| September 29, 2009 |
Refinements put precision behind a big dozer’s brute power
Even though it’s the second biggest dozer in Komatsu’s lineup, the D375A series serves in a lot of different roles. In addition to being a production mining dozer, this size dozer also performs general purpose/utility tasks, including large construction and earthmoving applications such as pushing scrapers, stockpiling materials, removing overburden, and building and clearing haul roads, says Rich Smith, product manager for mechanical drive equipment for Komatsu.
The company surveyed of its customers in different parts of the country to find out what they were looking for in a big dozer, says Smith. “The three top things customers said they wanted were production, production and production.”
So in upgrading the machine from the dash-5 models to the new D375A-6, Komatsu included features that boost basic productivity in straight mining applications, but also added a number of refinements that conserve fuel and improve the operator environment.
Horsepower got a boost, up to 636 gross horsepower from the dash-5′s 551 horsepower. Komatsu also optimized the engine to match the capabilities of a new transmission with torque converter lockup. All this muscle gets channeled into the powertrain using an “ECMV,” or electronic controlled modulation valve. Sensors in the ECMV automatically adjust each clutch engagement depending on gear speed, rpms, shifting pattern, slope and load. This reduces counter steering on downhill travel makes dozing and turning smoother.
Automatic or manual gearshifts can be selected with a switch. For general dozing, the automatic mode shifts up and down depending on load. For ripping or tough slogging the manual mode downshifts when loaded but doesn’t upshift when the load is reduced. And if you do not need the maximum output of the engine you can switch from the “P” or power mode to the “E” economy mode, which electronically drops the horsepower and cuts fuel consumption by 8 percent.
Hydraulics in the new dozer are based on a variable piston pump design as found on Komatsu’s next larger dozer, the D475A-5EO, replacing the tandem gear pump design of the dash-5 models. The new hydraulics make efficient use of the engine’s energy output and also power a variable-speed cooling fan on a demand basis. When the engine and ambient temperatures are cold, the fan turns slow or not at all. In hot weather the fan turns at maximum speed. This results in quicker warm ups and less heat stress on the engine in hot weather. An optional fan reversing capability, to blow out debris, is also available.
The shape of the blade on the D375A-6 was taken from the bigger D475A-5EO dozer and increases production without increasing the blade width or reducing digging force. The blade was also moved 8 inches closer to the cab to improve visibility and machine balance.
Inside the cab the multi-lingual LCD monitor displays information using a thin film transistor technology that maintains visibility at various angles and lighting conditions. Cab pressurization keeps out dust, and an adjustable left armrest and integrated seat and travel control enable operators of different sizes to position the controls in an ergonomic manner. “Palm command electronic controlled” joysticks for the travel control and blade controls enable operators to work without fatigue.
Komatsu also included 16 new mining specifications as standard in the D375A-6, some of which include:
· High-mounted headlights
· Battery and starter isolator box
· Centralized grease points
· Manual engine stop switches
Optional mining specs include:
· Right and left hand platforms with handrails
· High intensity work lights.
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