Explosive atmospheres - Part 22: Protection of equipment and transmission system using optical radiation English
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
GB/T 3836.22-2017 The following standards are cited：
