Pit fire

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In mining, a pit fire is a damaging fire (fire) that has broken out underground . The peculiarity of this fire is that it can develop in an uncontrolled manner. The miner differentiates between an open and a covert pit fire. Fires without open flames are called smoldering fires. In the case of mine fires, the mine rescue service is often required.

Basics

For a fire to even start, three conditions must be met. There must be combustible, flammable material, there must be enough oxygen in the vicinity of the fire site and there must be a sufficiently high-energy source of ignition to ignite the combustible material. There are many combustible materials underground. The range includes pit wood , plastics , paper and flammable liquids. In coal mines, coal or lignite and the mine gas are added. All of these flammable substances are called incendiary material. The mine workings are supplied with oxygen via ventilation . Various electrical devices or flame-generating tools such as B. Acting torch. But pit fires can also arise from friction with belt conveyors.

causes

Often carelessness is the cause of a mine fire. Other causes of mine fires are negligence and lack of care on the part of miners. In some cases, arson was also the cause of a mine fire.

Outbreak of fire

When a fire breaks out, there are two ways in which a pit fire can develop, through spontaneous combustion and through external ignition. Auto-ignition occurs only in coal mines. Particularly when coal contains pyrite ( pyrites ), the absorption of oxygen can lead to a chemical reaction. This reaction creates heat that can ignite the coal. This self-ignition is favored by the large surface of the coal. This is especially the case with fine coal. In particular, if a lot of small coal remains in the old man , a spontaneous combustion fire can occur. In the case of external ignition, there must always be a separate ignition source. This can ignite the fire material either directly through open flames or through sufficiently high frictional heat. When using underground weather ovens , the flame of the oven can flash over onto the track room if it is too close to the track joint or otherwise improperly set up. It has also happened that sparks were found in the combustion gases, which then ignited the finely deposited coal dust. The open lighting used in the past could set the room on fire if the lamps were forbidden to be attached to the room. The fire of daytime facilities in the vicinity of the shaft can spread to the mine building . This is particularly beneficial if the shaft lining is made of combustible materials. Leaking mine gas can be ignited by sparks on mining machines such as the coal plow or the cutting chisels of a roadheader. Even the radiant heat from headlights on loading machines can ignite materials such as explosives. Pit fires can also occur as a result of firedamp explosions .

Effects

A mine fire can, depending on its severity, result in very high economic losses for the mine concerned. As long as the fire cannot spread over a large area, the effects are less dangerous. When certain materials fire, poisonous gases are produced. These poisonous gases, known by the miners as bad weather , lead to severe symptoms of poisoning in the miners concerned, which are often fatal. If the fires cannot be extinguished in time, serious consequences can arise. This can lead to the fact that the fire can no longer be controlled and the flames are so violent that they even burst out of the shaft . A firedamp explosion can in turn occur as a result of a mine fire. In the event of a fire in the area of ​​coal seams, the fire can spread to the seam and lead to a seam or coal fire . This danger exists especially with spontaneous combustion fires.

Fire fighting

To fight a mine fire, the miner must use the appropriate extinguishing agent, depending on the type of fire. If the mine fire spreads less, extinguishing it with water is often sufficient. This is particularly feasible in the case of fires caused by external ignition. A sufficient water supply is important when fighting fires with water. Small fires can also be put out by throwing rock dust at them. So that the fire can be effectively smothered, the rock dust layer must be around 50 millimeters thick. Portable fire extinguishers can also be used effectively to fight incipient fires. Larger pit fires can no longer be fought with such simple means. Here it is often necessary to put out the fire by adding large amounts of water. For this purpose, pumps must be installed underground that flood the source of the fire with water. Pit water is also used for this if necessary . Fires caused by spontaneous combustion, in particular, are often difficult to extinguish with these agents. Here there is the possibility to bypass the source of the fire. For this purpose, the source of the fire is bypassed at a favorable point and the resulting cavities are sealed with building material. This is to prevent it from spreading to other parts of the seam. Sludging of the fire with clay, sand or rock dust is suitable for extinguishing backfilling fires. For this purpose, holes are drilled in the joints and the filling material is pumped into the seat of the fire. To extinguish deep-seated fires, measures have proven to be effective which deprive the fire of oxygen and thereby suffocate it. One possibility is to set up fire barriers . The fire dam cuts off the necessary oxygen supply and suffocates the fire. After a long period of time, which can vary depending on the fire, the dam can be opened again. If the dam is opened too early, the fire can break out again. Another possibility is to fight larger mine fires by introducing inert gases such as nitrogen or carbon dioxide. The purpose of inerting is to reduce the oxygen content of the weather in the area of ​​the fire source. This measure enables open and concealed mine fires to be fought. This procedure was first used by Golds Worthy in a mine fire.

