March 09, 2006 | Recommend this Article »

Block extraction in Norway

High-tech for blocks

Increased production thanks to modern drilling equipment and diamond wire saws: The Norwegians use the latest technologies in their quarries.

To satisfy the big demand, Norwegian companies like block supplier Larvik Granite or slate producer Skifer & Naturstein invest in modern extraction equipment. Pneumatic hammer drills mounted on buckets or carriages drill the holes for explosive charges and the guide holes for the saw wires. They are also used for dressing the rough blocks. Trimmers are used for drilling and splitting the walls into rough blocks for cost reasons and with a view to the safety of employees.
There is a big demand for homogeneous blocks without cuts and with dimensions suitable for machines. The larger and more perfect a rough block is, the higher the price that can be achieved. Explosives are used less and less, as stones like Blue Pearl, Silver Pearl or Emerald Pearl are too precious.

One of the newest Norwegian block producers is Larvik Granite. In view of high labour costs and low material yield, the company set up in 1987 has concentrated on using the latest extraction methods with diamond wire saws and automatic drilling units in its four quarries right from the beginning. Diamond wire saws are used to a large extent for extracting blocks. At temperatures down to minus 25 degrees, however, the wire and water must be kept moving around the clock after cutting the stone.

As soon as cutting is interrupted, the drilled hole and the cut must be cleaned and dried before cutting can proceed.
The drilled holes are normally 10 to 20 metres deep. The walls are up to 10 metres high, 20 metres long and 2 metres wide. These walls weighing up to 900 tons are moved away from the rock after sawing using a water cushion and laid down with hydraulic rakes. Trimmers are then used to divide them into rough blocks or at least into block size. Each quarry has three fully automatic Tamrock 440 trimmers for splitting, which appreciably increase the capacity.
Drilling is also the first step in slate production. Skifer & Naturstein quarries and processes the three slates Alta, Otta and Oppdal. For Otta, Tamrock machines are used to drill up to ten metres deep in the vertical direction, up to four metres long in the horizontal direction and 50 millimetres wide for holes. The diamond wire is then used for cutting away the walls with some 80 cubic metres volume; a wall of ten metres length, four metres width and two metres thickness is sawn each day. The walls are split into transportable blocks in the quarry before being transported to other locations.