Pit stamp
A mine support , even stamp called, is a supporting element in the mining underground for supporting the hanging wall is used. Pit punches are made of wood , steel or light metal. As a rule, stamps are used in conjunction with caps , but in certain areas it is also possible to use stamps without caps.
Basics
Due to the design, each stamp can only carry a certain load. The insertion resistance generated mechanically or hydraulically in continuous operation is called the punch support force. The punch support force is the nominal force that the punch provides. The highest load-bearing capacity of a punch is called the load-bearing capacity. This load-bearing capacity is checked in advance with 1.5 times the nominal force with a fully extended punch length. The stamp setting density can be determined on the basis of the data determined in this way. The stamp setting density is the number of stamps that the miner has to set per square meter of exposed hanging end area in the mining . The punch setting density depends on the configuration.
Wooden stamp
Wooden stamps are placed in such a way that they are loaded by the hanging wall in the direction of the grain. Depending on the local conditions, the stamps are placed between the hanging wall and the horizontal wall at a distance of 0.8 to 2 meters . The stamps are perforated in the sole when the rock pressure is low . When the pressure is stronger, short headwoods, which the miner calls piles, are placed between the stamp and the hanging wall in the hanging wall area. The pile is also often used to support the hanging wall. The length of the post is chosen to be slightly longer than 2.5 times the punch thickness, the post must not be longer. Also, this length may only be used if the rock pressure is moderate. Otherwise, if the rock pressure is greater, the pile may act like a lever and push the punch around. In the case of fissured hanging walls, continuous beams are used instead of several piles. If the patient is soft, sticks are placed under the stamp. If the post does not give the stamp sufficient flexibility, the stamps are sharpened in the foot area. The length of the sharpened piece must be 1.5 to 2.5 times the punch diameter. This sharpening allows the stamp to be shortened by up to ten percent of its original length under pressure without breaking. In mountainous conditions in which movements that run transversely to the stamp axis are to be feared, the stamps must always be sharpened. The punches must also be sharpened in inclined or steep storage . When setting the stamp, the sharpened side must be in the direction of the greatest load.
Steel stamp
When it comes to steel pit punches, a basic distinction is made between two types of punches, friction punches and hydraulic punches . Steel stamps are much more expensive than wooden stamps, but they are easier and easier to steal and can also be reused much more often.
Friction stamp
Friction stamps consist of two tubes that can be slid inside one another, the top of which is also called the inner stamp. The lower tube, the lower punch, is called the outer punch accordingly. Both are connected by a ram lock in which, in the event of a heavier load, a friction resistance is opposed to the pushing together. This is increased by wedges, which are provided with friction linings made of light metal. The wedges are compressed and tension the lock strap around them, which is stretched in the process. This means that the friction rams can absorb increased rock pressure by yielding without being destroyed. Friction stamps have been used in hard coal mining since the first half of the 20th century. There are different versions of friction stamps. The uneven supporting force of the individual punches is a disadvantage.
Hydraulic ram
Hydraulic rams are two-part or multi-part rams in which the telescoping is controlled by a hydraulic system. Hydraulic rams are used as a single ram or with a walking extension. The stamp consists of an outer stamp tube to which a collar ring is attached in the upper part and the stamp foot is attached to the lower end. There is an inner punch tube in the outer punch tube. The inner punch tube is movable and is attached to the outer punch tube by means of a steel spring. A specially shaped plate, the punch head, is mounted on the upper end of the inner punch tube. The inner punch tube is pushed up by means of a hydraulic piston. The hydraulic ram has a stroke limiter so that the hydraulic cylinder is not overloaded. To set the stamp there is a setting valve on the outer stamp tube and a robbery valve to steal the stamp. There are hydraulic rams where the ram head can be loosened for expanding the shield . The ram head is attached to the rod end of a piston rod that is moved out of the hydraulic ram.
Light metal stamp
In longwall mining , for weight reasons, punches made of light metal are used for dismantling individual punches, which are made from an alloy of aluminum, zinc and magnesium. The punches are used in low seams with flat and moderately inclined storage. With the exception of the lock parts, these stamps are made entirely of light metal. There are also combinations of steel and light metal, here the upper punch is made of light metal and the lock and the lower punch are made of steel. The upper punch consists of two semi-cylindrical shells that are made plane-parallel. For reasons of cost, medium-quality steel tubes are used for the lower punch, as steel punches are cheaper than equivalent kink-resistant light metal tubes. Light metal stamps are manufactured as friction stamps. The use of light metal stamps was banned in the coal mining of the Ruhr area. If components made of aluminum or other light metals strike rusty iron parts, sparks with great ignitability are generated. This reaction , known as the 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 .
Individual evidence
- ↑ 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
- ↑ a b c d e f g Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962
- ^ A b c Emil Stöhr, Emil Treptow: Basics of mining science including processing. Spielhagen & Schurich publishing house, Vienna 1892
- ↑ Ernst-Ulrich Reuther: Introduction to mining. 1st edition, Verlag Glückauf GmbH, Essen, 1982, ISBN 3-7739-0390-1
- ↑ Hydraulic pit ram. Patent No. DE4221941A1 January 5, 1994 (accessed November 3, 2011)
- ↑ Pit punch with piston rod and detachable punch head. Patent No. DE202005008328U1 08/17/2006 (accessed on November 3, 2011)
- ↑ Otto Proempeler, Hermann Hobrecker, Günther Epping: pocket calendar for mine officials of the coal industry in 1956. Karl Marklein-Verlag GmbH, Dusseldorf 1956
- ↑ 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.