标准编号:	GB/T 3836.35-2021
中文名称:	爆炸性环境 第35部分：爆炸性粉尘环境场所分类
英文名称:	Explosive atmospheres—Part 35：Classification of areas for explosive dust atmospheres
中标分类:	K35    防爆电器
行业分类:	GB    国家标准
ICS分类:	29.260.20 29.260.20    易爆环境用电气设备 29.260.20
发布机构:	国家市场监督管理总局 国家标准化管理委员会
发布日期:	2021-10-11
实施日期:	2022-5-1
标准状态:	现行
替代旧标准:	GB/T 12476.3-2017 可燃性粉尘环境用电气设备 第3部分：存在或可能存在可燃性粉尘的场所分类
翻译语言:	英文
文件格式:	PDF
中文字符数:	23000 字
翻译价格(元):	1510.00 元
交付时间:	付款后 1 个工作日

Codeofchina.com is in charge of this English translation. In case of any doubt about the English translation, the Chinese original shall be considered authoritative.



This document is drafted in accordance with the rules given in the GB/T 1.1-2020 Directives for Standardization — Part 1: Rules for the Structure and Drafting of Standardizing Documents.



This part is Part 8 of GB/T 3836 Explosive Atmospheres. The following parts of GB/T 3836 have been published:



— 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 12: Material Characteristics for Combustible Dusts — Test Methods;



— 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: Equipment Protection by Pressurized Room “p” and Artificially Ventilated Room “v”;



— Part 18: Intrinsically Safe Electrical Systems;



— 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



— Part 24: Equipment Protection by Special Protection “s”;



— Part 25: Requirements for Process Sealing between Flammable Process Fluids and Electrical Systems;



— Part 26: Electrostatic Hazards — Guidance;



— Part 27: Electrostatic Hazards — Test;



— Part 28: Non-electrical Equipment for Potentially Explosive Atmospheres — Basic Method and Requirements;



— Part 29: Non-electrical Equipment for Explosive Atmospheres — Constructional Safety “c”, Control of Ignition Source “b”, Liquid Immersion “k;



— Part 30: Equipment and Components in Explosive Atmospheres in Underground Mines;



— Part 31: Equipment Dust Ignition Protection by Enclosure “t”;



— Part 32: Intrinsically Safe Systems with Electronically Controlled Spark Duration Limitation;



— Part 33: Equipment in Adverse Service Conditions;



— Part 34: Equipment Assemblies;



— Part 35: Classification of Areas for Explosive Dust Atmospheres;



This document replaces GB/T 12476.3-2017 Electrical Apparatus for Use in the Presence of Combustible Dust — Part 3: Classification of Areas Where Combustible Dusts Are or May Be Present in whole, and the following technical deviations have been made with respect to the GB/T 12476.3-2017:



— dust cloud density and concentration are added as the factors for consideration of release (see 4.1);



— the requirement for competence of personnel is added (see 4.3);



— the requirement for “dust layers to be raised to form a dust cloud must be taken into consideration” is added (see Clause 7);



— EPL is added in documentation (see 8.1).



This document has been redrafted and modified adoption of International Standard IEC 60079-10-2:2015 Explosive Atmospheres — Part 10-2: Classification of Areas — Combustible Dust Atmospheres.



For the purposes of this document, the following structural adjustments have also been made:



— Annex A corresponds to Annex C of IEC 60079-10-2:2015, Annex B corresponds to Annex A of IEC 60079-10-2:2015, and Annex C corresponds to Annex B of IEC 60079-10-2:2015.



The technical deviations between this document and the International Standard IEC 60079-10-2:2015, together with their justifications, are given below:



— The adjustments on technical deviations have been made for the normative references of this document to adapt to the technical conditions in China, which are mainly reflected in Clause 2 "Normative References”, with the following specific content:



 IEC 60079-0 is replaced by GB/T 3836.1 which is modified in relation to the international standard (see Clause 3);



 IEC 60079-10-1 and ISO/IEC 80079-20-2 are deleted, and the corresponding documents GB 3836.14 and GB/T 3836.12 are moved to the Bibliography.



