ON THE GROUND
C
one crushers and feeders often
have a lifespan of 30 years or
more so it is not easy to change
buying habits; therefore, maintenance is
frequently the deciding factor, along with
price and quality.
Efficient crushing and screening are
the best methods of dropping the overall
cost per tonne on a plant but, sadly, it is
often the most neglected facet faced by
inexperienced plant owners.
Picture a 100t per hour plant, where
the correct screen could make a 2%
difference. In a five-day, seven-hour-a-
day operation, that’s an additional 70t
of production a week, or 14 tipper truck
loads a month for the same overheads.
Cheaper equipment, such as meshes on
screens, can result in more downtime and
loss of production.
With crushing, you start with
the end
Hyundai is distributed by HPE.
The final product
requirement is the
cornerstone of
equipment selection
and plant design, and
particular combinations
of jaw crushers and
secondary crushes
have proven more
effective in achieving
desired outcomes.”
www.equipmentandhire.co.za
To execute the crushing process cost-
effectively, it’s necessary to choose the
correct crusher for the application as
this saves time and money over the long
term. The size and geography of the site
determines the configuration of the feeder.
Max Bajkay, Metal’lum marketing
manager, explains that the most important
determinants in choosing a crusher are the
strength, size and shape required of the
end product. All tooling deliberations such
as the most economical crusher for the job
at hand, must be informed by the quality of
the final product at the end – whether the
end product is, for example, filter sands,
road construction or asphalt topping.
“Once quality is determined, the process
is to go step-by-step from the end process
to the primary crushing stage. The final
product requirement is the cornerstone of
equipment selection and plant design, and
particular combinations of jaw crushers
and secondary crushers have proven more
effective in achieving desired outcomes,”
says Bajkay. That final product also governs
the grading envelope that must be achieved
(or the ratio between coarser and finer
aggregates). The intended throughput rate
is another key consideration in the choice of
crusher and its size.
The size of the run of mine (ROM), the
strength of the material and the desired
product shape determines how many
crushers and crushing ratios are required
to crush the ROM to achieve the desired
product sizes. An impact crusher, for
example, will be required to achieve a
high quality shape specification.
The needs of road base construction
are particularly specific, because they
are exposed to heavy traffic: the COLTO
specs on G1 and G2 base and sub-base
material require at least 4% to 12%
of 0.075mm material, produced from
clean parent rock. The micro fines act as
a lubricant when compacting the road
base to ensure that one gets the correct
compaction levels and have a sturdy base
on which to lay the road. Generally, this
can only be achieved with the use of a
vertical shaft impact (VSI) crusher as a
tertiary stage in the process. Other end
uses, such as many construction projects,
don’t require such a high specification
aggregate, so the added expense of
shaping the end-product does not make
financial sense.
An impact crusher will give the best
quality shape to a stone like a VSI and,
in some cases, a horizontal shaft impact
(HSI) crusher. An impact crusher reduces
the amount of flaky material from the feed
ROM or from the jaw or cone crushers,
to create a higher quality cube shape. The
VSI breaks down the edges of the stone
and makes them more cube shaped.
What quarries want
Most quarry managers understand their
mining operations well and which plant
and equipment they need. Consequently,
the older generation in particular are often
reluctant to change equipment, says
Bajkay. “It’s difficult to break into a new
client because people don’t like change.”
Another challenge is to convince a new
client of the quality of what (for them) is
an untried machine. “Quarries want to
improve their quality, and consequently
have to be convinced that our equipment
delivers that.”
However, they may not be up-to-date
regarding what equipment is on the
market if they have not had exposure
to it. An equipment salesman has the
advantage of visiting many different
quarries and is exposed to a variety
of applications than typically a quarry
manager would be. Therefore, a salesman
enables best practice solutions to be
brought to an individual site.
Lani van der Watt, marketing manager of
HPE Africa, holding company of McCloskey,
says, “McCloskey is supplied by HPE Africa
and is supported by an expert team of
technical, sales and aftermarket team. We
offer a wide range of crushers, screens and
stackers. The latest addition to McCloskey
product range is the Modular Crushing
Solutions as well as the S250 screen. Our
extensive knowledge of our customer’s
operations enables us to provide unique
and comprehensive solutions. HPE Africa
SEPTEMBER 2019
23