Scarifiers are the technology of the past: For some time, Saarland-based Kies-Hector has been mining "natural concrete" with a Rockwheel D30 Cutting Unit on a 36-tonne excavator. With this innovative cutting technology its output has doubled and, in some cases, tripled.
The gravel-sand-conglomerate in the middle bunter sandstone is being mined in the open-cast mine belonging to August Hector KG near Saarlouis-Lisdorf. "We are mining the oldest gravel in Germany in the ‘Erika’ field," explains Technical Manager, Dipl. Ing. Andreas Fink. The bed, laid down some 150 to 240 million years ago at the edge of the Paris Basin, has a thickness of 60 m. Below it lie layers of carbon. Extraction takes place between 230 and 180 metres AMSL in compliance with mining regulations and the Rockwheel Cutting Unit can also be used with ease in sandy groundwater.
For decades scarifiers have been used to mine the highly abrasive rock 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," states Andreas Fink, explaining why Kies-Hector were looking for an alternative excavation method. Fink’s attention was then drawn to the innovative cutting technology provided by cutting unit attachments.
Compared with the competition, 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’s Managing Director Robert Piasecki explains. Ian Webster, who exclusively works for Rokla, is convinced that a gearbox simply offers no benefits at outputs between 30 and 110 kW, yet costs money and makes the cutting units heavier. The native Englishman has the reputation in the industry for being the world’s most innovative developer of cutting and hammer technology.
A gearless Rockwheel D30 was delivered to Kies-Hector in November 2013. This 1200 mm wide, extremely robustly constructed cutting unit with direct drive has an output of 110 kW. The two excavating drums are equipped with 60 wear-proof special picks for use in 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, in the view of Technical Operations Manager Andreas Fink. "The bolts on the excavator boom are exposed to much less mechanical stress," according to Andreas Fink. And for Michel Weisse, the vibrations of the cutting unit are significantly less physically strenuous and exhausting than the powerful impacts he felt using the scarifier. It is therefore absolutely clear which technology the driver prefers: "The cutting unit – without a doubt!"
Its removal speed is one advantage of the cutting technology that should not be underestimated. "The cutting unit has literally stepped up performance," stresses Robert Piasecki. The Rockwheel D30 and the special pick equipment for abrasive rock now mine 15 tonnes per hour of "natural concrete" at Hector’s site in Lisdorf. With a scarifier fitted to the same 36-tonne Volvo excavator, the output in the conglomerate layer, containing an extremely high proportion (95%) of quartz (silica), was only 4 tonnes per hour. Nevertheless, the company will initially continue using a scarifier on a bulldozer on the flat in the Erika field in Lisdorf. In future it will use 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,” emphasises Michel Weisse. The excavator driver 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 scarifier." This profiling precision on the steep faces has a direct impact on the mining yield. And there’s no longer any question in his mind about using the cutting technology when Michel Weisse considers his back.
The material extracted from the Erika field is also processed in Lisdorf. Gravel sand 0/4a mm and coarse aggregates are obtained from the open pit: Gravel and/or gravel chipping 4/8, 8/16 and 16/32 mm. 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 state-of-the-art certified laboratory. Gravel sand and gravel from Lisdorf are generally used as the main additive to fresh concrete.
The company was founded by Peter Hector in 1874 as a transport and mining company based in Dillingen, Germany. Since August Hector greatly expanded the business in the 1920s and 1930s, today Saarland-based Kies-Hector is a leading gravel and sand quarrying company, which is also committed to protecting the environment: for many years the Lisdorf site has been the breeding ground for endangered sand martins. Since 2009 Managing Director Frank Hector is the fourth generation to lead the family-owned business – jointly with his nephew, Max van der Heyde.
The cooperation between Kies-Hector and Rokla GmbH, the company that brings Ian Webster’s innovative Rockwheel cutting technology to life, was completely straightforward and open from the outset. The Rockwheel D30, which fits the 36-tonne excavator with the Verachtert CW45S quick-change system, was selected with the sales expert Robert Piasecki. It is the most powerful of the four direct-driven Rockwheel cutting units: D10 (29 kW for excavators between 7 and 15 tonne operating weight), D15 (44 kW, 12-18 tonnes), D20 (70 kW, 16-26 tonnes) and D30 (110 kW, 26-38 tonnes).
"Our gearless models have a significant weight advantage and therefore deliver the maximum power required even with smaller excavators," stresses Robert Piasecki. The Rockwheel C2 is the lightweight champion for small excavators or micro-excavators, with operating weights of between one and three tonnes. This cutting unit has a maintenance-free chain drive (C = Chain) therefore no gearbox and motor.
"Only Rokla builds both a gearless D-range with direct drive as well as lower and/or upper output class cutting units with a gearbox (G = Gearbox)," emphasises Robert Piasecki. The G5 (22 kW) is ideal for excavators with operating weights of between three and eight tonnes. The output can be doubled to 44 kW with a second motor, without jeopardising the stability of the midi-excavator. The most powerful Rockwheel G45 and G55 units inherently deliver double the motor power. These extremely solidly built models with lightweight, ultra-robust motors are designed for high outputs. Delivering 140 or 220 kW, 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 / Baden-Württemberg. As a rule, maintenance times are short, as all components can be easily replaced.