should be noted that these long-term comparisons assume that costs are spread over the entire economic lives of the machines．It should also be remembered that the purchase of wheel loaders and hydraulic shovels could generally be considered to be reversible decisions．At almost any point in their working lives，they can be fairly easily resold and moved without a severe cost penalty．The same is unlikely to be true of electric shovels．In practice，it is unlikely that a mines choice would be between a wheel loader and an electric shovel．A more likely decision would be to make the choice between hydraulic excavators and wheel loaders．Choosing between these two options can have significant effects on truck maintenance costs．For example，controlled dumping of material into the truck has a great influence．Dumping heavy boulders into an empty truck can cause damage．However ，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 boulders．Reach and dump heights also play a considerable role in truck repair costs．A 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 truck's side wall．In the case of the wheel loader， the use of high lift versions can compensate somewhat for this．However ，a wheel loader will always，essentially ，be nearer to the truck during the dump phase．Versatility and mobility are other important considerations．In one minute a cable shovel will travel about 21 meters， a hydraulic shovel about 37 meters and a wheel loader about 370 meters．Mobility 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 more．Blending，multiple faces and shove1 backup are all functions that can be performed well due to the wheel loader's mobility．However，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 stability．However ，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 area．The method of digging is different for all three machines．Because 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 tool．This is because，due to geometry，a hydraulic excavator can apply its breakout force over its reach of the face，while a wheel loader’s best digging occurs low--from the toe of the face to about the height of the loader's bucket．Wheel loaders can get the best bucket fill factors in production rock face conditions，if used properly．Both 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 shovels．WHEEL 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 decisions．The 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 passes．The cycle time per pass should be between 30 and 35 seconds．The 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 mixtures．The ability of the chosen machine to achieve these performance criteria will be influenced by the loader's 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 times．The dump height clearance and forward reach of the loader should be compared with the truck side board height and body width．Wheel 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 sites．It 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 possible．However ，wheel loaders can provide their own clean-up support in the loading area，where required．The big onesHigh capacity wheel loaders are not new to the industry，LeTourneau has pioneered such machines for many years．As 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 ago．More recently，both Caterpillar and Komatsu have launched monster units．LeTourneau is the specialist，offering all-wheel; electric drive wheel loaders based on concepts initially explored by founder R．G．LeTourneau back in 1923．The 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 grip．The 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 accepted．A major milestone and a catalyst that led to much more widespread use of large wheel loaders was Caterpillar’s launch of the 994 back in late 1990．That was also a significant milestone in Cat’s programme of development of large mining machines which has seen the company take the mining world by storm，particularly in large trucks．Caterpillar has certainly proved that the mining industry is interested in large wheel loaders．Its 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 hours．Announcing this at the Las Vegas American Mining Congress in1992，the manager of Caterpillar’s Mining Vehicle center，Don Hopkins，admitted that this volume of sales was higher than expected．That 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 world．The largest electric drive machine was a LeTourneau，as it is today．But today，the largest mechanical drive honor goes to Komatsu with the WA1200-3．Traditionally the much greater mobility of wheel loaders allows their use in secondary loading applications in very large open pits．They are also widely used in smaller operations such as eastern US coal mines and medium to smaller gold mines．But 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 elsewhere．The smaller units with bucket capacities of 10 to15 cubic meters are used only with the smaller truck sizes，but Komatau’s WA1200， Cat’s 994 and the bigger LeTourneaus can be matched with all but the very largest trucks．There 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 shovels．WHEEL 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 994D．Significant among the technology updates were Cat’s Steering and Transmission Integrated Control (STIC) system that combines gear selection and steering into one control lever that requires less effort and makes shifting smoother．Caterpillar reports that this allows up to 10% greater productivity．A number of older machines were retrofitted before the 994 launch and displayed anything from 7 to 12% greater productivity in field trials．Retrofits are available for all 994s already operating．The rim pull control with new left-pedal operation also is important．This allows the operator to match rim pull to conditions for improved tyre life，loadability and increased control．