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Evolution not Revolution: The Evolution of Conventional Mining Equipment ...

World Mining Equipment - March 2005

May 25,2001

While big mining trucks may grab many headlines, innovations further down the payload scale may have more of an impact on the mining industry as a whole. This is particularly true of the 216 tonne/240 short ton payload truck class but can also be seen in wheeled loader and excavator markets. As predicted by WME in early 2004, this hauler size range is seeing notable developments with the introduction of Caterpillar's 793D due later this year and Komatsu's 830E-AC, while Terex's TMT260AC/MT4400AC is already available.
This truck category is extremely well proven and has been a popular choice with customers since the early 1990s, when Cat's 793 and the Haulpak 830E joined Wiseda's KL-2450 (now Liebherr's T262) on the market. Although the Ultra haulers have since topped the range in terms of capacity, reaching as high as 360 tonnes, the 216 tonne/240 short ton machines still dominate in terms of sales volumes. And these trucks have also been able to benefit from technology developed for the larger machines, such as the beefed-up mechanical drives in Caterpillar's 793D or the AC drives in Komatsu's latest 830E or Terex's MT4400AC.
And Caterpillar is taking an interesting route with the 793D, which will take over from the successful 793C later this year. Gone is the 'one size fits all' approach and instead, the 793D is offered in a range of guises to suit specific user requirements (WME Nov 2004). Realising that different customers have different needs, the firm has decided to build in various performance options at the factory, rather than leaving any site-specific modifications to dealers or distributors. The customer can order the truck for high speed, downhill hauling, rugged duty or high altitude duties or in standard specification. These models share basic components--the intention is akin to the car market where buyers choose engine, trim and fitting options as required. Put simply, the high speed version is fitted with higher ratios while the downhill hauling model has additional retardation capabilities. The rugged duty model has beefed-up components in key areas so it can withstand particularly tough duty cycles. And the high altitude version has the engine modifications (with tweaks to the fuel injection system and larger turbochargers) as well as the extra cooling it needs to run at operations in countries like Chile and Peru at altitudes of 2590 m and higher. Other upgrades for the 793D include the latest version of the 3516 diesel and a power increase of 9% at the wheels, speeding cycle times. Safety improvements to the 793D include wider stairs, powerful HID lighting and a three point seat belt (rather than a lap strap).
Caterpillar is also extending its range of body options for the 793D in a move intended to reclaim some sales from the specialist suppliers like Trinity or Phillippi-Hagenbuch. The new Mine Specific II offers a longer wear life than before thanks to the use of extra reinforcement and plating. More radical though is the firm's Performance Plus body, which was at MINExpo in Las Vegas last year. This is 20-30% lighter than conventional truck bodies as its design is intended to reduce the truck's unladen weight and maximise its payload capacity. Caterpillar has achieved this using a visually striking honeycomb design, instead of conventional horizontal side-stiffeners. However the Performance Plus Body is also far more complex and needs more welding during manufacture and assembly. As payload is increased to a maximum 234 tonnes/260 short tons without increasing GVW, payback time should be rapid, though the body will have limitations on where it can be used. Another important feature of the Performance Plus Body is that its side profile shows it to have an S-shaped floor, which is intended to allow more even tipping. The Performance Plus body attracted considerable interest at MINExpo, generating a good deal of comment from the industry and it is worth noting the contrast this design makes with earlier Cat designs. The original 793 featured a conventional body that was rugged and durable when it was first launched in the early 1990s. However as one mine manager pointed out to WME these old truck bodies were heavy, affecting their payload. He went on to say that while his mine is still running its early 793Bs, the bodies were later replaced with newer units. The original bodies were put aside even though they still have some life left in them, "they were costing us too much to wear out," he explained. (In this respect, a similar design approach was taken by other manufacturers--Caterpillar was not alone in over-engineering early 240 ton truck bodies.)
Komatsu is turning up the pressure with its rival to the 793, the Haulpak 830E-AC truck. This revised model benefits from the drive technology developed originally for the top-of-the-range 930E, the first of the successful 'Ultra haulers' to come to market. The new GE B25 drives in the 830E-AC have features from the motors used in the 930E, though the 240 short ton units are not designed exclusively for Komatsu machines as were the larger drives. Using AC technology means the truck now has a 225 tonne/25 short ton payload capacity, with power from a 16 cylinder Komatsu/Cummins diesel delivering 1,864 kW/2,500 hp. Bear in mind though that Cummins is introducing an upgraded version of the QSK60 rated at 2014 kW/2700 hp (WME Sept 2004) and this will no doubt be made available in the 830E-AC truck. A GTA-41 alternator replaces the earlier GTA26 and while engine output is unchanged, an immediate indicator of the improved performance is top speed, now 64 kp/40 mph instead of 48 kph/30 mph as on the earlier DC drive machine. The more efficient AC drives allow the 830E-AC to operate on gradients of 10% and although the reduction ratios are unchanged, this machine offers better speed on ramp too. Although the new drive has the same retardation power as the DC system it offers the operator finer control as well as superior start-up characteristics from rest.
