Modern Mining May 2017

CRUSHING, SCREENING AND MILLING

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.” 

A Series 625 secondary sizer (segment machine) ready for delivery to West Africa.

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. 

feature

May 2017  MODERN MINING  37