ABSTRACT
This chapter describes the steps that are taken in the design stages of a refinery or petrochemical plant to ensure worker safety and health. The plant layout carefully segregates hazardous areas from nonhazardous areas for classification purposes and for the use of electrical equipment such as switchgear, motors, controls, etc. Flammable dusts that have properties of primary interest from an ignition point of view are those of particle size, minimum explosive concentration, dust-layer ignition temperature, and dust-cloud ignition energy. To keep electrical installations from becoming a major source of ignition in areas where there may be explosive concentrations of gases, vapors, or dusts, there are special rules in Article 500 of the National Electrical Code that deal with electrical equipment in hazardous locations. The ignition temperature is that to which a fuel-air mixture needs to be heated for the mixture to ignite spontaneously, without the introduction of a flame or spark.
