FEATURE
(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.
Each stone has a crystalline shape
which is normally hexagonal and impact
crushing systems crush the material along
this crystalline structure because it is
the easiest part of the rock to crush. This
gives a better shape than crushing with
shearing or pressing forces offered by
cone and jaw crushers.
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.
ELB Equipment divisional sales manager
Wakefield Harding.
“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
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
“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.”
One of McCloskey’s range of screening equipment
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QUARRY SA | JULY/AUGUST 2019_23