Plough system for low thickness coal seams

The job of a plough system in underground mining can be described in a nutshell as “eating through coal at a depth of 1300 m”. In 2015, a new Cat GH 800 B will be put into operation for RAG Anthrazit Ibbenbüren GmbH, a subsidiary of RAG AG, in Germany’s northernmost coal mine, in Ibbenbüren, and there to cut and extract the around 1-m-thick coal seam. The company made this investment with Zeppelin. To develop the operative business with surface and underground mining equipment from Cat, Zeppelin has set up its own Competence Centre. In under a year after takeover of the sales and service activities for Cat mining machines, this was able to report its first incoming order.

“With this order, we have achieved a minor sensation. We were the first Cat distributor worldwide to report such a sales success after the start of the sales and service activities for surface and underground mining equipment. But it is also extraordinary in another respect, if you consider that coal mining is coming to an end in Germany in 2018,” says a delighted Christian Dummler as Zeppelin Group Director for Finances and responsible for the integration of the new business segment, commenting on the order (Fig. 1). For this was anything but a foregone conclusion. On the contrary, owing to the discontinuation of the subsidies in Germany, it might be assumed that, for Zeppelin, business potential in German mining could primarily be found in services.

But the productivity of the GH 800 B was able to convince the Ibbenbüren mine. Prior to the investment, an economic efficiency calculation was conducted based on the data and experience so far. For a long time now, the company has addressed the issue of how coal can be extracted efficiently when the seams are less than one metre thick? The answer is: with the help of a plough system that the experts at RAG Anthrazit Ibbenbüren GmbH have developed together with Caterpillar since 2010 and was put into operation at Ibbenbüren for the first time in summer 2013. “With the existing system, on account of its small dimensions and its weight, it has a lower energy balance and has a 50 % higher capacity than conventional equipment. It is significantly more economic for our customers to invest in new systems of the type GH 800 B than to maintain old equipment,” says Stephan Bäumler, Area Manager for Marketing and Director at the Competence Centre, in explanation. Its daily capacity averages 3000 to 4000 t. Around 360 000 t anthracite have been extracted with the Cat plough system.

Anthracite has the highest calorific value, which makes its extraction still so attractive for private households, but especially for gardening businesses and for the lime and chemicals industry. Main buyer of the coal in Ibbenbüren is, however, the 840-MW RWE coal power station located directly next to the mine. The ploughing technology is what is known internationally as longwall mining, an extraction process for thin, seam-like (that is relatively thin and wide-area) deposits as found in Ibbenbüren. Main components are shield supports, armoured face conveyor as well as the extraction machine, the coal plough, which cuts the seam. They are produced by Caterpillar at the German Lünen site for worldwide operation – as the new GH 800 B for the RAG, which will start operation in mid-2015. The invitation to tender for the investment was issued by RAG Anthrazit Ibbenbüren GmbH this July. Together with the mining engineer Roland Redlich, Zeppelin Sales Manager for Underground Mining, and Jürgen Ingendahl, Sales Manager for Western Europe at Caterpillar Global Mining, the team around Stephan Bäumler prepared the bid. Jürgen Ingendahl has looked after RAG AG and especially the Ibbenbüren mine for decades – he is underground almost every second day and has been at home in mining for 40 years so that he was sufficiently familiar with the local geological conditions.

In 60 years of cooperation with Caterpillar, Zeppelin has extensive expertise with machines for surface operations such as huge hydraulic excavators and off-road dumper trucks. But it is not possible to approach the mining business like traditional construction machine business. A plough is a completely different matter than a Cat 966KXE wheel loader and accordingly here we are working with traditional project business. Here there are only individual solutions. For underground technology like longwall mining, it is a matter of highly specialized systems that no other “global players” among the construction machine manufacturers include in their range. This demands a great deal of know-how with regard to sales, consultation and service,” explains Stephan Bäumler. “Our first business deal with the plough shows that mining has a future. German mining technology is in demand worldwide – many raw materials around the globe are extracted with mining technology ‘made in Germany’. The forerunner of the plough technology is a good example of this. It is an invention of German engineers and is still developed and manufactured at Caterpillar at the Lünen site,” explains Christian Dummler. Existing technology is constantly being refined and technical innovations introduced to make extraction efficient and effective. So, for instance, with the newly developed plough, the loading height has been optimized to the armoured face conveyor (AFC), and accordingly especially thin but valuable seams can be extracted at low cost without any cutting of worthless adjacent rock (Fig. 2).

The Ibbenbüren Mine conducted the first tests after an idea of Konrad Grebe extract the coal by shearing it. In terms of the design, it was similar to the ploughs of today, like the Cat GH 800. It was further developed from 1947 by Wilhelm Löbbe for the Altlüner Eisenhütte Westfalia – and it was used worldwide as the “Löbbe plough”. Behind the Eisenhütte Westfalia is a chequered history of takeovers and fusions, which resulted in 1995 in the DBT, the Deutschen Bergbau Technik (DBT), a subsidiary of RAG. The DBT was sold in May 2007 to Bucyrus International – three years later, Caterpillar entered into the venture and took over the supplier of machinery and equipment for surface and underground mining. Since 2013 Zeppelin offers not only Cat hydraulic, cable and dragline excavators and drilling equipment, but also machines and equipment for extracting raw materials underground, like such ploughs. So the circle between RAG AG, Cat and ­Zeppelin has been closed through their history too.

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