इंटरनेट मानक Disclosure to Promote the Right To Information Whereas the Parliament of India has set out to provide a practical regime of right to information for citizens to secure access to information under the control of public authorities, in order to promote transparency and accountability in the working of every public authority, and whereas the attached publication of the Bureau of Indian Standards is of particular interest to the public, particularly disadvantaged communities and those engaged in the pursuit of education and knowledge, the attached public safety standard is made available to promote the timely dissemination of this information in an accurate manner to the public. “जान1 का अ+धकार, जी1 का अ+धकार” “प0रा1 को छोड न’ 5 तरफ” Mazdoor Kisan Shakti Sangathan Jawaharlal Nehru “The Right to Information, The Right to Live” “Step Out From the Old to the New” IS/IEC 60079-28 (2006): Electrical apparatus for explosive gas atmospheres, Part 28: Protection of Equipment and Transmission Systems Using Optical Radiation [ETD 22: Electrical Apparatus for Explosive Atmosphere] “!ान $ एक न’ भारत का +नम-ण” Satyanarayan Gangaram Pitroda ““IInnvveenntt aa NNeeww IInnddiiaa UUssiinngg KKnnoowwlleeddggee”” “!ान एक ऐसा खजाना > जो कभी च0राया नहB जा सकता हहहहै””ै” Bhartṛhari—Nītiśatakam “Knowledge is such a treasure which cannot be stolen” IS/IEC 60079-28 : 2006 Hkkjrh; ekud foLiQkVs h i;koZ j.k Hkkx 28 çdk'kh; fofdj.k }kjk miLdj ,oa Vªkalfe'ku ra=k dh lqj{kk Indian Standard EXPLOSIVE ATMOSPHERES PART 28 PROTECTION OF EQUIPMENT AND TRANSMISSION SYSTEMS USING OPTICAL RADIATION ICS 29.260.20 © BIS 2012 B U R E A U O F I N D I A N S T A N D A R D S MANAK BHAVAN, 9 BAHADUR SHAH ZAFAR MARG NEW DELHI 110002 November 2012 Price Group 11 Electrical Apparatus for Explosive Atmospheres Sectional Committee, ETD 22 NATIONAL FOREWORD This Indian Standard (Part 28) which is identical with IEC 60079-28 : 2006 ‘Explosive atmospheres — Part 28 Protection of equipment and transmission systems using optical radiation’ issued by the International Electrotechnical Commission (IEC) was adopted by the Bureau of Indian Standards on the recommendation of the Electrical Apparatus for Explosive Atmospheres Sectional Committee and approval of the Electrotechnical Division Council. The text of IEC Standard has been approved as suitable for publication as an Indian Standard without deviations. Certain conventions are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following: a) Wherever the words ‘International Standard’ appear referring to this standard, they should be read as ‘Indian Standard’. b) Comma (,) has been used as a decimal marker while in Indian Standards, the current practice is to use a point (.) as the decimal marker. In this adopted standard, references appear to certain International Standards for which Indian Standards also exist. The corresponding Indian Standards, which are to be substituted in their respective places are listed below along with their degree of equivalence for the editions indicated: International Standard Corresponding Indian Standard Degree of Equivalence IEC 60079 (All parts) Electrical IS/IEC 60079 (All parts) Electrical Identical for the apparatus for explosive gas apparatus for explosive gas editions adopted atmospheres atmospheres IEC 60079 - 0 Electrical apparatus IS/IEC 60079-0 : 2007 Explosive Identical to for explosive gas atmospheres — atmospheres: Part 0 Equipment — IEC 60079-0 : 2007 Part 0: General requirements General requirements (first revision) IEC 60079-10 Electrical apparatus IS 5572 : 2009 Classification of Modified for explosive gas atmospheres — hazardous areas (other than mines) Part 10: Classification of hazardous having flammable gases and vapours areas for electrical installation IEC 60079-11 Explosive IS/IEC 60079-11 : 2006 Explosive Identical to atmospheres — Part 11 : Equipment atmospheres: Part 11 Equipment IEC 60079-11 : 2006 protection by intrinsic safety “i” protection by intrinsic safety “i” IEC 61508 (All parts) Functional IS/IEC 61508 (All parts) Functional Identical for the safety of electrical/electronic/ safety of electrical/electronic/ editions adopted programmable electronic safety- programmable electronic safety- related systems related systems IEC 61511 (All parts) Functional IS/IEC 61511 (All parts) Functional Identical for the safety — Safety instrumented safety — Safety instrumented editions adopted systems for the process industry systems for the process industry sector sector The technical committee has reviewed the provision of the following International Standard referred in this adopted standard and has decided that it is acceptable for use in conjunction with this standard: International Standard Title IEC 60825-2 : 2000 Safety of laser products — Part 2: Safety of optical fibre communication systems (Continued on third cover) IS/IEC 60079-28 : 2006 INTRODUCTION Optical equipment in the form of lamps, lasers, LEDs, optical fibers, etc. is increasingly used for communications, surveying, sensing and measurement. In material processing, optical radiation of high irradiance is used. Often the installation is inside or close to potentially explosive