Weather speed
In mining, the weather speed is the flow speed that the weather has in a mine or a duct . The speed of the weather has a direct influence on the effective temperature and is therefore of great importance for the air conditioning of the mine workings.
Basics
Mine structures have to be continuously traversed by a certain amount of weather , which depends on various factors. The respective amount of weather and the cross-section of the mine construction through which the air flows determine the level of the weather speed. It should be emphasized that the speed of the weather in a mine is not always the same. The speed of the weather in mines with several branches, with the same cross-section, decreases according to the amount of branched off weather. For a fresh- weather manhole with several floors , this means that the weather speed in the manhole becomes correspondingly smaller after each floor from the grass bank . But even in mine workings without branches, the weather speed in the mine workings is not the same at every point of the respective mine work. As a rule , it is highest in the middle of the pit and gradually decreases towards the impacts ; it is then lowest in the area of the impacts. The reason for the lower weather speed in the area of the bumps is due to the friction of the weather in the vicinity of the bumps. This knowledge is important when measuring the weather speed and then calculating the amount of weather. Since the stretches on the weather bed often have smaller cross-sections than the tracks on the other levels, the weather speed of the downweather is usually much greater than the weather speed of the fresh weather.
Height of the weather speed
Certain minimum and maximum values apply to the weather speed, in accordance with the respective mountain laws . In hard coal mines, values of 0.1 m / s to one meter per second are prescribed as the minimum speed for the weather speed, depending on the mine. These minimum values are necessary so that methane can not accumulate in the ridge area of the mine workings . Since the weather speed also plays a large part in cooling the weather, it is often necessary to work with higher weather speeds at warm operating points. Studies from 1930 have shown that even at weather speeds of 0.2 m / s there is a significant cooling effect on the miners working there. If the weather speed is increased to 0.5 m / s, 2/3 of the maximum cooling effect is achieved by the weather speed. The maximum value here is two meters per second. However, the weather speed cannot be increased indefinitely. In particular, where dry coal dust is lying around, higher weather speeds can cause the coal dust to be swirled up. These weather speeds, at which there is turbulence, are known as the critical weather speed. Depending on the mine, they are of different heights. In pursuit were once so weather speeds of two to 2.3 meters per second standard. Thanks to technical improvements, it is now possible to use higher weather speeds in this area. So-called optimal speeds, which are between four and four and a half meters per second, apply today. If the material to be conveyed is well moistened, weather speeds of up to five meters per second can be used without significantly increasing dust concentrations. Ultimately, an upper limit was set for the weather speed by the authorities. In the Weather Police Ordinance, which came into force on January 1, 1902, a maximum permissible weather speed was specified for the first time. The maximum value was six meters per second. This ceiling applied to all major airways and main cross passages in which no regular funding or driving experiences took place. Only weather channels and weather shafts are excluded from this rule . The reason for this maximum value was the risk of the flame penetrating the gasoline weather lamps used at the time . After the introduction of the electric mine lamps, in order not to unnecessarily endanger the health of miners, z. B. by dust turbulence, the maximum value is maintained.
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 .
- ^ Commission of the European Communities: Mine gas, mine climate and weather management in the hard coal mining of the European Communities. Volume 1, Verlag Glückauf GmbH, Luxembourg 1980, p. 387 ff.
- ↑ a b c Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1 , pp. 578, 614–615, 658–659, 712.
- ↑ a b Leo Brandt (Ed.), S. Schimanski: Status and evaluation of research work on temperature and humidity limits in mining work . Research reports from the North Rhine-Westphalia Ministry of Economics and Transport, No. 253, Springer Fachmedien GmbH, Wiesbaden, p. 13.
- ^ A b c d e Association for Mining Interests in the Upper Mining District Dortmund: The Development of the Lower Rhine-Westphalian Hard Coal Mining in the Second Half of the 19th Century. Volume VI Wetterwirtschaft, Springer Verlag Berlin Heidelberg, Berlin 1903, pp. 320–336.
- ↑ Chr. Mezger: The weather train in its meaning for the cooling of the mine workings. In: Glückauf, Berg- und Hüttenmännische magazine. Association for Mining Interests in the Upper Mining District Dortmund (Ed.), No. 23, 57th year, June 4, 1921, pp. 536-540.
- ↑ a b Commission of the European Communities: Influence of the weather speed on the whirling up and prospects of dust . Final scientific report, research no. 6253-31 / 1/056, Bergbau Forschungs GmbH, Essen 1978, pp. 1–32.
- ↑ a b c B. Stoces, B. Cernik: Combating high pit temperatures. Published by Julius Springer, Berlin 1931, pp. 198–202.
- ↑ a b John-Glen Swanson: Development of spraying concepts taking into account the environmental influences for technical dust control in hard coal mining. Approved dissertation from the University of Clausthal, Clausthal 2011, pp. 24–25.