The automation of the forestry industry has reached a high level. While this trend is expected to continue, two further challenges will increasingly occupy centre stage. Firstly, the actual productivity of the equipment depends on the reliability and serviceability of all the components. Secondly, the green sector must become even greener.
One is accustomed to thinking for the long term in the forestry industry. The renewable raw material requires decades of care and targeted cultivation before it can be used productively. Similarly planned for the long term are investments in machinery and equipment, which facilitate, for example, the felling, dressing and transportation of timber.
The increased automation in the industry is presenting new challenges. The more strongly the work cycles are geared to highly modern harvesters and other operating machinery, the more sensitively they react to technical problems. The teams often work far away from service stations and must be able to count on no problems arising during the operations.
In order to ensure the availability of the mobile operating equipment, manufacturers are developing strategies for preventive error diagnostics. The aim is to detect problems before they arise. This is an important addition to the already high requirements of the components.
Intelligent diagnostics requires several innovations. Firstly, the item of equipment must be viewed as a complete system, because diesel engines and hydraulics influence one another and only jointly provide a realistic picture of the state of the equipment. In the forest it does not matter which component fails if the equipment is non-operable as a result.
The availability of spares and consumables and the safety of a technology for the entire life cycle of the equipment are also important factors. Individual solutions run the risk that construction series will not be continued, which jeopardises the long-term use of the equipment.
Protection by filters
Long-term thinking always starts with the seemingly simplest components. Forestry equipment puts high demands on hydro pumps and motors, the valves and the hydraulic oil. Maximum protection against wear of hydraulic and lubrication cycle components is provided by modern filters, which automatically clean the operating fluids of machines and equipment and ensure a uniform quality. Removing particulates from the oil reduces damage to the system.
Rexroth, for example, supplies high-pressure filters for an operating pressure of up to 450 bar. Geared to volume flows of over 500 L/min, they minimise the pressure loss by their optimised flow control. Larger filters possess a two-part housing for a simpler filter change. All Rexroth filters use an optical/mechanical fouling display so that prompt replacement is possible.
Monitoring of the hydraulic oil is an important contribution to the optimisation of the service cycles. Oil changes are expensive, pollute the environment and are often carried out according to rigid servicing cycles. By guaranteeing the quality of the oil, the goal of more flexible service cycles that are determined by the actual condition is brought closer.
The optimised use of the consumables contributes to increasing the serviceability of forestry equipment. By the elimination of potential error sources and permanent monitoring of the condition of the equipment by condition monitoring systems (CMSs), many stoppages can be prevented.
Prompt recognition of wear or heavy stressing of components permits preventive measures, resulting in increased availability of the equipment. To enable the components to ‘speak’, they must first of all be made intelligent. A starting point for this is the integration of decentralised electronics directly into the individual components. Such an intelligence, frequently called on-board electronics (OBE), uses sensors built into the component which record important data on site and forward them to the central controller.
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The controller monitors all drive systems and ensures the optimum interaction of all the components. If a problem becomes apparent, the controller can warn the operator or the service personnel in good time.
Intelligent electronics
Robust and flexible electronics is the pre-requisite for ensuring that, starting from intelligent individual systems, a unit is created that is of real benefit to the user. The advantages must not be obtained at the expense of a new error source or sharply increased development costs. Rexroth, therefore, supplies a complete kit with control units, sensors, displays and essential peripheral devices, such as cameras that enable the operator to view inaccessible areas.
The Bodas system is geared to the hydraulic and mechanic drives of mobile operating equipment, in order to ensure a short development period. The whole of the electronics are carefully toughened to withstand the often extreme working conditions encountered in the wild. Heat, cold, vibrations, shock or electromagnetic radiation cannot affect them.
Advanced drive concepts
Deliberate interaction between the individual components is a prerequisite for adhering to the future environmental standards on mobile operating equipment. The environment authorities across the globe have standards related to reducing environmental pollution due to so-called off-highway vehicles.
This requires from the manufacturers a careful consideration of the strategy by which they will reconcile the power requirements of the equipment with the environmental requirements. This is a major challenge in technical terms since, depending on motor size, for example, the nitrogen oxide emissions may have to be reduced by up to 93%.
It is clear that this cannot be achieved simply with measures within the diesel engines. Instead, additional systems for the after-treatment of exhaust gases must be introduced. Various solutions are available, which must be selected according to the manufacturer’s strategy.
Every system offers various advantages and disadvantages. Common to all of them, however, is that the design of the whole drive unit has to be revised - if for no other reason than the additional components require more space.
Due to the measures within engines for achieving the new emission standards, the requirement for cooling also rises. First of all, this means that the cooling modules will probably be bigger in future; secondly, there will be less room for mounting them in the vicinity of the diesel engine. The cooling module, including the fan impeller, must therefore be fitted elsewhere in the vehicle, which makes a direct drive of the fan impeller impossible. A possible solution to this is the use of a hydraulic fan drive. The latter allows the vehicle manufacturer to position the cooling module in the vehicle independently of the diesel engine.
For optimum combustion, the new diesel engines must observe a narrow temperature window. Here, also, a hydraulic fan drive has advantages as it can influence the cooling independently of the diesel speed, in order to optimally operate the diesel engine. This takes place automatically in an energy-saving manner. For compared with a belt-driven fan, which runs continuously and consumes energy, the hydraulic variant operates only if cooling is actually needed and is therefore more energy efficient.
Written by Martin Birk, Head of the Forestry Application Centre.