The design of the new Caterpillar D-Series wheel excavators — models M313D, M315D, M316D and M322D — has been considerably enhanced, compared with that of their C-Series predecessors. According to Caterpillar, the new machines deliver increased lift capacity, faster cycle times, expanded versatility and enhanced control. Overall, the new models range in net horsepower from 127 to 165, in operating weight from 30,865 to 48,502 pounds, and in maximum digging depth from 18 feet 11 inches to 21 feet 11 inches.
The four new models are equipped with Caterpillar ACERT diesel engines, with the two smallest models using the C4.4, and the three larger models using the C6.6. The new engines are said to not only provide significant increases in horsepower and torque, but also deliver fuel-efficiency gains on the order of 7 to 8 percent. Electronic controls built into the new excavators recognize "roading applications," says Cat, and adjust engine parameters "to the most efficient operating point to save fuel without compromising road performance." Also, hydraulically driven, variable-speed cooling fans are designed to further boost fuel efficiency — and promote quiet operation.
Hydraulic refinement of the new excavators includes the use of a dedicated pump to power the swing function. The purpose of this design, says the company, is to maximize swing performance without reducing power to other hydraulic functions — resulting in smoother combined-function operation and more efficient use of hydraulic flow. Also, at the touch of a button, the operator can activate a heavy-lift mode to boost lifting force by 7 percent.
The versatility of these new models can be expanded, says Cat, with a variety of auxiliary-hydraulic control circuit options. At the heart of the machines' Tool Control System is the multi-combined valve, which allows the operator to use the monitor in the cab to select pre-programmed hydraulic parameters for as many as 10 work tools. In addition, a hydraulic-breaker circuit is available, as is a medium-pressure-function valve for controlling tilting buckets or rotating tools.
The monitor in the cab, by the way, is in color and newly designed to be easier to read. In fact, the entire cab is new, sealed and pressurized to keep out dust. It is also designed to enhance visibility and promote overall operator comfort and safety with such amenities as a deluxe seat that is ventilated and heated and cooled, fully automatic climate control, and an optional rear-view camera that displays on the monitor.