“Lutumba Quarry” grunted into life on 15 July,2021 in a cloud of dust, initially spitting out crusher run for our next phase of the construction project towards the completion of rehabilitation between Beitbridge and Harare.
Currently there are two sets of crushers with their associated personnel and support equipment. The plan being that every month one would produce 20,000 tons of crusher run and the other,6,000 tons of surfacing and concrete aggregate. Each product must satisfy certain quality and grading specifications to meet the stringent Ministry of Transport requirements.
All aggregates are normally produced using two different types of crushers. The first being a Jaw crusher which crunches the rock between a set of jaws moving just like the jaws of a Crocodile. The second crusher is called a Cone Crusher. This crusher moves in a circular grinding motion between the Concave and the Mantle. Imagine a pestle and mortar being used in a grinding motion for making peanut butter and you get the idea of how a Cone Crusher works. If the grading of the material being produced does not fit between the lines of a grading envelope, it’s possible that a third type of crusher could be added to ensure suitable quality crushed product.
This third type of Crusher is called a Vertical Shaft Impact[VSI] crusher. The VSI produces aggregates that are mostly cubical in shape as opposed to being what is termed “flaky” [elongated aggregate]. The VSI Crusher works by feed material dropping through the feed tube onto the impeller table or enclosed rotor which, through centrifugal force, throws the material against stationary anvils made up of composite metal alloys.
The crushers are supported by a number of excavators and tippers which are used to haul the blasted rock from the quarry to the crushers. Another set of excavators, feeds the crusher’s themselves, with a pair of Front-End loaders moving the material into stockpile.
Between August 2021 and March 2023, it is envisaged that the quarry will produce approximately 400,000 tons of crusher run and surfacing aggregate for the Company.
Lutumba, unlike Tsomboli which is an exposed surface rock, is a rock just apparent on the surface, meaning that once the quarry is closed down after extraction of the estimated 400,000 tons of aggregate, there will remain quite a large hole in the ground which will need careful rehabilitation to ensure that it does not become an eyesore or a hazard to humans and animals alike.
