Pyrotechnic igniter with 1 kJ energy content 4.5 ms after activation
Source: BAM, division Explosion Protection Gases and Dusts
In explosion protection safety characteristics are used to determine, when a substance (gaseous, liquid or solid) is flammable when mixed with air to prevent such formation or to estimate how to minimize the consequences if an explosion occurs with that substance. Standards exist for single phase substances but not if they are mixed (for example gas with dust). For the determination of the safety characteristics of dusts it is necessary to disperse the dust in the oxidating atmosphere (usually air). In the standard procedures for dusts this is realized by a partially evacuated explosion vessel in which the dust gets injected from a dust chamber pressurized with air. Shortly after that injection the dust cloud gets ignited. While there has been a lot of research about many influencing factors of this procedure in the recent years little attention was paid to the pressure rise before ignition and the allowed variations in the standards. Even though hybrid mixtures are an emerging risk problem in an interconnected industry there is no standard for the determination of their safety characteristics. In this work it is shown that especially for the preparation of hybrid mixtures of flammable dust and gas the pressures after injection of the dust and the mixing procedure have a large influence on the composition of the tested mixtures and therefore on the safety characteristics.
Influence of pre-ignition pressure rise on safety characteristics of dusts and hybrid mixtures
Stefan Spitzer, Enis Askar, Alexander Benke, B. Janovsky, U. Krause, Arne Krietsch
published in Fuel, 122495, 2021
BAM, division Explosion Protection Gases and Dusts