The fires which recently occurred in flocking machines in North America have shown that there is a need for better understanding the ignitability of textile fiber clouds (so-called flock). The ignition behavior of combustible flock clouds has, therefore, been intensively investigated at the PTB within the scope of a research project. The investigation covered clouds of flock, raised by air overpressure or falling down from a flock sieve. The resulting clouds were ignited by electrical sparks (with and without additional inductance), arcs (AC and DC) at their optimum ignition concentration and at their flammability limit. The experimental results obtained have led to a deeper knowledge about the behavior of combustible clouds upon ignition by electrical sparks and open flames. Pictures and theories are presented which describe the phenomena found and allow their application in similar situations. The test results will be incorporated in future European standards.
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