Avaliação de blindagem com correntes em caminhões fora de estrada CAT 777 F/G da mina de bauxita da Mineração Paragominas S/A

Abstract

The mining of bauxite, the main ore used for aluminum production, is performed by the method known as strip mining. This method is developed in strips due to the morphology of the deposits, which generally present tabular geometry and are close to the surface. To perform the mining it is necessary to remove the overburden in the mining area in order to expose the ore, and this operation can be held by different equipments according to the height of the layer of waste rock. In the Mineração Paragominas SA (MPSA), an enterprise of Norsk Hydro, located in the city of Paragominas - PA, the layer of waste rises over 13 meters high. The overburden removal is then performed in three ways depending on that height: using bulldozers CAT D11 with trident-shape ripper attached (H>8m); using tractor CAT D11 with trident-shape ripper attached and hydraulic excavator to remove the remaining material (13m< H >8 m); and using the off-road truck CAT 777F/G and excavator system for waste layer recess, operation with bulldozer D11 and hydraulic shovel. The off-road trucks, which are characterized by having greater adhesion and resistance to operate in unfavorable conditions, are responsible for 15% of all movements of waste in MPSA, ensuring best rates of overall equipment effectiveness, in addition to continuity and synchronism of the overburden removal process. However, in the MPSA area, the historical levels of precipitation in the period from December to May are quite high, which directly impacts the mining system and other operations. Faced with this problem, shields were installed on the external rear tires of the off-road trucks CAT 777 F/G of Mineração Paragominas S/A, pulling them in order to facilitate the operation of such equipments. The results were satisfactory, for the chains increased the trucks rate of physical use, ensuring the continuity of methodologies of overburden removal productively, and ensure a safe operation, since the chains prevent slippage and/or lateral slippage during cornering and maneuvers. The economic analysis also led to the conclusion that the use of chains is feasible, because the costs are recovered, and there is no excessive wear of the tires of the trucks, not decreasing their useful life.