Harvester (forestry)
As timber harvesting, forest harvesting or Harvester (English " harvester" ) refers to special harvesting machines.
The machines fix the trees, cut them down and can delimb the tribes, the rind and place it on a forwarder. If, simultaneously or the branches chopped into chips, one speaks of a wood chip harvesters. As heavy forest machinery they need a engmaschigeres skid trail network as their inherited processing and allow some operations such as the assignment of the wood sections to so-called assortments immediately on the spot to do. They have changed the forest management worldwide and accelerated. In Germany they " Wiebke " ( 1 March 1990 ) and " Kyrill" ( 18 January 2007) was first widely used for the processing of windfalls by the intense low-pressure "Vivian" (26 February 1990), are used; Since then, the proportion of timber harvesting in the woof volume constantly, which seems to be useful also because of the reduced risks of accidents.
Equipment
Today, mainly the following types of timber harvesting are used ( commonly referred to in accordance with the definition of a machine that performs a number of steps as a processor, in order of frequency ):
In forestry, timber harvesting are mainly used for softwood. When the Hardwood delimbing is unsatisfactory. There are special designs for use in low, medium or heavy wood.
The machines usually have a long between ten to fifteen meters boom, at the end of the felling head (processor) is mounted for free movement. The felling head is equipped with feed wheels ( rolls ), measurement unit, hydraulically driven chain saw and limbing knives. Instead of a chain saw and a circular saw blade is installed in rare cases. Some machines are equipped with a tiltable cabin according to the slope, wherein the other, the entire machine can be brought into the horizontal position despite the slope grounds. Air conditioning is installed, often an automatic pre-heating of the hydraulic oil and the cabin before starting work. Wheel Holzvollernter have low pressure, low profile tires to 70 cm tire width for soilprotecting use. When wet or snow chains or metal strips can be installed additionally. Despite these features significant damage are not excluded on soft soils. Partial reports of lanes with up to 70 cm depth.
The engine power is 120 kW models of smaller, specialized machinery can reach well over 220 kW. The average is around 170 kW for moderate growth forests. The force is transmitted exclusively hydraulically, the control of all functions is electrical or hydraulic pilot control. The very extensive hydraulic system must be filled according to the latest PEFC and FSC standards with biodegradable oils. A vacuum pump repairs at reduced oil leakage; In addition, the crane with a stop valve or cock is provided which closes the oil flow to the engine and so on an accident holding back the oil. Excavator Holzvollernter were predominantly flattened to the side chains with rounded ridges for less soil or inventory damage. Damage in forest stands occur in the form of underground root cracks as a result of shear forces in the rule. On the forest roads occur during rotational movements damage to the top layer.
Main applications of the excavator - wood harvester are due to the low ground pressure ( to avoid soil compaction ) on the one hand wet soils, on the other hand, steep slopes up to about 50 % slope because of its relation to the wheel Holzvollernter better climbing ability. However, with the track-type drives the disadvantage that they can be damaged by tree stumps or other sharp objects. When moving the excavator timber harvester low drive speed ( 5 km / h) and the risk of damage to asphalt roads ( use a low loader needed) and a disadvantage. The machines are fully equipped with about 15 halogen headlights that allow it to also work at night.
The timber harvesters are now equipped with GPS, mobile communication and an on-board computer that supports the wood Housekeeping and grade education. The reclaimed wood materials can be saved and printed timber lists. The accuracy of the measured timber volume sensor system is used to a great extent, the felled tree, the proper consideration of the necessary beef deduction and not least regular, documented calibration dependent. Measuring deviations from the factory surveying or manual recording wood are the rule. In well-controlled systems, the deviations are acceptable in 2 to 4 % higher than the Werkseingangsmaß, but stronger deviations are not rare. For this reason, a Raummaßerfassung of logged timber on the forest road is useful in addition to determining the number of units.
Area of application
Originally Holzvollernter were used in the thinning of weak coniferous forests, but now also in stem wood harvest (mostly coniferous, sometimes in Hardwood beech stands ). The strongest Fällköpfe can handle logs up to 70 cm diameter at breast height ( DBH ). Harvesters can choose between five and thirty cubic meters (fm) reappraise wood per hour, depending on the strength of the wood harvested in particular.
In more inclined terrain special crawler - wood harvesters are used (eg Valmet 911.1 X3M ). Another special development is the six-legged walking - timber harvesters, which was developed in Finland to the thinning of herds on waterlogged or boggy soils. For use on steep slopes this equipment but proved to be unsuitable.
