NFPA 497 Recommended Practice for the Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas
NFPA 497 化学工艺区易燃液体、气体、蒸气分类及电气安装危险性分类
1.1 Scope.
1.1.1 This recommended practice applies to those locations where flammable gases or vapors, flammable liquids, or combustible liquids are processed or handled; and where their release into the atmosphere could result in their ignition by electrical systems or equipment.
1.1.2 This recommended practice provides information on specific flammable gases and vapors, flammable liquids, and combustible liquids whose relevant combustion properties have been sufficiently identified to allow their classification into the groups established by NFPA 70, National Electrical Code (NEC), for proper selection of electrical equipment in hazardous (classified) locations. The tables of selected combustible materials contained in this document are not intended to be all-inclusive.
1.1.3 This recommended practice applies to chemical process areas. As used in this document, a chemical process area could be a large, integrated chemical process plant or it could be a part of such a plant. It could be a part of a manufacturing facility where flammable gases or vapors, flammable liquids, or combustible liquids are produced or used in chemical reactions, or are handled or used in certain unit operations such as mixing, filtration, coating, spraying, and distillation.
1.1.4 This recommended practice does not apply to situations that could involve catastrophic failure of or catastrophic discharge from process vessels, pipelines, tanks, or systems.
1.1.5 This recommended practice does not address the unique hazards associated with explosives, pyrotechnics, blasting agents, pyrophoric materials, or oxygen-enriched atmospheres that might be present.
Trust the 2008 NFPA 497 to help you perform accurate hazardous (classified) area classification in Class I hazardous (classified) locations.
NFPA 497 Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas has a close relationship to the electrical installation requirements for hazardous (classified) locations contained in NFPA 70® National Electrical Code®. To ensure correlation with revisions made to the 2008 NEC®, the 2008 NFPA 497 now includes
· Changes to the scope to specify that explosives, pyrotechnics, and blasting agents have unique hazards that are not addressed by the recommendations of the document
· Recognition of areas as being unclassified where the gas or vapor concentration is insufficient to reach 25% of the lower flammable limit (LFL)
· Additions and revisions to Table 4.4.2 on physical properties of selected chemicals in order to provide information on commonly used materials not previously covered and to resolve differences that existed between this table and similar information contained in other documents
· Revision to the Annex B example on determining the maximum experimental safe gap and NEC group classification for mixtures
Make sure you have the up-to-date knowledge you need to properly select and install electrical equipment so it will not be an ignition source in environments where flammable or combustible liquids, gases, or vapors are processed or handled. Order the 2008 NFPA 497 today. (Softbound, 63 pp., 2008)
