1、 AMERICAN NATIONAL STANDARD ANSI/ISA-60079-28 (12.21.02)-2013, Edition 1.1 Explosive Atmospheres Part 28: Protection of equipment and transmission systems using optical radiation Approved 21 August 2013 ANSI/ISA-60079-28 (12.21.02)-2013, Explosive Atmospheres Part 28: Protection of equipment and tra
2、nsmission systems using optical radiation, Edition 1.1 ISBN: 978-0-876640-40-1 Copyright 2013 by IEC and ISA. 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 m
3、echanical, 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-60079-28 (12.21.02)-2013 Preface This preface, as well as all footnotes and Informative annexes,
4、 is included for information purposes and is not part of ANSI/ISA-60079-28 (12.21.02)-2013. 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 real value, this document should not be static but should be subject to peri
5、odic 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: standards
6、isa.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 benefits to USA u
7、sers 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 practice
8、s, and technical reports to the greatest extent possible. Standard for Use of the International System of Units (SI): The Modern Metric Syst em, published by the American Society for Testing direct laser induced breakdown of the gas at the focus of a strong beam, producing plasma and a shock wave bo
9、th eventually acting as the ignition source. These processes can be supported by a solid material close to the breakdown point. NOTE 1 See items a) and d) of the introduction. This standard applies to optical fibre equipment and optical equipment, including LED and laser equipment, other than as det
10、ailed below: Non-array indicator LEDs used for example to show equipment status or backlight function. Luminaires involving light sources as follows: LED light sources for Gc and Dc applications. light sources, other than LED, that are continuous and divergent for all EPL applications. Optical radia
11、tion sources for Gc and Dc applications which comply with Class I limits in accordance with US Code of Federal Regulations, 21 CFR Part 1040. Optical radiation sources for Mb, Gb or Gc, and Db or Dc applications which comply with Class 1 limits in accordance with IEC 60825-1. NOTE 2 Class I limit ev
12、aluations in accordance with US Code of Federal Regulations, 21 CFR Part 1040 are based on normal operating conditions. Class 1 limit evaluations in accordance with IEC 60825-1 are based on normal operating and single fault conditions. This standard does not cover ignition by ultraviolet radiation a
13、nd by absorption of the radiation in the explosive mixture itself. Explosive absorbers or absorbers that contain their own oxidizer as well as catalytic absorbers are also outside the scope of this standard. This standard specifies requirements for equipment intended for use under atmospheric condit
14、ions. This standard supplements and modifies the general requirements of ANSI/ISA-IEC 60079-0. Where a requirement of this standard conflicts with a requirement of ANSI/ISA-IEC 60079-0, the requirement of this standard will take precedence. ANSI/ISA-60079-28 (12.21.02)-2013 - 12 - NOTE 32 Although o
15、ne should be aware of ignition mechanism b) and c) explained in the introduction, they are not addressed in this standard due to the very special situation with ultraviolet radiation and with the absorption properties of most gases (see Annex B). NOTE 43 Safety requirements to reduce human exposure
16、hazards from fibre optic communication systems are found in IEC 60825-2:2000. NOTE 64 Types of protection “op is“, “op pr“, and “op sh“ can provide equipment protection levels (EPL) Ga, Gb, or Gc. For further information, see Annex E. 2 Normative References The following referenced documents are ind
17、ispensable 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. ANSI/ISA-IEC 60079 (all parts), Electrical apparatus for explosive gas atmospheres ANSI/ISA
18、-IEC 60079-0, Electrical apparatus for explosive gas atmospheres Part 0: General requirements IEC 60079-10, Electrical apparatus for explosive gas atmospheres Part 10: Classification of hazardous areas ANSI/ISA-IEC 60079-11, Explosive atmospheres Part 11: Equipment protection by intrinsic safety “i“
19、 IEC 60825-1, Safety of Laser Products Part 1: Equipment Classification and Requirements IEC 60825-2, Safety of laser products Part 2: Safety of optical fibre communication systems IEC 61508 (all parts), Functional safety of electrical/electronic/programmable electronic safety-related systems IEC 61
