Breakthrough in Sweden

With an average compressive strength of around 180 Mega-Pascals (MPa), granite is one of the hardest rocks on earth. The granite found in the Boda quarry near Vrigstad, a small town in southern sweden, even yields values of more than 300 MPa in some cases. This imposes particularly high demands when it comes to processing the material.

TJ Gräv AB, a provider of crushing services from Brandstorp, was contracted to process 40,000 tons of this material. The company was already familiar with Kleemann and its products and was quick to decide when new machines had to be purchased for the new order. "We bought our first crusher in 2007 after seeing the machines at work during a visit to Germany. In my opinion, they are durable and exceedingly robust," says Tomas Johansson, proprietor of TJ Gräv AB.

Johansson chose a combination comprising a mobile jaw crusher and a mobile cone crusher with integrated triple-deck screening unit. The granite is first loaded onto the MOBICAT MC 120 Z jaw crusher with separate screening unit by an excavator. The primary crusher reduces the original material with an edge length of up to 1,000 millimetres to a size of not more than 200 millimetres and then transfers it directly to the secondary crushing screen, a MOBICONE MCO 11 S.

The mobile cone crusher produces three final products of different grain sizes in a single pass. This is achieved by the unit's three screen decks measuring 2,050 mm x 5,000 mm (middle and top deck) and 2,050 mm x 4,800 mm (bottom deck). A fairly large amount of material is in the material loop due to spreading the granite over three decks. As a result, the MCO 11 S cannot achieve its normal maximum total output of 280 t/h. Despite this, the mobile combination of plants produces more than 1,000 tons of crushed stone aggregate per day.

Tomas Johansson considers the Kleemann plants to be particularly suitable for the job in Boda: "Both plants have a diesel-electric drive, which is very good as regards the fuel consumption - in spite of the high load." But other features of the plant system are also important to Johansson. "We sometimes have operations in rock where prescreening is especially important. The final product then has to be almost completely free of organic fine particles and this can only be achieved if the crusher is equipped with an independent prescreening unit." For the provider of crushing services, it is essential that the units are easy to transport and that they are quickly operational after arriving at the new location. Mobile plants from Kleemann are ideal for such jobs.