The new 90-metric-ton (198,000-lb) Cat^® 390D L Hydraulic Excavator, which replaces the 385C L, incorporates a refined design that provides greater hydraulic power, stronger structural components, added safety and convenience features, plus improved serviceability. The net result is a more productive, more durable, more efficient machine that is comfortable to operate and can take on the toughest jobs in a range of aggregates, coal and hard rock mining applications.

Engine and hydraulics

Powering the new 390D L is the 18,1-liter (1,104 in³) Cat C18 ACERT^® diesel engine, Tier III compliant and rated at 523 net horsepower (390 kW). The C18 features advanced electronic control, precise fuel delivery and refined air management for optimum performance, fuel efficiency and emissions control. The torque characteristics of the engine allow full power at maximum rpm, resulting in efficient hydraulic-pump operation and positive hydraulic response. Refinements in the crankcase, cylinder heads and proprietary MEUI (Mechanical Electronic Unit Injector) fuel system provide enhanced performance and durability for the C18.

Design enhancements in the implement hydraulic system allow the 390D L to deliver significantly greater digging and lifting forces than its 385C predecessor. Main relief pressure in the implement circuits has been increased to 5,080 psi (35 000 kPa), up nearly 10 percent from that of the 385C.

This increase in operating pressure, combined with larger-diameter hydraulic cylinders, results in a 9 percent boost in digging-arm and bucket breakout forces for the general-purpose and reach front-end configurations, and a 7 percent increase for the mass excavation configuration. Increased breakout force promotes faster trenching and loading cycles, plus stronger performance at the quarry face. In addition, lifting capacity over the end is increased by 9 percent, and over-the-side capacity is up nearly 20 percent—the result of stronger hydraulics and a heavier counterweight.

Also new in the implement hydraulic circuits are electrically controlled regeneration valves, which assure rapid, positive response from the boom and digging-arm cylinders, while also significantly improving overall hydraulic efficiency. The resulting benefits include quicker cycle times and estimated fuel savings of more than 2 percent.

A universal quick-coupler circuit is available for factory installation and is compatible with both dedicated and pin-grabber type couplers. The system features an offset lifting eye and easy-to-use controls.

Structures and undercarriage

An improved undercarriage for the 390D L features redesigned links that operate with lower stress, forged idlers for improved durability and heavy-duty track rollers and carrier rollers. In addition, the recoil spring has been lengthened, giving the recoil mechanism greater impact-absorbing capability to protect the undercarriage system from shock loads.

To accommodate the higher digging and lifting forces generated by the 390D L, the carbody (the structure mounting the machine upper to the track assemblies) is fabricated with thicker reinforcing plates at critical locations. Complementing this change are thicker plates at the boom-foot mounting in the upper frame, as well as thicker reinforcing plates in the rails and bottom pan to accommodate the heavier counterweight and increased swing-torque.

Both the standard counterweight and the optional removable counterweight weigh 13.7 tons (12,4 mt), making them slightly more than 6 percent heavier than the 385C counterweight. As a safety enhancement, activation of the optional counterweight-removal system locks out travel and implement-hydraulic functions to prevent unexpected movement of the machine.

Booms and digging arms also are stronger, the result of thicker material used in their fabrication and an improved welding process.

Operator comfort and convenience

The 390D L operator station is spacious, quiet and comfortable with commanding visibility.

The cab is pressurized to keep out dust, and the positive, filtered ventilation system combines with automatic climate control to maintain a constant, comfortable environment. The monitor provides full-color graphic displays with comprehensive machine information presented in either an English or ISO format