Longwall mining

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Longwall construction with wood

In mining , longwall mining is the term used to describe all types of construction that serve to keep the hanging wall between the mining face ( coal face ) and the offset edge free of falling rock .

history

Single stamp

For decades, wood was used as a construction material in the mining . Starting in 1925, the mining operations in the Ruhr mining industry were converted from small push operations to face length front operations with a face length of 80 to 150 meters. Wood was still used as construction material at this time. From 1930 onwards, wooden construction was increasingly replaced by friction stamps and steel caps . Towards the end of the first half of the 20th century, hinged steel caps were developed and used in the struts. From 1950 the stamp-free coal front with a protruding dome cap was introduced into the struts. At the same time, fully mechanical extraction was introduced, which in turn meant that the shaking chute in the struts was replaced by the scraper chain conveyor . From 1960 the work flow in the struts was further mechanized, the friction stamps were replaced by hydraulic single stamps. From 1965, the fully mechanical walking support was introduced into the struts and by 1970 this was the predominant type of longwall support. In 1981, 98 percent of all struts in the German hard coal mining industry were equipped with hydraulic support.

Expansion types

The longwall mining usually consists of punches and caps. A distinction is made between pure wood construction, pure metal construction and mixed construction. In the case of mixed expansion, there is the variant of stamps made of wood and caps made of metal and the variant of stamps made of metal and caps made of wood.

Timber construction

Wood finishing stamp and cap

The oldest form of longwall construction is probably the wooden single stamp with a head wood, which was then followed by cap pulls supported by several wooden stamps. In order to save resources, the stamps were stolen from the offset edge and set again at the coal face. In addition, pillars ( boxes ) were placed in particularly polluted areas . These pillars are boxes made of round wood or flattened round wood, more rarely square wood such as railway sleepers, stacked in a square . Another variant of the wood construction was the wooden stamp construction with linear support. Half-timbers were used as caps. Longwall construction made of wood has the advantage, among other things, that the construction material is easy to work with. However, the finishing material can rarely be used again. In addition, a stamp must be placed directly on the coal face to support the hanging wall .

Metal construction

If the longwall structure is created as a pure metal structure, it is created either as a single punch structure or as a step structure.

Single stamp extension

In the case of single ram removal, the longwall construction is implemented using several individual rams in conjunction with caps. Instead of the construction material wood, iron is used here as construction material. Initially discarded railway tracks were used as caps, later in special constructions such as the van Wersch cap. By using steel punches, the distance to the dismantling front can be increased, making it possible to keep the dismantling front free of punches. This has the advantage that mining machines such as coal planers or shearers can now be used . In the case of the stamp, development went through various friction stamps to the hydraulic stamp . The most common form was the Ferromatik stamp . This stamp was produced in sizes from 0.4 m to 5.6 m and can be set with an adjustment range of up to 0.8 m using externally supplied pressurized water (up to 160 bar).

Striding extension

Shield extension

All expansion units that move mechanically are referred to as striding expansion. Here, several hydraulic rams are combined to form an extension group. All work steps - robbing , advancing, setting - are mechanical. Each expansion unit can be operated via a valve control. The development of the step extension took place in several steps. To make the difficult and dangerous work of relocating the extension, extension frames and extension trains were developed from the middle of the 20th century. Two punches and a cap were rigidly connected and connected to another pair of punches with a cap via a walking mechanism. This expansion train with frames arranged one behind the other in the dismantling direction did not prove itself and soon disappeared.

The next step in development was the team . The trestle extension was developed from these teams . Carriages and trestles are also referred to as conventional walking frames. The last development step is the shield extension . Shield support is used from a thickness of 0.8 m, one of these shield units weighs approx. 7 t. The largest expansion shields can be extended up to 6 m and weigh more than 25 t. A central pressure generation system is used to supply the step extension with hydraulic fluid. The hydraulic fluid has a pressure of up to 200 bar .