For the purposes of this document, the following editorial changes have also been made:



— In order to be consistent with the current standard series, the name of this document is modified to Explosive Atmospheres — Part 35: Classification of Areas for Explosive Dust Atmospheres;

— a paragraph on ISO and IEC terminology maintenance addresses is added in Clause 3;



— the incorrect reference of sub-clause number in Note 1 of 3.9 is deleted;



— the note on competence of personnel is delete from 4.3.



Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. The issuing body of this document shall not be held responsible for identifying any or all such patent rights.



This standard was proposed by China Electrical Equipment Industry Association.



This document is under the jurisdiction of National Technical Committee 9 on Explosion Protected Electrical Apparatus of Standardization Administration of China (SAC/TC 9).



The previous editions of this document and documents replaced by this document are as follows:



— The first edition was issued in 2007 as GB 12476.3-2007;



— The first edition was revised in 2017 as GB/T 12476.3-2017;



— This is the second revised edition, and the entire texts of GB/T 3836 were amalgamated.

 

Introduction



GB/T 3836 Explosive Atmospheres is prepared in order to establish the basic technical requirements for equipment used in explosive atmospheres and its application, covering the design, manufacture, inspection, selection, installation, inspection, maintenance, repair and site classification of equipment used in explosive atmospheres, and adopts the form of partial standards, including but not limited to the following parts:



— 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 12: Material Characteristics for Combustible Dusts — Test Methods;



— 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: Equipment Protection by Pressurized Room “p” and Artificially Ventilated Room “v”;



— Part 18: Intrinsically Safe Electrical Systems;

— 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



— Part 24: Equipment Protection by Special Protection “s”;



— Part 25: Requirements for Process Sealing between Flammable Process Fluids and Electrical Systems;



— Part 26: Electrostatic Hazards — Guidance;



— Part 27: Electrostatic Hazards — Test;



— Part 28: Non-electrical Equipment for Potentially Explosive Atmospheres — Basic Method and Requirements;



— Part 29: Non-electrical Equipment for Explosive Atmospheres — Constructional Safety “c”, Control of Ignition Source “b”, Liquid Immersion “k;



— Part 30: Equipment and Components in Explosive Atmospheres in Underground Mines;



— Part 31: Equipment Dust Ignition Protection by Enclosure “t”;



— Part 32: Intrinsically Safe Systems with Electronically Controlled Spark Duration Limitation;



— Part 33: Equipment in Adverse Service Conditions;



— Part 34: Equipment Assemblies;



— Part 35: Classification of Areas for Explosive Dust Atmospheres;



The classification of areas for explosive dust atmospheres can provide guidance and basis for the selection and implementation of equipment and various explosion-proof measures. In terms of the standardization of this technology, GB 12476.3-2007 on the classification of areas for explosive dust atmospheres was prepared by modified adoption of IEC 61241-10 in 2007. Subsequently, it was revised as GB/T 12476.3-2017 on the base of IEC 60079-10-2 in 2017. Since the release and implementation of the standard, there has been a certain new development in the technology and methods of classification of areas for explosive dust atmospheres. In terms of international standards, the current edition of the corresponding standard is IEC 60079-10-2:2015, and its main technical contents may also be applied to China. At present, GB 12476 in China is also being revised and the entire texts of GB/T 3836 are amalgamated. In order to adapt to the development of technology and be consistent with the development of international standards, and coordinate with the revision of Chinese standard series, it is necessary to revise GB/T 12476.3 and amalgamate the entire texts of GB/T 3836.



Based on the main technical content of IEC 60079-10-2:2015, appropriate modifications have been made in this revision to adapt to the specific situation in China.



The following information is useful when using this document.



Dusts, as defined in this document, are hazardous because when they are dispersed in air by any means they may form potentially explosive atmospheres. Furthermore, layers of dust may ignite and act as ignition sources for an explosive atmosphere.



This document gives guidance on the identification and classification of areas where such hazards from dust can arise. It sets out the essential criteria against which the ignition hazards can be assessed and gives guidance on the design and control parameters which can be used in order to reduce such a hazard. General and special criteria, along with examples, are given for the process of identification and classification of hazardous areas.





Explosive Atmospheres — Part 35: Classification of Areas for Explosive Dust Atmospheres



1 Scope



This document specifies the identification and classification of areas where explosive dust atmospheres and combustible dust layers are present, in order to permit the proper assessment of ignition sources in such areas.



