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May 2017
MODERN MINING
37
CRUSHING, SCREENING
AND MILLING
feature
MMD mineral sizers offer three-stage breaking action
The basic concept of the MMD sizer is the use of two rotors with
large teeth, on small diameter shafts, driven at a low speed by
a direct high torque drive system. This design produces three
major effects which all interact when breaking materials using
sizer technology. The unique effects are: a three-stage breaking
action, a rotating screen effect, and a deep scroll tooth pattern.
Initially, the material is gripped by the leading faces of
opposed rotor teeth. These subject the rock to multiple point
loading, inducing stress into the material to exploit any natural
weaknesses. At the second stage, material is broken in tension
by being subjected to a three-point loading, applied between
the front tooth faces on one rotor, and rear tooth faces on
the other rotor. Any lumps of material that still remain over-
size are broken as the rotors chop through the fixed teeth
of the breaker bar, thereby achieving a three-dimensional
controlled product.
A Series 625 secondary sizer
(segment machine) ready
for delivery to West Africa.
Mineral Sizing (Africa) has managed to remain
busy over the past couple of years and has not
had to downsize, a fate which has befallen
many other companies dependent on the min-
ing sector. “There are very few big projects
around at the moment which require the utili-
sation of our bigger mineral sizers, either in
South Africa or elsewhere on the continent,”
notes Nel. “Where we have excelled is with the
smaller to medium-sized projects where we’ve
typically supplied our smaller machines such
as the 500 Series or the 625 Series.”
Among the orders that Nel mentions are two
625 Series sizers for a gold mine in Burkina
Faso, a 625 Series sizer for a mineral sands
operation in Sierra Leone, an 850 Series sizer
for a copper mine in the DRC, two 500 Series
sizers for a coal mine in the Kriel area in South
Africa and several machines for Sasol Mining,
also in South Africa.
In Mozambique, a complete turnkey semi-
mobile installation at a graphite mine in the
north of the country is about to be commis-
sioned. This comprises a D4 apron plate feeder
and a 500 Series machine acting in a primary
crushing role. MMD is hoping to receive further
orders in the graphite field.
Concludes Nel: “We are moderately opti-
mistic on the prospects for the next year. There
are a couple of potential upcoming projects
along with a consistent demand for our sizer
and feeder technology so we are confident that
MMD Mineral Sizing (Africa) will continue to
show healthy growth.”