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GB/T 3836.22-2017 consists of the following parts under the general title of “Explosive atmospheres”:
——Part 1: Equipment - General requirements;
——Part 2: Equipment protection by flameproof enclosures “d”;
——Part 3: Equipment protection by increased safety “e”;
——Part 4: Equipment protection by intrinsic safety "i";
——Part 5: Equipment protection by pressurized enclosure “p”;
——Part 6: Equipment protection by oil immersion “o”;
——Part 7: Equipment protection by powder filling “q”;
——Part 8: Equipment protection by type of protection “n”;
——Part 9: Equipment protection by type of protection “m”;
——Part 11: Material characteristics for gas and vapour classification - Test methods and data;
——Part 13: Equipment repair, overhaul and reclamation;
——Part 14: Classification of areas - Explosive gas atmosphere;
——Part 15: Electrical installations design, selection and erection;
——Part 16: Electrical installations inspection and maintenance;
——Part 17: Construction and use of rooms or buildings protected by pressurization;
——Part 18: Intrinsically safe electrical systems;
——Part 19: Fieldbus intrinsically safe concept (FISCO);
——Part 20: Equipment with equipment protection level (EPL) Ga;
——Part 21: Application of quality systems for equipment manufacture;
——Part 22: Protection of equipment and transmission system using optical radiation;
——Part 23: Group I, Category EPL Ma equipment intended to remain functional in atmospheres endangered by firedamp and/or coal dust.
...
This part is Part 22 of “Explosive atmospheres”.
This part is developed in accordance with the rules given in GB/T 1.1-2009.
This part has been redrafted and modified in relation to IEC 60079-28: 2006 (First Edition) Explosive atmospheres - Part 28: Protection of equipment and transmission systems using optical radiation.
Technical deviations between this part and IEC 60079-28: 2006 are as follows:
——Adjustment has been made to "Normative References" of this part due to technical deviations so as to meet the technical specification in China; the adjustment situations are embodied in a concentrated way in clause 2 "Normative References" and the specific adjustments are as follows:
? IEC 60079-0 is replaced by GB 3836.1-2010 which is modified in relation to the international standard;
? IEC 60079-10 is replaced by GB 3836.14-2014 which is identical to the international standard;
? IEC 60079-11 is replaced by GB 3836.4.-2010 which is modified in relation to the international standard;
? IEC 60825-2 is replaced by IEC 60825-2: 2010;
? IEC 60079 (all parts) is replaced by GB 3836 (all parts), IEC 61508 (all parts) is replaced by GB/T 20438 (all parts), and IEC 61511 (all parts) is replaced by GB/T 21109 (all parts); see Annex E for the degree of consistency among all parts;
——The Annex E “Introduction of an alternative risk assessment method encompassing “equipment protection levels” for Ex equipment” has been deleted.
The following editorial changes have been made in this part:
——The standard name has been modified.
This part was proposed by the China Electrical Equipment Industrial Association.
This part is under the jurisdiction of SAC/TC 9 National Technical Committee on Explosion Protected Electrical Apparatus of Standardization Administration of China.
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 part is to inform industry about potential ignition hazards associated with the use of optical systems in hazardous locations as defined in GB 3836.14-2014 and the adequate protection methods.
This part details the integrated system used to control the ignition hazard from equipment using optical radiation in hazardous locations.
Explosive atmospheres -
Part 22: Protection of equipment and transmission system using optical radiation
1 Scope
This part of “Explosive atmospheres” explains the potential ignition hazard from equipment using optical radiation intended for use in explosive gas 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 part also covers equipment, which itself is located outside but its emitted optical radiation enters such atmospheres.
This part 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 part 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 part.
This part specifies requirements for equipment intended for use under atmospheric conditions.
This part supplements and modifies the general requirements of GB 3836.1-2010.
Note 2: Although one shall be aware of ignition mechanism b) and c) explained in the introduction, they are not addressed in this part 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: 2010.
Note 4: Types of protection "op is", "op pr", and "op sh" can provide equipment protection levels (EPL) Ga, Gb, or Gc.
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.
GB 3836 (all parts) Explosive environment [IEC 60079 (all parts)]
GB 3836.1-2010 Explosive atmospheres - Part 1: Equipment - General requirements (IEC 60079-0: 2007, MOD)
GB 3836.4-2010 Explosive atmospheres - Part 4: Equipment protection by intrinsic safety “i” (IEC 60079-11: 2006, MOD)
GB 3836.14-2014 Explosive atmospheres - Part 14: Classification of areas - Explosive gas atmosphere (IEC 60079-10-1: 2008, IDT)
GB/T 20438 (all parts) Functional safety of electrical/electronic/programmable electronic safety-related systems [IEC 61508 (all parts)]
GB/T 21109 (all parts) Functional safety - Safety instrumented systems for the process industry sector.
IEC 60825-2: 2010 Safety of laser products - Part 2: Safety of optical fibre communication systems
3 Terms and definitions
For the purposes of this document, the terms and definitions given in GB 3836.1-2010 and the following apply.
Note: Additional definitions applicable to explosive atmospheres can be found in GB/T 2900.35-2008.
3.1
absorption
in a propagation medium, the conversion of electromagnetic wave energy into another form of energy, for instance heat
3.2
beam diameter (or beam width)
distance between two diametrically opposed points where the irradiance is a specified fraction of the beam’s peak irradiance
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 part referring to an optical beam’s power, irradiance, energy, or radiant exposure
3.4
core
central region of an optical fibre through which most of the optical power is transmitted
3.5
cladding
that dielectric material of an optical fibre surrounding the core
3.6
fibre bundle
an assembly of unbuffered optical fibres
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
Note: A fibre optic terminal device always has one or more integral fibre optic connector(s) or optical fibre pigtail(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
3.9
irradiance
radiant power incident on an element of a surface divided by the area of that element
3.10
light (or visible radiation)
any optical radiation capable of causing a visual sensation directly on a human being
Notes:
1 Nominally covering the wavelength in vacuum range of 380 nm to 800 nm.
2 In the laser and optical communication fields, the term light includes the much broader portion 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 specified test conditions
3.12
optical fibre
filament shaped optical waveguide made of dielectric materials
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 environmental influences while retaining the transmission qualities of the fibres
Foreword i
Introduction iv
1 Scope
2 Normative references
3 Terms and definitions
4 General requirements
5 Types of protection
6 Type verifications and tests
7 Marking
Annex A (Normative) Reference test data
Annex B (Informative) Ignition mechanisms
Annex C (Normative) Ignition hazard assessment
Annex D (Informative) Typical optical fibre cable structure
Annex E (Informative) Degree of consistency between each part of normative references and that of international standard
Bibliography
