Quarry Southern Africa July 2018 | Page 19

TECHNOLOGY and more environmental constraints can make blasting uneconomical or undesirable. Compared to other mechanical excavation methods (such as excavators with hydraulic rock breakers or rippers), the Tesmec Rock Hawg is the more cost-effective solution (provided that the job site extension is not too small and that it is sufficiently flat). The productivity of a single Tesmec Rock Hawg can be more than three times that of an excavator of the same weight (or up to 15 times a 25-ton class excavator), equipped with hydraulic rock breaker, and a few Rock Hawg units can replace an entire fleet of excavators. Rock Hawg machines are relatively small-sized machines, engineered with the scope of crushing rock, thanks to the special drum attachment with carbide digging tools and the high engine power that allows a very high hourly output per single unit. The high capacity of Rock Hawg machines reduce to one the number of units simultaneously working on the proposed job sites. Excavating with one single machine increases efficiency, safety, and costs for manoeuvring and servicing. Rock Hawg produces small and quite uniform material with a tight particle size. Excavation and crushing are carried out in one single phase, and this always allows avoiding primary crushing and more efficient settings on secondary and tertiary crushing systems. In large part, the size fractions obtained are a function of how the rock is laid into the ground (rock strength, rock brittleness, and rock mass fracture degree). The ‘reverse’ cutting mode of the Rock Hawg allows some degree of control of the grain size of excavated material, both in terms of oversized blocks (larger than 6” or 15cm) and sand/fines generation, allowing some variation in the size fractions obtained during cutting. Since all the excavated material passes under the drum and the tooth penetration reduces with depth, the shallower the cut, the bigger the size of the excavated material. Conversely, smaller-sized particles can be achieved by increasing the digging depth and reducing the advance speed of the machine. Having this small-sized material produced in a uniform configuration allows the material to be handled much more efficiently than the product achieved in excavation with drill and blast or rock breakers. This means savings for reduced wear and tear on truck bodies and loader buckets. What are the benefits of the Rock Hawg? There are many advantages to using the Tesmec Rock Hawg technology. Rock Hawg machines can excavate vertical side walls, thanks to the drum being wider than the tracks and it being supported in the centre. Moreover, the rear-mounted drum also allows for the excavation of square corners. This means that the excavated pit in many cases will not need any further finishing by other excavation means. The shock and vibration from Rock Hawg excavation are negligible and therefore, the danger zone becomes a non-issue. Rock Hawg machines generally produce low amounts of dust. In case the requested level of dispersed dust must be strictly limited, the Rock Hawg machine QUARRY SA | JULY/AUGUST 2018 _ 17