Análise técnica e econômica de um sistema de colheita florestal / Technical and economic analysis of a forest harvest system

AUTOR(ES)
DATA DE PUBLICAÇÃO

2007

RESUMO

Hand logging systems were the first adopted, mostly, in the exploitation of native forests, with no concern with the rationalization and productivity of such activities. In Brazil, the first activities of forest harvesting were carried out along the coast, at that time of discovery, when the main traded species was brazilwood. Machine selection and development of operating systems constitute a great challenge to the reduction of costs and dependence on labor in harvesting operations and forest transport. The general objective of this research was to optimize the forest harvesting system, and the specific ones were to evaluate the technical and economic characteristics of the machines, simulate the tractive effort of the Skidder and to develop an electronic device for automatic demarcation of wood bucking point. The technical analysis was based on a study of times and movements to identify and analyze the phases of the operating cycle of each studied machine and their delays. The economic analysis consisted of determining machine operating and production costs. Feller-Buncher and Slacher data were evaluated in a complete randomized design, with six replications, in a split-plot arrangement, with the phases of the machine operating cycle in whole plots and the levels of productivity 100, 200 and 300 m ha-1 in subplots. Data were subjected to analysis of variance and the Tukey test at 5% of probability. To evaluate the effect of the times spent in the operating cycle by the Skidder at the productivity levels of 100, 200 and 300 m ha-1 and the dragging distances of 100, 200 and 300 m, as well as evaluating the significant interactions, a randomized block design was used, in a 6x3x3 factorial arrangement (six operations, three productivities and three dragging distances), with four replications. Data were subjected to analysis of variance and the Tukey test at 5% of probability. To model the dynamic behavior of the skidding tractor we used the model proposed by the Standard 497.4 (ASAE, 2000), developing a piece of software to predict the efficiency behavior of traction, force and the available potency on the log tong of the Skidder. To accomplish the simulations, a piece of software was developed using the programming language VISUAL BASIC version 6.0. To simulate the Skidder tractive effort, the program was supplied with data on wheel characteristics, tire specifications, operational parameters and soil properties. The control of bucking length used a TP 02 WEG programmable counter, working through a pulse generator based on an inductive proximity sensor M12 X 1 CC in metal housing, with protection against short circuit and automatic rearming. The results led to the conclusion that the Feller-Buncher recorded the highest production cost and was the most important machine within the system, with productive capacity based on its productivity, i.e., 6,197.93, 10,623.09, and 18,328.99 m month-1, when working in forests of 100, 200 and 300 m ha-1 respectively. The simulation model generated values for simulated traction force similar to the experiments of dragging heights, with the maximum height giving the largest effort. The results were conclusive, since for 6 to 9% skidding, there were no significant differences, independently of the dragging height, and at maximum height the tractor showed the largest effort. The values found for the log lengths when electronically measured and by the standard log were close to the required and showed no significant differences. The sensor was not automatically capable of reset the values when the operator surpassed the required length. The time values were not satisfactory, being the ones electronically measured above those measured with the standard log. The device produced no bucking times feasible for its use, needing adjustment. For optimization, the system should work in a 300 m ha-1 forest with dragging distance up to 200 m, with volumes of bunches larger than the currently in use.

ASSUNTO(S)

feller-buncher maquinas e implementos agricolas machinery testing mecanização florestal feller-buncher ensaios de máquinas forest mechanization

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