Latest developments in screening at work at world centre of marble

The quarries of Carrara marble spa in Vennai Guglielmo di Fantiscritti in the Italian Alps have long been the center of producing marble that formed some of the greatest works of art in history.  Now increasing use of modern equipment has helped improve operational efficiency, with a Sandvik QE341 scalping screen being a highly prized addition to the production process.

The white marble quarries now operated by William Vennai SpA in the Italian Alps have proved to be a source of the highest quality material, providing marble for the statues of the great Michelangelo himself amongst others. These are considered to be amongst the oldest and most prestigious in the entire area, with the company having quarried the marble since its incorporation in 1924. Located in the marble basin of Fantiscritti, they are capable of producing annually an amount equal to about 60,000 tons of marble blocks, rising to 100,000 tons through commercial connections with affiliated companies such as the Major Excavation Fantiscritti Marmi srl Scarl and E.T.A. Scarl.

Precise quarrying methods
In order to supply such a prestigious and valuable resource, the marble has to be extracted precisely.

Although many techniques have remained the same, new technology is also playing its part. “Diamond wire saws have replaced the old helical wire ones allowing a radical lowering of work times, so much so that whereas to produce a block 10m x 10m it took three days of work it now takes only 4 hours,” explains Paul Abbot, head of excavation at William Vennai SpA.

After using horizontal and vertical drilling holes or joints with jackhammers, holes are screwed to the diamond wire which is connected to a powerful cutting machine. This scrolls down automatically during cutting phases or rotates the point of axis according to various requirements, When the marble block is separated from the mountain complete detachment is facilitated using special inflatable ‘pillows’ or hydraulic jacks using powerful excavators to a specially prepared ‘bed’ of debris to provide a safe resting place for the extremely valuable end product.

However, the marble is not all of a consistent high quality. The ‘perfect’ block represents only 20% of the production; the remaining 80% consists of semi-formed blocks as well material that does not possess the desired homogeneous structure due to contamination with metamorphic rock, rubble and other materials. Earth and gravel are always present which needs to be removed in order to preserve the quality of the marble. In order to effectively and efficiently remove contaminants (which themselves are valuable products) from non-block marble production, a mobile screen was acquired. In this case a Sandvik QE341 which was supplied by Sandvik’s authorized distributor in Italy, CGT. Compagnia Generale Trattori (CGT) S.p.A.

An essential tool for our end product
Erich Padlocks, a partner of William Vennai said of the new screen: "Acquiring the QE341 was a necessity in order to maximize and improve the quality of our end product. We could only really choose Sandvik, above all for the quality of the machines and then for our relationship with CGT, a relationship established over time and dating with me personally 30 years. We place so much emphasis on our relationship that now our quarries only use CAT machines. In future, if we require screening (or crushing equipment) we will put our faith in CGT again and choose Sandvik as well.”

Ideal mobile solution
The QE341 is a heavy duty scalper with class leading open scalping area delivering enormous rates of production. This means that production of even the most hard wearing of materials is facilitated through a wear resistant steel apron feeder, with massive stockpiling capability with over-wide conveyors to maximise delivery. With a one piece wear resistant rigid hopper it features a robust crusher-style chassis and has been designed to be compatible for 2-way or 3-way split configurations, as well as the ability to interchange side conveyors thereby demonstrating the ultimate flexibility of the unit.  The screen-box jack up facility allows easier access to the bottom deck for maintenance and screen media changes. Other key customer-focused features include:

• Aggressive screenbox with 9mm of throw at over 1000 rpm enables peak productivity
• Radio tracking and feeder control as standard help ensure operator safety
• Unique colour-coded control panel with one touch start/stop enables easy operation
• Optimum fuel economy at less than 15 litres per hour reduces your operating costs
• Hydraulic folding maintenance platforms simplify service and maintenance

The QE341 has all the attributes required to help maximize production of some of the world’s most sort after marble.