atmospheres, and radiation from such equipment may pass through these atmospheres. Depending on the characteristics of the radiation it might then be able to ignite a surrounding explosive atmosphere. The presence or absence of an additional absorber significantly influences the ignition. There are four possible ignition mechanisms. a) Optical radiation is absorbed by surfaces or particles, causing them to heat up, and, under certain circumstances, this may allow them to attain a temperature which will ignite a surrounding explosive atmosphere. b) Thermal ignition of a gas volume, where the optical wavelength matches an absorption band of the gas. c) Photochemical ignition due to photo dissociation of oxygen molecules by radiation in the ultraviolet wavelength range. d) Direct laser induced breakdown of the gas at the focus of a strong beam, producing plasma and a shock wave both eventually acting as the ignition source. These processes can be supported by a solid material close to the breakdown point. The most likely case of ignition occurring in practice with lowest radiation power of ignition capability is case a). Under some conditions for pulsed radiation, case d) also will become relevant. Optical equipment is used in most cases in conjunction with electrical equipment, for which clear and detailed requirements and standards for use in potentially explosive atmospheres exist. One purpose of this standard is to inform industry about potential ignition hazards associated with the use of optical systems in hazardous locations as defined in IEC 60079-10 and the adequate protection methods. This standard details the integrated system used to control the ignition hazard from equipment using optical radiation in hazardous locations. i IS/IEC 60079-28 : 2006 Indian Standard EXPLOSIVE ATMOSPHERES PART 28 PROTECTION OF EQU IPMENT AND TRANSMISSION SYSTEMS USING OP TICAL RADIATION 1 Scope This part of IEC 60079 explains the potential ignition hazard from equipment using optical radiation intended for use in explosive gas atmospheres. It also covers equipment, which itself is located outside but its emitted optical radiation enters such atmospheres. It describes precautions and requirements to be taken when using optical radiation transmitting equipment in explosive gas atmospheres. It also outlines a test method, which can be used to verify a beam is not ignition capable under selected test conditions, if the optical limit values cannot be guaranteed by assessment or beam strength measurement. This standard contains requirements for optical radiation in the wavelength range from 380 nm to 10 µm. It covers the following ignition mechanisms: • optical radiation is absorbed by surfaces or particles, causing them to heat up and, under certain circumstances, this may allow them to attain a temperature which will ignite a surrounding explosive atmosphere; • direct laser induced breakdown of the gas at the focus of a strong beam, producing plasma and a shock wave both 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 does not cover ignition by ultraviolet radiation and 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 conditions. This standard supplements and modifies the general requirements of IEC 60079-0. Where a requirement of this standard conflicts with a requirement of IEC 60079-0, the requirement of this standard willll take precedence. NOTE 2 Although one 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 3 Safety requirements to reduce human exposure hazards from fibre optic communication systems are found in IEC 60825-2:2000. NOTE 4 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. 1 IS/IEC 60079-28 : 2006 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 60079 (all parts), Electrical apparatus for explosive gas atmospheres 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 IEC 60079-11, Explosive atmospheres – Part 11: Equipment protection by intrinsic safety "i" 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 61511 (all parts), Functional safety – Safety instrumented systems for the process industry sector 3 Terms and definitions For the purposes of this document, the terms and definitions given in IEC IEC 60079-0 and the following apply. NOTE Additional definitions applicable to explosive atmospheres can be found in IEC 60050-426 [1]1. 3.1 absorption 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 beam’s peak irradiance [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 beam’s power, irradiance, energy, or radiant exposure ————————— 1 Figures in square brackets refer to the bibliography. 2 IS/IEC 60079-28 : 2006 3.4 core the central region of an optical fibre through which 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] 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 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 NOTE 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 of that element [IEV 731-01-25] 3.10 light (or visible radiation) any optical radiation capable of causing a visual 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 of the electromagnetic spectrum that can be handled by the basic optical techniques used for the visible spectrum. 3