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Coasting To Gradation Control

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Global Mining Review,

Knowing how to anticipate mining evolution and the development of related technologies represents a keystone for successful companies in the mining sector. The achievement of high performance and top productivity levels must go hand in hand with the continuous improvement of safety standards and the reduction of operating costs.

Conventional drill and blast are still the most widely used excavation methods in quarrying and opencast mining, and in many cases they remain the most productive and cost effective techniques. However, mining activities must benefit from the latest technological developments as they produce new and more productive working methods.

Furthermore, the use of explosives is being subject to restrictive regulations, controls and limitations throughout the world, especially in politically unstable countries where increasing environmental constraint can make it uneconomical or undesirable. Safety, efficiency, productivity and precision are the challenges that the mining sector must face. New solutions have to be customised for their specific area in accordance with the project targets and the country’s legislative framework.

Tesmec Rock Hawg 1475 has been specifically designed and personalised for bulk excavations and mining projects, giving priority to performance and ore quality into a fully safe context. Rock Hawg excavation systems allow for a selective extraction of the material, avoiding the use of explosives and hammers and consequently reducing dust, noise, vibration and risk for the personnel involved. It is a philosophy that reduces the environmental impact while increasing extracted material quality in terms of productivity and size.

Levels of dust and noise are significantly lower than explosives; vibrations and shocks are negligible, with no danger for existing structures. Rock Hawg technology allows for the potential use in areas close to bridges, roads, railways and towns. The system currently supports mining activities for Lizetta, a project carried out in the Ivory Coast by the group Lagune Exploitation Bongouanou (LEB), and its manager Michel Moumouni Bictogo, on a rich bauxite reserve in the Bongouanou department.

The Tesmec trencher, a 108 t machine with 630 hp of engine power, has been optimised for the area’s specific needs, based on an accurate site stratigraphic analysis carried out by specialists with the aim of maximising excavation efficiency in terms of production volumes, material selection, safety and work speed.

In this project, the 150 in. (381 cm) wide drum works in down-cutting mode, excavating up to 20 in. (50 cm) deep. The ore is excavated and crushed at the same time, and is left on the ground behind the machine. Down cutting mode means that the teeth hit the rock from the top downward and the impact increases the efficiency of excavation if the rock is brittle (easy to fracture).

In any event, the same unit can be converted from down cutting to up cutting by reversing the cutting drum and the digging chains and adding the track guards, with the advantage to always have, with a single piece of equipment, the most appropriate technology for the jobsite. Drum picks geometry also impacts on the grain size of the excavated material, according to the rock characteristic and to the project peculiarity. Teeth pattern can be modified depending on specific needs, giving flexibility to modify the configuration as desired.

The specially designed picks lacing of Rock Hawg allows operators to swap among five different configurations in terms of the number of picks and spacing between the picks. This operation can be done by the customer very quickly in the mine by replacing picks with blanks in specific positions with no need for any cutting, welding or permanent modification to the machine, quickly adapting the machine to the specificity of each application concerning productivity and excavated material size.

This feature easily allowed the 1475 Rock Hawg in the Ivory Coast during the Lizetta project works to be fully compliant with tight customer request related to excavated material size (at least the 95% of the material size smaller than 100 mm).

Thanks to the consistent size of excavated material, the customer is immediately able to carry the ore from the job site to the port without any need for further crushing, with a significant saving in terms of time and cost. The small and uniform size of the excavated material makes loading and hauling phases easier, also allowing for the use of standard trucks for its transportation, instead of special mining dumpers.

Finally, the rear-mounted drum is wider than the undercarriage and it is supported in the centre, allowing for excavation of vertical side walls and square corners.

The machine’s high production capacity reduces the need for multiple units to a single unit working in the area, guaranteeing an easy yard to manage. Compared to other mechanical excavation methods, such as excavators with hydraulic rock breakers or rippers, the Rock Hawg represents a cost-effective option, provided that the job site extension is not too small and it is sufficiently flat.

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