By mechanizing the extension work by means of step extension, the dismantling performance could be increased several times compared to manual work. Initially, there were several accidents when the walking support was being extended and retracted. The reason for this was the oversizing of the hydraulic lines. As a result of this oversizing, the expansion was lowered or extended faster than usual. These sources of danger were eliminated by means of appropriate throttle devices. In the German mining industry, special safety regulations apply to the bringing in and robbing of striding supports. All components for the step extension are subject to approval by the regional mining authority .

Others

While in the 1950s, face equipment comprised less than 100 t of material, which was moved by hand several times a day, today's face equipment weighs up to 5000 t. It is used with minimal human effort, but the logistical effort for transport from above ground into the pit, installation and removal (robbery) is considerable.

literature

  • Alfred Ehrhardt, Hermann Franke, Hans Grothe, Otto Lueger: Lexicon of mining . Ed .: Otto Lueger (=  Lexicon of Technology . Volume 4 ). 4th completely revised and expanded edition. Deutsche Verlags-Anstalt, Stuttgart 1962, p. 536 .

Individual evidence

  1. ↑ a b c d e Walter Bischoff , Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining dictionary. 7th edition, Verlag Glückauf GmbH, Essen 1988, ISBN 3-7739-0501-7 .
  2. ↑ a b Joachim Huske: The hard coal mining in the Ruhr area from its beginnings to the year 2000. 2nd edition, Regio-Verlag Peter Voß, Werne, 2001, ISBN 3-929158-12-4
  3. ↑ a b c d Ernst-Ulrich Reuther: Introduction to mining. 1st edition, Verlag Glückauf GmbH, Essen, 1982, ISBN 3-7739-0390-1 .
  4. ↑ Karl Fröhlich: Longwall construction for stamp-free mining front. In: Glückauf, Berg- und Hüttenmännische magazine. Association for Mining Interests in the Upper Mining District Dortmund (Ed.), Issue 37/38, Volume 79, September 18, 1943, pp. 433–438.
  5. ↑ a b Heinz Kundel: coal production. 6th edition, Verlag Glückauf GmbH, Essen, 1983, ISBN 3-7739-0389-8 .
  6. ↑ a b c d Otto Proempeler, Hermann Hobrecker, Günther Epping: Pocket calendar for mine officials in the coal industry 1956. Karl Marklein-Verlag GmbH, Düsseldorf 1956.
  7. ^ A b c Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962.
  8. ↑ Fritz Heise, Fritz Herbst: Textbook of mining science with special consideration of hard coal mining. Second volume, fifth increased and improved edition, published by Julius Springer, Berlin 1932.
  9. ↑ Types of expansion. On: Headframes in Ruhr mining (accessed October 19, 2011).
  10. ↑ a b c d e Gerhard Ludwig: Mining research. In: Deilmann Haniel Unser Betrieb, No. 4, July 1969, online (accessed on October 19, 2011; PDF; 5.6 MB).
  11. ^ Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1 , pp. 367-374.
  12. ↑ Horst Roschlau, Wolfram Heinze, SDAG Wismut (Hrsg.): Knowledge storage mining technology. 1st edition. Deutscher Verlag für Grundstoffindindustrie, Leipzig 1974, pp. 88-89.
  13. ↑ Heinz M. Hiersig (Ed.): VDI-Lexikon Maschinenbau. VDI-Verlag GmbH, Düsseldorf 1995, ISBN 978-3-540-62133-1 .
  14. ↑ Collective sheet of the Arnsberg district government, Department 6: Use of Schreitausbau (accessed on October 20, 2011).
  15. ↑ Collective sheet of the Arnsberg district government, Department 6: Introduction of step support as well as removal of support in struts, routes and other mine structures (accessed on October 20, 2011).
  16. ↑ Approval of extension parts for step extension. Online (accessed October 21, 2011; PDF; 2.8 MB).
  17. ↑ Approvals of stamps and caps for step extension. Online (accessed October 21, 2011; PDF; 2.7 MB).