In a granite quarry

Grit in only two stages with Kleemann PRO plant

I‌n Schlag, in the Bavarian Forest, Berger Rohstoffe GmbH has been operating a granite quarry since 2020. This granite is crushed to road stone and grit in different fractions. The company was already working with a Kleemann plant train in a similarly structured quarry in the neighbouring Czech Republic. Due to this positive experience, a decision was also made in Schlag in favour of the mobile crushers, screens and stackers from Kleemann.


The robustness, stability and efficiency of the crushers were of decisive importance. For Markus Penz, operating engineer and plant operator at Berger, the well functioning maintenance and spare parts supply concept of Kleemann and the Wirtgen Group also played a role. This machine service ensures a high machine availability and trouble-free processes. The mobile plants from Kleemann allow quarries to operate with a high rate of return because, even as extraction advances, the transport paths always remain short.


High productivity and stable processes

The mobile PRO plant train has been in operation since August 2020. The core of the plant comprises the jaw crusher MOBICAT MC 120 Zi PRO and the cone crusher MOBICONE MCO 11i PRO. The screening plants MOBI­SCREEN MS 952i and MS 953i EVO and the stacker MOBIBELT MBT 20 supplement the plant train, which impresses in daily operation with its high productivity and cost-effectiveness. Hard granite is turned into grit for high-quality concrete and mixed aggregates are produced for anti-frost layers.


The desired grit sizes are produced from the loaded granite in only two crushing stages. In the pre-crushing stage, the grain shape is only altered to a slight degree; the second stage consists of crushing to the specified size. “Normally, this is almost impossible. But, before starting work, for test purposes we had material from the quarries tested in Kleemann’s own laboratory. After fine-tuning of the plant according to these parameters, we produce continuously to this high quality level,” explains Andreas Wagner, Kleemann special consultant from Wirtgen Germany. Markus Penz is extremely satisfied with the result. “Approximately half of the material is transferred to our concrete mixing plants. Their requirements are stricter than the applicable standards. This plant allows us to easily meet all our target specifications because it works even better than we thought.”


The complete plant train consists of five machines and operates as a line coupling. This means that automatic control stabilises the complete process. Each machine basically operates independently but forwards signals to the upstream and downstream machines in the event of malfunctions or overfilling. The feed control Continuous Feed System (CFS) also guarantees optimum utilisation of the crusher.


All components are loaded evenly. This is not taken for granted in stone processing where a natural product is to be turned into a standardised product. The stone crushes differently and there are fluctuations in the deposits: in the structure, due to the weather and the type of feeding. Output fluctuations are therefore normal. It is precisely these fluctuations that are balanced out by the optimised process thanks to line coupling in combination with the machine control system, the correct selection of machines and not least through qualified personnel. The automated tuning relieves the burden on the operators and harmonises the process.


The connection of all machines also guarantees safety: if an emergency-stop button is pressed anywhere on the plant train, all machines are safely stopped. This concept prevents damage or overload situations. All of this combined results in a high availability and output with low wear.


Increased safety and high machine availability

After delivery of the new plants, the three-man core crew in Schlag also had to familiarise themselves with operation of the mobile crushing and screening plants. They found this really easy because the crushing plants are equipped with SPECTIVE. SPECTIVE is an operating concept with an intuitive structure. It is started at the 12 inch touch panel. All data is displayed as values but also in image form. This means that the plant is also easy to operate by staff who are only deployed on rare occasions. Furthermore, the clearly arranged user guidance contributes to safety. “There’s not a lot you can do wrong during operation because the machine does not permit incorrect settings,” says Markus Penz.


After the first few months and experience from the Czech Republic, the team in Schlag realised that machine availability was an additional plus point. Instructions are short and concise for everyday work, but are very precise. A lot of tasks that go beyond the daily check can therefore be carried out single-handedly. This is guaranteed by the practical machine design that places the focal point on the needs of operators. And if we ever need a Service technician, the specialists from Wirtgen Group are easy to reach.


Kleemann machines with Dual Power have a module well along the path to sustainable stone extraction and processing. Berger Rohstoffe GmbH wants to produces in an environmentally friendly manner. Fossil fuels no longer meet contemporary standards in the long-term – also in quarries. Berger therefore ordered all components of the plant train equipped with the external power supply option. The screens can be driven, for example, either electrohydraulically or diesel-hydraulically. At present, the purely electric drive is used in the quarry in Schlag to operate the mobile screening plant MOBISCREEN MS 953i EVO using the power from the jaw crusher MOBICAT 120 Zi PRO.


In the long term, the company wants to convert the complete structure of the quarry to electric drives. Apart from the machine selection, photovoltaic systems are also used in many of their plants.


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