Although Doosan is a relatively new brand in North America, the company has a global history of equipment manufacturing stretching back more than 75 years. Since 2005, in fact, Doosan has claimed fifth place among the world’s largest construction-equipment suppliers, with a product range that includes wheel loaders, articulated dump trucks, hydraulic excavators, and the Bobcat brand of compact equipment. Construction Equipment recently borrowed one of Doosan’s newest excavator models, the DX350LC-3, and on a cold, blustery day in early April, we asked the pros at the Operating Engineers’ Local 150 to run the new machine and give us their thoughts.
Aaron Kleingartner, marketing manager for Doosan Infracore Construction Equipment America (DICEA), met us at the Local’s 300-acre training facility in Wilmington, Ill., where operator/instructors Sean Poyner, Mike Evans and Jeff Cromer had the coffee ready. Kleingartner began the day with a detailed walk-around of the DX350LC-3, pointing out the design highlights and features of the new 77,000-pound model.
With the DX350LC-3, said Kleingartner, Doosan has advanced its 35-metric-ton model to Tier 4-Interim status, retaining the DX350LC Tier-3 model’s common-rail fuel system and adding a variable-geometry turbocharger, diesel oxidation catalyst, diesel particulate filter, and a cooled-exhaust-gas-recirculation system. Although developing the same 271 net horsepower as its predecessor from the 8-liter DL08K Doosan engine, the new model does so at a lower, fuel-saving speed: 1,800 versus 1,900 rpm.
Along with equipping the DX350LC-3 with new emissions-related technology, Doosan also has essentially redesigned the machine’s hydraulic systems, using hydraulic motors of greater displacement and greater torque in the swing and propel systems, but focusing primarily on the new D-ECOPOWER electronic control system, which, says the company, can yield productivity gains of more than 25 percent and fuel savings on the order of 12 percent, compared with its predecessor.
Kleingartner explained that when designing the new implement hydraulic system, Doosan engineers combined aspects of both open- and closed-center systems, with the objective of incorporating the best attributes of both for optimum power, control and efficiency.
“The system uses much of the oil typically returned to the reservoir,” he said. “Based on electronic pilot signals from the joysticks, the system determines how much oil to direct to the positive side of the system for increasing overall flow. That’s oil the pump doesn’t have to produce, so the load on the pump and engine is reduced—along with fuel consumption.”
The DX350LC-3 also has four power modes available in its Electronic Power Optimizing System—economy, standard, power and power-plus—and allows an increase in main pressure, to 5,512 psi, via its one-touch power-boost button on the right joystick. Complementing the power modes are four work modes—digging, lifting, breaker (one-way auxiliary flow) and shear (optional two-way auxiliary flow). Pressure and flow can be configured through the monitor for 10 attachments, five one-way and five two-way. In addition, said Kleingartner, single- or dual-pump flow is programmable, depending on application demands.
“The ability to program attachments would be really helpful on a demolition site,” said Local 150’s Poyner, “where you might frequently be changing between a hammer and a shear.”
Another substantial design change is the new model’s revamped cooling system. The hydraulic-oil cooler and the radiator, which were stacked in the predecessor model and shared a fan, now occupy separate compartments, and each uses a dedicated fan (an electric-clutch type for the radiator and a hydraulically driven type for the oil cooler), allowing independent temperature control for the two systems.
These changes, said Kleingartner, give the new machine a 15-percent boost in overall cooling capacity, allowing the use of smaller components and, in conjunction with a dedicated fuel cooler, improving the combustion process.
Also new for the DX350LC-3 is an optional “intelligent floating boom” that can be set to allow the boom to move freely up and down with the contours of the ground when grading, or can be set to move freely only downward to maintain optimum pressure on hydraulic hammers. A reset button allows momentarily disengaging the float mode and enabling hydraulic flow.
Although major structures (mainframes, carbody and track frames) are little changed from the predecessor model, the DX350LC-3 does incorporate added internal gussets in the digging arms (two are available at 10.5 and 13.0 feet). Like its predecessor, said Kleingartner, the new model uses high-strength castings at all pivots in the digging mechanism, and at the lift-cylinder-to-boom connections, the casting extends across the width of the boom.
After spending the better part of the day using the DX350LC-3 for trenching, truck loading, and lifting a 15,000-pound section of a manhole box, the overall consensus among the Local 150 operators was that the newDoosan was powerful, quiet and smooth.
