Article 500-516 of the National Electrical Code® with product recommendations for use in hazardous (classified) areas.
Crouse-Hinds Code Digest
Cooper Crouse-Hinds has revised its Code Digest for 2002 to meet the needs of design personnel for a ready reference to equipment and installation ideas in hazardous locations. Selected Articlesfrom the National Electrical Code® have been explained with diagrams and photographs of electrical hardware taken from our Cooper CrouseHinds Product Catalog. Exhaustive laboratory testing and extensive research, development and field experience have proven that these items meet or exceed the requirements set forth by the National Electrical Code and Underwriters Laboratories Inc.® This latestrevision to the series of Cooper Crouse-Hinds service-oriented bulletins reflects the most recent changes in the National Electrical Code. Reproduction of these Articles has been made with the permission of the National Fire Protection Association. Diagrams of recommended power and lighting installations have been included in Appendices V, VI, VII, VIII, IX and X to assist engineers involved in thedesign of these systems for hazardous locations. A “Quick-Selector” Guide for electrical equipment used for Class I, Class II and Class III installations is included in Appendix XI. Tables included are those of most frequent applicability and usage. Photographs of actual application of Cooper Crouse-Hinds hardware for a variety of environments have been added for clarity and specific reference. Wesincerely hope that this Digest will be of value to you. We ask you to feel free to call on your Cooper Crouse-Hinds representative for personal assistance in your installation planning at any time.
I. Classification of Hazardous Atmospheres
The National Electrical Code, widely used for classification purposes, divides atmospheric explosion hazards into three broad classes; they are summarizedin Table I. However, it must be understood that considerable skill and judgment must be applied when deciding to what degree an area contains hazardous concentrations of vapors, combustible dusts or easily ignitible fibers and flyings. Many factors, such as temperature, barometric pressure, quantity of release, humidity, ventilation, distance from the vapor source, etc., must be considered. Wheninformation on all factors concerned is properly evaluated, a consistent classification for the selection and location of electrical equipment can be developed. For further information on classification of areas see NFPA 497: Recommended Practice for the Classification of Flammable Liquids, Gases or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical ProcessAreas – 1997 and NFPA 499: Recommended Practice for the Classification of Combustible Dusts and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas – 1997. Appendices I and II list all of the flammable gases and combustible dusts which have been classified by NFPA along with their ignition temperatures.
The definitions below are extracted fromthe National Electrical Code. These definitions are included to define and clarify the meaning and intent of Crouse-Hinds when terms such as “Explosionproof” and “Dust-ignitionproof” are used in this publication. “Explosionproof Apparatus”: Apparatus enclosed in a case that is capable of withstanding an explosion of a specified gas or vapor that may occur within it and of preventing the ignitionof a specified gas or vapor surrounding the enclosure by sparks, flashes, or explosion of the gas or vapor within, and that operates at such an external temperature that a surrounding flammable atmosphere will not be ignited thereby. (FPN): For further information, see ExplosionProof and Dust-Ignition-Proof Electrical Equipment for Use in Hazardous (Classified) Locations, ANSI/UL 1203-1994....