In this document, explosive dust atmospheres and combustible dust layers are treated separately. In Clause 4, area classification for explosive dusts clouds is described, with dust layers acting as one of the possible sources of release. In Clause 7, ignition hazards for dust layers are described.



The examples in this document are based on a system of effective housekeeping being implemented in the plant to prevent dust layers from accumulating. Where effective housekeeping is not present, the area classification includes the possible formation of explosive dust clouds from dust layers.



The principles of this document can also be followed when combustible fibres or flyings might cause a hazard.



This document is intended to be applied where there can be a risk due to the presence of explosive dust atmospheres or combustible dust layers under normal atmospheric conditions (see Note 1).



Note 1: Atmospheric conditions include variations in pressure and temperature above and below reference levels of 101.3 kPa and 20°C, provided that the variations have a negligible effect on the explosive properties of the combustible materials.



This document is not applicable to:



— underground mining areas;



— dusts of explosives that do not require atmospheric oxygen for combustion such as pyrophoric substances, propellants, pyrotechnics, munitions, peroxides, oxidizers, water-reactive elements or compounds, or other similar materials;



— catastrophic failures which are beyond the concept of abnormality dealt with in this document;

— any risk arising from an emission of toxic gas from the dust.



This document is not applicable to where a hazard might arise due to the presence of flammable gas or vapour, but the principles may be used in the assessment of a hybrid mixture (see also GB 3836.14).



Note 2: Additional guidance on hybrid mixtures is provided in Annex A.



This document does not take into account the effects of consequential damage following a fire or an explosion.



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/T 3836.1 Explosive Atmospheres — Part 1: Equipment — General Requirements (GB 3836.1-2021, IEC 60079-0:2017, MOD)



3 Terms and Definitions



For the purposes of this document, the terms and definitions given in GB/T 3836.1 and the following apply.



ISO and IEC maintain terminological databases for use in standardization at the following addresses:



— IEC: http://www.electropedia.org/;



— ISO: http://www.iso.org/obp.



Note: Additional definitions applicable to explosive atmospheres can be found in GB/T 2900.35.



3.1

area

three-dimensional region or space



3.2

hybrid mixture

mixture of a flammable gas or vapour with a dust



 

3.3

dust

generic term including both combustible dust and combustible flyings



3.4

combustible dust

finely divided solid particles, 500 μm or less in nominal size, which may form an explosive mixture with air at atmospheric pressure and normal temperatures

Note 1: This includes dust and grit as defined in HJ 492.

Note 2: The term solid particles is intended to address particles in the solid phase and not the gaseous or liquid phase, but does not preclude a hollow particle.

Note 3: Materials passing a U.S. No. 40 Standard sieve as defined in ASTM E 11-04 are considered to meet the 500 μm criterion.

Note 4: Combustible dust test methods can be found in GB/T 3836.12.



3.5

explosive dust atmosphere

mixture with air, under atmospheric conditions, of flammable substances in the form of dust, which, after ignition, permits self-sustaining propagation



3.6

conductive dust

combustible dust with electrical resistivity equal to or less than 103Ω·m

Note: Conductive dust is classified as Group IIIC.



3.7

non-conductive dust

combustible dust with electrical resistivity greater than 103Ω·m

Note: Non-conductive dust is classified as Group IIIB.



3.8

combustible flyings

solid particles including fibers, greater than 500 μm in nominal size, which may form an explosive mixture with air at atmospheric pressure and normal temperatures

Note 1: Examples of flyings include rayon, cotton (including cotton linters and cotton waste) sisal, jute, hemp, cocoa fiber, okum and waste kapok.

Note 2: Combustible flyings are classified as Group IIIA.



3.9

hazardous area (dust)

area in which combustible dust, in the form of a cloud is present, or may be expected to be present, in quantities such as to require special precautions for the construction, installation and use of equipment

Note 1: Hazardous areas are divided into zones based upon the frequency and duration of the occurrence of explosive dust atmospheres (see 6.2).

Note 2: The potential of creating an explosive dust cloud from a dust layer also needs to be considered.



3.10

non-hazardous area (dust)

area in which combustible dust in the form of a cloud is not expected to be present in quantities such as to require special precautions for the construction, installation and use of equipment



3.11

dust containment

process equipment housing which is intended to handle, process, transport or store materials inside of it, while minimizing the risk of the release of dust to the surrounding atmosphere



3.12

source of dust release

point or location from which dust may be released into the atmosphere

Note: The source of dust release can be from a dust containment or from a dust layer.



