1、 AMERICAN NATIONAL STANDARD ANSI/ISA-60079-2 (12.04.01)-2010 Supercedes ANSI/ISA-12.04.01-2004 (IEC 60079-2 Mod) Explosive Atmospheres Part 2: Equipment protection by pressurized enclosures “p” Approved 27 August 2010 ANSI/ISA-60079-2 (12.04.01)-2010 Explosive atmospheres - Part 2: Equipment protect
2、ion by pressurized enclosures “p“ ISBN: 978-1-936007-57-8 Copyright 2010 by the International Society of Automation (ISA). These materials are subject to copyright claims of IEC, ANSI, and ISA. All rights reserved. Not for resale. Printed in the United States of America. No part of this publication
3、may be reproduced in any form, including an electronic retrieval system without the prior written permission of the Publisher. All requests pertaining to this Standard should be submitted to ISA. ISA 67 Alexander Drive P.O. Box 12277 Research Triangle Park, North Carolina 27709 - 3 - ANSI/ISA-60079-
4、2 (12.04.01)-2010 Preface This preface, as well as all footnotes and annexes, is included for information purposes and is not part of ANSI/ISA-60079-2 (12.04.01)-2010. This document has been prepared as part of the service of ISA toward a goal of uniformity in the field of instrumentation. To be of
5、real value, this document should not be static but should be subject to periodic 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
6、, 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 the metric system of units in general, and the International System of Units (SI) in particular, in the preparation of instrume
7、ntation standards. The Department is further aware of the benefits to USA users 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-acc
8、eptable metric units in all new and revised standards, recommended practices, and 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 figures to be deleted are marked wi
9、th the overlay “X.“ There are ten annexes in this standard. Annexes B, C, D, F, H, I and J are informative and are not considered part of this standard. Annexes A, E and G are normative and are considered part of this standard. This page intentionally left blank. -13- ANSI/ISA-60079-2 (12.04.01)-201
10、0 INTRODUCTION This part of IEC 60079 standard gives requirements for the design, construction, testing and marking of electrical apparatus for use in potentially explosive atmospheres in which a) a protective gas maintained at a pressure above that of the external atmosphere is used to guard agains
11、t the formation of an explosive gas atmosphere within enclosures which do not contain an internal source of release of flammable gas or vapour and, where necessary; b) a protective gas is provided in sufficient quantity to ensure that the resultant mixture concentration around the electrical parts i
12、s maintained at a value outside the explosive limit appropriate to the particular conditions of use. The protective gas is supplied to an enclosure containing one or more internal sources of release in order to guard against the formation of an explosive gas atmosphere. This standard includes requir
13、ements for the apparatus and its associated equipment including the inlet and exhaust ducts, and also for the auxiliary control apparatus necessary to ensure that pressurization and/or dilution is established and maintained. This page intentionally left blank. -15- ANSI/ISA-60079-2 (12.04.01)-2010 1
14、 Scope This part of IEC 60079 standard contains the specific requirements for the construction and testing of electrical apparatus with pressurized enclosures, of type of protection “p”, intended for use in explosive gas atmospheres hazardous (classified) locations defined as Class I, Zone 1 or Zone
15、 2 by the National Electrical Code (NEC), ANSI/NFPA 70. It specifies requirements for pressurized enclosures containing a limited release of a flammable substance. This standard supplements and modifies the general requirements of IEC ANSI/ISA-60079-0. Where a requirement of this standard conflicts
16、with a requirement of IEC ANSI/ISA-60079-0, the requirements of this standard takes precedence. This standard does not contain the requirements for: pressurized enclosures where the containment system may release a) air with an oxygen content greater than normal, or b) oxygen in combination with ine
17、rt gas in a proportion greater than 21 %; pressurized rooms or analyser houses; see IEC 60079-13 and IEC 60079-16. NOTE 1 Due to the safety factors incorporated in the type of protection, the uncertainty of measurement inherent in good quality, regularly calibrated measurement equipment is considere
18、d to have no significant detrimental effect and need not be taken into account when making the measurements necessary to verify compliance of the equipment with the requirements of this standard. NOTE 2 When the user acts in the role of the manufacturer, it is typically the users responsibility to e