early detection

For timely fire fighting, early fire detection is of great importance. Mine fires make themselves felt through an increase in the weather temperature and the appearance of combustion gases. A sure sign of a mine fire is the increased occurrence of carbon oxide in the weather. The perception of a burning smell or smoke also suggests an open pit fire. Smoldering pieces of coal can also appear in the vicinity of the source of the fire. In the case of a hidden fire, sweat points often form in the ridge area. However, such fire signs can usually only be recognized if one is in the immediate vicinity of the source of the fire. With larger weather currents, smaller amounts of fire gases can hardly be detected. For this purpose, special systems for early fire detection have been developed that can be used in the area of ​​belt conveyors.

prevention

In order to prevent mine fires from starting, the miner must carry out his work with great care and caution. He must refrain from doing anything that could promote a mine fire. This includes careful handling of open flames and devices and tools that generate flames. Flammable liquids must be stored according to regulations. Smoking is prohibited underground in hard coal mines. To avoid self-ignition fires, no coal residues or coal islands must be left in the old man . The miners have to seal the area of ​​the old man accordingly. In near-surface mining of coal seams cracks can in the earth's surface occur that are appropriately sealed to prevent smoldering fires. Diesel-powered vehicles must be equipped with on-board fire extinguishing systems to prevent mine fires.

literature

The pit fire and the bad weather in the mines of the Upper Harz . Schweiger Buchhandlung Verlag, Clausthal 1848

Individual evidence

  1. ^ Heinrich Veith: German mountain dictionary with evidence. Published by Wilhelm Gottlieb Korn, Breslau 1871.
  2. ↑ a b c d e f g h Guidelines for fire protection in underground hard coal mining from December 19, 2001 Online (accessed on May 7, 2011).
  3. ^ Walter Bischoff , Heinz Bramann, Westfälische Berggewerkschaftskasse Bochum: The small mining dictionary. 7th edition, Verlag Glückauf GmbH, Essen 1988, ISBN 3-7739-0501-7 .
  4. ↑ Guidelines of the Central Mine Rescue Service of. Mining professional association for organization, equipment and. Use of mine rescue teams. As of April 2006 Online (accessed May 7, 2011; PDF; 124 kB).
  5. ↑ Reinald Skiba : Taschenbuch Arbeitsicherheit. 8th revised edition, Erich Schmidt Verlag, Regensburg and Münster 1994, ISBN 3-503-03520-6 .
  6. ↑ a b c d e f g Carl Hellmut Fritzsche: Textbook of mining science. Second volume, 10th edition, Springer Verlag, Berlin / Göttingen / Heidelberg 1962.
  7. ^ A b c d Emil Stöhr, Emil Treptow: Basics of mining science including processing. Spielhagen & Schurich publishing house, Vienna 1892.
  8. ^ A b c Carl von Scheuchenstuel: IDIOTICON of the Austrian mountain and hut language. kk court bookseller Wilhelm Braumüller, Vienna 1856.
  9. ↑ a b c d e f g h i j Albert Serlo: Guide to mining science. Second volume, 4th improved edition, published by Julius Springer, Berlin 1884.
  10. ^ Gustav Köhler: Textbook of mining science. 6th improved edition, published by Wilhelm Engelmann, Leipzig 1903.
  11. ↑ a b c General Mountain Police Ordinance Online ( Memento from June 7, 2012 in the Internet Archive ).
  12. ^ District government Arnsberg: Mine gas ignition on hot surfaces. Online ( Memento of October 20, 2004 in the Internet Archive ) (accessed on September 12, 2012).
  13. ↑ District government Arnsberg: Mine gas ignition in a roadheading machine. Online ( Memento from October 20, 2004 in the Internet Archive ).
  14. ↑ District government Arnsberg: Fire of an explosives carrier box. Online ( Memento from December 20, 2007 in the Internet Archive ).
  15. ↑ Franz Ritter von Rziha: Schlagende Wetter. Lecture from February 10, 1886.
  16. ↑ E. Fuchs, HG Blasgude: Standards for explosion protection in mining - safety, economy, environmental protection . In Glückauf 142 (2006) No. 12 Online ( Memento of the original from May 9, 2014 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. (accessed on May 7, 2012; PDF; 1.9 MB). @1@ 2Template: Webachiv / IABot / www.faberg.de
  17. ↑ District government Arnsberg: Early fire detection - Increase in mine safety through a new system. Online ( Memento of December 7, 2010 in the Internet Archive ).
  18. ↑ Dieter Fetting, Udo Cerny, Matthias Alze: New on-board extinguishing system on diesel-powered vehicles in underground German hard coal mining. In special print Glückauf. Online ( Memento of May 9, 2014 in the Internet Archive ) (accessed via Archive Org. On January 8, 2016; PDF; 4.3 MB).