3.13

continuous grade of release

release which is continuous or is expected to occur frequently or for long periods



3.14

continuous formation of a dust cloud

locations in which a dust cloud may exist continuously, or may be expected to continue for long periods or for short periods which occur frequently



3.15

primary grade of release

release which can be expected to occur periodically or occasionally during normal operation



3.16

secondary grade of release

release which is not expected to occur in normal operation and, if it does occur, is likely to do so only infrequently and for short periods



3.17

extent of zone

distance in any direction from the edge of a source of release to the point where the hazard associated with the release is considered to exist no longer



3.18

normal operation

operation of equipment conforming electrically and mechanically with its design specification and used within the limits specified by the manufacturer

Note: Minor releases of dust which may form a cloud or layer (e.g. releases from filters) can be part of normal operation.



3.19

abnormal operation

process-linked malfunctions that occur infrequently



3.20

catastrophic failure

occurrence which exceeds the design parameters of the process plant and control system resulting in major release of flammable material

Note: Catastrophic failure in this context is applied, for example, to the rupture of a storage silo or a pneumatic conveyor.



3.21

equipment (for explosive atmospheres)

general term including apparatus, fittings, devices, components, and the like used as a part of, or in connection with, an installation in an explosive atmosphere



3.22

ignition temperature of a dust layer

lowest temperature of a surface at which ignition occurs in a dust on the surface

Note: The ignition temperature of a dust layer may be determined by the test method given in GB/T 3836.12.



3.23

ignition temperature of a dust cloud

lowest temperature of the hot inner wall of a furnace at which ignition occurs in a dust cloud in air contained therein

Note: The ignition temperature of a dust cloud may be determined by the test method given in GB/T 3836.12.



3.24

verification dossier

set of documents showing the compliance of electrical equipment and installations

Note: Requirements for a ‘verification dossier’ are given in GB/T 3836.15.



3.25

zones



3.25.1

Zone 20

a place in which an explosive dust atmosphere, in the form of a cloud of dust in air, is present continuously, or for long periods or frequently



3.25.2

Zone 21

a place in which an explosive dust atmosphere, in the form of a cloud of dust in air, is likely to occur in normal operation occasionally



3.25.3

Zone 22

area in which an explosive dust atmosphere, in the form of a cloud of combustible dust in air, is not likely to occur in normal operation but, if it does occur, will persist for a short period only

Note: The potential of creating an explosive dust cloud from a dust layer also needs to be considered.



4 Area Classification



4.1 General



This document adopts the concept, similar to that used for flammable gases and vapour, of using area classification to give an assessment of the likelihood of an explosive dust atmosphere occurring.



Dusts form explosive atmospheres only at concentrations within the explosion range. Although a cloud with a very high concentration may not be explosive, the danger nevertheless exists that, should the concentration fall, it may enter the explosive range. Depending on the circumstances, not every source of release will necessarily produce an explosive dust atmosphere. Dust clouds are also rarely of uniform density and consideration should be given to possible variances in concentration within a cloud for any condition or release.



Dusts that are not removed by mechanical extraction or ventilation, settle out at a rate depending on properties, such as particle size, into layers or accumulations. It shall be taken into account that a dilute or small continuous source of release, in time, is able to produce a potentially hazardous dust layer.



The hazards presented by dusts are as follows:



— the formation of a dust cloud from any source of release, including a layer or accumulation, to form an explosive dust atmosphere (see Clause 5);



— the formation of dust layers, which are not likely to form a dust cloud, but may ignite due to self-heating or exposure to hot surfaces or thermal flux and cause a fire hazard or over- heating of equipment. The ignited layer may also act as an ignition source for an explosive atmosphere.



Since explosive dust clouds and dust layers may exist, any source of ignition should be avoided.



If the source of ignition cannot be avoided, then measures shall be taken to reduce the likelihood of dust and/or ignition sources so that the likelihood of coincidence is so small as to make the risk negligible.



Note: In some cases, where the risk of explosion cannot be completely avoided, it can be necessary to employ some form of explosion protection such as explosion venting, explosion suppression or explosion isolation.



