Hydraulic excavators to evolve
WNERS of hydraulic excavators have to consider several factors when seeking to upgrade. “The three key issues are engines, fuel consumption and hydraulic control, followed by the more general considerations of up time and maintenance,” says Ian Johnston, product manager at Case Construction Equipment . Although Australia does not have legislation requiring European-level emission standards, Tier III engines are being fitted by the major excavator manufacturers.
Tier III engines are a big step forward for owners who still work with excavators that are one and two generations behind. Many of the engine processes, such as fuel control, are electronically processed. With excavators, so is much of the hydraulic system. “This is not a reason to be concerned,” explains Johnston. “Tier III engines are more productive, use far less fuel and the technology has been proven on highway trucks over some years and many millions of kilometres.”
To meet the stringent emission standards of Tier III engines, a combination of electronic and mechanical means is used. Electronic controls precisely meter the amount and timing of fuel injected into the combustion chamber. Combined with turbo charging and charge air coolers, engine efficiency has improved. This has resulted in more power and torque from smaller engines using less fuel. “We are now seeing major fuel savings over older models and Case reports savings of around 10 per cent with certain applications of their 20t CX210 model using between 13 and 17 litres per hour,” says Johnston.
Automatic power boost
The increased use of electronics for hydraulic functions has also improved efficiency. The electronic pump controller communicates with the engine controller, optimising engine speed and power with hydraulic flow and pressure, based on the load. “Greater productivity, moving more tonnes with less fuel, is the outcome,” says Johnston. “Using the latest Case models as the example, there is an auto mode that varies engine revs and pump torque to suit the load on the work tool.”
Auto mode varies engine speed between 85 per cent and 90 per cent and hydraulic pump torque between 90 per cent and 93 per cent of maximum. The engine speed and pump torque varies to achieve a balance between productivity and economy. An Automatic PowerBoost in the hydraulic system is another feature now offered. This automatically increases system pressure by 10 per cent for eight seconds. The operator does not have to hit the power boost button – the hydraulic controller makes the decision.
The electronic engine control diagnostics of performance is now possible. Fuel consumption, amount of idle time, amount of walking, working modes used and the amount of work performed can be downloaded from an onboard controller. Should there be an operational problem; fault codes will be stored for later access by a service technician. For fleet operators, remote access of fault codes makes it possible to get an excavator up and running more quickly. The new excavators can also protect themselves from abuse or damage in the event of loss of engine oil or overheating of the engine or the hydraulics. The electronic controller can allow work to continue with reduced performance or trigger a shut down until rectification.
Hydraulic oil change
Another “electronic” feature is the password security system on some models. Service intervals have also increased resulting in greater uptime and as well as reduced service costs. For example, engine oil changes at 500-hour intervals are now common. Hydraulic oil change intervals have extended to 4,000 hours and 5,000 hours with special filtration systems. Case has been using a one micron filter which is enabling 5,000-hour intervals. Grease intervals on booms and arms are going out to 1,000 hours with the aid of graphite impregnated brass bushes and hardened chrome pins.
“In the near future we will see the introduction of an ISO standard for ROPS,” says Johnston. At the National Construction Exhibition last November, Case displayed models that represent the future including a remote controlled machine. Without the need for a cab, this machine would be able to get into areas where conventional machines of equivalent power could not go. “As to the future, design engineers are focussing on increasing performance with improved efficiency, greater comfort and easier maintenance,” concludes Johnston.
Source: Construction Contractor
28-Sep-2006