Published Apr 14, 2014

An in-pit crushing system increases safety and efficiency at Marocca Costruzioni’s limestone quarry

Operating the primary section up in a steep quarry face created a major challenge for the Italian company Marocca Costruzioni. A totally truckless, economical and safe solution was found by choosing a Metso Lokotrack track-mounted jaw plant and connecting it to a unique and flexible mobile conveying system.

  • Marocca Costruzioni Fosso della Foresta quarry
  • Family-owned companies have a long reputation in Italy. Marocca Costruzioni is no different: the company has been in the same family for over 90 years.
  • Feed size and type: white-colored limestone, 0–240 mm in size, bulk density 1.6 t/cum
  • End products: over 21 different products, including 0–4 mm, 4–6 mm, 6–10 mm, 10–15 mm, 15–23 mm, 23–30 mm and 30–70 mm
  • Area of use: aggregates for concrete, asphalt and for road works
  • Production per year: 1.4 million tons
  • Number of employees: 50

The main challenge for Marocca is the big altitude difference between the new quarry face situated 495 meters above sea level and the stationary processing plant some 200 meters lower. The gradation along the quarry roads is more than 15 degrees.

“Metso’s mobile concept the best alternative”

After trying conventional trucking to move the limestone after primary crushing down to secondary processing, it was quickly discovered that trucks were a costly solution, consuming a lot of tires and fuel. An alternative solution was crucial for the quarry’s future.

“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,” comments Managing Director  Alberto Marocca 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 over 25-million-ton limestone reserves 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 525-meter level. In fact, we have made a solid investment in our future,” Alberto Marocca adds.

Tracked primary, stationary secondary and tertiary crushing

Metso’s Lokotrack LT140 primary jaw plant started to crush the limestone feed in November 2012. The unit is connected to the two-piece LL12 series mobile conveyor system and further to the stationary, locally manufactured, 400-meter-long field conveyor.

After just a week’s training, the Metso mobile system could reach a continuous crushing capacity of 800 tons per hour.

The limestone feed contains a lot of fine materials. The LT140 was first run with a closed side setting of 160 mm and was later increased to 200 mm. With this, the fuel consumption of the primary unit fell by 10 liters per hour to 21 liters.

  • Metso equipment on site
  • Lokotrack LT140 mobile jaw plant
  • CSS 200 mm
  • Nordberg LL12 mobile conveyor

“Actually, the C140 jaw crusher can crush up to 1200 tons per hour. Because of the steepness of our static conveyor, it gets overheated with bigger materials volumes, so we limited the production to 800 tons per hour. As a side product, our static, downhill conveyor produces 220 kW of electricity when operated,” Alberto Marocca says.

Presently, after the static conveyor, the limestone is being fed to the secondary circuit by front-end loaders. When the tunnel feeder with new conveyors is completed, the Fosso della Foresta quarry will become totally truckless.

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