Solvay method of estimating the risk of electrostatic ignition

Abstract

IEC TS 60079-32-1 “ATEX - Electrostatic hazards, guidance” gives us the best practice to avoid ignition from electrostatic sources. In Solvay we follow this guideline but, when we find that our existing practice, at a particular site for a particular chemical process in a particular piece of equipment, does not comply with that guidance, we are faced with a difficult question: what priority should we give to putting it right? To answer that question we have to analyse the risk associated with electrostatic ignition sources for the particular process and that particular piece of equipment. It depends on many factors, including the frequency of the presence of an explosive atmosphere, the Minimum Ignition Energy of the flammable gas or combustible dust and the number of people who would be exposed to the blast wave or shrapnel from an explosion or the thermal radiation from a fire. Such considerations allow us to prioritize the risk in three levels, ranging from Risk 1 (Unacceptable), through Risk 2 (Intermediate) to Risk 3 = Acceptable. This paper shows how to estimate the risk level of scenarios involving electrostatic and indeed other ignition sources using the Solvay method.