Subsequent to the completion of the area classification, a risk assessment may be carried out to assess whether the consequences of ignition of an explosive atmosphere requires the use of equipment of a higher equipment protection level (EPL) or may justify the use of equipment with a lower equipment protection level than normally required.



In this document, explosive dust atmospheres and dust layers are treated separately. In this clause, area classification for explosive dust clouds is described, with dust layers acting as one of the possible sources of release. Considerations for dust layers are described in Clause 7.

Foreword II
Introduction VI
1 Scope
2 Normative References
3 Terms and Definitions
4 Area Classification
4.1 General
4.2 Area classification procedure for explosive dust atmospheres
4.3 Competence of personnel
5 Sources of Release
5.1 General
5.2 Dust containment
5.3 Identification and grading of sources of release
6 Zones
6.1 General
6.2 Extent of zones
7 Dust Layers
8 Documentation
8.1 General
8.2 Drawings, data sheets and tables
Annex A (Informative) Hybrid Mixtures
Annex B (Informative) Area Classification Examples
Annex C (Informative) Housekeeping
Bibliography

爆炸性环境
第35部分：爆炸性粉尘环境场所分类
1 范围
本文件规定了存在爆炸性粉尘环境及可能出现可燃性粉尘层的场所识别和场所分类，以便对出现在这些场所的点燃源进行适当的评定。
在本文件中，对爆炸性粉尘环境和可燃性粉尘层区别对待。第4章描述了爆炸性粉尘云的场所分类，而粉尘层则作为可能的释放源之一。第7章对粉尘层的点燃危险进行了描述。
本文件采取以工厂清理防止粉尘层积聚为基础的有效现场清理。如果不进行有效的现场清理，场所分类将包括粉尘层可能形成的爆炸性粉尘云。
对可燃性纤维或可燃性飞絮可能引起危险的场所，也可遵循本文件的原则。
本文件适用于在正常大气条件下，由于爆炸性粉尘环境或可燃性粉尘层的存在而可能引起危险的场所(见注1)。
注1：大气条件包括高于或低于基准的101.3kPa和20℃的压力和温度变化，前提是这些变化对可燃性材料爆炸特性的影响可忽略不计时。
本文件不适用于：
——煤矿井下场所；
——不需大气中的氧燃烧的自燃物质，如发火物质、推进剂、烟火、弹药、过氧化物、氧化剂、水反应性元素或化合物，或其他类似材料；
——超出本文件涉及的异常灾难性事故；
——随粉尘喷出的有毒气体引起的危险。
本文件不适用于由于存在可燃性气体或蒸气而可能产生危险的场所，但该原则可用于评估杂混物(另见GB 3836.14)。
注2：关于杂混物的补充指南见附录A。
本文件未考虑继火灾或爆炸之后的损害而产生的影响。
2 规范性引用文件
