INDUSTRY EQUIPMENT: MINING
African interest
According to Calvin Fennell, business
development manager at Wirtgen SA,
surface miners are also being used at a salt
harvesting operation in Botswana and at De
Beers’ Orapa diamond mine in the same
country, while a unit has been deployed
in the Northern Cape of South Africa. The
biggest demand for its machines, however,
is in the West African country of Guinea,
where 25+ machines are in operation,
mostly on bauxide mines. The first Wirtgen
surface miner was commissioned in
Guinea way back in 2001, in a mine close to
Kindia, a small town 120km from Conakry.
According to Fennell, the most commonly
used models for bauxite mining in Guinea
are the 2200 SM and the 2500 SM.
But despite its proven success, and the
obvious benefits attached to deploying the
Wirtgen surface miner, the South African
market has been resistant to using the
machines. Nevertheless, there are several
mining contractors that are proponents of
the surface miner, and word has it that a
few coal mining companies have shown
real interest in the benefits of using such
technology. But why the resistance in
South Africa?
According to Fennell, conventional drill
and blast operators in South Africa are not
always that easy to convince or change.
Moreover, the surface miner needs a
relatively big surface area to start working.
The longer the run the cheaper it becomes.
The machine requires at least a 250m long
by 400m wide strips to operate effectively,
which means a lot of overburden stripping.
This is of course not the traditional way of
mining in South Africa, where companies
normally operate in mining blocks. Fennell
says that the initial capital outlay in
equipment as well as overburden stripping is
a prime deterrent.
can vary according to seam thickness.
“Even thin seams of just 10cm thick can
be mined and precisely separated from
the layers above and below. This level of
precision makes for a cost-effective and
more environmentally sensitive approach
to mining of mineral deposits without any
drilling or blasting, says Fennell.
By using the machine, one eliminates a
couple of steps in the operations. Drill and
blast, for example, becomes null and void,
and it eliminates the need for a shovel and
a primary crusher. The material is tipped
straight from the machine into a truck
and then into a secondary crusher. By not
blasting there is the added benefit that you
can operate closer to areas inhabited by
people. The machine is ideal for selective
mining, especially in shallow coal mining
operations as you mine out different layers.
It has also been used very successfully on
several gold mining operations. In Australia
the machines are used extensively in the
iron ore sector.
Fennell says the surface miner
performs better when used in soft material
applications like coal for example. “There are
different classes of machines depending on
the hardness of the material being mined.
A larger machine could probably produce
about two and a half thousand tons an hour
with material at an unconfined compressor
strength of between zero and 15MPA. When
the material strength is about 80MPA the
production of our biggest machine drops
down to just under 500 bench cubic metres
an hour. It also depends on the size of the
machine, but we do now have specific hard
rock machines,” says Fennell. However, in
extremely hard material of 160MPA or more,
Wirtgen surface miner to make its mark,
as does other bulk operations in the rest
of Africa.
The Wirtgen surface miner needs a large surface area to mine effectively.
The Wirtgen surface miner is indeed a beast,
but many questions remain. However, on
the face of it, the benefits do outweigh the
initial capital costs. The Wirtgen surface
miner is a crawler-mounted mining machine
with a rotating cutting drum for rock
penetration mounted at the centre of gravity.
The cutting drum transfers the material onto
a conveyor belt from which it is directly
loaded onto a dump truck.
The machine mines layer by layer down
to the required depth and the cutting depth
www.equipmentandhire.co.za
Benefits outweigh costs
The cutting drum transfers the material onto a conveyor belt from where it can be
stockpiled.
JANUARY/FEBRUARY 2020
21