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Improvement in surface mining technology

By Dineo Phoshoko

Technology in the mining industry is improving and leading to safer, more efficient mining practices.

In response to improving mining safety and efficiency, Italian manufacturer Tesmec has developed the Rock Hawg – a machine specialising in surface mining. Mining and Minerals Product Review (MMPR) spoke to Tesmec technical chief Flavio Villa, to find out more...

Tesmec 001
The high capacity of the Rock Hawg reduces the need of units to a single unit working simultaneously on proposed jobs sites.
Image credit: Tesmec

How long has the Rock Hawg been available on the market?

The first Tesmec Rock Hawg was built in 2003, from the original Tesmec idea of adapting a drum attachment to the famous Tesmec trenchers, world leader in hard rock excavation.

The result was an innovative surface miner, with an outstanding excavation effectiveness thanks to the special features of Tesmec design.

Since then, there has been a constant evolution of this machine concept, and a continuous improvement have been carried out over the years, to improve productivity, reliability and to extend the application range of this technology to several different applications.

List the applications best suited for the Rock Hawg, particularly in the mining industry.

Specially born for surface mining, Tesmec Rock Hawg are – to date – used in the following application fields:

  • Bulk excavation of rock for construction
  • Site preparation (cut and fill applications)
  • Quarries and open-pit mines (surface mining)
  • Excavation of big ditches (large diameter pipeline)
  • the use of explosives is subject to more and more restrictive regulations, controls and limitations throughout the world, especially in politically unstable countries; and
  • More and more often environmental restraint can make blasting uneconomical or undesirable.
  • 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.
  • Rock Hawg machines can excavate vertical side walls, thanks to the drum wider than the tracks and supported in the centre. Moreover, the rear-mounted drum also allows 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 is 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 can be equipped with the dust suppressing system (optional).
  • Rock Hawg machine, using a laser system to control digging depth can produce a very smooth and gently inclined surface. The inclination can be easily controlled directly on-site, and a one- or two-degree slope can be imposed on the excavation floor allowing any emerging water to be drained toward a sump for dewatering operations.
  • Operators must be properly trained to operate the machine in a more productive way.
  • Machine service, greasing and periodic maintenances must be properly managed to maximise machine availability and minimise down times.
  • It must be considered that Rock Hawgs are completely different from excavators with rock hammers, and they cannot just be brought in the job site and start working as if they were barely another piece of equipment in the site.
  • We can say that the working plan of the Rock Hawg becomes the driver in the site and gives the pace to all other equipment (and not vice versa).
  • To deploy their excavation capability, the Rock Hawg must have proper site management.
  • A poor site management (in terms of loading and hauling of the excavated material) will mean an increase the stand-by / idle time for the Rock Hawg, therefore low efficiency of the site (net excavation hours compared to total working hours).

For the sake of clarity, we must say that conventional drill and blast methods are still the most widely used excavation methods in quarrying and open pits mining, and in many cases, they remain the most productive and cost-effective techniques.

That being said, Tesmec Rock Hawg technology allows excavating in a cost-effective way even strong and unfractured rock completely substituting and avoiding the use of explosive.

This aspect can be of primary importance and make (under certain conditions), the Rock Hawg a viable alternative to drill and blast methods, considering that:

Compared to other mechanical excavation methods (such as excavators with hydraulic rock breakers or rippers) the Tesmec Rock Hawg is always the more cost-effective solution (provided that the job site extension is not too small, and it is sufficiently flat).

The productivity of a single Tesmec Rock Hawg can be more than three times the one 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 to the high engine power that allow a very high hourly output per single unit.

The high capacity of Rock Hawg machines reduce to one the number of units simultaneously working in 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.

Tesmec 002
The shock and vibration from the Rock Hawg excavation process is negligible, making the danger zone a not an issue.

Image credit: Tesmec

Since all the excavated material passes under the drum and the tooth penetration reduces with depth:

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 mean savings for reduced wear and tear on truck bodies and loader buckets.

What are the benefits of the Rock Hawg?

There are many advantages in using the Tesmec Rock Hawg technology:

What contribution does it make to health, safety and environmental performance?

The Rock Hawg is environmentally-friendly. Level of dust and noise significantly are lower than that generated by explosives. Vibrations and shocks caused by surface miners are negligible, with no danger for existing structures are reduced. The use of explosives is subject to increasing regulations and restrictions. The use of surface miners avoids this problem, and no special permit is necessary.

Does the Rock Hawg have specific maintenance requirements?

Like any earthmoving / mining equipment, maintenance is utmost important to keep machine availability at its highest level.

In the operating and maintenance manual of the Rock Hawg all the periodic controls, maintenance and preventive refurbishment are listed in detail.

Undercarriage and digging attachment (drum and chain) are the parts that need the higher care, since they are in direct contact with the excavated material / ground and in case of highly abrasive material they can be more subject to wear compared to other machine parts.

How long is it expected to last when used regularly in the mining industry?

Provided that scheduled maintenance is executed as per Tesmec instructions, a Rock Hawg can last more than 30 000 hours. Overhauls and replacement of some major parts (such as diesel engine, hydraulics, undercarriage) have of course to be executed in between.

Is the Rock Hawg available in South Africa?

The Tesmec Rock Hawg has not been introduced in South Africa, yet, and we are sure there is a huge potential for its successful application. Tesmec has several negotiations in progress with different mining companies in the country, there will be some Rock Hawgs in South Africa soon.

Does the Rock Hawg come with any warranty or aftersales service?

The Rock Hawg is covered by a standard warranty of one year / 1 000 engine hours. Standard warranty extensions are available (up to three years / 3 000 hours).

Special warranty extensions can be provided according to customer’s needs, and they are usually linked to contracts for service and maintenance; all scheduled services carried out by the local Tesmec team.

What advice would you give users to get the most out of the Rock Hawg?

  • Operators must be properly trained to operate the machine in a more productive way.
  • Machine service, greasing and periodic maintenances must be properly managed to maximise machine availability and minimise down times.
  • It must be considered that Rock Hawgs are completely different from excavators with rock hammers, and they cannot just be brought in the job site and start working as if they were barely another piece of equipment in the site.
  • We can say that the working plan of the Rock Hawg becomes the driver in the site and gives the pace to all other equipment (and not vice versa).
  • To deploy their excavation capability, the Rock Hawg must have proper site management.
  • A poor site management (in terms of loading and hauling of the excavated material) will mean an increase the stand-by / idle time for the Rock Hawg, therefore low efficiency of the site (net excavation hours compared to total working hours).

 

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