The Big Excavators
Size will always be a sensible consideration. If you have a large excavation project, you will probably need a large excavator if you wish your job to be profitable. Again, however, check to find out the advantages for your project of one excavator over another. The US Open Golf Championship is in Pinehurst, NC, this year. That will mean thousands of visitors and good roads for them to travel to reach their enjoyable destination. The S.T. Wooten Corp. is the premier contractor for this big task: expand Highway NC-211 rapidly to accommodate the golf fans. The overall project includes widening the road to a multilane highway with curbs, gutters, and sidewalks, as well as installing traffic signals and signs. What kind of excavator do you want for such a major project? Wooten chose the Caterpillar 336 Hybrid excavator. The operator describes the excavator as “powerful in its breakout force, comfortable, and fuel efficient.” This excavator is large; it has an operating weight of 82,000 pounds. Its maximum drawbar pull is 66,319 pounds. The maximum flow of the hydraulic system is 150 gallons per minute, with maximum flow of the swing system 73 gallons per minute. The bore of the boom cylinder is 5.9 inches, the stroke 56.7 inches. The bore of the stick cylinder is 6.7 inches, the stroke 68.4 inches. But it burns only 5 gallons per hour on the site to prepare for the US Open, and it strikes the workers there as “very quiet.” A quiet excavator? The noise for the operator station is measured at only 69 decibels (which is lower than some household vacuum cleaners and blow dryers).
“A hybrid is independent of any particular technology,” advises Ken Gray, global product manager for large hydraulic excavators for Caterpillar’s Excavation Division. “It doesn’t have to be electric. There are many ways to store and reuse energy, including our patented hydraulic hybrid system. Caterpillar has developed, built, and tested electric hybrid excavators but, until now, we had not found a hybrid approach that would actually lower our customers’ owning and operating costs. Large excavators operate in high-production applications in which fuel is a significant operating cost. This hybrid excavator meets stringent Tier 4 Interim/Stage IIIB emission standards, and it’s extraordinarily quiet. The hybrid version of our workhorse 336E is ideal for introducing our new hydraulic hybrid technology, with its more than 300 filed patents.”
It’s another triumph for innovative technology in construction equipment. “Caterpillar’s corporate technology strategy centers on research and development in advancing technology to meet customers’ needs,” explains Tana Utley, Caterpillar’s chief technology office and vice president of the Product Development and Global Technology Division. “We’re also continuously working on innovations that we anticipate will meet their future needs. At Caterpillar, we don’t simply engage in creating new technologies like the hydraulic hybrid system just for technology’s sake, or to prove that we can! Our technology strategy’s focus never loses sight of what our research and development efforts can mean to our customers’ success, today and in the future.” Is it worth it? It’s difficult to estimate the return on investment for an excavator, because so much depends on fuel prices and particular applications. It is quite possible, estimates the manufacturer, that with today’s fuel costs and typical high-production applications, the customer may see a return on investment for the hybrid excavator in as little as one year.
You would probably call the Doosan DX225LC crawler excavator midsized with its operating weight of 48,722 pounds (with standard boom, arm, and a 0.92-cubic-yard bucket). With a bucket breakout force of 33,510 pounds and an arm breakout force of 23,810 pounds, it has a maximum digging reach of almost 32 feet at ground level and a maximum digging depth of 21 feet, 9 inches. Dump height is 22 feet, 11 inches. This excavator has an electronic power optimizing system (EPOS) that maximizes productivity but minimizes fuel consumption. EPOS connects the excavator’s hydraulic system and engine controls through a data transfer link. Among the practical advantages of this system are the availability of a power mode and a normal operating mode for best efficiency under all conditions, electronic control of fuel consumption, automatic deceleration (to give even more fuel savings), and regulation and control of the hydraulic flow rate required by various machine components.
Not all big excavators have to have tracks! Another of Doosan’s excavators that deserves more attention than it probably gets in our country is the DX140W, a wheel excavator with interim Tier 4 updates. It’s powered by a 137-horsepower, 6-cylinder, DLO6KB, water-cooled diesel engine, a 359-cubic-inch engine with a high-pressure common rail design with direct fuel injection, electronic control, and four valves per cylinder. This powerful excavator is most appropriate for projects like highway and street development, construction of commercial buildings, bridge work, and railroad work. It also seems a good excavator for dealer rental. The DX140W also has the EPOS system described above to give it superior power and fuel efficiency through four work modes, auto-idle, and machine diagnostics. The multiple operating modes make the work more straightforward for operators. The Power+ mode gives improved performance and faster workgroup speeds for heavy-duty work. Four work modes (digging, breaker, shear, and a new lifting mode) allow operators to get the best efficiency (and fuel economy) in specific applications.