In the workup of storm wood, the use of these machines reduces the risk of accidents considerably as the dangerous voltages of the reflected trees outside the human danger zone to be resolved. In Switzerland great track harvesters were first used for cutting of old trees and head to the capping of whole trees in 3 to 5 meters in height. By capping is expected to arrive at new head trees, which are very rich cave as a cultural form in 15 to 20 years.
Due to the increasing importance of bioenergy were of known forest machine manufacturers combinations of harvesters and mobile chipper, wood chips so-called Harvester developed. In this type of machine accumulating waste wood and crown sections are processed in the same operation into wood chips during harvesting. Another combination comes from the Finnish manufacturer Pinox. Here, with an additional aggregate principal crown portions pressed to transport just bundles, which are also used for energy.
International use
In Scandinavia (especially Sweden and Finland), these machines are used since the early 1980s. By now, almost the entire timber harvesting is carried out highly mechanized there. In Central Europe, these machines work on a stake of between 30 and 50 percent of the impact volume - with a very strong upward trend. In Germany they " Wiebke " (1 March 1990) and " Kyrill" ( 18 January 2007) was first widely used for the processing of otherwise unmanageable windfalls by the intense low-pressure "Vivian" (26 February 1990), are used; Since then, the proportion of timber harvesting in the woof volume steadily increasing. Holzvollernter be used in smaller numbers in North America. There are so-called Feller Buncher ( Feller Buncher ) set up under the wood dimension, which can make up to a DBH of one meter, with its much larger Fällköpfen trees. Another field of application are tropical plantations, where they are used for the harvesting of pine (Pinus radiata) and eucalyptus stands. The tree dimensions and the full- biking the area can work rates of up to 50 fm in the hour.
Working procedures
The harvester falls delimbed and splits the wood. Transport to the nearest truck motorable forest road, the wooden back is done by the following forwarder ( forwarder ) or a cable crane system. Except in the storm of wood harvesting of alleys works from which he invests at the first thinning of the herd itself, and on which then also runs the forwarder. At each interval of 5 to 10 years following thinning the same skid trails are used over and over again. Crane ranges of up to 10 m as areas with streets intervals of 20 m can be edited. If additional lanes distances required or working on steep slopes, it is motor manually, that is, with the chain saw, supplied falls.
In flat terrain the harvesting lays the stripped branches as a cushion on the tramline. Thus, the ground pressure of the driving machine is additionally reduced. The reclaimed logs are sideways, broken down by product lines stored. A color coding of the ranges according to buyer is also possible to identify difficult to distinguish from each other assortments. The special design of the chips harvester processed as described above, even the stripped branches. However, the branches and treetops may be crushed and taken away with subsequent small mobile hacking machine, or a combination of forwarders and Great hackers into wood chips.
Impacts on forest work
Since harvesting in the Vornutzungsbeständen productive and cost-effective than classic lumberjack, takes her to use in Germany resistant.
In Endnutzungsbeständen or in stocks with takeover enabled rejuvenation shares of the impact is the processor using at least the equal of forest workers, taking all facts.
Meanwhile, 30 to 40 percent of the timber harvest be mastered in Germany with harvesters - with a strong upward trend. Harvesters reduce at harvesting with the chainsaw very high accident risk and contribute to the reduction of occupational diseases. The use of harvesting leads to reductions in forest operations and to a change in qualification structure in forest work. When using trained and experienced machine operator to use is extremely consisted friendly, as a controlled precipitation is possible by the machine, which can not be achieved in motor manual methods even in the best conditions.
Ecological impact
The damage caused by the use of several tons of heavy machinery, are the subject of long-term studies. Above all, the problem of soil compaction and root damage is examined. Some studies have suggested that the busy forest floor more than 100 years needed for regeneration. Since the soil compaction by weights of up to 60 t is immense and a skid trail system is needed with a distance of 20 m, about 20-25% of the forest floor surface be damaged in the long term.
In addition, in twigs of trees is a major part of the nutrients and trace elements. In the workup of the brushwood is transported to the skid trail. It is feared that by doing the standing stock of important nutrients are removed. It could come to the impoverishment of the soil. It would also be affected by the biking the gas exchange and soil life. Trees that are directly on the streets, deceptive severe root damage which would grow and often asymmetrical. As the machines sail hanging in the fall line, the soil erosion is encouraged. It is also criticized the fuel consumption of around 20 liters per hour when considering the ecological balance.