Caterpillar says its new 90-metric-ton (198,000-lb) 390D L hydraulic excavator, which replaces the 385C L, incorporates a refined design that results in a more productive, durable and efficient machine that can handle jobs in a range of aggregates, coal and hard rock mining applications. Powering the new 390D L is the 18.1-liter (1,104 in3) C18 ACERT diesel engine, rated at 523 net hp (390 kW).

Refinements in the C18’s crankcase, cylinder heads and proprietary MEUI (Mechanical Electronic Unit Injector) fuel system provide enhanced engine performance and durability, while design enhancements in the implement hydraulic system allow the 390D L to deliver greater digging and lifting forces than its predecessor. Main relief pressure in the implement circuits has been increased to 5,080 psi (35,000 kPa), up nearly 10% from the 385C. This increase in operating pressure, combined with larger-diameter hydraulic cylinders, results in a 9% boost in digging-arm and bucket breakout forces for the general-purpose and reach front-end configurations, and a 7% increase for the mass excavation configuration. In addition, lifting capacity over the end is increased by 9%, and over-the-side capacity is up nearly 20%—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 significantly improving overall hydraulic efficiency. The resulting benefits include quicker cycle times and estimated fuel savings of more than 2%.

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 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.

To facilitate easier, environmentally sound routine maintenance, the 390D L is equipped with protected, valve-controlled fluid-drain ports and self-contained hoses for fuel, coolant and lubricant systems. Easy-to-change spin-on filters are used in the fuel and lubricant systems, and pressurized fluid-sampling ports (in all pressurized-fluid circuits) assure reliable fluid samples. An electronic warning system alerts the operator if the air filter or hydraulic filter is approaching restriction limits. The Electronic Power Control (EPC) has been relocated from the cab to the air-cleaner compartment, allowing the cab floor to be washed without risk of damage to the EPC. For further reliability, the EPC and its electrical terminals are weatherproof.

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