Planing method (mining)
In mining , the planing process refers to different processes for extracting hard coal using a coal plow . There are several planing methods that relate to the relationship between the speed of the planer and that of the tank conveyor . Depending on the speed of the planer and the conveyor, a distinction is made between the conventional planing process, the combination process and the overtaking process.
Basics
When extracting hard coal using a coal plow in longwall mining , certain parameters must be observed in order to obtain the maximum amount of coal in one layer from a longwall. One of these parameters is the area chopping , i.e. the area that the planer exposes on the lying surface in a certain time unit . A certain amount of coal is conveyed in the conveyor, depending on the area covered and the speed of the conveyor. The conveyor must be dimensioned according to this amount of coal. The appropriate planing method is then selected on the basis of the respective local conditions.
Conventional planing method
With the conventional planing process, the speeds of both the planer and the conveyor are constant. However, the two machines have different speeds. In this process, the conveyor runs faster than the planer. This planing process results in two filling cross-sections of the conveyor. One filling cross-section for the descent, when the planer travels in the same direction as the conveyor, and one for the ascent, when the planer travels in the opposite direction to the conveyor. When traveling downhill, the required filling cross-section of the conveyor is larger than when traveling uphill. This cross-section must be taken into account when dimensioning the conveyor in order to avoid overloading the conveyor and the resulting cleaning work on the face .
Combination method
The speed of the conveyor is constant in the combination process. Theoretically, the speed of the conveyor corresponds to the speed of the planer in the best case. The planer travels slower than the conveyor on the descent. When traveling uphill, the planer travels faster than the conveyor. With this planing method, the load cross-section is just as large on the descent as on the ascent. The discharge of the face conveyor thus remains constant in both directions of travel of the plow. The area ratio is almost constant in the combination process. The advantage of this process is that only a quarter of the filling cross-section of the conventional process is required. This makes the combination process particularly suitable for large seams .
Overtaking procedure
During the overtaking process, the speeds of the conveyor and the plow are constant. The planer travels either twice or three times as fast as the conveyor. Depending on the planing speed, a distinction is made between the 2: 1 overtaking process and the 3: 1 overtaking process. Depending on the speed of the planer, the conveyor is loaded one or three times during a planing run. The 2: 1 overtaking procedure achieves a significant increase in area coverage. However, this process leads to an uneven discharge of the extracted coal. A triple load is achieved during half of the running time, while only a single load is achieved during the remaining running time. The 3: 1 overtaking process achieves the greatest area coverage. However, the filling cross-section is much smaller than in the 2: 1 overtaking process. The reasons for this are the lower cutting depth and the process-related uneven discharge over the entire duration. The third overtaking process is the modified overtaking process. With this planing method, the speed of the planer is constant. The conveyor speed is changed in each case; the conveyor runs slowly when traveling down the planes and the conveyor runs quickly when traveling uphill. In this process, the area chopping and the extraction flow are just like in the overtaking process 2: 1. Due to the higher conveyor speed during half the running time, the need for filling cross-section is lower. The discharge is also very uneven with this method.
Individual evidence
- ↑ a b Heinz M. Hiersig (Ed.): VDI-Lexikon Maschinenbau. VDI-Verlag GmbH, Düsseldorf 1995, ISBN 9783540621331 .
- ↑ 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 Heinz Kundel: coal production. 6th edition, Verlag Glückauf GmbH, Essen, 1983, ISBN 3-7739-0389-8 .