Laden weight has been trimmed by 290 kg to 385,558 kg, though the weight distribution has been altered as the new version of the truck is nearly two tonnes heavier at the front axle than before and is lighter at the rear. Body capacity remains unchanged at 117 [m.sup.3]/153 [yd.sup.3] struck and 147 [m.sup.3]/193 [yd.sup.3] heaped and the truck is designed for 3-4 pass loading by shovels with bucket capacities of 31.3-43.1 [m.sup.3]/40-55 [yd.sup.3], such as Komatsu's own PC8000. In other respects, the 830E-AC is little changed from the earlier DC model with the same main castings and chassis components used and Komatsu says there is a good deal of compatibility, which will keep fleet spares costs in trim.
Terex's Unit Rig MT4400AC was the first truck in this size class announced with AC drive and its GVW is increased slightly to 404,535 kg/892,000 lbs while maximum payload is 236 tonnes/260 short tons. The truck also features GE's sophisticated B25 motors and the GE GTA-41 alternator and is offered with either Cummins QSK60 or Detroit Diesel 16V4000 engines rated at 2014 kW/2700 hp. Top speed is now 64 kph/40 mph thanks to the new drive and the power increase from the 1865 kW/2500 hp engines offered in the earlier MT4400. The new drive system allows the truck to switch from full propel power to 90% retard in less than two seconds, as well as dynamic retarding down to speeds of less than 1.6 kph/1 mph without needing to use the brakes. As with Komatsu's 830E-AC, the MT440AC features the same basic structural components as its predecessor, though the weight distribution is altered slightly. The crucial difference is with the new AC wheel motors and alternator, as well as the new generation engines. The MT4400AC also retains the straightforward front beam axle, as this is said to make maintenance considerably easier.
The key advance common to the revised Komatsu 830E-AC and Terex MT4400AC trucks are their new GE drives, which allow substantial gains in operating performance and should reduce maintenance costs as AC motors are simpler than comparable DC systems.
Full load
In the wheeled loader market, Komatsu's WA900-3 and WA700-3 loaders may have missed out on some of the headlines as these models feature relatively conventional technology, but these are improved designs with real-world benefits for customers. Meanwhile, LeTourneau is also competing in this size class with its new L-950 Pit Bull, introduced at MINExpo (WME Nov 2004) and comes up against the Komatsu WA900 and and Caterpillar 992G for markets such as quarrying, as well as mining.
In the wheeled loader market, Komatsu's WA900-3 and WA700-3 loaders may have missed out on some of the headlines as these models feature relatively conventional technology, but these are improved designs with real-world benefits for customers. Meanwhile, LeTourneau is also competing in this size class with its new L-950 Pit Bull, introduced at MINExpo (WME Nov 2004) and comes up against the Komatsu WA900 and and Caterpillar 992G for markets such as quarrying, as well as mining.
Weighing just under 103 tonnes, Komatsu's WA900-3 loader is fitted with the firm's new dual-speed hydraulics, which better match hydraulic demand to the application for faster cycling. During digging and break out, oil from the switch pump is returned to the hydraulic tank, cutting flow and boosting pressure for better performance, while reducing fuel consumption. This dual-stage system also allows faster raising or lowering of the boom, further cutting cycle times.
The WA900-3 not only moves faster, it can stop quicker as well. Fully hydraulic brakes are fitted and these respond faster (including warming up from rest) than air-brake systems, as well as offering better performance in low temperatures, with no risk of freezing in cold weather. Power is from a 12 cylinder engine rated at 636 kW/853 hp and the machine can load trucks in the 91-135 tonne/100-150 short ton class with its 13.3 [m.sup.3]/17 [yd.sup.3] bucket. Standard 4.72 m reach and 5.48 m high reach booms are offered and the WA900-3 is equipped with a conventional twin arm/z-bar linkage configuration.
The revised cab is equipped with Komatsu's latest joystick steering system (AJSS). Steering and control for the full powershift planetary transmission are integrated into a single lever for faster loading cycles. Other cab features include an air-suspension seat, A/C, better vibration damping in the cab mounts and Komatsu's Edimos II electronic display and performance monitoring system. This provides service alerts when required and provides diagnostics checks, while even allowing the operator to check air filters, battery charge, brake oil pressure, engine oil and coolant levels, fuel level and torque converter temperature.
Komatsu reckons its 71 tonne WA700-3 can beat its nearest competitor in terms of stability, power, turning radius and bucket size. A broad range of options is available--Komatsu claims this is the only loader on the market offering both 45.65 R39 and 40.65 R39 rims, allowing either radial or bias tyres to be fitted to best match the application. A complete range of buckets is offered with capacities ranging from 8.7-9.4 [m.sup.3]--customers can select teeth options as well as standard or high lift booms. The SAA6D170-E3 diesel delivers 478 kW/641 hp (7% more power than its nearest rival) and meets Tier 2 emissions legislation. To minimise maintenance downtime, the WA700-3 is equipped with the Edimos II system, has the same large cab with vibration damped mountings as its larger sibling and is offered with either a steering wheel or joystick control as fitted to the WA900-3.