1、 AMERICAN NATIONAL STANDARD ANSI/ISA-60079-26 (12.00.03)-2011 Supersedes ANSI/ISA-60079-26 (12.00.03)-2008 Explosive atmospheres - Part 26: Equipment for Use in Class I, Zone 0 Hazardous (Classified) Locations Approved 11 July 2011 ANSI/ISA-60079-26 (12.00.03)-2011 Explosive atmospheres - Part 26: E
2、quipment for Use in Class I, Zone 0 Hazardous (Classified) Locations ISBN: 978-1-936007-98-1 Copyright 2011 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
3、 by any means (electronic mechanical, photocopying, recording, or otherwise), 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-60079-26 (12.00.03)-2011 Preface This preface, as well as all footnote
4、s and annexes, is included for information purposes and is not part of ANSI/ISA-60079-26 (12.00.03)-2011. This document has been prepared as part of the service of ISA towards a goal of uniformity in the field of instrumentation. To be of real value, this document should not be static but should be
5、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, NC 27709; Telephone (919) 549-8411; Fax (919) 549-8288; E-m
6、ail: 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 instrumentation standards. The Department is further aware of the ben
7、efits 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-acceptable metric units in all new and revised standards, recomm
8、ended 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 requirements of a partition wall combined with an air-gap with natural ventilation; introduction
9、 of equipment protection levels (EPL) and substitution of the references to zones to corralte with the NEC. change of heading from “Mechanical connection” to “Process connection” together with a clarification of requirement for any release from zone 0 of explosive gas atmospheres. This page intentio
10、nally left blank. - 11 - ANSI/ISA-60079-26 (12.00.03)-2011 1 Scope This part of IEC 60079 standard specifies the particular requirements for construction, test and marking for electrical equipment that provides equipment protection level (EPL) Ga of Group II intended for use in Class I, Zone 0 as de
11、fined in the National Electrical Code, ANSI/NFPA 70. This electrical equipment, within the operational parameters specified by the manufacturer, ensures a very high level of protection that includes rare faults related to the equipment or two faults occurring independently of each other. NOTE 1 A ma
12、lfunction may result from a failure of the component parts of the electrical equipment or from anticipated externally applied influences. Two independent malfunctions which may occur more frequently and which, separately, would not create an ignition hazard but which, in combination, could create a
13、potential ignition hazard, should be regarded as occurring together to form a rare fault. Note 2 This electrical equipment is intended for use in Class I, Zone 0 hazardous areas, in which explosive gas atmospheres caused by mixtures of air and gases, vapours or mists under normal atmospheric conditi
14、ons are present continuously, for long periods or frequently. This standard also applies to equipment mounted across the boundary where different protection levels may be required. EXAMPLE: In the wall of a storage vessel containing zone 0 with an ambient defined as zone 1. This standard also applie
15、s to equipment installed in an area requiring a lower protection level, outside Class I, Zone 0, but electrically connected to equipment protection level (EPL) Ga inside Class I, Zone 0 (associated apparatus). This standard supplements the general requirements in IEC 60079-0 ANSI/ISA-60079-0 and the
16、 requirements of the standardized types of protection, in accordance with the IEC 60079 series, to adapt the level of safety provided by those standards in order to provide EPL Ga. NOTE 3 In designing equipment for operation in explosive gas atmospheres under conditions other than the atmospheric co
17、nditions given in IEC 60079-0 ANSI/ISA-60079-0, this standard may be used as a guide. However, additional testing is recommended related specifically to the intended conditions of use. This is particularly important when the types of protection Flameproof enclosure (IEC 60079-1 ANSI/ISA-60079-1) and
18、 Intrinsic safety (IEC 60079-11 ANSI/ISA-60079-11) are applied. NOTE 4 The classification of hazardous areas in zones is defined in IEC 60079-10 the National Electrical Code. NOTE 5 There may be other non-electrical sources of ignition (for example ultrasonic, optical or ionizing radiation) that are