“It’s smooth, it’s responsive, it’s strong,” said Cromer. “The bucket was a bit small [1.4 cubic yards, the only bucket available from the local dealer], but judging from the machine’s performance, it would be fine with a larger bucket. You’d be able to easily carry a grade.”
Cromer also noted that the DX350LC-3’s swing movement was slightly different than that of most excavators: “The swing seems to have a gradual braking action. It’s a nice feature. You don’t have to be as cautious with it, because on most machines it’s going to come to a screeching halt, so you can’t come around running too hot, so to speak. But on this one you can, because it’s got that gradual drag that doesn’t give you a jolt.”
Kleingartner explained that the swing system is designed to provide a cushioned stop in the interest of operator comfort.
“I like it,” said Evans. “It’s a nice machine, very quiet, smooth to operate. I didn’t experiment with the power modes—just throttled up and went to work. It’s got power—and a nice radio. Running with the door shut, there’s hardly any noise.”
Cromer added that even bystander noise seemed to be reduced. Kleingartner told us that contributing to the machine’s reduced sound levels—whether inside or outside the cab—is the machine’s recently refined common-rail fuel system, which, he said, runs with considerably less noise than conventional fuel systems.
Thinking about Evans’ comment about not experimenting with the power modes, we asked Poyner and Cromer if they had tried them. They told us that power modes are pretty much lost on most operators when they’re trenching or loading trucks.
“Honestly,” said Poyner, “I’d never put this machine in anything but power-plus. I’d never use the standard or economy modes. As an operator, I’m not paying for fuel, so economy isn’t much my concern—my concern is production. I tried the boost button in the standard mode, and it made a difference, but not as much as when you’re in power-plus. Power-plus with boost—now you’ve got something. I sunk it into that thick, wet clay, and no problems.”
Cromer echoed Poyner’s opinion: “Realistically, you’re not going to run in anything but full speed. Most of the contractors I’ve worked for, if they catch you running in anything but that, they’ll chew you out. They’re just looking for dirt coming out of the hole.”
One feature all the operators liked was the ability to switch between the ISO and “backhoe” control pattern, but all agreed that the feature would be further enhanced if the pattern could be switched from the cab. (Turning an adjusting screw in a small valve positioned in the left-front compartment changes the pattern.)
“With the number of students we train, the ability to switch patterns is important,” said Evans, “because you always want them running with controls that are comfortable. When you have to think about what you’re doing, you’re going to get into trouble—it has to be intuitive. Yes, it would be more convenient to have a switch in the cab, but at least the pattern changer is there, and it’s really not all that difficult to use.”
All agreed, as well, that the DX350LC-3’s backup camera was an excellent feature, displaying crisp images on the machine’s 7-inch color monitor.
“All-around visibility is very good,” said Cromer, “and I like the backup camera. That’s usually where the foreman likes to park his truck—right in your blind spot.”
The monitor also digitally displays what appear to be analog gauges and serves as an intuitive interface for setting machine operating parameters, such as pressure and flow for various attachments.
“The controls were self-explanatory,” said Poyner, “and the display was easy to use.”
Evans also mentioned other features that he thought important: “I like the rotary switch for the battery disconnect in the back compartment. If it’s a key-type switch, you usually end up losing the key. And the tracks would be easy to clean, because the undercarriage is up high enough and the track frames are sloped.”
Cromer commented on the machine’s lifting ability, saying it was “hydraulically strong and smooth.” He added, though, that he preferred lifting in the power modes.
Poyner said he found the cab roomy and comfortable—plenty of leg room—and the “creature features” welcome. But he’d change a few items if he could.
“I’d change the location of the radio—there’s a space under the left armrest to accommodate it, and I’d move the coffee holder to the right front, under the monitor,” he said. “But, remember, this is typical operator talk when you don’t have anything else to cry about.”
But Poyner did bring up a serious issue: “All I’ve seen are smaller Doosan machines, so with a machine this size, would I have a problem getting parts?”
Kleingartner said that Doosan has had a parts-distribution facility in North American since the late 1980s, and that the facility recently moved from Suwanee, Ga., to Chicago.
“Doosan also has a 48-hour parts guarantee,” he said, “which means that we’ll ship any machine-debilitating part in 48 hours or less, and if for some reason the company can’t meet that commitment, we pay for a rental machine.”
“Important in today’s market,” said Poyner.