ISA 60079-10-1-2014 Explosive Atmospheres C Part 10-1 Classification of areas C Explosive gas atmospheres (12 24 01).pdf

1、 AMERICAN NATIONAL STANDARD ANSI/ISA-60079-10-1 (12.24.01)-2014 Explosive Atmospheres Part 10-1: Classification of areas Explosive gas atmospheres Approved 15 August 2014 ANSI/ISA-60079-10-1(12.24.01)-2014 Explosive atmospheres - Part 10-1: Classification of areas Explosive gas atmospheres ISBN: 978

2、-0-876640-90-6 Copyright 201X by ISA. All rights reserved. Not for resale. Printed in the United States of America. No part of this publication may be reproduced, stored in a retrieval system, or transmitted, in any form or by any means (electronic, mechanical, photocopying, recording, or otherwise)

3、, without the prior written permission of the Publisher. ISA 67 Alexander Drive P. O. Box 12277 Research Triangle Park, North Carolina 27709 - 3 - ANSI/ISA-60079-10-1 (12.24.01)-2014 Preface This ISA standard is based on IEC Publication 60079-10-1, Edition 1. It is the intention of the ISA12 Committ

4、ee to develop an ANSI standard that is harmonized with IEC 60079-10-1 to the fullest extent possible. This preface, as well as all annexes, is included for informational purposes and is not part of ANSI/ISA-60079-10-1. The document is a modification of the IEC document and includes U.S. deviations e

5、ncompassing both additions and deletions of information. The standards referenced within this document may contain provisions which, through reference in this text, constitute requirements of this document. At the time of publication, the editions indicated were valid. All standards are subject to r

6、evision, and parties to agreements based on this document are encouraged to investigate the possibility of applying the most recent editions of the standards indicated within this document. Members of IEC and ISO maintain registers of currently valid International Standards. ANSI maintains registers

7、 of currently valid U.S. National Standards. This standard has been prepared as part of the service of the International Society of, Automation (ISA) toward a goal of uniformity in the field of instrumentation. To be of real value, this standard should not be static but should be subject to periodic

8、 review. Toward this end, the Society welcomes all comments and criticisms and asks that they be addressed to the Secretary, Standards and Practices Board; ISA; 67 Alexander Drive; P. O. Box 12277; Research Triangle Park, NC 27709; Telephone (919) 549-8411; Fax (919) 549-8288; E-mail: standardsisa.o

9、rg. The ISA Standards and Practices Department is aware of the growing need for attention to the metric system of units in general, and the International System of Units (SI) in particular, in the preparation of instrumentation standards. The Department is further aware of the benefits to USA users

10、of ISA standards of incorporating suitable references to the SI (and the metric system) in their business and professional dealings with other countries. Toward this end, this Department will endeavor to introduce SI-acceptable metric units in all new and revised standards, recommended practices, an

11、d technical reports to the greatest extent possible. Standard for Use of the International System of Units (SI): The Modern Metric System, published by the American Society for Testing b) the processing and manufacture of explosives; c) areas where a hazard may arise due to the presence of combustib

12、le dusts or fibres (refer to IEC 61241-10 / IEC ANSI/ISA-60079-10-2); d) catastrophic failures which are beyond the concept of abnormality dealt with in this standard (see Note 5); e) rooms used for medical purposes; f) domestic premises. This standard does not take into account the effects of conse

13、quential damage. Definitions and explanations of terms are given together with the main principles and procedures relating to hazardous area classification. For detailed recommendations regarding the extent of the hazardous areas in specific industries or applications, reference may be made to natio

14、nal or industry codes relating to those applications. NOTE 1 Flammable mists may form or be present at the same time as flammable vapors. Liquids not considered to be hazardous in terms of this standard (due to the flash point), when released under pressure may also generate flammable mists. In such

15、 cases, the strict application of area classification for gases and vapors may not be appropriate as the basis for selection of equipment. Information on flammable mists is provided in Annex D. NOTE 2 The use of IEC 60079-14 for selection of equipment and installations is not required for mist hazar

16、ds. IEC 60079-14 has not been adopted for use in the US. NOTE 3 For the purpose of this standard, an area is a three-dimensional region or space. NOTE 4 Atmospheric conditions include variations above and below reference levels of 101,3 kPa (1 013 mbar) and 20 C (293 K), provided that the variations