19、nsure that all relevant parts of this standard are applied to the manufacturing and testing of the equipment. NOTE 3 Types of protection “px” and “py” provide Equipment Protection Levels (EPL) Mb or Gb. Type of protection “pz” provides Equipment Protection Level (EPL) Gc. For further information, se
20、e Annex H. 2 Normative references The following 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 60034-5, Ro
21、tating electrical machines Part 5: Degrees of protection provided by the integral design of rotating electrical machines (IP code ) Classification IEC 60050(151), International Electrotechnical Vocabulary Chapter 151: Electrical and magnetic devices IEC 60050(426), International Electrotechnical Voc
22、abulary Chapter 426: Electrical apparatus for explosive atmospheres IEC ANSI/ISA-60079-0:2007, Electrical apparatus for explosive gas atmospheres Part 0: General requirements ANSI/ISA-60079-2 (12.04.01)-2010 -16- IEC 60112, Method for the determination of the proof and the comparative tracking indic
23、es of solid insulating materials IEC 60529, Degrees of protection provided by enclosures (IP Code) IEC 60664-1:1992, Insulation coordination for equipment within low-voltage systems Part 1: Principles, requirements and tests ANSI/NFPA 70 National Electrical Code 3 Terms and definitions For the purpo
24、ses of this document, the terms and definitions given in IEC 60050(151), IEC 60050(426) and IEC ANSI/ISA-60079-0, as well as the following apply. NOTE Unless otherwise specified, the terms “voltage“ and “current“ mean the r.m.s. values of an alternating, direct or composite voltage or current. 3.1 a
25、larm piece of apparatus that generates a visual or audible signal that is intended to attract attention 3.2 containment system part of the apparatus containing the flammable substance that may constitute an internal source of release 3.3 dilution continuous supply of a protective gas, after purging,
26、 at such a rate that the concentration of a flammable substance inside the pressurized enclosure is maintained at a value outside the explosive limits at any potential ignition source (that is to say, outside the dilution area) NOTE Dilution of oxygen by inert gas may result in a concentration of fl
27、ammable gas or vapour above the upper explosive limit (UEL). 3.4 dilution area area in the vicinity of an internal source of release where the concentration of a flammable substance is not diluted to a safe concentration 3.5 enclosure volume volume of the empty enclosure without internal apparatus.
28、For rotating electrical machines, the free internal volume plus the volume displaced by the rotor 3.6 flammable substance gases, vapours, liquids or mixtures thereof that are capable of being ignited -17- ANSI/ISA-60079-2 (12.04.01)-2010 3.7 hermetically sealed device device which is so constructed
29、that the external atmosphere cannot gain access to the interior and in which any seal is made by fusion, for example, brazing, welding or the fusion of glass to metal 3.8 ignition-capable apparatus (ICA) apparatus which in normal operation constitutes a source of ignition for a specified explosive g
30、as atmosphere. This includes electrical apparatus not protected by a type of protection listed in 7.13 3.9 indicator piece of apparatus that shows whether flow or pressure is adequate and is monitored periodically, consistent with the requirement of the application 3.10 internal source of release po
31、int or location from which a flammable substance in the form of a flammable gas or vapour or liquid may be released into the pressurized enclosure such that in the presence of air an explosive gas atmosphere could be formed 3.11 leakage compensation providing a flow of protective gas sufficient to c
32、ompensate for any leakage from the pressurized enclosure and its ducts 3.12 overpressure pressure above ambient pressure within a pressurized enclosure 3.13 pressurization technique of guarding against the ingress of the external atmosphere into an enclosure by maintaining a protective gas therein a
33、t a pressure above that of the external atmosphere 3.14 pressurization system grouping of safety devices and other components used to pressurize and monitor or control a pressurized enclosure 3.15 pressurized enclosure enclosure in which a protective gas is maintained at a pressure greater than that
34、 of the external atmosphere 3.16 protective gas air or inert gas used for purging and maintaining an overpressure and, if required, dilution NOTE For the purposes of this standard, inert gas means nitrogen, carbon dioxide, argon or any gas which, when mixed with oxygen in the ratio 4 parts inert to
