Cradle to grave
Mining and quarrying equipment specialist
Osborn has secured a significant order from
Petra Diamonds for an apron feeder that will be
employed at the diamond mining group’s renowned
Cullinan Diamond Mine in Gauteng.
Cullinan’s new Osborn apron feeder will be
deployed in the mine’s shaft and plant interface
project. Eight Osborn apron feeders of the same
size were installed underground at the Cullinan
Mine as part of a previous order. These are
successfully servicing the operation’s underground
silos and crushing stations. A further five Osborn
apron feeders have since been supplied to the
operation’s process plant.
With their heavy-duty construction, Osborn
apron feeders are designed to handle feed sizes of
up to 1 500mm where no fines removal is required
or where fines are removed by a separate dribble
conveyor.
Equipment shines at Cullinan
An Osborn apron feeder will be employed at Petra Diamonds’ Cullinan mine in Gauteng.
Pumping water at heights
Deep opencast mines pose great challenges
for the dewatering process. Often, long
distances, especially vertical ones, cannot
be bridged with conventional submersible
pumps. Most pumps can only pump up to
a height of about 40m. In practice, they can
only lift a small part of the stated maximum
pumping capacity to this height, because
height and capacity are intricately connected:
the higher the height, the less water passes.
As a solution, some operators use a series
of pumps ‒ two pumps that are operated
sequentially in one section. This will almost
double the achievable distance, although the
pumping capacity remains the same. Usually,
hoses are fitted between the aggregates. The
problem with this concept is the same core
risk associated with all complex systems: (too)
many components are involved, some of which
might not be in their best condition, are not
installed to the optimum, or simply should not
have been combined in the first place.
The process can be enhanced by using
an adapter manufactured by the pump
manufacturer Tsurumi, which allows two
identical pumps to be directly coupled to
create a kind of ‘super pump’. Nevertheless:
the limiting factor here is the physics of the
speed and impeller, which is why the pump
programmes of most manufacturers end at
this point.
If this is insufficient for the dewatering
process, things become difficult for tunnel
builders and miners. In contrast to clear
water, there are few pumps in the dewatering
field that can improve the output noticeably.
High-pressure pumps are the best choice.
For instance, the LH series by Tsurumi
basically covers the pumping height range
from 42m to more than 100m. This is where
classic pump designs reach their physical
limits.
Another pump concept is required if you
want to go any higher ‒ you need multi-
level pumps. From a technological point
of view, this means that several impellers
are mounted inside the casing. While the
pumping capacity remains the same, the
pumping height increases with the number
of these levels: The pump supplies more
pressure and is therefore able to reach a
higher head. As simple as the idea sounds, it
is very difficult to realise if the pumped water
contains solid matter.
Tsurumi from Japan is the only supplier
of these kinds of dewatering pumps in the
world. These models are marked with a ‘W’
in the product catalogue. The LH4110W
is the premium model. It is able to pump
waste water vertically to a height of 216m. To
put this into perspective: this is higher than
from the base to the viewing platform of the
Berlin Television Tower. The aggregate can
move 400ℓ/min. If requirements are lowered,
for instance to a pumping height of 170m,
the pumping output is increased five-fold
to 2 000ℓ/min. The power required for this
is generated by a 110kW motor. If two of
these 1 825 × 616mm large monsters with a
dry weight of 1 270kg were to be combined,
a 432m-deep pit could be supplied with the
smallest amount of conceptual effort.
Geosynthetic materials are of great value for
environmental projects on mines, especially
during mine closure. Typical applications for
geosynthetics include mine tailings facilities,
heap leach pads, and water retention ponds.
Geosynthetics are used for mine closures, as
well as for access roads and other geotechnical
structures, says Johnny Oriokot, geotechnical
engineer at Fibertex SA. “Fibertex’s highly
UV-stabilised 100% virgin polypropylene (PP)
geotextiles and geosynthetic solutions take
the uncertainty and risk out of the design of
crucial applications like landfills, dams, and
tailings dams.
www.miningmirror.co.za
“Geotextiles have advantages in installations
where the cost of failure may be extreme, in
both financial and environmental terms. Virgin
PP offers a high level of chemical stability
under a wide pH range and for this reason,
Fibertex geotextiles are particularly well suited
for installation in areas where the textile may
be in contact with alkaline conditions, for
example in certain types of slimes dams and
waste sites.
“Fibertex geotextiles have important
functions — for separation, filtration, drainage,
protection, and reinforcement. These materials
can also act as a stress-relieving waterproofing
Geosynthetic value in environmental management
Fibertex mining installation.
membrane when used with bitumen in road
applications.”
JUNE 2019 MINING MIRROR [39]