Electrical design guide for zone classified areas

Most papers in the past that have addressed issues with zone classified areas, have discussed the concept of the three zone classification method, the merits of the methods of explosion protection (EEx/AEx) developed for use in these areas or some experience with such installations. It is a large jump to decide to design and install a zone classified electrical installation based on the content of these papers. Presented here is a guideline for developing a design for facilities classified by the three zone method, as allowed in the U.S. by NEC (NFPA 70) Article 505. It is intended to help make the choice of zones an easy step from previous design experience for electrical systems in hazardous (classified) locations. The process of area classification is covered briefly, with some considerations that are intended to simplify the process. The specification and selection of electrical devices and equipment and guidance in the actual use of these is presented. Hints for estimation of materials and labor as well as design time are included. Requirements for the electrical portion of mechanical equipments such as pumps, heaters, compressors and other skid-configured equipments are discussed. The cloud of mystery about zones is dispelled.