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Surface miner at coal mine a first for Southern Africa

3rd July 2015

By: Mia Breytenbach

Creamer Media Deputy Editor: Features

  

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Diversified engineering company Wirtgen South Africa (SA) in May commissioned its Wirtgen 4200 SM surface miner at Brazilian mining major Vale’s Moatize mine, in Tete, Mozambique.

The supply of this miner to Vale is one of Wirtgen SA’s largest projects in Southern Africa to date.

“The 4200 SM supplied to the Moatize mine is the first Wirtgen surface miner used in a coal application in Southern Africa,” says Wirtgen SA mineral technologies head Mike Newby, noting that the machine is currently executing trial cuts at the mine.

Wirtgen’s range of surface miners includes the 2200 SM, the 2500 SM and the 4200 SM miners.

Advantages of the 4200 SM surface miner, valued at more than R50-million, include the elimination of drilling and blasting, primary crushing, loading, rehandling and often the coal washing process, as the miner can manage these multiple functions in a single operation by a single operator, Newby emphasises.

The 4200 SM further features production rates of up to 3 000 t/h. It is capable of mining rock with an unconfined compressive strength of up to 50 MPa at a cutting depth of up to 830 mm in soft-rock mining. The miner can also mine rock with an unconfined compressive strength of up to 80 MPa at a working depth of up to 650 mm in hard-rock mining.

In tough opencast mining conditions, the miner’s mechanical cutting drum drive with multiple V-belts provides high efficiency and ease of maintenance. Other features include slope control, drum speed selection ability, automatic performance regulators for outputs, a pneumatic knock-out tool that saves time on tool changes, advanced speed control, four-track steering that controls each crawler track individually and a conveyor system to load cut material directly onto haul trucks.

The surface miners could also stack mined products using the “windrow” method – stacking in small lines that enables operators to identify and collect the different grades, Newby first told Mining Weekly in 2012, adding that this form of depositing “results in high daily production rates and low operating costs”.

The machines are equipped with four separate height-adjustable crawler tracks, while a height adjustable slewing conveyor system enables immediate transfer of the product to waiting trucks or dumpers.

“The crawlers adapt to undulating surfaces, owing to a level pro system for the drum and tilt sensors to ensure a clean, stable and flat cut after the first few cuts,” Newby says.

About 463 of the 2200 SM, 2500 SM and 4200 SM machines are operating worldwide in different applications, including coal, iron-ore, limestone, kimberlite, gypsum, bauxite and salt. Up to August 2014, 59 surface miners had been sold in Africa. Nine of those are in Southern Africa and the remainder in North Africa.

The Wirtgen surface miners are also being used in Guinea in bauxite applications and in limestone applications in Nigeria.

Further, a 2200 SM machine is being used by salt supplier Botswana Ash and a 2500 SM is being used in kimberlite and mudstone applications at one of diamond miner Debswana’s mines. One 2200 SM currently operates at a gypsum mine in the Northern Cape, in South Africa.

Key Target
Wirtgen SA’s target – “first and foremost” – remains local coal mining operations, Newby stresses.

“Surface mining is a worldwide-accepted mining method, owing to the safety and environment-friendly features of the surface miners,” he emphasises, pointing out that 109 surface miners are currently used in coal applications in India, which constitutes about 26% of the country’s total yearly coal output.

Surface miners are currently also used in coal applications in Australia, the US and Europe.

Newby further reaffirms that, owing to the surface miners’ timesaving cutting, crushing and loading features, they are suitable for the selective mining of thin and high-grade coal seams containing coal average of 30 MPa locally.

He explains that, while South African coal mining traditionally entails drilling, blasting, shovelling and trucking, this form of mining and the resultant blending of coal and waste impact on the quality of the final product.

However, as Newby believes that the South African coal mining industry is starting to focus more on product quality, rather than only quantity, the Wirtgen surface miners allow for selective strip mining of interburden and coal seams.

“Mines can achieve almost a 100% quality, as they eliminate the ash content produced from traditional drilling and blasting methods,” he adds.

The surface miner also enables the mine, which might be situated in or near residential areas, to exploit more of its seams or mining area by working to the perimeter of the mine.

Attesting Model
Following the commissioning of the 4200 SM, Wirtgen SA aims to introduce a 2200 SM surface miner as a demo model locally as part of a rental agreement for mines that prefer the concept to be proven before buying, Newby explains.

“The machine will then move to the next mine or the next mining equipment contractor,” he says, pointing out the need from local operations to have a proven concept, particularly in their specific mining applications.

Newby highlights that mining equipment contractors are also receiving requests from clients to explore opportunities and options for surface mining. “Several mines have to consider surface mining as an alternative mining method to achieve the required product quality and quantities, as well as to ensure clean and safe mining,” he concludes.

Edited by Leandi Kolver
Creamer Media Deputy Editor

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