19、 not addressed by this standard; these should also be taken into consideration (see, for example, EN 1127-1). NOTE 6 This concept provides equipment protection level (EPL) Ga. For further information, see Annex A ANSI/ISA-60079-0. 2 Normative references The following referenced documents are indispe
20、nsable 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 60079-0: Electrical apparatus for explosive gas atmospheres Part 0: General requirements AN
21、SI/ISA-60079-0 (12.00.01), Explosive atmospheres - Part 0: Equipment- General Requirements ANSI/ISA-60079-26 (12.00.03)-2011 - 12 - IEC 60079-1: Electrical apparatus for explosive gas atmospheres Part 1: Flameproof enclosures “d“ ANSI/ISA-60079-1 (12.22.01), Explosive Atmospheres - Part 1: Equipment
22、 Protection by Flameproof Enclosures “d” IEC 60079-10: Electrical apparatus for explosive gas atmospheres Part 10: Classification of hazardous areas ANSI/NFPA 70, National Electrical Code, IEC 60079-11, Electrical apparatus for explosive gas atmospheres Part 11: Intrinsic safety “i” ANSI/ISA-60079-1
23、1 (12.02.01), Explosive Atmospheres - Part 11: Equipment Protection by intrinsic safety “i” IEC 60079-14, Electrical apparatus for explosive gas atmospheres Part 14: Electrical installations in hazardous areas (other than mines) IEC 60079-18: Electrical apparatus for explosive gas atmospheres Part 1
24、8: Construction, test, and marking of type of protection encapsulation “m”electrical apparatus ANSI/ISA-60079-18, Electrical Apparatus for Use in Class I, Zone 1 Hazardous (Classified) Locations: Type of Protection Encapsulation “m” IEC 60695-11-10, Fire hazard testing Part 11-10: Test flames 50 W h
25、orizontal and vertical flame test methods ANSI/UL 94, Tests for Flammability of Plastic Materials for Parts in Devices and Appliances 3 Terms and definitions For the purposes of this document, the terms and definitions given in IEC 60079-0 ANSI/ISA-60079-0 and the following apply. NOTE Additional de
26、finitions applicable to explosive atmospheres can be found in IEC 60050-426. 3.1 EPL abbreviation of equipment protection level as defined in Annex A. 3.2 Class I, Zone 1 types of protection protection measures for electrical equipment for use in Class I, Zone 1 in accordance with the National Elect
27、rical Code. - 13 - ANSI/ISA-60079-26 (12.00.03)-2011 4 Requirements for design and construction 4.1 General The equipment shall comply with the requirements of 4.2 for the electrical circuits and with the requirements of 4.3 to 4.6 for mechanical and electrostatic ignition hazards. 4.2 Protection me
28、asures against ignition hazards of the electrical circuits 4.2.1 General The equipment shall comply with the requirements of either: a) 4.2.2 or 4.2.3 in the event of two faults occurring independently of each other in a single equipment means of protection; or b) 4.2.4 or 4.2.5 in the event of a fa
29、ilure of one equipment means of protection, by the provision of a second independent means of protection. Electrical connections and permanently connected cables of the equipment sited within EPL Ga equipment shall comply with the same level of protection required by this standard, e.g. an Ex “e” ca
30、ble additionally protected by a flameproof conduit or an Ex “e” cable provided with an earth leakage protection. NOTE 1 Detailed cable and installation requirements for non-intrinsically safe circuits in Zone 0 are given in IEC 60079-14. NOTE 2 Because of ignition hazards which can arise from faults
31、 and/or transient circulating currents in the potential equalization system, galvanic isolation in the power and signal connections to the equipment according to 4.2.2, 4.2.3 and 4.2.4 is preferred. Consideration should also be given to minimize the effect of transient fault currents in the potentia
32、l equalization network by the use of electrical protection equipment such as sensitive earth leakage monitors. 4.2.2 Intrinsic safety as a sole means of protection Intrinsically safe electrical equipment providing EPL Ga located in Class I, Zone 0 and intrinsically safe electrical circuits of associ
33、ated apparatus entering an area requiring EPL Ga Class I, Zone 0 shall comply with the requirements of IEC 60079-11 ANSI/ISA-60079-11, intrinsic safety “ia”. NOTE Intrinsic safety “ib” in accordance with IEC 60079-11 may be considered as one of two independent means of protection according to 4.2.4.
