Creeping weather

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As Schleich Weather designating Bergmann small, uncontrolled weather currents caused by discarded mines such as the Old Man emphasize and re-enter the normal weather current at a different location. Since these creeping currents contain potential dangers, the miner endeavors to prevent them by suitable means.

Emergence

Creeping weather occurs when part of the weather current can flow as a creeping current through the rugged mountains and escapes uncontrollably at another point. This possibility exists if the fracture zone in the longwall , the so-called offset, does not seal tightly or if a dam is leaking. In the case of dams, this is usually the case at the side edges. Due to the difference in air pressure between the entry point and the exit point, the creeping weather can make its way through the " old man " in such a case .

Negative impacts

The effects of creeping weather are very different. On the way through the cavities of the rugged mountains, the stream of weather enriches itself with gases such as B. methane . At the point where the methane can in the ridges gather and there may be hazardous concentrations of methane-air mixture form, which the miner as gassy referred. This is particularly the case when the weather speed is low at the exit point . Another danger is self-ignition fires in the "old man". These arise when oxygen reaches the residual coal remaining in the fracture chamber. The crushed coal oxidizes with the oxygen and heats up. This chemical process is increased even more by adding more oxygen. If the heat generated during the reaction cannot be dissipated, the critical temperature will ultimately be exceeded . Exceeding the critical temperature for self-ignition fires leads to self-ignition of the carbon and smoldering fire .

recognition

Creeping weather can usually hardly be recognized, especially if there is a high speed of the weather in the route or in the face. Dams can be checked for leaks using special smoke test tubes. The miner usually only recognizes creeping weather by its negative consequences. Increased methane concentrations in certain places suggest leaks in the mountains. Sweat spots in the ridge area and unusually high temperatures are often signs of a smoldering fire. In order to recognize the negative effects of creeping weather in good time, CO measuring devices are installed in many places throughout the mine, especially in the weather area of ​​mining operations. These measuring devices continuously measure the CO content in the weather stream and transmit the measurement data to the mine control room above . An alarm is given if certain values ​​are exceeded.

Preventing creeping currents

Creeping weather can be prevented as far as possible by consistently sealing the fracture area and the line edge. The Streckensaum is in this case immediately after the passage of the longwall with a load-bearing and gas-tight route accompanying dam sealed from construction material. Dams that have become leaky are sealed using special foam. This special foam is a two-component hard foam that is sprayed against the leaks using spray nozzles. When the two liquid components are mixed, they react and the fast-hardening foam forms in a short time. The rigid foam is also used to fill cavities, for gas-tight sealing of roadside embankments against creeping weather. Another measure is the establishment of a weather pressure equalization by reducing the weather flow and thus the weather pressure gradient or by creating pressure equalization chambers. These pressure equalization chambers are created in certain sections of the route or in front of terminal dams. Since abandoned and still open pits are a particular danger point for spontaneous combustion fires due to creeping weather, the longwall is immediately stolen after the end of the dismantling and dammed by means of a dam with hydraulically setting building materials. During the robbery phase, all weather flows are closely monitored. Subsequently, the no longer required routes will be closed by means of a closing dam.

Combating the negative effects

The negative effects can be combated in a number of ways. Methane gas accumulations in the roof can be swirled and flushed away by means of airmovers, small compressed air fans. Smoldering fires must be fought systematically. This is done by increasing the sealing of the fracture area or by pressing or spraying the section seams using setting building materials or rigid foam. It is sprayed on over such a large area that no more creeping weather can penetrate. These measures serve to cut off the oxygen supply to the source of the fire and thus to suffocate the fire. Another measure is the introduction of inert gases such. B. nitrogen or carbon dioxide . The introduction of inert gases displaces the oxygen and ultimately suffocates the fire. The shedding of the affected mine workings by setting fire barriers is only used as a measure if the previous measures do not bring the desired success. Submerging fire fields is only used in extreme emergencies.

Individual evidence

  1. ^ A b c d Walter Bischoff, Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining encyclopedia. 7th edition, Verlag Glückauf GmbH, Essen 1988, ISBN 3-7739-0501-7 .
  2. ↑ Horst Roschlau, Wolfram Heinze, SDAG Wismut (Hrsg.): Knowledge storage mining technology. 1st edition. German publishing house for basic industry, Leipzig 1974, p. 132.
  3. ↑ G. Spackeler: The technical development of the Upper Silesian hard coal mining. In: Glückauf, Berg- und Hüttenmännische magazine. Association for Mining Interests in the Upper Mining District Dortmund (Ed.), No. 37, 76th year, September 14, 1940, pp. 500–505.
  4. ↑ a b c d e f g h Ernst-Ulrich Reuther: Textbook of mining science. First volume, 12th edition, VGE Verlag GmbH, Essen 2010, ISBN 978-3-86797-076-1 .
  5. ^ A b c Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962, pp. 272, 703.
  6. ↑ Patent of Bauer Schaum Chem. No. DE3216896 Method for securing the fracture field of underground mine rooms against spontaneous combustion fires.
  7. ↑ John-Glen Swanson: Development of spraying concepts taking into account the environmental influences for technical dust control in hard coal mining. Dissertation at the Faculty of Energy and Economics at Clausthal University of Technology, Clausthal 2011.
  8. ↑ Minova Carbo Tech GmbH: CARBOFILL, phenolic resin foam for cavity filling, gas sealing and fire fighting in mining.
  9. ↑ a b c d Arnsberg district government (ed.): Collective sheet of the Arnsberg district government department 6 fire protection guidelines. Online (last accessed June 1, 2015).