Abstract
The possibility of igniting an explosive atmosphere by an electrostatic discharge occurring upon the activation of a safety valve is a major concern to chemical process industries. In order to investigate this matter, we carried out various experiments using an original experimental apparatus. Conductive liquids (water, methyl ethyl ketone, tetrahydrofuran) produced much higher charges than non-conductive liquids (styrene, hexane, kerosene). In particular, Tetrahydrofuran, is found to produce abnormally large charges if certain conditions are met. A nonconductive liquid, however, generated a huge charge when non-soluble powder was added and dispersed in the liquid. Other factors that affected the charge generation were the inner pressure of the liquid container, the difference between the inner pressure and the popping pressure of the valve, the condition of the gas-liquid mixture, the length of the outlet pipe, the liquid temperature, and the size of the safety valve. Considering the quantity of charge obtained in our experiments, we conclude that a strong space charge sufficient to cause an incendiary brush discharge may be formed when a safety valve is activated and, therefore, appropriate preventive measures for explosion and fire should be planned and executed.
