In the year 1942, the Accident Prevention Regulation BGV D 13 "Production and Processing of aluminium powder" (former VBG 56) was developed following numerous explosion accidents; since then, it is kept up in the BG experts' committee "Iron and Metal V" (new: Engineering, production systems, steel construction - FA MFS). § 7 of the BGV D 13 determines safety distances between buildings in which aluminium powder is produced. It should be verified whether it is possible to reduce these distances.
For certain procedures in the production of aluminium powder, UVV BGV D 13 requires structural works, into which a socalled blowout wall is integrated, which, in the event of an explosion occurring, detaches itself easily from the building. Within the area in front of this wall, the presence of persons is prohibited, which is why no building or roads shall be within this safety distance (about 10 to 50 m). As in the recent past, the aluminium powder manufacturers concerned continue to query this safety distance, the distance is to be reduced in order to allow a better utilization of the company site.
The distances laid down in UVV BGV D 13 are based upon experimental values obtained from accidents which had occurred in the 40s of the 20th century. An extensive complex of issues was compiled in cooperation with the companies concerned. A scientific study was to show how a resistance wall should be dimensioned which is positioned parallel to a blowout wall at a distance of 10 m. If these scientific studies yield satisfying results, it is possible to reduce the defined distances.
a) Calculation of the explosion pressures in rooms with a base area of 75 m² and 150 m², taking into account that a blow-out wall is provided which covers 1/6 (16,7 %) or ¼ (25 %), respectively, of the wall surface.
b) Determination of the pressures at a distance of 10 m in front of the blow-out wall. A protective wall erected at a distance of 10 m in front of the blow-out wall should be dimensioned in such a way that it is capable of withstanding these pressures.
c) Then, an estimation of the path of flying debris in the event of destruction of a roof would follow. In particular, the hazards occurring at a distance of 25 m were of interest.
d) The calculations were done several times, for the following aluminium dust concentrations: 30 g/m³, 100 g/m³, 500 g/m³.
Furthermore, the necessary size of the blow-out wall was calculated backwards, if the permissible pressure is 0.2 bar (Ü) or 0.3 bar (Ü), respectively. The data (explosion pressure, pressure increase speed) of the aluminium/air mixtures with 30 g/m³, 100 g/m³, and 500 g/m³ were determined by performing explosion experiments in a 1.2 m² vessel. These measurement values formed the basis for the calculations of a), b) and d).
The final report is available.
-cross sectoral-Type of hazard:
Brand- und Explosionsschutz, UnfallgefahrDescription, key words:
explosion accidents, production of aluminium powder, resistance wall