Metso In-pit Crushing System for Italian Limestone Quarry

27 May, 2015

First published in the May 2015 issue of Quarry Management as Reaching New Heights

Metso in-pit crushing system increases site safety and efficiency at Marocca Costruzioni’s Fosso della Foresta limestone quarry

Operating the primary crushing section adjacent to a new working face situated at a high level at Fosso della Foresta Quarry posed a major challenge for family-owned Italian company Marocca Costruzioni. The main problem was the large altitude difference between the new quarry face situated 495m above sea level and the stationary processing plant some 200m below, with the gradient of the quarry haul roads between the two locations being more than 15 degrees.

After trying conventional trucking to move the primary crushed limestone down to the secondary processing area, it quickly became apparent that trucks were a costly solution, consuming a lot of tyres and fuel. An alternative totally truckless solution was crucial for the quarry’s future.

To this end, an economical and safe solution was found by choosing a Metso Lokotrack LT140 track-mounted primary jaw crusher and connecting it to a unique and flexible Nordberg mobile conveying system.

‘Based on studies of available options, it became clear to us that Metso’s mobile primary crushing and conveying system would provide us with the biggest benefits and the capacity, economy and reliability we were looking for,’ commented Alberto Marocca, managing director of Marocca Costruzioni.

‘With half a year’s experience now behind us, we are fully convinced of the benefits of the Metso mobile system. It works just as we expected and secures our profitable operation. As a bonus, we have gained a dust-free and safe quarrying environment.’

The 25-million-tonne-plus limestone reserves at Fosso della Foresta Quarry will ensure Marocca’s operational future for several decades to come.

‘The mobile system allows us to exploit our quarry with just minor modifications during the planned six phases, reaching up to the 525m level. In fact, we have made a solid investment in our future,’ Mr Marocca added.

The Lokotrack LT140’s limestone feed material, which is 0–240mm in size and has a bulk density of 1.6 tonnes/m3, contains a significant amount of fine material. The crusher was initially run with a closed-side setting of 160mm, but this was later increased to 200mm, which reduced the unit’s fuel consumption by 10 litres/h to 21 litres/h.

The LT140 is connected to a two-piece Nordberg LL12-series mobile conveyor system which, in turn, is connected to a stationary, locally manufactured, 400m long field conveyor. After just one week of training on the Metso mobile system, staff at the site were able to reach a continuous crushing capacity of 800 tonnes/h.

Annual production at Fosso della Foresta Quarry is currently around 1.4 million tonnes, with more than 21 different aggregate end products, including 0–4mm, 4–6mm, 6–10mm, 10–15mm, 15–23mm, 23–30mm and 30–70mm, being produced for use in concrete and asphalt, and for road works.

For more information visit: www.metso.com