GB/T 25285.1-2021 PDF English
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Explosive atmospheres - Explosion prevention and protection - Part 1: Basic concepts and methodology
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GB/T 25285.1-2021: Explosive atmospheres - Explosion prevention and protection - Part 1: Basic concepts and methodology
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GB
NATIONAL STANDARD OF THE
PEOPLE’S REPUBLIC OF CHINA
ICS 29.260.20
CCS K 35
Replacing GB 25285.1-2010
Explosive atmospheres - Explosion prevention and
protection - Part 1.Basic concepts and methodology
Issued on. OCTOBER 11, 2021
Implemented on. MAY 01, 2022
Issued by. State Administration for Market Regulation.
Standardization Administration of PRC.
Table of Contents
Foreword... 4
Introduction... 6
1 Scope... 7
2 Normative references... 8
3 Terms and definitions... 9
4 Risk assessment... 15
5 Possible ignition sources... 21
6 Risk reduction... 29
7 Usage information... 52
Appendix A (Informative) Equipment tightness... 54
Appendix B (Informative) Relationship between equipment protection level (EPL) and
zones... 57
Appendix C (Normative) Tools for explosive atmospheres... 58
Appendix D (Normative) Verification procedure for ultrasonic threshold limits in
liquids... 59
References... 61
1 Scope
This document specifies methods for identifying and assessing hazardous situations that
may lead to explosions, as well as design and structural measures that are consistent
with safety requirements, through the following aspects.
- Risk assessment;
- Risk reduction.
Safety of equipment, protective systems, components can be achieved, by eliminating
hazards and/or limiting risks, i.e., by.
a) Proper design (no safety protection devices);
b) Safety protection devices;
c) Usage information;
d) Any other precautionary measures.
Explosion protection measures corresponding to a) (prevention) and b) (protection) are
covered in Chapter 6.Explosion protection measures corresponding to c) are covered
in Chapter 7.The explosion protection measures corresponding to d) are not covered in
this document. They are covered in GB/T 15706 (Chapter 6 in GB/T 15706-2012).
The preventive and protective measures, which are specified in this document, can only
provide the required level of protection, when the equipment, protective systems and
components are operated within the scope of their intended use and are installed and
maintained in accordance with the corresponding operating procedures or requirements.
This document specifies general design and manufacturing methods, to help designers
and manufacturers achieve explosion-proof safety, when designing equipment,
protective systems, components.
This document applies to any equipment, protective systems, components, which are
intended to be used in explosive atmospheres under atmospheric conditions. These
environments may be caused by flammable substances that are handled, used or
released by equipment, protective systems, components, OR by flammable substances
around equipment, protective systems and components and/or by the constituted
materials from which equipment, protective systems, components.
This document applies to equipment, protective systems, components at all stages of
use.
This document applies to category II and category III equipment, which is used in other
places except coal mine equipment. For equipment requirements in underground areas
of coal mines and coal mine surface facilities, that are dangerous due to gas and/or
combustible coal powder, see GB/T 25285.2.
This document does not apply to.
- Medical equipment for medical environments;
- Equipment, protective systems, components used in explosion hazard locations, as
caused entirely by the presence of explosive substances or unstable chemicals;
- Equipment, protective systems, components in places where explosions are caused
by the reaction of substances with oxidants other than oxygen in the atmosphere,
OR where explosions are caused by other dangerous reactions or non-atmospheric
conditions.
2 Normative references
The contents of the following documents constitute essential provisions of this
document through normative references in the text. Among them, for dated reference
documents, only the version corresponding to the date applies to this document; for
undated reference documents, the latest version (including all amendments) applies to
this document.
GB/T 2900.35 Electrotechnical terminology - Equipment for explosive atmospheres
GB/T 3836.15 Explosive atmospheres - Part 15.Electrical installations design,
selection and erection
GB/T 3836.28 Explosive atmospheres - Part 28.Non-electrical equipment for
explosive atmospheres - Basic method and requirements
GB/T 15706 Safety of machinery - General principles for design - Risk assessment
and risk reduction
EN 15198 Methodology for the risk assessment of non-electrical equipment and
components for intended use in potentially explosive atmospheres
3 Terms and definitions
The terms and definitions, as defined in GB/T 2900.35, as well as the following terms
and definitions, apply to this document.
3.1
Flammable substance
A substance in gas, vapor, liquid, solid form, or a mixture of these forms, that reacts
exothermically with air when ignited.
3.2
Component
Devices, that are essential to the safety functions of equipment and protective
systems but have no independent function.
3.3
Deflagration
An explosion, that travels at subsonic speeds.
3.4
Detonation
An explosion, that travels at supersonic speeds and has the characteristics of a shock
wave.
