Ultra-large excavator has high-efficiency hydraulics

Ultra-large excavator has high-efficiency hydraulics

Hitachi Construction Machinery plans to add the EX2000-7 ultra-large hydraulic excavator to its line of mining machinery. The redesigned unit, slated for introduction next year, is based on the current EX1900-6. The model reportedly will feature an entirely new hydraulic circuit that reduces fuel consumption by up to 19% with no loss in productivity.

Powered by a Cummins QST30-C engine rated at 1,000 hp (746 kW @ 1,800 rpm) and with an operating weight of 193 tons, the EX2000-7 is considered one of the “smaller” Hitachi EX-7 ultra-large excavators. High demand is expected from small to medium-sized mining and quarrying operations, where fuel efficiency is critically important, said company officials.

For reference, the EX1900-6 main circuit has three tandem axial-piston pump groups (six pumps total) supplying a maximum 531 gpm (2,010 lpm) with relief valve settings of 4,264 psi (294 bar).

The EX2000-7’s impressive 19% fuel saving results from a range of energy-efficient features. Hydraulic oil flow is controlled according to the operating pattern and front-end attachment geometry. An all-new hydraulic control system has been developed and, for the first time, employed for an ultra-large hydraulic excavator. That allows for more-precise management of hydraulic oil flow in each control valve throughout the digging and loading cycle.

The operator uses control levers to finely adjust the boom, arm, bucket and swing speed and manage digging, loading and dumping of material. Under this scenario a conventional hydraulic circuit would return unused or excess oil circulated throughout this cycle from the hydraulic pumps back to the oil tank, which constitutes a loss of energy and offers room for improvement. In the EX2000-7’s new hydraulic circuit, oil flow to each boom, arm, and bucket cylinder, and to the swing motor, is independently controlled for each operational pattern — such as excavation, swinging or dumping — and by the load on the front-end attachment.

Further, all hydraulic pumps are equipped with electric regulators to precisely control oil flow based on operating lever positions and engine load. Finely managing the delivery rate of each pump according to operating lever positions also improves efficiency and, thus, keeps fuel consumption as low as possible.

Work-mode selection functions, which have been applied to medium- and small-sized hydraulic excavators, will be part of the upgraded EX2000-7. The new feature lets operators select one of three working modes – High Power, Power or Economy – to match productivity and fuel efficiency for different types of operation. The high-power mode is for heavy-duty operations such as bedrock excavation. It reduces fuel consumption by up to 19% with the same productivity as the EX1900-6. The Power mode suits most general operations. It reduces fuel consumption by about 25% and productivity by 10%. Economy mode is for light operations, where fuel consumption can drop by 40% and productivity by about 30%, compared to the EX1900-6.

The EX-7 series machine also includes an upgraded oil cooler and radiator. Rotating speed of the oil cooler fan rises in proportion to an increase in hydraulic oil temperature, to cool the hydraulic fluid. Control of radiator fan speed takes into account both ambient temperature and engine coolant temperature. This helps prevent thermal degradation of hydraulic seals and, likewise, prevents cracking and scoring of components’ internal parts due to thermal expansion. The result is increased reliability of the hydraulic pumps, cylinders and motors, along with energy efficiency increases that contribute to lower fuel consumption.

To improve structural integrity, the EX2000-7 boom-arm joint area and main frames are now designed in line with Hitachi’s larger mining machines. The pin connection between boom and arm has changed from a single pin to a double pin, which makes the boom and arm stronger but lighter. The main frame has also been stress-analyzed and redesigned to distribute forces as evenly as possible during operation, increasing machine durability.

The EX2000-7 incorporates ICT (control and operations based on 3D design data) to improve safety and productivity and reduce life-cycle costs. And Hitachi’s ConSite Mine (scheduled for release in 2021) will reportedly improve mine-site efficiency through the use of IoT and AI technologies, and contribute to higher utilization rates and minimize machine downtime. The EX2000-7 will readily integrate into remote-control and autonomous operations, by coordinating hydraulic excavators and AHS (Autonomous Haulage System), which will further protect workers and lower costs.