IEC_79-0__1998.pdf

American National StandardANSI/ISA-S12.0.01-1998(IEC 79-0 Mod)Approved October 15,1998Electrical Apparatusfor Use in Class I,Zones 0&1Hazardous(Classified)LocationsGeneral RequirementsANSI/ISA-S12.0.01(IEC 79-0 Mod)Electrical Apparatus for Use in Class I,Zones 0&1Hazardous(Classified)LocationsGeneral RequirementsISBN:1-55617-652XCopyright1998 by the Instrument Society of America.All rights reserved.Printed in theUnited States of America.No part of this publication may be reproduced,stored in a retrievalsystem,or transmitted,in any form or by any means(electronic,mechanical,photocopying,recording,or otherwise),without the prior written permission of the Publisher.ISA67 Alexander DriveP.O.Box 12277Research Triangle Park,North Carolina 27709Certain provisions of this document differ from analogous provisions of ANSI/UL2279.ISA and UL are actively working to harmonize these provisions andanticipate jointly publishing a single set of American National Standards whenthese differences are resolved.ANSI/ISA-S12.0.01-1998(IEC 79-0 Mod)3PrefaceThis ISA standard is based on IEC Publication 79-0.It is the intention of the ISA SP12Committee to develop an ANSI Standard that is harmonized with IEC 79-0 to the fullest extentpossible.This preface,as well as all footnotes and annexes,is included for informational purposes and isnot part of ANSI/ISA-S12.0.01(IEC 79-0 Mod).The suffix Mod indicates the document is amodification of the IEC document and includes U.S.deviations encompassing both additions anddeletions of information.This standard has been prepared as part of the service of the ISA,the international society formeasurement and control,toward a goal of uniformity in the field of instrumentation.To be of realvalue,this document should not be static,but should be subject to periodic review.Toward thisend,the Society welcomes all comments and criticisms,and asks that they be addressed to theSecretary,Standards and Practices Board;ISA;67 Alexander Drive;P.O.Box 12277;ResearchTriangle Park,NC 27709;Telephone(919)549-8411;Fax(919)549-8288;E-mail:standardsisa.org.The ISA Standards and Practices Department is aware of the growing need for attention to themetric system of units in general,and the International System of Units(SI)in particular,in thepreparation of instrumentation standards,recommended practices,and technical reports.TheDepartment is further aware of the benefits to USA users of ISA standards of incorporatingsuitable references to the SI(and the metric system)in their business and professional dealingswith other countries.Toward this end,this Department will endeavor to introduce SI units in allnew and revised standards to the greatest extent possible.Standard for Use of the InternationalSystem of Units(SI):The Modern Metric System,published by the American Society for Testing&Materials as IEEE/ASTM SI 10-97,and future revisions,will be the reference guide fordefinitions,symbols,abbreviations,and conversion factors.It is the policy of the ISA to encourage and welcome the participation of all concerned individualsand interests in the development of ISA standards.Participation in the ISA standards-makingprocess by an individual in no way constitutes endorsement by the employer of that individual,ofthe ISA,or of any of the standards,recommended practices,and technical reports that ISAdevelops.CAUTIONTHE USE OF THIS STANDARD,RECOMMENDED PRACTICE,ORTECHNICAL REPORT MAY INVOLVE HAZARDOUS MATERIALS,OPERATIONS OREQUIPMENT.THE STANDARD,RECOMMENDED PRACTICE,OR TECHNICALREPORT CANNOT ANTICIPATE ALL POSSIBLE APPLICATIONS OR ADDRESSALL POSSIBLE SAFETY ISSUES ASSOCIATED WITH USE IN HAZARDOUSCONDITIONS.THE USER OF THIS STANDARD,RECOMMENDED PRACTICE,OR TECHNICALREPORT MUST EXERCISE SOUND PROFESSIONAL JUDGMENT CONCERNINGITS USE AND APPLICABILITY UNDER THE USERS PARTICULARCIRCUMSTANCES.THE USER MUST ALSO CONSIDER THE APPLICABILITY OFANY GOVERNMENTAL REGULATORY LIMITATIONS AND ESTABLISHED SAFETY4ANSI/ISA-S12.0.01-1998(IEC 79-0 Mod)AND HEALTH PRACTICES BEFORE IMPLEMENTING THIS STANDARD,RECOMMENDED PRACTICE,OR TECHNICAL REPORT.ADDITIONALLY,IMPLEMENTATION OF THE STANDARD,RECOMMENDEDPRACTICE,OR TECHNICAL REPORT MAY REQUIRE USE OF TECHNIQUES,PROCESSES,OR MATERIALS COVERED BY PATENT RIGHTS.ISA TAKES NOPOSITION ON THE EXISTENCE OR VALIDITY OF ANY PATENT RIGHTS WHICHMAY BE INVOLVED IN IMPLEMENTING THE STANDARD,RECOMMENDEDPRACTICE,OR TECHNICAL REPORT.ISA WILL NOT BE RESPONSIBLE FORIDENTIFYING ALL PATENTS THAT MAY REQUIRE A LICENSE BEFOREIMPLEMENTATION OF THE STANDARD,RECOMMENDED PRACTICE,ORTECHNICAL REPORT OR FOR INVESTIGATING THE VALIDITY OR SCOPE OFANY PATENTS BROUGHT TO ITS ATTENTION.THE USER SHOULD CAREFULLYINVESTIGATE RELEVANT PATENTS BEFORE USING THE STANDARD,RECOMMENDED PRACTICE,OR TECHNICAL REPORT FOR THE USERSINTENDED APPLICATION.The following people served as members of ISA SP12-Working Group 12.0:NAMECOMPANYW.Lawrence,ChairmanFactory Mutual Research Corp.A.BallardCrouse-Hinds CompanyA.EnglerAppleton ElectricT.FeindelR.Stahl,Inc