下列文件中的内容通过文中的规范性引用而构成本文件必不可少的条款。其中，注日期的引用文件，仅该日期对应的版本适用于本文件；不注日期的引用文件，其最新版本(包括所有的修改单)适用于本文件。
GB/T 3836.1 爆炸性环境 第1部分：设备 通用要求(GB/T 3836.1—2021，IEC 60079-0：2017，MOD)
3 术语和定义
GB/T 3836.1界定的以及下列术语和定义适用于本文件。
ISO和IEC在以下地址维护用于标准化的术语数据库：
——IEC：http：//www.electropedia.org/；
——ISO：http：//www.iso.org/obp。
注：爆炸性环境适用的其他术语和定义见GB/T 2900.35。
3.1
场所 area
三维的区域或空间。
3.2
杂混物 hybrid mixture
可燃性气体或蒸气与可燃性粉尘的混合物。
3.3
粉尘 dust
包括可燃性粉尘和可燃性飞絮的通称。
3.4
可燃性粉尘 combustible dust
标称尺寸500μm及以下，在标准大气压力和温度下可能与空气形成爆炸性混合物的微小固体颗粒。
注1：该术语包括HJ 492中定义的粉尘和尘粒。
注2：术语“固体颗粒”是用来说明固态和非气态或非液态中的颗粒，但不排除空心颗粒。
注3：通过ASTM E 11-04中定义的美国40号标准筛的材料被认为满足500μm标准。
注4：可燃粉尘测试方法可在GB/T 3836.12中找到。
3.5
爆炸性粉尘环境 explosive dust atmosphere
在大气条件下，可燃性物质以粉尘、纤维或飞絮的形式与空气形成的混合物，被点燃后，能够保持燃烧自行传播的环境。
3.6
导电性粉尘 conductive dust
电阻率等于或小于103Ω·m的可燃性粉尘。
注：导电粉尘属于Ⅲ C类。
3.7
非导电性粉尘 non-conductive dust
电阻率大于103Ω·m的可燃性粉尘。
注：非导电粉尘属于Ⅲ B类。
3.8
可燃性飞絮 combustible flyings
标称尺寸大于500μm，在标准大气压力和温度下可能与空气形成爆炸性混合物的固体颗粒，包括纤维。
注1：例如，人造纤维、棉花纤维(包括棉绒和棉纱头)、剑麻纤维、黄麻纤维、大麻纤维、椰壳纤维、麻絮、包装用的废木棉。
注2：可燃性飞絮属于Ⅲ A类。
3.9
危险场所(粉尘) hazardous area (dust)
可燃性粉尘以粉尘云的形式大量出现或预期可能大量出现，以致要求对设备的结构、安装和使用采取专门预防措施的场所。
注1：根据爆炸性粉尘环境出现的频次和持续时间的长短对危险场所进行分区(见6.2)。
注2：由粉尘层形成的粉尘云的潜在危险也需考虑。
3.10
非危险场所(粉尘) non-hazardous area (dust)
可燃性粉尘以粉尘云的形式预期不会大量出现，以致不要求对设备的结构、安装和使用采取专门预防措施的场所。
3.11
粉尘集尘器 dust containment
用于处理、加工、输送或存储物料时防止可燃性粉尘泄露到周围环境中的工艺装置。
3.12
粉尘释放源 source of dust release
能向大气环境中释放可燃性粉尘的地点或部位。
注：粉尘释放源可能来自粉尘集尘器或粉尘层。
3.13
连续级释放 continuous grade of release
连续释放或预计经常出现或长时间出现的释放。
3.14
连续形成粉尘云 continuous formation of a dust cloud
粉尘云可能连续存在，或者预期可能会持续长时间或短时间频繁发生的位置。
3.15
1级释放 primary grade of release
正常运行时预计定期释放或偶尔出现的释放。
3.16
2级释放 secondary grade of release
正常运行时，预计不可能出现释放，如果出现，也仅是不经常且是短时间出现的释放。
3.17
区域范围 extent of zone
从释放源边缘到不再出现危险释放的地点之间任何方向的距离。
3.18
正常运行 normal operation
设备在电气上和机械上符合设计规范并在制造商规定的限制范围内使用的运行状况。
注：可形成粉尘云或粉尘层的一些少量的粉尘释放(如过滤器的释放)可视为正常运行。
3.19
异常运行 abnormal operation
很少发生的工艺关联故障。
3.20
