The popularity of mobile plants which host a crusher and a screen on a single chassis is testament to the benefits they deliver to the market; but the design should not compromise production performance. This is according to Charl Marais, Pilot Crushtec’s sales manager for South Africa, who highlights how the Metso LT220D embodies an innovative new way of combining crusher and screen.
“The powerful Nordberg GP220 cone crusher feeds the ample three deck screen of 1 524 metre by 5 480 metre (18’x5’), with crusher and screen being optimally matched to ensure high throughput capacity of a single sized product or up to three calibrated end products,” says Charl. “The fact that the screen does not constrain the crusher output – or vice versa – is an important factor making the LT220D a real world-beater.”
Combining both elements on a single chassis through a compact design reduces the number of service parts, lubricants, moving parts such as engines and conveyors, making for more uptime and lower cost of ownership. Using crushers and screens in a train, he says, the maintenance of the engines for each component often doubles the downtime – this leads to an interruption in production and the double handling of material while the other is being serviced.
Driving both crusher and screen, the powerful CAT C9.3B diesel engine also delivers better efficiency with the direct drive power transmission through a Katsa gearbox, with optimised consumption levels of around 35 l/h.
The versatility of the Metso LT220D has made the unit a star performer in both construction and mining applications in South Africa – thanks to its considerable production capacity and easy mobility. In road building, the units sold locally have produced sub-base material from G1 to G5 categories, as well as aggregates. In the local mining sector, it has been successfully employed to crush and screen lower grade chrome and in other cases blast hole stemming material.
“In our South African context, the LT220D unit has achieved G1 production rates of 260 tph, and 300 tph of G4 and G5 material,” says Charl. “It has also produced 140 tph of aggregates, products split into a minus 19 mm, minus 13 mm and minus 6 mm categories. In the mining space, production rates of 160 tph on average have been achieved, generating a minus 8 mm chrome product.”
Less conveyor wear
The screen-first feed configuration means that natural fines and fines generated by the primary crushing stage are removed by the screen so that only material which requires crushing actually reports to the cone crusher, enhancing production capacity. Contributing to its performance and economy is the centrifugal conveyor returning crushed material onto a lifting conveyor to feed the screen. Using centrifugal forces rather than pinching material between two conveyors means less conveyor wear and lower replacement costs. The one metre wide centrifugal conveyor also supports the high tonnages and ensures there are no limitations on the GP220 cone crusher’s throughput.
Charl highlights that the single chassis configuration makes the model ideal for applications where it needs to be moved frequently around a site – or between sites. Transport costs are reduced, as the whole structure – weighing just 48 t – can be moved on one lowbed truck. There is also the benefit of not having to align and configure separate mobile screen and mobile cone crusher components every time it is moved.
“By reducing the set-up time, contractors can enjoy more uptime which, of course, boosts production levels,” he adds.
The compact inline mobile cone crusher and screen combination allows for a smaller plant footprint. The smaller footprint is a distinct advantage, especially as it enhances the high product stockpile heights. The fines conveyor has a stockpile height capacity of 4,3 metres, while the side conveyors can create 3,7 metre high stockpiles. All these stockpiles are well spaced from each other due to the inline footprint of the Metso LT220D.
“The benefit of these high stockpiles is that you can reduce the movement of the front-end loaders which conduct the clearing-out function,” he notes. “Less movement is more economical, and also improves health and safety on site.”
The unit even offers a power take-off (PTO) feature that can drive an additional conveyor for more stockpile capacity. The IC600 intelligent controller monitors key operational process parameters. The information can be viewed by the customer from a remote location. The IC600 is also responsible for protecting the machine, looking after its health; where a jaw crusher is added to the train, it can also communicate with this unit to balance throughput rates and optimise production.