What's New In Plant & Equipment
The Future of Excavators continued >>>
To date, the simple and most-popular solution in industry has been to optimize only the hydraulics. Such an approach does offer some improvement but, unfortunately, neglects the importance of the engine and its effects on efficiency of the entire machine.
In contrast, the new STEAM mobile-hydraulic system for excavators represents the first holistic approach to optimize both energy efficiency and performance of mobile machinery.
In contrast to today’s load-sensing and flow-controlled systems, STEAM does not use the engine and pump to directly supply flow to the actuators but, rather, to maintain pressure levels in two separate hydraulic accumulators (high and medium pressure).
This accumulator charging circuit makes it possible to completely decouple the hydraulic actuators from the engine and pump, letting these components operate far more efficiently.
This not only enables operation at a considerably lower and quieter engine speed of 1200 rpm but also minimizes throttling losses and permits recovery of both potential and kinetic energy from all the actuators. Consequently, the machine is considered a hydraulic hybrid.
In contrast to other hybrids, STEAM does not use electrical storage devices or actuators. The already installed hydraulic system only needs to be modified, which keeps costs low and avoids unnecessary energy conversions. The robust and easy-to-maintain hydraulic hybrid technology reportedly increases profitability for operators, as they can expect a more agile machine with significantly lower fuel consumption.
Considering the constant concern over fuel costs and more-stringent emission guidelines, STEAM is clearly a very relevant and possibly game-changing innovation for the construction equipment industry.
The prototype is currently being tested with preliminary measurements showing that the hybrid is just as fast and powerful as standard machines, but it operates up to 40% more efficiently. More testing is underway to accurately quantify the potential of the new technology and make the results available to industry, thereby encouraging implementation in future applications.
Hybrid and Other Technologies
hilst advances in hybrid technology will provide a viable solution, there are alternatives such as electric, battery or hydraulic driven. Electric driven excavators have been a common feature in specific industries such as waste and port handling where the machines are not required to move very often.
However, the past few years has seen alternatives to diesel power being introduced to mini and compact excavators.
The Institute for Fluid Power Drives and Controls (IFAS) of RWTH Aachen University
Steinbachstraße 53 - D-52074 Aachen
Dipl.-Ing. Milos Vukovic
Group Leader System and Control Technology
Roland Leifeld, M.Sc.
Are Power Packs the Future for Compact Equipment?
Another alternative is to use a hydraulic power pack. Today, virtually all movement of excavators is hydraulically driven, therefore, if a feeder can provide the necessary hydraulic flow then the engine become virtually obsolete. This is a development of Wacker Neuson and now adopted by Caterpillar.
A benefit of this option is the dual power versatility it enables. Unplug the power pack and the excavator immediately returns to a diesel power.
Caterpillar has added the model 300.9D VPS (Versatile Power System) to the Cat range of mini-hydraulic excavators under the partnering agreement with Wacker Neuson.
It will be an attractive option to existing Caterpillar plant hire and rental companies as well as those contractors who often have to work in very restricted areas where engine emissions may not be permuted (i.e. internal refurbishment of shopping malls, etc.)
The versatile design benefits both the owner/operator and the rental company by allowing the machine—in conjunction with its separate hydraulic power unit—to work either with its diesel engine or from a remote electrical power source, with no loss of performance.
|Net power||9.6 kW (13 hp)|
|Stick force||4.5 kN (1012 lbf)|
|Bucket force||8.9 kN (2000 lbf)|
|Digging depth||1,731 mm (68 in)|
|Dump height (max.)||2,035 mm (80 in)|
|Reach at ground level||3,027 mm (119 in)|
|Operating weight (min.)||1,088 kg (2399 lbs)|
|Shipping weight (min.)||988 kg (2178 lbs)|
Having an electrical drive system remote from the machine enhances utilization and rental options. The 300.9D VPS can be rented alone for regular applications—or with the hydraulic power unit when the job requires low noise and zero emission.