Deflagration Test I

Deflagration, is the subsonic propagation of a reaction front through the organic peroxide without the participation of oxygen from the air. 

The test is performed with a Dewar vessel (see Fig.3.33) provided with vertical observation windows at opposite sides. A timer with an accuracy of 1 second is used to measure the deflagration rate. 

Any gas flame with a flame length of at least 20 mm can be used to ignite the substance. For safety reasons it is necessary to perform exploratory tests in glass-pyrex-tubes prior to the Dewar test The diameter of the glass tube should be significantly smaller than that of the Dewar vessel. It is recommended to perform the test in a 14 mm diameter tube first and subsequently a test in a 28 mm diameter tube. If the deflagration rate in any of these exploratory tests exceeds the value of 5 mm/s, the substance can be classified as a fast deflagrating substance and the main test can be omitted for the sake of safety. 

For personal protection the test is performed in an explosion-proof fume-chamber or in a well-ventilated test-cell. The capacity of the exhaust fan should be large enough to dilute the decomposition products to the extent that no explosive mixtures with air can be obtained. A stable, shatter-proof glass shield must be placed between the observer and the Dewar. 

The Dewar vessel as well as the substance are brought to the emergency temperature as defined in the Recommendations. If the substance is sufficiently stable as to require no emergency temperature, a test temperature of 50 °C is to be used. The Dewar is filled with 265 cm 3 of the organic peroxide. Granular substances are filled into the Dewar in such a way that the bulk density of the substance is comparable with that in practical situations. Liquids are poured into the glass tube. 

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