Operator comfort is becoming more and more important．In 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 shift．The 994D’s payload has been increased to 34．5 tonne for standard models and 31 tonne for the high-lift arrangement．Bucket 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 hours．LeTourneau’s monsters LeTourneau’s designers have been busy recently．First 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-2350．The 1120KW L-1350 has a 20cubic meter bucket capacity，6．6 meter lift height，and 2．9 meter reach．It 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 units．Many of the major components incorporated on the loader have already been field proven on the other LeTourneau loader models．At 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 40．5 cubic meter bucket capacity，a 7．3 meter lift height and 3．8 meter reach，is now，clearly ，the world’s largest wheel loader．The 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 claims．The information it provides includes bucket weights，cycle times，preventative maintenance data，self-diagnostics and more．LINCS 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 cab．The RCMs are distributed around the machine providing the MCM with the hands and eyes needed to control and monitor the machine．The MCM is located in the cab of the loader．It has more than 350 input/output points and the ability to store more than a month’s worth of operating and production data．The RCMs use a high-speed 30-bit processor and connect directly to sensors，drive outputs and operator controls．They are housed in environmentally sealed enclosures，designed to withstand high-pressure hot water washes and drenching in any vehicle fluids．Other features include reliable gold-to-gold connections and short circuit and reverse polarity immunity．These EMC tested modules automatically programme themselves to the needs of the location．Thus they operate on a quick pull-out/plug-in procedure．Among the advances is that the second reduction gear is centre-hung between two bearings with a splined interface between this gear and the middle pinion．This design change results in more equal load share between the middle pinion and the three reduction counter-shaft gears．Better load share results in lower shaft and gear stress at the third and fourth reductions．The splined interface enables the middle pinion to be removed so that the loader can continue to run if a motor is disabled．In addition，the middle pinion can be replaced if the other driver gearing is in good condition．Both operations can be accomplished without removing the driver from the machine LeTourneau’s proven taper lock design and a unique timing method further ensure equal load share．The driver ratio minimizes the required motor torque while simultaneously minimizing the shock loads at the counter-shaft pinion．Before the L-2350，LeTourneau’s 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 larger．The 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 reliability．It can lift loads up to 50 tonne．Other features include full helical gearing in the final drive units and a cab designed for better operator comfort and visibility，enhanced by the machine’s sloped design which provides a superior rear view．There is an L-1800 at work at Triton Coal’s North Rochelle coal mine in Wyoming’s Powder River Basin (the proving ground for so many of today’s largest earthmovers) in the early stages of North Rochelle’s development (opened in December 1998)． Its narrow pits required manoeuvrability and this was ably supplied by the L-1800 with its 13．4 meter turning radius in high-lift configuration． Mobility is one of the reasons the mine purchased this loader．The 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 7．3-meter dump clearance allows it to load 218 tonne capacity trucks with ease．The world’s biggest mechanical drive loader today，Komatsu’s WA1200-3，is powered by Komatsu’s SDA16V160 electric-controlled engine．Its standard 16．3 cubic meter bucket will load 216 tonne trucks in just six passes．Its modulated clutch system offers adjustable travel speed，traction control and tyre specification settings for multiple applications．The 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 life．The Traction Control setting features a traction power selection of 20 to 100% to accommodate various application conditions．The Tire Saver setting controls tyre slip，preventing wear and prolonging tyre life．The WA1200-3 features the Remote Boom Positioner．This allows the operator to set maximum and minimum bucket positions， promoting smooth component movement and preventing spillage．The Variable Output Hydraulic System(VOHS) is a self-adjusting hydraulic system that reduces oil consumption and increases tractive effort and saves fuel．In addition，a new 65/65-67-62PR ultra-wide tyre with additional rubber on the ground and increased air volume is now available．As 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 history．Caterpillar brought about a radical change in wheel loader design in 1997 when it launched the 992G．The 992 wheel loader has long been a workhorse of the mining industry，and widely used in stockpiling．The 992G began an innovative concept，the cast box section boom，the first major change in wheel loader design in about 20 years．This increases dump clearance， improves bucket visibility and requires no maintenance． It also offers three times the tortional strength of a traditional design，according to Caterpillar．Compared 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 meters．It will four-pass load a 90 toone payload 777D truck (around 2000 toones/hour) in the high reach version．Caterpillar’s testing of the machine showed that in truck loading it is 43% more productive than the 992C in coal operations．