灾难性故障 catastrophic failure
超过工艺装置和控制系统的设计参数，导致可燃性材料的严重释放的事件。
注：文中的灾难性故障应用于例如储料仓或气动输送机的破裂。
3.21
(爆炸性环境用)设备 equipment (for explosive atmospheres)
爆炸性环境中作为电气装置的部件或与其有关的包括仪器、附件、组件、元件的总称。
3.22
粉尘层的点燃温度 ignition temperature of a dust layer
在规定的试验条件下，粉尘层在热表面上发生点燃时，热表面的最低温度。
注：粉尘层的点燃温度可根据GB/T 3836.12规定的试验方法测定。
3.23
粉尘云的点燃温度 ignition temperature of a dust cloud
在规定的试验条件下，最易点燃的粉尘空气混合物在热表面上被点燃时，热表面的最低温度。
注：粉尘云的点燃温度可根据GB/T 3836.12规定的试验方法测定。
3.24
验证档案 verification dossier
显示电气设备和装置符合性的成套文件。
注：对“验证档案”的要求见GB/T 3836.15。
3.25
区域 zones
3.25.1
20区 Zone 20
爆炸性粉尘环境以粉尘云的形式在空气中连续或长时间存在或频繁出现的场所。
3.25.2
21区 Zone 21
正常运行时，爆炸性粉尘环境以粉尘云的形式在空气中可能出现的场所。
3.25.3
22区 Zone 22
正常运行时，爆炸性粉尘环境以粉尘云的形式在空气中不可能出现，如果出现也仅是短时间存在的场所。
注：还需要考虑从粉尘层产生爆炸性粉尘云的可能性。
4 场所分类
4.1 通则
本文件采用了与可燃性气体和蒸气相似的场所分类原理，对可能出现的爆炸粉尘环境进行评定。
粉尘只有在某个浓度范围内才能形成爆炸性环境。虽然高浓度粉尘云可能不会爆炸，但仍然存在危险，如果浓度下降，就可能进入爆炸范围。根据环境，不是每个释放源一定会形成爆炸性粉尘环境。粉尘云也很少具有均匀的密度，宜考虑任何条件或释放时粉尘云内浓度的可能差异。
不能由抽气式机械通风方法移除的粉尘，根据其特性，如颗粒的大小，会以一定的速率沉积而形成粉尘层或堆积物。应考虑稀释的或小的连续释放源最终能形成潜在的危险粉尘层。
粉尘出现导致如下危险：
——释放源形成粉尘云，包括粉尘层或粉尘堆积物形成的爆炸性粉尘环境(见第5章)。
——不可能形成粉尘云的粉尘层，但可能由于自加热或热表面或热流而出现点燃，并引起火灾危险或设备过热。对爆炸性环境来说，自燃的粉尘层也是点燃源。
由于爆炸性粉尘云和可燃性粉尘层可能存在，因此宜避免点燃源的出现。
如果无法避免点燃源，则应采取措施减少粉尘和/或点燃源的可能性，以使重合的可能性很小，使风险可以忽略不计。
注：在某些情况下，如果不能完全避免爆炸的危险，可能需要采用某种形式的防爆揩施，如泄爆、抑爆或隔爆。
在场所分类完成之后可进行危险评定，评定随后的危险场所是否要求更高设备保护级别(EPL)的设备，或者证明使用比通常要求更低的设备保护级别(EPL)的设备可行。
在本文件中，对爆炸性粉尘环境和粉尘层将区别对待。在本章中，描述了爆炸性粉尘云的场所分类，同时把粉尘层作为可能的释放源之一。在第7章中，描述了粉尘层的点燃危险。
4.2 爆炸性粉尘环境场所的分 类程序
场所分类是基于多种因素考虑的，可能需要引入大量的信息源并进行分析，这些因素包括：
——粉尘是否具有可燃性。粉尘的可燃特性可按照GB/T 3836.12的规定在试验室通过试验确定。
——相关的粉尘的材料特性。这些可以从各种公开来源、工艺专家或通过测试获得。从公开来源获得的特征宜针对特定应用进行验证，因为从一个数据源到另一个数据源的粉尘特征值通常存在显著变化。
——特定装置的释放特性，可能要求这方面相关的专业技术知识。
——设备的操作和维护方式，包括现场清理。
——其他设备和安全信息。
安全和设备方面的专家需要密切合作。尽管区域的定义仅涉及粉尘云的危险，但应考虑被搅扰的粉尘层可形成粉尘云。确定危险区域的程序如下：
a) 第一步是确定材料是否具有可燃性。为了评定点燃源，应确定材料特性，如颗粒大小、含水量、粉尘云和粉尘层的最低点燃温度、电阻率和适当的爆炸性粉尘环境用设备类别，Ⅲ A类用于可燃性飞絮环境，Ⅲ B类用于非导电性粉尘环境，Ⅲ C类用于导电性粉尘环境。
