1、 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 2017IMPORTANT NOTICES AND DISCLAIMERS CONCERNING NFPA STANDARDS NOTICE AND DISCLAIMER OF LIABILITY CONCERNING TH
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11、ww.nfpa.org/docinfo.497-1 NFPA, and National Fire Protection Association are registered trademarks of the National Fire Protection Association, Quincy, Massachusetts, 02169 Copyright 2016 National Fire Protection Association . All Rights Reserved. NFPA 497 Recommended Practice for the Classication o
12、f Flammable Liquids, Gases, or Vapors and of Hazardous (Classied) Locations for Electrical Installations in Chemical Process Areas 2017 Edition This edition of NFPA 497, Recommended Practice for the Classication of Flammable Liquids, Gases, or Vapors and of Hazardous (Classied) Locations for Electri
13、cal Installations in Chemical Process Areas, was prepared by the Technical Committee on Electrical Equipment in Chemical Atmospheres. It was issued by the Standards Council on May 13, 2016, with an effective date of June 2, 2016, and supersedes all previous editions. This edition of NFPA 497 was app
14、roved as an American National Standard on June 2, 2016. Origin and Development of NFPA 497 The Technical Committee on Electrical Equipment in Chemical Atmospheres began the development of this recommended practice in 1973. The committee based the diagrams in the document on various codes and standar
15、ds of the National Fire Protection Association and on the accepted practices of the chemical process industries and the petroleum rening industry. The rst edition of NFPA 497 was adopted by the Association at the 1975 Annual Meeting. The committee began a thorough review of the document in 1980 and
16、completed its work in 1985. The designation was changed to NFPA 497A in anticipation of a similar recommended practice for Class II hazardous (classied) locations. In 1989, the committee recognized a need for editorial revisions to the drawings referenced in Section 3.4. New drawings were included f
17、or ammable liquid tank truck loading and unloading and for marine terminal handling of ammable liquids. In 1993, the committee decided to combine the information on group classications of ammable liquids, gases, and vapors located in NFPA 497M, Classication of Gases, Vapors, and Dusts for Electrical
18、 Equipment in Hazardous (Classied) Locations, with the information in NFPA 497. The expanded version of 497 was renamed Recommended Practice for the Classication of Flammable Liquids, Gases, or Vapors and of Hazardous (Classied) Locations for Electrical Installations in Chemical Process Areas. For t
19、he 1997 edition, table information was expanded; examples were provided in the appendix; and Class I, Zones 0, 1, and 2 information was incorporated into the text. In 2001, the committee entered NFPA 497 into the November 2003 revision cycle. The 2004 edition was signicantly revised and reorganized
20、for conformance with the 2003 NFPA Manual of Style. The organizational and editorial changes enhanced the usability of this recommended practice. In addition, editorial changes were made to the text to harmonize with the text of NFPA 70 , National Electrical Code , and the denitions of combustible l
21、iquid and ammable liquid were revised to harmonize with the text of NFPA 30, Flammable and Combustible Liquids Code. The 2008 edition was the culmination of a revision cycle that began in January 2006. NFPA 497 is closely tied to the electrical installation requirements for hazardous (classied) loca
22、tions contained in NFPA 70. To ensure correlation with revisions to any pertinent requirements in the 2008 NEC, the Technical Committee on Electrical Equipment in Chemical Atmospheres was granted permission by the NFPA Standards Council to enter into a three-year (Fall 2007) revision cycle. Signican
23、t revisions to the 2008 edition included the following: (1) 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 (2) Recognition of areas as being unclassied where the gas or vapor concent
24、ration is insufcient to reach 25 percent of the lower ammable limit (LFL) (3) 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 resolveELECTRICAL INSTALLATIONS IN CHEMICAL ATMO
25、SPHERES INVOLVING FLAMMABLE LIQUIDS, GASES, OR VAPORS 497-2 2017 Edition differences that existed between this table and similar information contained in other documents (4) Revision to the Annex B example on determining the maximum experimental safe gap and NEC group classication for mixtures For t
26、he 2012 edition, the committee revised the references and denitions extracted from other updated NFPA codes, including NFPA 30, Flammable and Combustible Liquids Code, and NFPA 70, National Electrical Code. The Committee added a new denition for unclassied locations to assist in the effective use of
27、 the document. A new provision was added for the use of portable electronic products (PEP) in hazardous (classied) locations to meet the provisions of ANSI/ISA RP 12.12.03, Recommended Practice for Portable Electronic Products Suitable for Use in Class I and II, Division 2, Class I, Zone 2 and Class
28、 III, Division 1 and 2 Hazardous (Classied) Locations. The Chemical Abstract Service (CAS) numbers in Table 4.4.2 and Table 4.4.3 were amended for three materials: n-butane, methyl isobutyl ketone, and process gas 30 percent H 2 . Several diagrams were amended to identify a single-source release con
29、dition on all gures that did not previously have a single-source release identied. The committee also revised Annex B, adding an example of a method for determining the NEC Group Classication for a mixture of solvents. For the 2017 edition, the committee has revised the references and denitions extr
30、acted from other updated NFPA codes, including NFPA 30, Flammable and Combustible Liquids Code, NFPA 59A, Standard for the Production, Storage, and Handling of Liqueed Natural Gas (LNG), and NFPA 70, National Electrical Code. Text in Chapter 4 dealing with Material Group has been relocated to Chapte
31、r 5. The document also has been revised to clarify the action to be taken when the maximum experimental safe gap (MESG) and minimum igniting current (MIC) ratio data support different Group classications.COMMITTEE PERSONNEL 497-3 2017 Edition Technical Committee on Electrical Equipment in Chemical A
32、tmospheres William T. Fiske, Chair Intertek Testing Services, NY RT Donald W. Ankele, UL LLC, IL RT Babanna Biradar, Bechtel India Pvt Ltd, India SE Ronald M. Brown, PPG Industries, Inc., PA U Jonathan L. Cadd, Electrical Systems and Instrumentation, Inc., TX M John H. Cawthon, State of Alaska Division of Fire (2) making recommendations for the prevention of res and explosions through the use of continuously purged, pressurized, explosion-proof, or dust-ignition-proof electrical equipment where installed in such chemical atmospheres.
