Metal fire
Under metal fire refers to the uncontrolled and damage-causing burning of metals . At the high temperatures of over 2000 ° C that occur, water decomposes into hydrogen and oxygen . As a result, there is a risk of oxyhydrogen explosions , which is why water must not be used as an extinguishing agent. At fire temperatures of 1500 ° C, around 0.2% of the water is split up by the heat, around 2% up to 2000 ° C and 9% at 2500 ° C. This means that the hotter a metal fire, the more dangerous the use of water. CO 2 is also unsuitable because metals also burn in CO 2 at high temperatures . The CO 2 is reduced with the formation of metal oxides. The reaction sustains the metal fire, but is not as violent as that with water.
In principle, most metals are flammable, but under normal atmospheric conditions, alkali and alkaline earth metals are particularly affected. Iron is flammable in finely divided form like steel wool or iron powder. Fine, non- phlegmatized aluminum powder is extremely reactive and ignites explosively on contact with air. Titanium and zirconium also burn under suitable circumstances. Zirconium fires develop particularly high temperatures and are very difficult to extinguish.
Burns caused by metal fires lead to wounds that are difficult to treat and heal very poorly.
Fire fighting and extinguishing media
The fire brigade fights such fires by suffocating. If metal fire extinguishing powder (D powder) is not available, the fire fighting with dry sand , cement powder or sodium chloride (table, gritting or cattle salt) is effective, which melt over the burning material and thus form an airtight coating that suffocates the fire . Metal fire extinguishing powder consists of salt (alkali or alkaline earth chlorides ; mostly sodium, rarely barium chloride ) with additives. Magnesium fires can also be extinguished by covering them with gray cast iron powder or chips.
Metal fires are assigned to fire class D.
literature
- Ulrich Kortt, Rolf Schmid, Hermann Schröder (editor): Hamilton. Handbook for the firefighter , 20th edition 2004, Richard Boorberg Verlag, ISBN 3-415-03176-4
- Lothar Schott, Manfred Ritter: Fire Brigade Basic Course FwDV 2 . 20th edition. Wenzel-Verlag, Marburg 2018, ISBN 978-3-88293-220-1 .
- Hermann Schröder (Ed.): Lexikon der Feuerwehr , 2nd edition 2001, Verlag W. Kohlhammer Stuttgart, ISBN 3-17-015767-1