Suppression of dust explosions by means of different explosive charges

The research was aimed at the development and testing of a super fast explo sion suppression system using different explosive charges. The experiments were carried out on a prototype device (steel container) of 2 1 capacity, c losed by means of a membrane. Below the membrane, there was an exhaust conn ector pipe, at the end of which was a dispersing head. About 1 kg of exting uishing material was located inside the container. The membrane was rupture d by the explosion of a miniature cumulative charge placed on the membrane surface inside the container. In some experiments the explosive charge was located both on the membrane surface and in the upper part of the container -over the extinguishing material. Pentryt, pyrotechnic charge and powder ch arge were used as the explosive material. In the first case, the container was filled up (above the extinguishing material surface) with nitrogen unde r pressure in the range of 30-50 bar. In two other cases, there was no over pressure inside the container. The pyrotechnic charge and powder charge wer e used as gas generators in order to produce the overpressure only after tr iggering the system by the signal from the protected volume. Standard elect ric igniters were applied to initiate the explosive material. The main reas on for using the explosive materials for membrane perforation was their hig h combustion velocity, that enabled opening of the membrane within several microseconds. The dust explosion suppression occurred as a result of the ac tivity of extinguishing material blown out of the container by means of com pressed gases. The suppressing powders were used as the extinguishing mater ial. The results of the research into optimization of the shape and miniatu rization of the explosive charge mass are presented. Also, the process of s haping of the exhaust stream of the extinguishing material was recorded. Fi nally, the dust explosion suppression process in a 1.25 m(3) chamber, using the developed super fast extinguishing system was studied. (C) 2000 Elsevi er Science Ltd. All rights reserved.