3.5
Equipment
Machinery, equipment, fixed or mobile devices, control units, instruments, detection
or prevention systems, which are used alone or in combination, for the generation,
transmission, storage, measurement, control, conversion and/or material processing
of energy, AND which can cause explosions due to their own potential ignition
sources.
4 Risk assessment
4.1 General
For non-electrical equipment, components, protective systems, devices and their
combinations, if they themselves have potential ignition sources and are expected to be
used in explosive atmospheres, a risk assessment shall be carried out in accordance with
GB/T 3836.28.
4.2 Identification of explosion hazard
4.2.1 General
Explosion hazards are often associated with materials and substances that are handled,
used or released by equipment, protective systems, components, as well as with the
materials from which equipment, protective systems, components are made. Some of
these released substances undergo a combustion process in the air.
4.2.2 Combustion characteristics
Since the material itself is not used here, but the contact or mixing of dust and air is
used to illustrate potential hazards; therefore, it shall determine the characteristics of
the mixture of flammable substances and air.
4.2.3 Explosion characteristics
The characteristics of explosive atmospheres after ignition shall be described using the
following data.
4.2.4 Possibility of hazardous explosive atmospheres
The possibility of a hazardous explosive atmosphere occurring depends on the
following.
4.3 Identification of ignition hazard
4.3.1 General
First, it shall be determined which types of ignition sources are possible and which are
associated with the equipment (or components, protective systems).
4.3.2 Ignition characteristics
The ignition characteristics of hazardous explosive atmospheres shall be determined.
Relevant data such as.
4.3.3 Possibility of effective ignition source
Potential ignition sources shall be classified, according to their likelihood of becoming
an effective source of ignition, as follows.
4.4 Estimating the possible effects of an explosion
In order to estimate the possible effects of an explosion, the following factors need to
be considered, such as.
5 Possible ignition sources
5.1 Hot surfaces
If an explosive atmosphere comes into contact with a heated surface, ignition may occur.
Not only the hot surface itself can become an ignition source, but also the dust layer
and combustible solids that are in contact with or ignited by the hot surface can become
an ignition source in explosive atmospheres (see 5.2).
5.2 Flames and hot gases (including hot particles)
Combustion reactions at temperatures above 1000 °C are usually accompanied by
flames. Hot gases are the products of the reaction; in dusty and/or soot-laden flames,
5.3 Impact, friction, grinding caused by machinery
As a result of friction, impact or abrasive processes such as grinding, particles can be
produced that are separated from the solid material and heated by the application of
energy during the separation process. If these particles contain oxidizable substances,
such as iron or steel, they can undergo oxidation processes, that reach higher
temperatures.
5.4 Electrical equipment and components
Sparks and hot surfaces (see 5.1) of electrical equipment and components can become
sources of ignition. Sparks and hot surfaces can be generated under the following
conditions.
5.5 Stray current and cathode anti-corrosion measures
Stray currents may occur in conductive systems or conductive parts of systems for the
following reasons.
currents and cathodic corrosion.
6 Risk reduction
6.1 Basic principles
Based on the necessity of the simultaneous existence of a dangerous explosive
atmosphere and an effective ignition source, as well as the expected effects of
explosions described in Chapter 4, the basic principles of explosion prevention and
explosion protection are derived directly in the following order.
6.2 Avoid explosive atmospheres or reduce the amount of hazardous
explosive atmospheres
6.2.1 Process parameters
6.2.1.1 Replace or reduce the amount of substances capable of creating an
explosive atmosphere
6.2.1.2 Limit concentration
If it is unavoidable to handle substances that can form an explosive atmosphere,
measures can be taken to control the amount and/or concentration of flammable
substances, to prevent or limit the amount of hazardous explosive atmospheres within
equipment, protective systems, components.
6.2.2.3 Ventilation and dilution
Ventilation is important to control the effects of releases of flammable gases and vapors.
It can be used inside and outside equipment, protective systems, components.
Note. GB 3836.14 provides relevant content on the use of ventilation, to control and classify
gas and vapor hazardous locations.
6.3 Hazardous locations
6.3.1 General
Hazardous locations may depend on the design and use of certain equipment, protective
systems, components. They shall be taken into account, when planning the design and
specified uses (see GB 3836.14 and GB/T 12476.3).
6.7 Principles of measurement and control systems for explosion prevention and protection
GB/T 16855.1 covers general principles in this field.
7 Usage information
7.1 General
This Chapter specifies information on use and maintenance, which shall be provided
with the equipment, protective systems, components, OR as part of the instructions for
use (e.g., user manual).
7.3 Qualifications and training
Information on qualifications and training needs shall be provided, to enable users to
select competent staff for operations, in locations where explosive atmospheres may
occur.
......
Source: Above contents are excerpted from the full-copy PDF -- translated/reviewed by: www.ChineseStandard.net / Wayne Zheng et al.
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