Caterpillar Excavator Model Change Reflects Configuration

By Mike Anderson, Senior Editor | September 28, 2010

The ongoing evolution of the Caterpillar hydraulic excavator product line to the D-Series is bringing with it an actual new model designation.

Editors who gathered recently in Peoria, Ill., for extensive new equipment rollouts covering various Caterpillar product lines were introduced to three updated excavator models serving the key 19- to 24-metric-ton class. The standard-configuration 320D L replaces the 320C L and the compact-radius 321D LCR replaces the 321C LCR; while the reduced-radius machine, formerly identified as 320C LU designation for Utility, is now the 320D LRR.

"The compact radius has really come to signify zero," says John Walker, Caterpillar senior sales and market consultant for heavy construction, "and the reduced radius is not necessarily a zero machine, but where we have physically reduced the radius."

The RR designation is more true to the design of the former U model, he says, "and you'll see more of that down the road, we think, as we go on with our product development in future years.

"The other thing is the fact that U, meaning Utility, has a different connotation in North America than it does in other places around the world. The machine really is a very productive tool, and depending on where you apply it — what the job task and the work environment is — the machine does provide more output."

Each of the new models is powered by the Tier 3-compliant Cat C6.4 ACERT engine delivering 148 horsepower, an increase of 10 horsepower over the C-Series machines. The ADEM A4 electronic control module provides flexible fuel mapping, allowing the engine to respond fast to varying application needs. Additionally, the standard power mode can reduce fuel consumption as much as 8 percent when performing work not requiring full power; Automatic Engine Speed Control cuts engine speed in light-load situations; and the cooling system has a demand fan controlled by a viscous clutch.

With the new D-Series excavators, operating weights range from 47,554 pounds for the standard-configuration model to 53,361 pounds for the reduced-radius machine, which uses about 5,000 pounds in extra counterweight to best utilize the same design and footprint as the standard machine, just into tighter spots. Tail swing is reduced from 9 feet to 6 feet 6 inches.

The compact-radius machine, with a tail swing of 5 feet 6 inches, incorporates a different design in which the boom is positioned farther back in the upper frame, reducing the front swing radius when the boom is pulled up.

The choice boils down to application. Compared to the standard-configuration machine, the 321D LCR provides 22 percent more lift over the front and the 320D LRR provides 19 percent more lift over the side, says Walker. "Hence, the need for a different model."

For each of the three new models, higher pressure creates stick and bucket forces that are about 7 percent greater than their predecessors. For enhanced control, the redesigned main hydraulic valve improves joystick response. As with the previous models, the D-Series models use a hydraulic cross-sensing system that maximizes hydraulic power for faster implement speeds.

For operator comfort, fully automatic in-cab climate control determines which air outlet is best in each situation. With all glass affixed directly to the structure, thus eliminating a need for window frames, the D-Series cabs are new, be they the spacious operator station of the standard- and reduced-radius models or the efficient, smaller cab of the compact-radius machine.

The introduction of the 320D L, 320D LRR and 321D LCR models extends the Caterpillar D-Series upgrade to the entire core 19- to 35-metric-ton excavator line, right up to the 330D L and 328D LCR models.

Basic Specs: Caterpillar D-Series Excavators
320D L 320D LRR 321D LCR
Operating Weight 47,554 lb. 53,361 lb. 53,307 lb.
Cat Engine C6.4 ACERT C6.4 ACERT C6.4 ACERT
Net Power 148 hp 148 hp 148 hp
Bucket Force 28,079 lb. 28,079 lb. 28,079 lb.
Max. Reach 32′4″ 32′4″ 31′9″
Max. Dig Depth 20′11″ 20′11″ 21′9″
Track Length 14′7″ 14′7″ 14′7″