The new Caterpillar 320C L excavator features increases in power, hydraulic flow, swing torque, and drawbar pull, as well as the use of boom and stick regeneration, and the introduction of a new main system relief valve.

The Caterpillar 320C L retains the successful 300 family concept with significant innovations for a new look and feel among excavators. The 320C L has a mass of 21,000 kg (46,300 lb) and is a direct replacement for the 320B L.

The 103-kW (138-hp) Cat 3066T engine provides an increase in full-time power of 8% over the 320B's 96-kW (128-hp) engine. The 3066T engine features a long-stroke design for high torque at medium to low speeds, good fuel consumption, and low sound. Fuel capacity has been increased on the 320C by 24% over the B model.

Single- and multi-function cycle times are faster with the 320C, which has 20% faster swing speed and increased swing torque of 9%. Drawbar pull has also increased 11% to 196 kN (44,040 lb).

The new excavator features a stick force of 97 kN (21,800 lb) and a bucket force of 129 kN (29,100 lb). High digging forces complement the increased power and flow rates for fast digging. Five sticks are available for the 320C, as well as a long- reach front.

A new electronic system links the movement of the 320C joystick with the hydraulic system to prioritize hydraulic flow to boom and swing circuits. The best mode for a particular job is automatically delivered based on the amount of joystick movement. The boom priority circuit, which is faster at boom-up operations, assists operators in and working through small swing angles. The swing priority circuit provides a large angle for good acceleration.

The 320C uses an open-centered, high-pressure 34-MPa (5000-psi) hydraulic system that increases performance through flow rates and efficiencies. The Cat 120 variable-displacement swash-plate piston pumps are controlled independently. The 320C's hydraulic pumps remain at a minimum angle when joysticks and travel controls are in the neutral position for less fuel consumption, lower sound levels, and extended component life. Pump flows increase in direct proportion to lever movement, making operation smooth and predictable. The 320C's maximum flow rates are 11% higher in comparison to the 320B. The hydraulic pump controls of the 320C feature cross-sensing for improved performance and faster speeds. Cross-sensing controls both hydraulic pumps to use 100% of available engine power under all operating conditions.

The x-shaped chassis design of the 320C yields a car body that is welded close to the ends of the track roller frame, increasing rigidity and resistance to torsional bending between the track roller frames and car body. Two undercarriage options are available. The 320C features a standard undercarriage with a length of 4.06 m (13.33 ft) and 2.21-m (7.25-ft) track gauge. The 320C L features a longer undercarriage length of 4.45 m (14.58 ft) and a 2.38-m (7.83-ft) track gauge.

The optional Multi Pro tool control system configures hydraulic flow and pressure to match a specific work tool. The ability to pre-program up to five different pressure and flow requirements for both one- and two-way work tools enables a diverse range of tools to be used on the 320C. The system comes complete with electronic joysticks and electronic controller and features stackable auxiliary control valves. The stackable valves are used in combination with the main control valve to provide the necessary flow to the various hydromechanical work tools. The system also has the capability of delivering a medium pressure flow rate.

The operator station of the 320C L has been redesigned. A compact, swivel-mounted monitor displays language-based information identifying various functions in a choice of seven different languages for North America. The monitor has a high-contrast LCD readout. Its gauges display fuel level, engine oil temperature, and hydraulic oil temperature. The message center of the monitor displays maintenance intervals for fluids and filters; and working times for engine, hydraulic pumps, travel motors, and five separate work tools. Settings are stored in the controller.

SAE Off-Highway Engineering June 2000