Avoidance of the ignition of textile fiber/air mixtures during the electrostatic flocking process

The fires which recently occurred in flocking machines in North America have shown that there is a need for better understanding of the ignitability of textile fiber clouds (so-called flock). The ignition behavior of combustible flock clouds has, therefore, been intensively investigated at the Physikalisch-Technische Bundesanstalt, Braunschweig, Germany, 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 and allow the safe construction and operation of flocking machines. The test results have been incorporated in the European standards EN 50050:2001 for hand-held and EN 50223:2001 for stationary flocking equipment