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The loader is powered by a Komatsu SSDA16B160E-2 diesel, a product of the Komatsu/Cummins Industrial Power Alliance engine joint venture. It is equiv- alent to the Cummins QSK60 Tier 2 diesel used in other mobile equipment applications.
The most recent dozer model from Komatsu is the D375A-6, introduced in 2010 with new technology that enables higher productivity—in the case of the -6 version, an estimated 8% more than its predecessor.
The D375A-6's lockup torque con- verter feature provides a direct-drive con- nection between the engine and trans- mission for more efficient use of engine power, particularly on long passes. For utility dozing in which maximum power isn't necessary, an economy work-mode setting reduces engine output to save on fuel consumption. For general dozing, the operator can use the transmission's automatic gearshift mode which down- shifts on its own when a load is applied and upshifts to a preset when the load is removed. When ripping, the operator can select manual shifting, which again downshifts automatically when load is applied but does not upshift when the load lightens.
The dozer senses when the track shoes start to slip under heavy load while ripping, and adjusts engine output accordingly to avoid the damaging effects of slippage, which can accelerate under- carriage wear. This feature also elimi- nates the need for the operator to con- stantly work the deceleration pedal dur- ing ripping and consequently reduces
operator fatigue during extensive ripping operations.
Drive-train parts are strengthened to handle the increased horsepower on the - 6, and primary power train components are sealed in a modular configuration that allows them to be removed and replaced without oil spillage. The under- carriage employs the improved eight- roller, "K-Bogie" design used on the larg- er D475 series, which increases the length of track on the ground and also provides an extended range of track-roller vertical travel. The -6's blade profile was modified to more closely resemble that used on the D475 series, and the blade shoulder angle raised to reduce spillage over the blade corners. Cross joints used at the connec- tion point of the lift cylinder and blade improve machine reliability and speed field assembly of the equipment. The -6's hydraulic system has the higher efficiency, more reliable piston-type pumps used on the D475 series rather than gear pumps. Other improvements on the -6 range from latching, dual insulated gull-wing engine side covers for better maintenance access, to an LCD color monitor in the pressurized, hexagonal-shaped cab. Mining-specific features include items ranging from standard work lights at the front, back and engine bay of the machine, to an uninterruptible power source in the cab that allows radio communication at all times. Manual engine shutdown switches are located in the cab and at the rear of the machine, and a battery/starter isolator box on the side of the dozer also includes a jump-start connection.
The -6's built-in versatility allows it to handle a wide variety of dozing tasks ranging from trap loading to a shovel, dragline and dump assistance, stripping and roadbuilding to stockpile mainte- nance, and Jackie D. Haney, product marketing manager for mining-class doz- ers, confirms the -6 has found broad pop- ularity in stockpile applications, as well as appreciation from operators who find the new machine easier to run and more comfortable than its predecessor. The D475A is the next model of
Komatsu's mining-class dozers sched- uled for an upgrade, according to Haney.
Cat's Loaders and Dozers Updated
Komatsu D375A-6 dozer. 64 E&MJ; • FEBRUARY 2012
Caterpillar has carried out a series of updates to its loader and dozer lines, starting in May 2010 with an Extended High Lift Option (EHL) for its model 994 loader. The EHL linkage provides 42 in. (1,075 mm) more dump clearance than the High Lift linkage option, and includes new lift arms, lift and tilt cylinders, tilt links and counterweight material. The additional lift height allows the operator to back away from a truck without rack- ing back the bucket, providing the poten- tial for faster cycle times. The additional lift also enables the operator to dump the last pass without pushing material. The latest version in the 994 series is the 430,858-lb (195 434-kg) 994H, which when equipped with EHL linkage is rated at 35 tons (32 metric tons) payload. Cat followed up later in 2010 with a High Lift option for its 992K loader, adding 24 in. (610 mm) of dump clear- ance over the standard configuration. Equipped with a 14-yd3 (10.7-m3) buck- et, a High-Lift 992K offers dump clear- ance of 17 ft 2 in. (5,232 mm). The High Lift option reduces payload to 21.4 tons (19.1 mt) from the standard unit's 24- ton rating but enables the 992K to effi- ciently load 100- and 150-ton-capacity trucks—possibly eliminating the need to move to a larger loader, which in the Cat product line would be the 993K with a payload rating of 27.5 tons (24.9 mt) for the High Lift version and 30 tons (27.2 mt) in the standard configuration. Cat's newest large loader, the 980K, was unveiled in March 2011 and, as the smallest of its mining-class wheel loaders with bucket capacities ranging from 5.25–16 yd3 (4–12 m3), is not typically found in high-production hardrock opera-
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