35、1 part oxygen as found in air, does not make the ignition and flammability properties, such as explosive limits, more onerous. ANSI/ISA-60079-2 (12.04.01)-2010 -18- 3.17 protective gas supply compressor, blower or compressed gas container that provides the protective gas at a positive pressure. The
36、supply includes inlet (suction) pipes or ducts, pressure regulators, outlet pipes, ducts, and supply valves. Components of the pressurization system are not included 3.18 purging in a pressurized enclosure, the operation of passing a quantity of protective gas through the enclosure and ducts, so tha
37、t the concentration of the explosive gas atmosphere is brought to a safe level 3.19 routine test test to which each individual device (equipment) is subjected during or after manufacture to ascertain whether it complies with certain criteria IEV 151-04-16, modified 3.20 static pressurization mainten
38、ance of an overpressure within a pressurized enclosure without the addition of protective gas in a hazardous area 3.21 type px pressurization that reduces the classification (equipment protection level) within the pressurized enclosure from Zone 1 (Gb) to unclassified (non-hazardous) or Mb to non-ha
39、zardous 3.22 type py pressurization that reduces the classification (equipment protection level) within the pressurized enclosure from Zone 1 (Gb) to Zone 2 (Gc) 3.23 type pz pressurization that reduces the classification (equipment protection level) within the pressurized enclosure from Zone 2 (Gc)
40、 to unclassified (non-hazardous) unclassified (non-hazardous) 3.24 type test test of one or more devices made to a certain design to show that the design meets certain specifications IEV 151-04-15 3.25 safety device device used to implement or maintain the integrity of the type of protection -19- AN
41、SI/ISA-60079-2 (12.04.01)-2010 3.26 hazardous area an area in which an flammable gas atmosphere is or may be expected to be present in quantites such as to require special precautions for the construction, installation and use of electrical apparatus. (IEC 60050-426-03-01) NOTE The NEC uses “Hazardo
42、us (Classified) Location” to describe these areas. The definition for hazardous location is “a location in which fire or explosion hazards may exist due to an flammable atmosphere of flammable gases or vapors, flammable liquids, combustible dust, or easily ignitable fibers or flyings.” 3.27 non-haza
43、rdous area 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, installations and use of electrical apparatus. (IEC 60050-426-03-02) NOTE The NEC uses “unclassified” to describe these areas. 3.28 autoign
44、ition temperature the minimum temperature required to initiate or cause self-sustained combustion of a solid, liquid, or gas independently of the heating or heated element 3.29 protected equipment the electrical equipment internal to the protected enclosure. 4 Protection types Protection by pressuri
45、zation is subdivided into three types of protection (px, py and pz) which are selected based upon the external Zone classification (equipment protection level) required for the external explosive gas atmosphere (Mb, Gb or Gc), whether there is the potential for an internal release, and whether the e
46、quipment within the pressurized enclosure is ignition-capable; see Table 1. The type of protection then defines design criteria for the pressurized enclosure and the pressurization system; see Table 2. ANSI/ISA-60079-2 (12.04.01)-2010 -20- Table 1 Determination of protection type Flammable substance
47、 in the containment system External Zone classification (Equipment protection level requirement for external explosive gas atmosphere) Enclosure contains ignition-capable apparatusEnclosure does not contain ignition-capable apparatus No containment system Zone 1 (Gb) or Mb Type px aType py No contai
48、nment system Zone 2 (Gc) Type pz No pressurization required Gas/vapour Zone 1 (Gb) or Mb Type px a Type py Gas/vapour Zone 2 (Gc) Type px (and ignition-capable apparatus is not located in the dilution area) Type py bLiquid Zone 1 (Gb) Type px a(inert) c Type py Liquid Zone 2 (Gc) Type pz (inert)cNo
49、pressurization required dNOTE If the flammable substance is a liquid, normal release is never permitted. aType of protection px also applies to group I. bIf no normal release; see Annex E. cThe protective gas shall be inert if “(inert)“ is shown after the pressurization type; see Clause 13. dProtection by pressurization is not required since it is considered unlikely that a fault causing a release of liquid will simultaneously occur with a fault in the equipment that would provide an ignition source. -21- ANSI/ISA-60079-2 (12.04.01)-2010 Table 2 Design criteria b