注：有关粉尘特性的信息见GB/T 3836.12。
b) 第二步是确定可能出现在粉尘集尘器的位置或粉尘释放源的位置，见第5章。应查阅工艺流程图和设备布局图。这个步骤宜包括确认如第7章所述的可能形成的粉尘层。
c) 第三步是确定粉尘从上述释放源释放的可能性，不同部位爆炸性粉尘环境出现可能性的识别见5.3。
只有在这些步骤进行后才能确定区域及其范围。关于区域类型和范围及出现粉尘层的决定通常应形成文件，并记录在场所分类图上，这些文件将作为随后对点燃源进行评定的基础。
做出决定的理由应记录在场所分类的研究记录中，使得将来场所分类评定时易于理解。应按照工艺的变化或处理物料的变化，或如果因设备的损坏使粉尘排放变得更加普遍的情况对场所分类进行审核。预计按照装置或工艺的用途进行审核和随后的定期审核。
因本文件涉及各种情况，因此不可能对每一种情况所需的措施逐一给出明确的规定。重要的是，本程序应由了解场所分类原则、物料特性、关联的设备以及设备功能的人员来进行。
4.3 人员能力
区域分类应由有能力并了解粉尘特性的相关性和重要性的人员、熟悉工艺过程和设备的人员，以及安全、电气、机械和其他合格的工程人员进行。
5 释放源
5.1 通则
爆炸性粉尘环境由粉尘释放源形成。粉尘释放源是指能释放或产生可燃性粉尘的地点或部位，从而形成爆炸性粉尘环境。该定义包括能够扩散形成粉尘云的可燃性粉尘层。
根据不同情况，不是每个释放源一定会产生爆炸性粉尘环境。另一方面，一个稀释的或小的连续释放源最终能形成潜在的危险粉尘层。
需确定到底是哪些加工设备中的条件，哪些加工过程中的条件或装置中预计的其他动作条件可形成爆炸性粉尘环境或形成粉尘层。粉尘集尘器内外的条件应分别考虑。
5.2 粉尘集尘器
在粉尘集尘器内部，粉尘不会释放到外部环境，但是，当它作为加工的一个部分时，在集尘器内可连续形成粉尘云。这些粉尘云可连续出现或预计长时间或短时间连续存在，其出现的频率取决于加工周期。应研究设备的正常运行、启动和停机时的异常运行状况，以便能确定粉尘云和粉尘层的形成，这些研究结果应包括在验证档案中。在厚的粉尘层形成的地方，这些宜引起注意(见第7章对粉尘层的要求)。
5.3 释放源识别及其释放等级
在粉尘积尘器外部，许多因素可能影响场所的分类。如果在粉尘积尘器(例如：正压气动传送装置)内采用高于大气压的压力，粉尘就很容易从泄漏设备中喷出。粉尘积尘器内为负压情况下，在设备外部形成粉尘危险场所的可能性就非常低。适用时，粉尘颗粒大小、湿度、传送速度、排尘速度和飘落高度都可能影响潜在的释放速率。一旦已知有潜在的释放工艺过程，就应识别释放源并确定其释放等级。
释放等级如下：
——连续级释放：
连续存在或预计可长时间连续存在或短时间频繁出现的释放。例如：经常填充和清空的混合容器或储存筒仓的内部。
——1级释放：
预计可定期出现或正常运行中偶尔出现的释放。例如：毗邻敞口袋灌包或倒包的位置周围。
——2级释放：
预计正常运行时不会出现，如果出现，也是偶尔出现或短时间出现的释放。例如：出现粉尘沉淀的粉尘处理装置。
重大的或灾难性的设备故障在评定潜在释放时不需要考虑，例如下列各项不宜被视为正常和异常运行的释放源：
——外壳主体结构有封闭的喷嘴和人孔的压力容器；
——无接合面的管道、导管和通风道；
——阀压盖和法兰接合面，只要在设计和结构，上对防粉尘泄露给予了适当的考虑。
6 区域
6.1 通则
按照爆炸性粉尘环境出现的频率和持续时间，被分类的爆炸性粉尘环境场所划分为几个区。区域划分的示例见附录B。粉尘层、沉积物和粉尘堆应被视为可能形成爆炸性粉尘环境的“任何其他来源”。
6.2 区域范围
6.2.1 总则
爆炸性粉尘环境的区域范围定义为粉尘释放源的边缘到被认为与该区域有关的危险不再存在的任何方向上的距离。
如果粉尘浓度有一个适当的安全裕度，该裕度小于爆炸性粉尘环境形成要求的最小粉尘浓度，则由粉尘云形成的爆炸性粉尘环境通常认为不存在。宜考虑细粉尘因建筑物内空气流动而从释放源向上扩散的实际情况。
当对已分类场所之间的小范围未分类场所进行分类时，该分类宜延伸至整个场所。对于位于建筑物外(露天)的21区和22区，由于风、雨等天气影响，区域可能会发生变化。对于室外区域，区域的边界宜提供这种差异。
注：虽然自然通风(风)可能导致稀释到爆炸极限以下(因此减小了区域的范围)，但它也可能导致对任何现有粉尘层的干扰(从而增大区域的范围)。
6.2.2 20区