17、 have a negligible effect on the explosion properties of the flammable materials. NOTE 5 Catastrophic failure in this context is applied, for example, to the rupture of a process vessel or pipeline and events that are not predictable. NOTE 6 In any process plant facility, irrespective of size, there

18、 may be numerous sources of ignition apart from those associated with equipment. Appropriate precautions will be necessary to ensure safety in this context. This standard may be used with judgement for other ignition sources. ANSI/ISA-60079-10-1 (12.24.01)-2014 - 12 - 2 Normative References The foll

19、owing referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. IEC 60050-426, International Electrotechnical Vocabulary

20、(IEV) Part 426: Equipment for explosive atmospheres IEC ANSI/ISA-60079-0, Explosive atmospheres Part 0: Equipment General requirements IEC 60079-4, Electrical apparatus for explosive gas atmospheres Part 4: Method of test for ignition temperature IEC 60079-4A, First supplement to IEC 60079-4 (1966),

21、 Electrical apparatus for explosive gas atmospheres Part 4: Method of test for ignition temperature IEC 60079-20, Electrical apparatus for explosive gas atmospheres Part 20: Data for flammable gases and vapors, relating to the use of electrical apparatus ISA-60079-20-1, Explosive atmospheres Part 20

22、-1: Material characteristics for gas and vapor classification - Test methods and data ANSI/NFPA 497, Classification of Flammable Liquids, Gases, or Vapors and of Hazardous (Classified) Locations for Electrical Installations in Chemical Process Areas ANSI/NFPA 70, National Electrical Code 29CFR, Code

23、 of Federal Regulations, Title 29, Labor 3 Terms and definitions For the purposes of this document, the terms and definitions given in ANSI/ISA-IEC 60079-0 and the following apply. NOTE Additional definitions applicable to explosive atmospheres can be found in the IEC 60050-426. 3.1 explosive atmosp

24、here mixture with air, under atmospheric conditions, of flammable substances in the form of gas, vapor, dust, fibres, or flyings which, after ignition, permits self-sustaining propagation IECANSI/ISA-60079-0, definition 3.22 3.2 explosive gas atmosphere mixture with air, under atmospheric conditions

25、, of flammable substances in the form of gas or vapor, which, after ignition, permits self-sustaining flame propagation IECANSI/ISA-60079-0, definition 3.24 NOTE 1 Although a mixture which has a concentration above the upper explosive limit (UEL) is not an explosive gas atmosphere, it can readily be

26、come so and, in certain cases for area classification purposes, it is advisable to consider it as an explosive gas atmosphere. NOTE 2 There are some gases which are explosive with the concentration of 100 %. - 13 - ANSI/ISA-60079-10-1 (12.24.01)-2014 3.3 hazardous area (on account of explosive gas a

27、tmospheres) an area in which an explosive gas atmosphere is or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of equipment NOTE The National Electrical Code defines hazardous areas as hazardous (classified) locations. 3.

28、4 non-hazardous area (on account of explosive gas atmospheres) an area in which an explosive gas atmosphere is not expected to be present in quantities such as to require special precautions for the construction, installation and use of equipment. See 3.30 NOTE The National Electrical Code does not

29、define a non-hazardous areas but instead uses the term unclassified location. 3.5 zones hazardous areas are classified into zones based upon the frequency of the occurrence and duration of an explosive gas atmosphere, or where adjacent to areas that are classified, as follows in 3.6, 3.7 and 3.8 3.6

30、 Class I, Zone 0 an area in which an explosive gas atmosphere is present continuously or for long periods or frequently a Class I, Zone 0 location is a location (1) in which ignitable concentrations of flammable gases or vapor are present continuously; or (2) in which ignitable concentrations of fla

31、mmable gases or vapors are present for long periods of time 3.7 Class I, Zone 1 an area in which an explosive gas atmosphere is likely to occur in normal operation occasionally a Class I, Zone 1 location is a location (1) in which ignitable concentrations of flammable gases or vapors are likely to e

32、xist under normal operating conditions; or (2) in which ignitable concentrations of flammable gases or vapors may exist frequently because of repair or maintenance operations or because of leakage; or (3) in which equipment is operated or processes are carried on, of such a nature that equipment bre

33、akdown or faulty operations could result in the release of ignitable concentrations of flammable gases or vapors and also cause simultaneous failure of electrical equipment in a mode to cause the electrical equipment to become a source of ignition; or (4) that is adjacent to a Class I, Zone 0 locati

