Analysis of electrostatic hazards during transport and storage of low-conductivity materials
The generation of static electricity during the transport of low-conductivity materials is a well-known but little understood phenomenon. Until recently, large scale experimentation has been the only means by which the hazard associated with such charging could be assessed. Furthermore, the wide range of materials which exhibit such charging characteristics, coupled with the wide variety of scale involved, make conclusions drawn from one arrangement difficult to apply to another. Consequently, the ability to model numerically the electrostatic fields arising from such charging is a useful design aid.In this thesis, the numerical methods most commonly used in the computation of electric fields are compared, and the most suitable technique for the analysis of a broad range of electrostatically hazardous situations, the finite element method, is examined in depth. This method is used to analyse three different types of problem. The first, which serves partly as a validation exercise, considers the interpretation of field mill readings, and lays down guidelines for their calibration. The second case involves the transport and subsequent storage of diesel fuel in glass reinforced plastic tanks. The third situation considered is the charging of high density polyethylene powder during pneumatic transport.Despite the diversity of materials involved and the widely differing scales of experimentation, the finite element method is shown to be capable of accurate assessment of the electrostatic conditions which exist in each of these three situations. Furthermore, the method has provided information which is unobtainable experimentally and has thus permitted the charging and relaxation mechanisms which are at work to be more fully understood.