ISA TR12.06.01 PDF

Introduction

When electrical equipment is used in locations in which fire or explosion hazards may exist due to flammable gases or vapors, flammable liquids, combustible dust, or ignitible fibers or flyings, the National Electrical Code (NEC), ANSI/NFPA 70 requires special precautions to be taken in equipment construction and installation to minimize risks of fire and explosions. There are several protection techniques in common use, each of which has its own set of advantages and disadvantages. Other countries, including Canada, utilize varying wiring methods, so the contents of this report may not be applicable to countries other than the United States.

A location in which the fire or explosion hazard exists infrequently and for short periods is designated as a Division 2/Zone 2 location. One suitable protection technique for a Division 2/Zone 2 location is "Nonincendive Equipment." This Technical Report is intended to explain this protection technique and to clarify the associated terminology. Clarification of the term "Nonincendive Equipment" is very important since it has been used in two different ways. This Technical Report also addresses field wiring for Division 2/Zone 2 locations.

The term "flammable material" will be used throughout this Technical Report to refer to any of the materials mentioned above, i.e., flammable gases or vapors, flammable liquids, combustible dusts, or ignitible fibers or flyings. Similarly, the term hazardous location will be used in place of the phrase hazardous (classified) location used in the NEC. Finally, although flammable materials pose a fire hazard, the primary concern is an explosion.