Oppau explosion

From Wikipedia, the free encyclopedia
Jump to: navigation, search
Caption from Popular Mechanics Magazine 1921




Compared to ammonium sulfate, ammonium nitrate is strongly hygroscopic, so the mixture of ammonium sulfate and nitrate clogged together under the pressure of its own weight, turning it into a plaster-like substance in the 20m high silo. The workers needed to use pickaxes to get it out, a problematic situation because they could not enter the silo and risk being buried in collapsing fertilizer. To ease their work, small charges of dynamite were used to loosen the mixture.

This apparently suicidal procedure was in fact common practice; it was well known that ammonium nitrate was explosive - it had been used extensively as such during World War I - but tests conducted in 1919 had seemed to indicate that mixtures of ammonium sulphate and nitrate containing less than 60% nitrate were unlikely to explode, on which grounds the material handled by the plant, nominally a 50/50 mixture, was considered stable enough to store in 50,000-tonne lots - more than ten times the amount involved in the disaster. Indeed, nothing extraordinary happened during an estimated 20,000 firings, until the fateful explosion on September 21. [1]

As all involved died in the explosion, the causes are not clear. However, it is known from work more recent than the abovementioned 1919 tests that the "less than 60% nitrate = safe" criterion is inaccurate; in mixtures containing 50% nitrate, any explosion of the mixture is confined to a small volume around the initiating charge, but increasing the proportion of nitrate to 55-60% significantly enhances the explosive properties and creates a mixture whose detonation is sufficiently powerful to initiate detonation in a surrounding mixture of a lower nitrate concentration which would normally be considered minimally explosive. Changes in humidity and density also significantly affect the explosive properties.[1]



Scale of the explosion[edit]

The explosion was estimated to be about 1–2 kilotonnes TNT equivalent, and was heard as a loud bang in Munich, more than 300 km away. The pressure wave ripped roofs off up to 25 km away and destroyed windows even farther away. In Heidelberg (30 km from Oppau), traffic was stopped by the mass of broken glass on the streets.

About 80 percent of all buildings in Oppau were destroyed, leaving 6,500 homeless. At ground zero a 90 m by 125 m crater, 19 m deep, was created. Damages were estimated by the New York Times in 1922 at then 321 million Marks[1] (since Germany suffered heavy hyperinflation in 1919–1924, given amounts and exchange-rates are not very descriptive).

According to some descriptions, only 450 tonnes exploded, out of 4,500 tonnes of fertilizer stored in the warehouse.[1]

See also[edit]


External links[edit]