20、511 (all parts), Functional safety Safety instrumented systems for the process industry sector ANSI/ISA-84.00.01 Part 1 (IEC 61511-1 Mod), Functional Safety: Safety Instrumented Systems for the Process Industry Sector - Part 1: Framework, Definitions, System, Hardware and Software Requirements ANSI/
21、ISA-84.00.01 Part 2 (IEC 61511-2 Mod), Functional Safety: Safety Instrumented Systems for the Process Industry Sector - Part 2: Guidelines for the Application of ANSI/ISA-84.00.01-2004 Part 1 (IEC 61511-1 Mod) Informative ANSI/ISA-84.00.01 Part 3 (IEC 61511-3 Mod), Functional Safety: Safety Instrume
22、nted Systems for the Process Industry Sector - Part 3: Guidance for the Determination of the Required Safety Integrity Levels - Informative NFPA 70, National Electrical Code (NEC) ANSI/UL 1651, Optical Fiber Cable - 13 - ANSI/ISA-60079-28 (12.21.02)-2013 US Code of Federal Regulations, 21 CFR Part 1
23、040, Performance standards for light-emitting products 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 IEC 60050-426 11. 3.1 abs
24、orption in a propagation medium, the conversion of electromagnetic wave energy into another form of energy, for instance heat IEV 731-03-14 3.2 beam diameter (or beam width) the distance between two diametrically opposed points where the irradiance is a specified fraction of the beams peak irradianc
25、e IEV 731-01-35 NOTE Most commonly applied to beams that are circular or nearly circular in cross section. 3.3 beam strength a general term used in this standard referring to an optical beams power, irradiance, energy, or radiant exposure 3.4 core the central region of an optical fibre through which
26、 most of the optical power is transmitted IEV 731-02-04 3.5 cladding that dielectric material of an optical fibre surrounding the core IEV 731-02-05 3.6 fibre bundle an assembly of unbuffered optical fibres IEV 731-04-09 1 Figures in square brackets refer to the bibliography. ANSI/ISA-60079-28 (12.2
27、1.02)-2013 - 14 - 3.7 fibre optic terminal device an assembly including one or more opto-electronic devices which converts an electrical signal into an optical signal, and/or vice versa, which is designed to be connected to at least one optical fibre IEV 731-06-44 NOTE A fibre optic terminal device
28、always has one or more integral fibre optic connector(s) or optical fibre pigtails(s). 3.8 inherently safe optical radiation visible or infrared radiation that is incapable of producing sufficient energy under normal or specified fault conditions to ignite a specific hazardous atmospheric mixture NO
29、TE This definition is analogous to the term “intrinsically safe” applied to electrical circuits. 3.9 irradiance the radiant power incident on an element of a surface divided by the area o f that element IEV 731-01-25 3.10 light (or visible radiation) any optical radiation capable of causing a visual
30、 sensation directly on a human being IEV 731-01-04 NOTE 1 Nominally covering the wavelength in vacuum range of 380 nm to 800 nm. NOTE 2 In the laser and optical communication fields, custom and practice in the English language have extended usage of the term light to include the much broader portion
31、 of the electromagnetic spectrum that can be handled by the basic optical techniques used for the visible spectrum. 3.11 minimum ignition energy MIE lowest electrical energy stored in a capacitor which upon discharge is sufficient to effect ignition of the most ignitable explosive atmosphere under s
32、pecified test conditions 3.12 optical fibre filament shaped optical waveguide made of dielectric materials IEV 731-02-01 3.13 optical fibre cable an assembly comprising one or more optical fibres or fibre bundles inside a common covering designed to protect them against mechanical stresses and other
33、 environmental influe nces while retaining the transmission qualities of the fibres IEV 731-04-01 - 15 - ANSI/ISA-60079-28 (12.21.02)-2013 3.14 optical fibre communication system OFCS engineered, end-to-end assembly for the generation, transference and reception of optical radiation arising from las
34、ers, LEDs or optical amplifiers, in which the transference is by means of optical fibre for communication and/or control purposes 3.15 free space optical communication system FSOCS an installed, portable, or temporarily mounted, through-the-air system typically used, intended or promoted for voice,
35、data or multimedia communications and/or control purposes via the use of modulated optical radiation produced by a laser or IR-LED. “Free space“ means indoor and outdoor optical wireless applications with both non-directed and directed transmission. Emitting and detecting assemblies may or may not b