34、on from which ignitable concentrations of vapors could be communicated, unless communication is prevented by adequate positive pressure ventilation from a source of clean air and effective safeguards against ventilation failure are provided 3.8 Class I, Zone 2 area in which an explosive gas atmosphe

35、re is not likely to occur in normal operation but, if it does occur, will persist for a short period only a Class I, Zone 2 location is a location (1) in which ignitable concentrations of flammable gases or vapors are not likely to occur in normal operation and, if they do occur, will exist only for

36、 a short period; or (2) in which volatile flammable liquids, flammable gases, or flammable vapors are handled, processed, or used but in which the liquids, gases, or vapors normally are confined within closed containers of closed systems from which they can escape, only as a result of accidental rup

37、ture or breakdown of the containers or system, or as a result of the abnormal operation of the equipment with which the liquids or gases are handled, processed, or used; or (3) in which ignitable concentrations of flammable gases or vapors normally are prevented by positive mechanical ventilation bu

38、t which may become hazardous as a ANSI/ISA-60079-10-1 (12.24.01)-2014 - 14 - result of failure or abnormal operation of the ventilation equipment; or (4) that is adjacent to a Class I, Zone 1 location, from which ignitable concentrations of flammable gases or vapors could be communicated, unless suc

39、h communication is prevented by adequate positive-pressure ventilation from a source of clean air and effective safeguards against ventilation failure are provided. IEV 426-03-05 NOTE Indications of the frequency of the occurrence and duration may be taken from codes relating to specific industries

40、or applications. 3.9 source of release a point or location from which a gas, vapor, mist or liquid may be released into the atmosphere so that an explosive gas atmosphere could be formed IEV 426-03-06, modified 3.10 grades of release there are three basic grades of release, as listed below in order

41、of decreasing frequency and likelihood of the explosive gas atmosphere being present: a) continuous grade; b) primary grade; c) secondary grade. A source of release may give rise to any one of these grades of release, or to a combination of more than one 3.11 continuous grade of release release whic

42、h is continuous or is expected to occur frequently or for long periods 3.12 primary grade of release release which can be expected to occur periodically or occasionally during normal operation 3.13 secondary grade of release release which is not expected to occur in normal operation and, if it does

43、occur, is likely to do so only infrequently and for short periods 3.14 release rate quantity of flammable gas, vapor or mist emitted per unit time from the source of release 3.15 normal operation situation when the equipment is operating within its designed parameters NOTE 1 Minor releases of flamma

44、ble material may be part of normal operation. For example, releases from seals which rely on wetting by the fluid which is being pumped are considered to be minor releases. NOTE 2 Failures (such as the breakdown of pump seals, flange gaskets or spillages caused by accidents) which involve urgent rep

45、air or shut-down are not considered to be part of normal operation nor are they considered to be catastrophic. NOTE 3 Normal operation includes start-up and shut-down conditions of the facility. - 15 - ANSI/ISA-60079-10-1 (12.24.01)-2014 3.16 ventilation movement of air and its replacement with fres

46、h air due to the effects of wind, temperature gradients, or artificial means (for example, fans or extractors) 3.17 lower explosive limit (LEL) concentration of flammable gas, vapor or mist in air below which an explosive gas atmosphere will not be formed IEV 426-02-09 NOTE The term “LEL” and the te

47、rm “LFL” are sometimes used interchangeably and are understood to be synonymous within the context of this document. For the purposes of area classification the lower value should be used. For example, the LEL for hydrogen is 9% yet the LFL is 4%. 3.18 upper explosive limit (UEL) concentration of fl

48、ammable gas, vapor or mist in air, above which an explosive gas atmosphere will not be formed IEV 426-02-10 NOTE The term “UEL” and the term “UFL” are sometimes used interchangeably and are understood to be synonymous within the context of this document. For the purposes of area classification the h

49、igher value should be used. For example, the UEL for methane is 15% yet the UFL is 17%. 3.19 relative density of a gas or a vapor density of a gas or a vapor relative to the density of air at the same pressure and at the same temperature (air is equal to 1,0) 3.20 flammable material (flammable substance) material which is flammable of itself, or is capable of producing a flammable gas, vapor or mist 3.21 flammable liquid liquid capable of producing a flammable vapor under any foreseeable operating conditions NOTE An example of a foreseeable operating con