Mechanical Technology — February 2014
17
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Materials handling and logistics
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Above:
The plant feed head chute onto the conveyor at
Nchwaneng II Plant at Black Rock Mine.
Left:
The bin discharge onto the feeder chute.
The conveyor head chute into the crusher.
circuit, is 900 mm wide and travels
at 2,0 m/s. The second chute on the
tilting conveyors moves material with
a particle size of minus 150 mm to
the silo circuit on the identically-sized
incoming and outgoing belts.
“We had to accurately determine
the conveyor feed trajectory to elimi-
nate spillage and at the same time
minimise the wear and tear. During
our discussions on the design with the
mine personnel and their vendors, we
utilised FEA (finite element analysis) to
ensure that the transfer point solution
would optimally transfer material in
line with the mine’s requirement,”
Cruickshank states.
“It was critical at this point in
the project to not only acquire
approval on the verification
of the design from the mine
input, but also to construc-
tively utilise their feedback
in the process. While this
portion of the contract was
extremely onerous, it was also
very fruitful and will ensure a
benchmark transfer point for the
mine,” Cruickshank says.
The design of the four chutes on top
of the silos was no less complicated.
The silos are fed from tilt conveyors,
with the material being transferred at a
maximum lump size of minus 150 mm,
with a throughput of 900 tph and a bulk
density of 2,5.
“We had to cater for reversible
conveyors by using shuttle discharge
boots to ensure that the material is
discharged in the direction of the outgo-
ing conveyor. As a specific requirement
in this instance, we had to ensure that
the tolerances were exact. This required
extensive design and engineering verifi-
cation during the design process.”
The four chutes which form part of
the upgrade on the crushing circuit will
supply a grizzly feed chute, a grizzly
oversize discharge chute to a crusher,
a fines discharge chute from the grizzly
(undersize), and a crusher discharge
chute.
“The maximum lump size feed-
ing into the crushing circuit is minus
450 mm and the oversize maximum
tonnage is 400 tph. The grizzly un-
dersize chute is designed to cater for
500 tph, with a maximum lump size
of 450 mm, while the oversize chute
feeding the crusher is designed to ac-
commodate 400 tph at minus 150 mm
lump sizes. The crusher discharge chute
was designed for ease of maintenance,
without affecting the requisite 500 tph
throughput of minus 150 mm crushed
material,” Cruickshank continues.
“M&J Engineering embraces chal-
lenges such as the design on Black
Rock Mine’s chutes. By stretching the
capabilities of our engineers we are able
to benefit customers on future projects
through this extended knowledge and
experience. Through the application of
what the engineers have learned, we
are then able to provide a chute system
that is a plant enhancement, rather
than a potential bottleneck,” concludes
Baller.
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