Screens & Feeders

Transverse cutting units step up performance

Rippers are the technology of the past, according to a German sand gravel producer.
For some time Kies-Hector, based in Saarland, Germany, has been mining “natural concrete” with a Rockwheel D30 cutting unit on a 36-tonne excavator. With this innovative cutting technology Kies-Hector estimates its output has doubled and, in some cases, tripled.
The gravel-sand conglomerate in the middle bunter sandstone is being mined in an open cast mine belonging to August Hector KG, near Saarlouis-Lisdorf.
“We are mining the oldest gravel in Germany in the ‘Erika’ field,” technical operations manager Andreas Fink said.
The bed, laid down 150 to 240 million years ago at the edge of the Paris Basin, has a thickness of 60m. Below it lie layers of carbon. Extraction takes place between 230m and 180m above mean sea level, in compliance with local mining regulations, and the Rockwheel cutting unit can also be used with ease in sandy groundwater.
For decades rippers have been used to mine the highly abrasive Class 7 conglomerate in the open cast mine. “The wear and tear was enormous. The extreme impact also placed huge stress on the excavator’s mechanics and the driver,” Fink said, explaining why Kies-Hector was looking for an alternative excavation method and was drawn to the innovative cutting technology provided by cutting unit attachments.
Compared with other suppliers, the novel Rockwheel cutting technology provided by the Baden-Württemberg based Rokla GmbH was way ahead of the pack.
“Our mid-sized and medium output cutting units have an extremely short construction and only three main components – housing, motor and cutting heads equipped with picks,” Rokla managing director Robert Piasecki said.
His business associate, engineer Ian Webster, is convinced that a gearbox simply offers no benefits at outputs between 30kW and 110kW, yet costs money and makes the cutting units heavier.
The Englishman has a reputation in the European industry for being an innovative developer of cutting and hammer technology.
A gearless Rockwheel D30, weighing in at 38 tonnes, was delivered to Kies-Hector in November 2013. This 1200mm wide, robust cutting unit with direct drive has an output of 110kW. The two excavating drums are equipped with 60 wear-proof special picks for use in a highly abrasive gravel-sand conglomerate. These picks have a smaller head and larger bodies than slimmer, traditional mining picks. 
After just a few hours of operation, the benefits of the cutting technology were already clear to Michel Weisse, the driver of the 36-tonne Volvo EC360CL.
Cutting is clearly the better solution for removing rock from the steep face of the quarry, according to Fink. “The bolts on the excavator boom are exposed to much less mechanical stress,” he said.
For Weisse, the vibrations of the cutting unit were significantly less physically strenuous than the powerful impacts he felt using the ripper.
He was quick to specify which of the technologies he preferred: “The cutting unit – without a doubt!”
The Rockwheel D30 now mines 15 tonnes per hour of “natural concrete” at Hector’s site in Lisdorf. With a ripper tyne fitted to the same 36-tonne Volvo excavator, the output in the conglomerate layer, containing an extremely high proportion (95 per cent) of quartz (silica), was only four tonnes per hour.
Nevertheless, the company’s plan was to continue using a ripper on a bulldozer on the flat in the Erika field, before using the Rockwheel cutting unit for removing rock from the vertical faces and for profiling in the 80-degree steep faces. 
“This cutting technology enables us not only to work faster, but also to work much more accurately,’’ said Weisse, who has 22 years of experience in the material excavation industry. “Using the cutting unit, you can see precisely what you’re removing and where overhangs still need reworking. That’s not the case with a ripper tyne.’’
This profiling precision on the steep faces has a direct impact on the mining yield.
Material extracted from the Erika field is also processed in Lisdorf. Up to 4mm gravel sand and coarse aggregates are obtained from the open pit, as well as 4-8mm, 8-16mm and 16-32mm gravel and/or gravel chipping.
Kies-Hector has all its products certified in line with DIN EN 12620 and DIN 20000-103 standards. The products are constantly monitored in the company’s own certified laboratory. Gravel sand and gravel from Lisdorf are generally used as the main additive to fresh concrete.
Kies-Hector was founded by Peter Hector in 1874 as a transport and mining company in Dillingen, Germany.
Since his successor August Hector greatly expanded the business in the 1920s and 1930s, Kies-Hector has become a leading gravel and sand quarrying company. Since 2009, managing director Frank Hector is the fourth generation to lead the family owned business.
The partnership between Kies-Hector and Rokla GmbH has proven to be a great success.
The Rockwheel D30, which fits the 36-tonne excavator with the Verachtert CW45S quick change system, was selected with the help of sales expert Piasecki. It is the most powerful of the four direct driven Rockwheel cutting units, which include the D10 (29kW for excavators between seven and 15 tonnes operating weight), D15 (44kW, 12 to 18 tonnes), D20 (70kW, 16 to 26 tonnes) and D30 (110 kW, 26 to 38 tonnes). 
“Our gearless models have a significant weight advantage and therefore deliver the maximum power required, even with smaller excavators,’’ Piasecki said. “Only Rokla builds both a gearless D range with direct drive and lower and/or upper output class cutting units with a gearbox [G range].’’
The most powerful Rockwheel G45 and G55 units inherently deliver double the motor power. These solidly built models with lightweight, robust motors are designed for high outputs. Delivering 140kW or 220kW, they are ideal for excavators with operating weights of between 40 and 65 tonnes.
All Rockwheel cutting units have solid drive shaft bearings and are designed for a long service life. Their sealing system also enables them to operate underwater without the need for conversion. All the components of Rockwheel cutting units are procured from reputable German suppliers and are assembled by experienced fitters in Langenburg. As a rule, maintenance times are short, as all components can be easily replaced. 
Source:  Roka GmbH/Semco Equipment Sales

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