When a project to re-mine stockpiles at a large iron ore operation discovered its planning assumptions had been too optimistic, Pilot Crushtec was able to save the day with its experience and its ready fleet of Metso crushing equipment.

The plan was initially to feed natural fines – less than 8 mm in size – from run-of-mine (ROM) stockpiles to the smelter, later introducing a mobile jaw crusher and then mobile cone crushers with a sizing screen. It was found, however, that the portion of fines in the stockpile was much less than expected, putting the whole project in jeopardy.

To rescue the situation, a fully mobile three-stage crushing and screening plant was urgently required to meet the required tonnages. Crushing and screening specialist Pilot Crushtec, who is also the local distributor of Metso equipment, had the answer and was able to deploy the necessary equipment on site within a few weeks. This included a Metso Lokotrack LT106 mobile jaw crusher, two mobile cones crushers – a Metso Lokotrack LT200HP standard and an LT200HP Short Head – and a Metso Lokotrack ST4.8 triple-deck mobile screen.

This was not the end of the challenges, though, as it soon became apparent that the concentration of iron within the stockpiled ore was lower than believed. Fortunately, the natural fines were richer than anticipated, presenting the opportunity of blending them with the lower-grade crushed ore. Here the Metso ST2.8 screen proved to be the key, with its two-way split providing a consistent supply of iron-rich natural fines to be blended with the stockpiles where required.

The next step was to find ways of improving production of minus 8 mm material, although the 150 tonnes per hour being achieved was already regarded as good. With Pilot Crushtec’s experience, supported by Metso’s Bruno simulation software, a further increase of 10 to 15% was targeted. The strategy involved a range of complex ‘tweaks’ including an optimised liner profile, a change in screening media and apertures, and splitting the process train.

This delivered the production target, with better continuity in the process while ensuring that the first two stages of crushing were not constrained by bottlenecks in the tertiary crushing and screening stage. This also reduced fuel and wear costs, as the equipment in the first half of the train could produce the same amount of material in fewer hours.