ISA TR12.12.04

Introduction

When electrical equipment is used in locations in which fire orexplosion hazards may exist due to flammable gases or vapours,flammable liquids, combustible dust, or ignitable fibers orflyings, the National Electrical Code® (NEC®), ANSI/NFPA 70requires special precautions to be taken in equipment constructionand installation to minimize risks of fire and explosions. Thereare several protection techniques in common use, each of which hasits own set of advantages and disadvantages. Other countries,including Canada, utilize varying wiring methods, so the contentsof this report may not be applicable to countries other than theUnited States.

A location in which the fire or explosion hazard existsinfrequently and for short periods is designated as a Division 2 orZone 2 location. Two of the primary protection techniques forDivision 2 or Zone 2 locations are “Nonincendive equipment” or”Non-sparking equipment”. This Technical Report is intended toexplain these protection techniques and to clarify the associatedterminology. This Technical Report also addresses field wiring forDivision 2/Zone 2 locations.

Division 2 equipment is permitted to be marked and used in Zone2 hazardous locations per the NEC®, Section 505.9(C)(1).

Zone 2 equipment, in accordance with ANSI/ISA-60079-15, ispermitted to be marked and used in Division 2 hazardous locationper the NEC®, Section 501.5.

The term “combustible material” will be used throughout thisTechnical Report to refer to materials mentioned above, i.e.,flammable gases, flammable liquid produced vapours, or combustibleliquid produced vapours. Similarly, the term “hazardous location”will be used in place of the phrase “hazardous (classified)location” used in the NEC® and in the product standards. Finally,although combustible materials pose a fire hazard, the primaryconcern is an explosion.

Edition:

11

Published:

06/20/2011

ANSI:

ANSI Approved

Number of Pages:

22

File Size:

1 file , 82 KB