Investigations of the formation of explosive mixtures in dryers for coatings.
In the following we will discuss a specific problem of explosion protection in dryers for coatings. It is mainly encountered in chamber dryers as these pose specific problems as regards occupational safety and health. During the drying process of most coatings, solvent vapours are released most of which can form explosive mixtures when a specific concentration, the lower explosion limit, is reached. The European Standard EN1539:2000 requires explosion venting areas for most of these dryers without adequate explosion protection measures such as appropriate limitation of the solvent input being taken into account. Different aspects of the model underlying the calculations are evaluated, and it will be shown that this model is still reliable in most applications. The investigations consisted of three parts. At first there have been made investigations of the operating conditions in different enterprises aimed to get information about specific parameters, problems and failures. Laboratory experiments have been made to investigate in detail the major influencing parameters. Attempts to set up a simple but basic physical model for the experimental data have also been made. Evaporation and diffusion have been examined. The numerical models have been kept as simple as possible to be a potential tool for designers/manufacturers and users.
Physikalisch-Technische Bundesanstalt, Bundesallee 100, Braunschweig 38116, Germany. frank.stolpe@ptb.de
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D004058:Diffusion; D004784:Environmental Monitoring / Q000379:methods; D004869:Equipment Safety; D005107:Explosions / Q000517:prevention & control*; D005740:Gases / Q000737:chemistry; D008420:Manufactured Materials / Q000032:analysis*; D008956:Models, Chemical; D012997:Solvents / Q000737:chemistry
D005740:Gases; D012997:Solvents