The 90-tonne 390D L excavator, which can be employed for a range of applications from heavy construction to mining, ensures maximum output while being easier and more comfortable to operate.

01 March 2011

THE new 90-tonne 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 heavy construction and mining applications, according to a spokesman for Caterpillar.

Powering the new 390D L is the 18.1-litre Cat C18 Acert diesel engine, which is EU Stage IIIA and US EPA Tier Three-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, he says.

“The engine’s torque characteristics 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,” he adds.

Design enhancements in the 390D L’s implement hydraulic system allow the new model to deliver significantly greater digging and lifting forces than its 385C predecessor. Main relief pressure in the new model’s implement circuits has been increased to 35 000 kPa, up nearly 10 per cent compared to that of the 385C.

“This increase in operating pressure, results in a nine per cent increase in digging force,” he explains. “Increased breakout force promotes faster trenching and loading cycles as well as stronger performance at the quarry face. In addition, lifting capacity over the end is increased by 14 per cent with over-the-side capacity up nearly 14 per cent – the result of stronger hydraulics and a heavier counterweight.”

Also new in the 390D L’s 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 two per cent, the spokesman says.

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.

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.

The counterweight weighs 12.4 tonnes, making it slightly more than six per cent heavier than that of the 385C.
Booms and digging arms also are stronger, the result of thicker material used in their fabrication and an improved welding process.

Operator comfort
The 390D L’s operator’s station is spacious, quiet and comfortable with good visibility. The cab is pressurised to keep out dust, and the filtered ventilation system combines with automatic climate control to maintain a constant, comfortable environment. The monitor provides full-colour graphic displays with comprehensive machine information presented in either an English or ISO format.

The monitor provides fluid level checks when the engine is started, can list approaching service intervals and can display real-time fuel consumption information numerically. Flexible power modes – high power or economy – allow the operator to adjust machine performance to the task. Both modes provide the same digging forces, but the economy mode allows the machine to work with fuel-saving efficiency when production requirements are less critical.

For the operator’s convenience, the height of the control-lever consoles is adjustable, and the response and modulation of the electro-hydraulic joysticks can be adjusted through the monitor. The control-pattern changer, also accessible through the monitor, allows the operator to select preferred lever functions. In addition, the monitor displays images from the 390D L’s optional rearview and wide area vision system cameras, the latter mounted on the boom or side of the machine.

To reduce the heat and noise in the cab, the hydraulic control valve, pumps and reservoir are positioned on the right side of the machine, away from the operator’s station. Cab lights are time delayed to allow safe exit from the machine at night.

Service improvements
The 390D L uses an electric fuel priming pump, which simplifies filter changes. A dual-element air cleaner with a double radial seal is standard. All filters, except for the high-pressure fuel filter, are accessible from the left side of the machine. Service safety features include a 24-volt service light receptacle and wider, 500-mm walkways that provide sure-footed access to maintenance points.

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. An electronic warning system alerts the operator if the air filter or hydraulic filter is approaching restriction limits.

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