Cap (mining)
In mining, a cap or cap rail is an extension part that rests on the hanging wall and is usually supported by pit punches . Caps are made of wood , light metal or steel .
Basics
Caps must be matched to the respective extension type. A distinction is made between different caps. With the caps, the hanging wall is underpinned either individually in a linear fashion or in linked cap chains. For the route expansion , there are rigid hats, which are provided at the ends with joints. The caps are shaped according to the cross-section of the route. Appropriate connecting elements are required to connect the caps to the punch. In the case of rectangular expansion, special angle brackets are used to rigidly connect the cap and punch. A distinction is made between rigid and articulated caps for longwall mining . To create a cap connection to so-called cap chains, capping shoes are required. To the longwall in single punch expansion in the range of Streckensaumes to secure cap connecting elements are mounted between the cap of the strut extension and the roadway support. These cap connecting elements are also called strut cap mounts or clamping web ends . In order to degradation routes the sheet extension in the transitional area between strut and track to be additionally secured, a Kappenabfangschuh is mounted on the cap. A hydraulic ram is placed under this cap catching shoe , which replaces the removed ram of the line extension and strengthens the extension.
Wooden caps
Wooden caps usually have a length of two to three a maximum of 3.5 meters. Initially, wood made of fir or spruce was used as the wooden caps . Since the cap should always be the stronger component in wood construction, caps made of oak were later used. These caps had greater flexural strength . This is particularly advantageous in the case of poor mountains, since caps are more difficult to change than punches. There is a risk that the hanging wall will collapse, especially with rough hanging walls . In the case of steep storage , caps with bevelled ends must always be installed so that the bevelled side faces the hanging wall. This is necessary in order to make it easier to drive in the stamps on caps.
Light metal caps
In the middle of the 20th century, caps made of light metal were used in hard coal mining . However, their use was limited to longwall mining . The reason was that the lower weight of the light metal caps was only beneficial here and not when upgrading the route. The light metal caps were mainly used in the flat and in the moderately inclined position. They were not used in the steep storage. The disadvantage of caps made of light metal is their sensitivity to acidic and salty mine water . The use of light metal caps was banned in the hard coal mining of the Ruhr area. If components made of aluminum or other light metals strike rusty iron parts, this creates sparks with great ignitability. This effect , known as thermite reaction , can also occur if there is rust film on the aluminum parts and z. B. is hit with a hammer. Methane gas mixtures can be ignited by these sparks .
Steel caps
Steel caps have a greater load-bearing capacity than oak caps. As early as the 19th century, this led to the increased use of steel caps, wherever particularly high reliability was required. Due to the widening of the routes or in the area of route branches, caps made of steel have considerable advantages over caps made of other materials because of their greater load-bearing capacity. Steel caps also have the advantage over wooden caps that they take up less space. Initially, steel caps were placed on wooden stamps or on side walls, later the entire construction was made of steel. In the beginning , the caps were made from discarded Vignol rails , which were provided with angle iron and screwed onto the wooden stamps. When the rock pressure was higher , several rails were laid next to each other and connected with screw-tightening straps. Later, instead of railroad tracks, T-profiles or, in the case of higher rock pressure, I-profiles were used. I-profiles were also used to build fillings , underground engine rooms and horse stables . Curved caps are also used in sections instead of the straight profiles.
Caps in longwall mining
Short caps, plate caps and joint caps are used for dismantling the individual ram. Short caps are required for the stamp-free dismantling front and are between 800 and 1600 millimeters long. Plate caps are used in thin seams. Since the use of normal caps is a hindrance here, these caps can be used with not bulky hanging walls . These types of caps are round or oval plates that are placed on the die head. The caps have no connection with each other. Hinge caps have the advantage that they allow pre-pledging . The caps consist of I-profiles, at the ends of which there is a joint. The caps can be connected to one another via this joint. The joint is designed so that it can be locked. This locking creates a firm connection between the two caps. The pre-seized cap can hold a weight of up to two tons without the support of a stamp. The stamp is only set later, usually after hours, for support. In the German coal mining industry, Vanwersch caps were very often installed as joint caps. These caps have a clevis at one end and a wedge-shaped tongue at the other end. There are two boreholes in the fork head and one in the wedge-shaped tongue. The holes in the fork head are round, the hole in the tongue is oval and larger. The two caps are connected by two bolts that are inserted through the holes in the fork head. At the end of the tongue, a bolt is inserted through the oval hole, the other bolt slides past the wedge-shaped tip and thus locks the joint.
Caps for walking expansion
There are different cap shapes for the step extension . There are rigid caps, hinged caps, locking hinge caps, pitch caps, and pitch slide caps. Joint caps are caps that are divided into two by a joint. Locking hinge caps are designed to articulate downward and rigid upward. Adjustment caps are provided with an additional joint, so that the front cap part can be moved by means of a hydraulic cylinder . In this way, the front part of the canopy can be better placed against poorly formed hanging layers. Due to the longer cap construction, a more favorable distribution of supporting forces is achieved. This enables better control of the slope on the coal face. Push-on caps are extendable bodies integrated into the step extension. The sliding flaps are automatically extended or retracted depending on the position of the face conveyor . You follow the extraction with the planer by extending the cap in steps of ten to fifteen centimeters. As a result, the sliding cap effectively supports the hanging wall.
Individual evidence
- ^ A b c Walter Bischoff , Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining dictionary. 7th edition, Verlag Glückauf GmbH, Essen 1988, ISBN 3-7739-0501-7 .
- ^ A b c d e Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962.
- ^ A b c Association for Mining Interests in the Upper Mining District Dortmund (ed.): The development of the Lower Rhine-Westphalian hard coal mining in the second half of the 19th century. Julius Springer's publishing bookstore, Berlin 1902.
- ↑ Otto Proempeler, Hermann Hobrecker, Günther Epping: pocket calendar for mine officials of the coal industry in 1956. Karl Marklein-Verlag GmbH, Dusseldorf 1956th
- ↑ a b Circular order of the North Rhine-Westphalia State Mining Authority No. 18.23.2-5-16, dated June 16, 1984 with attachments
- ↑ Technical rules for operational safety, TRBS 2152 Part 3. Dangerous explosive atmosphere - Avoiding the ignition of dangerous explosive atmosphere.
- ^ A b Gustav Köhler: Textbook of mining history. 2nd edition, published by Wilhelm Engelmann, Leipzig 1887.
- ↑ Albert Serlo: Guide to mining science. First volume, published by Julius Springer, Berlin 1884.
Web links
- De Vanwersch kappen (accessed November 17, 2011)