34、 4.2.3 Encapsulation as a sole means of protection Electrical equipment which is protected by encapsulation providing EPL Ga in Zone 0 shall comply with the requirements of IEC 60079-18 ANSI/ISA-60079-18, encapsulation “ma”. NOTE Encapsulation “mb” in accordance with IEC 60079-18 may be considered a
35、s one of two independent means of protection according to 4.2.4. 4.2.4 Application of two independent types of protection providing EPL Gb Electrical equipment shall comply with the requirements of two independent types of protection that provide EPL Gb. If one type of protection fails, the other ty
36、pe of protection shall continue to function. The independent types of protection shall not have a common mode of failure except as specified in this clause. ANSI/ISA-60079-26 (12.00.03)-2011 - 14 - An example of a common mode failure is if an Ex “d” enclosure with arcing contacts inside it is used i
37、nside an Ex “e” enclosure. If the Ex “d” enclosure is compromised, then arcing inside the enclosure will also compromise the Ex “e” enclosure. NOTE Combined types of protection providing EPL Gb should depend on different physical protection principles. For example the combination of Ex “d” and Ex “q
38、” both depend on the avoidance of flame propagation and may not be useful in combination. In practice, some combinations may not be useful, for example the combination of oil and powder filling. Where combined types of protection are used, it shall be possible for each type of protection to be teste
39、d individually (see 5.1). Both types of protection shall be assessed using the most arduous fault condition of the other type of protection. When combining intrinsic safety, type of protection “ib”, with other types of protection, the second type of protection shall be assessed, with the most arduou
40、s fault condition applied to the intrinsically safe circuit. When using two types of protection, which rely both on the same parameter (for example, the creepage distance combining Ex “ib” with Ex “e”), the most stringent requirement of both types of protection shall be applied. If two types of prot
41、ection are combined which both rely on the enclosure, one of the following shall be met: a) if two enclosures are used (one totally enclosed within the other), each enclosure shall comply with the requirements of the respective type of protection; or b) if only one enclosure is used, the enclosure a
42、nd the cable entries shall meet the impact test requirements of 26.4.2 of IEC 60079-0, using the Group I values. Examples of combinations of two independent types of protection are as follows: inductive transmitters (for example proximity switches, electrical position sensors) with intrinsic safety
43、“ib” enclosed by encapsulation “mb”. The connections to intrinsically safe “ib” circuits can be protected by the increased safety “e”; a lamp with the bulb designed as increased safety “e”, the lamp circuit with the switch as intrinsic safety “ib”. These components may be incorporated in a flameproo
44、f enclosure “d”; measuring transducers with intrinsic safety “ib” and a flameproof enclosure “d”; equipment with electrical circuits of intrinsic safety “ib”, additionally protected by a powder filling “q”; electromagnetic valves with encapsulation “mb”, enclosed by a flameproof enclosure “d”; incre
45、ased safety “e”, with pressurized equipment “px”. 4.2.5 Application of a type of protection providing EPL Gb Class I, Zone 1 type of protection and a separation element 4.2.5.1 General Equipment which is mounted through or forming part of the boundary wall to an area requiring EPL Ga Class I, Zone 0
46、 and containing electrical circuits which do not comply with protection level Ga the requirements of intrinsic safety “ia” or encapsulation “ma” shall comply at least with one of the types of protection providing EPL Gb Class I, Zone 1 types of protection. Additionally, they shall contain a mechanic
47、al separation element as part of the equipment to seal off the electrical circuits of the equipment from the area requiring EPL Ga Class I, Zone 0. - 15 - ANSI/ISA-60079-26 (12.00.03)-2011 If the type of protection fails, the separation element shall a) prevent flame propagation through the equipmen
48、t into the area requiring EPL Ga into Class I, Zone 0, b) maintain its safety characteristics, c) not be heated above the temperature class of the equipment. Separation elements consist of a partition wall, possibly combined with a flameproof joint or an air gap with natural ventilation. 4.2.5.2 Par
49、tition walls Partition walls shall be constructed of either a) corrosion resistant metals, glass or ceramics, which are specified in the manufacturers documentation; or b) other materials as long as the same level of safety can be demonstrated. In this case, X-marking or advisory marking in accordance with item 29.2 of IEC 60079-0 shall be applied, and the certificate For partition walls, the manufacturers instructions shall clearly specify the material and its thermal and mechanical properties to enable the user to confirm the suitability f
