Spotlight Feature Articles ME Elecmetal Comminution March 16 | Page 8

COMMINUTION
restraining curb in the floor. After dumping its
load on the skip floor, it then slowly pulls ahead,
lowers its bed, and pulls away. Once the truck
clears the end of the skip, the skip can be raised.
As the skip is elevated, it pours material from the
discharge of the skip and deposits the material
into the apron feeder hopper. As material is
introduced onto the apron feeder, it conveys the
material to the sizer where it is crushed to the
appropriate size. After being crushed, the
material is deposited onto the discharge
conveyor where it is taken to the bench conveyor.
This process is performed while another haul
truck is depositing material into the twin skip,
thereby increasing the number of truck cycles.
An operator’s cabin is mounted on the machine
to give a clear view of the skip loading and
material transition into the hopper. The DTMS
system includes all on-board hydraulics,
electrical equipment and instrumentation
necessary for safe daily operation. Main power
and control for each DTMS will be supplied by
means of an overhead line or through conveyor
supply. Each machine will house its own
transformer for reducing the incoming voltage as
needed by the machine.
Once in position beside a bench conveyor,
mine fleet haul trucks up to a nominal 400 t
capacity can present and dump material directly
onto the floor of each skip within a nominal 130
second cycle time. The truck will have 50 seconds
to lift its load body, clear material, lower load
body, and start moving out of the way so that the
skip can rise without “colliding” with the back of
the truck load body.
Once the trucks have exited, the loaded skips
are raised, with each skip alternating so that the
skips are not simultaneously dumping. One skip
will be at ground level for truck presentation
while the other skip is being raised to transfer
material from the skip to the apron feeder. The
hydraulics and operation of the skip are
independent of one another.
Once the skips dump the material into the
hopper, the apron feeder shears a material bed
from the bottom of the hopper and provides a
controlled feed into the sizer which sizes the
material to a conveyable size. Level sensors on
the apron feeder and in the centralised hopper
are used to automatically adjust the flow rate,
and even temporarily stop the feeder, while
overall throughput tonnage is being balanced
between other concurrently operating DTMS
machines. The sized material is sent to a bench
conveyor from the DTMS by means of the
discharge conveyor below the sizer. This
discharge conveyor includes a belt scale and a
tramp iron detection and removal system.
The DTMS allows a significantly reduced truck
fleet to service multiple benches or mine faces.
This provides much needed flexibility, while

MARCH 2016 | International Mining

allowing the mobility and high
productivity of a conventional,
shiftable, at-the-face mining
system. The system can be
relocated throughout the mine as
haul distances increase.
The DTMS machines are
capable of processing overburden
material ranging from 7,000 t/h
to 12,000 t/h. The number of
DTMS stations gives the flexibility
to vary the amount of material
being processed on each of the
benches to achieve the total out
of the pit production required.

HPGR
With the HRC3000, the largest fully operating
high-pressure grinding roll (HPGR) in the world,
Metso says it provides “an energy efficient
solution with an impressive range of industryleading features, aimed at getting more value
from every tonne of ore.”
The HRC3000 was the result of a close
collaboration between Metso and FreeportMcMoRan. The goal was to develop a highly
efficient HPGR crushing circuit for the newly
constructed Metcalf concentrator at FreeportMcMoRan's Morenci copper mine, Arizona. In
approximately four years, the team went from a
desig