36、e separated. NOTE The above definitions are from IEC TC 76. This standard is not only dealing with “communication systems”, so a more general definition could be useful. 3.16 optical (or radiant) power the time rate of flow of radiant energy with time IEV 731-01-22 3.17 optical radiation electromagn
37、etic radiation at wavelengths in vacuum between the region of transition to X -rays and the region of transition to radio waves, that is approximately bet ween 1 nm and 1 000 m IEV 731-01-03 NOTE In the context of this standard, the term “optical” refers to wavelengths ranging from 380 nm to 10 m. 3
38、.18 protected optical fibre cable optical fibre cable protected from releasing optical radiation into the atmosphere during normal operating conditions and foreseeable malfunctions by additional armouring, conduit, cable tray or raceway 3.19 radiant energy energy that is emitted, transmitted or rece
39、ived via electromagnetic waves IEV 731-01-21 3.20 radiant exposure the radiant energy incident on an element of a surface divided by the area of that element IEV 393-14-84, modified, and IEV 845-01-42, modified 2) 2 IEC 60050-393:2003, International Electrotechnical Vocabulary (IEV) Part 393: Nuclea
40、r instrumentation Physical phenomena and basic concepts ANSI/ISA-60079-28 (12.21.02)-2013 - 16 - 4 General requirements 4.1 Optical equipment All electrical parts and circuits inside and outside optical equipment shall comply with the appropriate standards for electrical apparatus. 4.2 Risk levels T
41、hree different equipment protection levels Ma/Ga/Da, Mb/Gb/Db, Gc/Dc are defined in ISA-60079-0 (also see Annex E). Table 1 shows the relationship between the EPL and the probability of an ignition source: Table 1 Relationship between EPL and the probability of an ignition source EPL Protection requ
42、ired Ma/Ga/Da Ignition not likely with one fault and two independent faults or in the case of rare malfunctions Mb/Gb/Db Ignition not likely with one fault or in the case of expected malfunctions Gc/Dc Ignition not likely in normal operation An ignition hazard assessment, as given in Annex C, has to
43、 be carried out to identify the ignition mechanisms and ignition sources caused by the specific working principle of the equipment using optical radiation. The types of protection selected from section 5 to protect the specific equipment depend on this ignition hazard assessment considering the tabl
44、e of ignition probabilities given above for the different EPLs. NOTE In IEC TC 31, the introduction of “equipment protection levels (EPL) Ga, Gb, Gc“ was decided. If, however, the optical radiation is confined inside an enclosure providing a protection of minimum IP 6X, after the tests specified in
45、IEC 60079-0 for enclosures, the ingress of absorbing targets from the outside of the enclosure need not to be taken into consideration. 5 Types of protection 5.1 General Three types of protection can be applied to prevent ignitions by optical radiation in potentially explosive atmospheres. These typ
46、es of protection encompass the entire optical system. These types of protection are a) inherently safe optical radiation, type of protection “op is”; b) protected optical radiation, type of protection “op pr”; and c) optical system with interlock, type of protection “op sh”. IEC 60050-845:1987, Inte
47、rnational Electrotechnical Vocabulary (IEV) Chapter 845: Lighting - 17 - ANSI/ISA-60079-28 (12.21.02)-2013 5.2 Requirements for inherently safe optical radiation “op is” 5.2.1 General Inherently safe optical radiation means visible or infrared radiation that is incapable of supplying sufficient ener
48、gy under normal or specified fault conditions to ignite a specific explosive atmosphere. The concept is a beam strength limitation approach to safety. Ignition by an optically irradiated target absorber requires the least amount of energy, power, or irradiance of the identified ignition mechanisms i
49、n the visible and infrared spectrum. The inherently safe concept applies to unconfined radiation and does not require maintaining an absorber -free environment. NOTE Research to date 17-22 has concluded the following values of visible and infrared beam strength are safe for explosive gas atmospheres. The safe values incorporate a modest safety factor on observed ignition values obtained under severe test conditions. Ignition of a carbon disulfide-air mixture has been reported recently using 24 m
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