Electrotechnical terminology - Explosive atmospheres
1 Scope
This document defines terms and definitions specifically relevant to explosive atmospheres.
This document is applicable to communication within the industrial sector and its related fields, and is also applicable to the preparation of relevant standardization documents and other publications.
As a basic document, this terminology is consistent with the terminology developed in the other specialized parts of the IEV.
2 Normative references
There are no normative references in this document.
3 Terms and definitions
The terms and definitions contained in this document were extracted from the Electropedia (www.electropedia.org).
426-01 General terms
426-01-01
equipment,
apparatus, fittings, devices, and the like used as part of, or in connection with, an installation
Note: Equipment incorporating a Type of Protection can be "Ex Equipment", or an "Ex Component".
426-01-02
Type of Protection,
set of specific measures applied to equipment to avoid ignition of a surrounding explosive atmosphere
426-01-03
equipment grouping
classification system of equipment related to the explosive atmosphere for which they are intended to be used
Note: IEC 60079-0 identifies three equipment groups:
——Group I, equipment for mines susceptible to firedamp;
——Group II, which is divided into sub-groups, equipment for all places with an explosive gas atmosphere other than mines susceptible to firedamp;
——Group III, which is divided into sub-groups, equipment for all places with an explosive dust atmosphere other than mines susceptible to firedamp.
426-01-04
maximum surface temperature
highest temperature which is attained in service under the most adverse conditions (but within the specified tolerances) by any part or surface of Ex Equipment
Note 1: For Ex Equipment in an explosive gas atmosphere, this temperature may occur on an internal component or on the external surface of the enclosure, depending upon the Type of Protection employed.
Note 2: For Ex Equipment in an explosive dust atmosphere, this temperature occurs on the external surface of the enclosure and may include a defined dust layer condition.
426-01-05
temperature class
classification system of Ex Equipment, based on its maximum surface temperature, related to the specific explosive gas atmosphere for which it is intended to be used
426-01-06
explosive atmosphere
mixture with air, under atmospheric conditions, of flammable substances in the form of gas, vapour, or dust, which, after ignition, permits self-sustaining propagation
426-01-07
explosive gas atmosphere
mixture with air, under atmospheric conditions, of flammable substances in the form of gas or vapour which, after ignition, permits self-sustaining flame propagation
426-01-08
explosive dust atmosphere
mixture with air, under atmospheric conditions, of flammable substances in the form of dust, which, after ignition, permits self-sustaining propagation
426-01-09
fixed equipment,
equipment fastened to a support, or otherwise secured in a specific location, when energized
426-01-10
personal equipment
equipment intended to be worn by and to be in contact with a person's body during its operation
426-01-11
portable equipment
equipment intended to be carried by a person during its operation
Note: Portable equipment carried by a person during its operation is sometimes referred to as hand-held equipment.
426-01-12
transportable equipment
equipment not intended to be carried by a person during its operation, nor intended for fixed installation
426-01-13
Ex Component
equipment intended to be part of Ex Equipment, marked with symbol "U", which is not intended to be used alone, and requires additional consideration when incorporated into Ex Equipment
426-01-14
Ex Equipment
equipment with explosion protection
Note: Such equipment often includes Ex Components, but additional evaluation is always required as part of their incorporation into equipment.
426-01-15
equipment protection level; EPL
Level of Protection assigned to equipment based on its likelihood of becoming a source of ignition and distinguishing the differences between explosive gas atmospheres, explosive dust atmospheres, and the explosive atmospheres in mines susceptible to firedamp
426-01-16
EPL Ma
equipment for installation in a mine susceptible to firedamp, having a "very high" Level of Protection, which has sufficient security that it is unlikely to become an ignition source in normal operation, during expected malfunctions or during rare malfunctions, even when left energized in the presence of an outbreak of gas
426-01-17
EPL Mb
equipment for installation in a mine susceptible to firedamp, having a "high" Level of Protection, which has sufficient security that it is unlikely to become a source of ignition in normal operation or during expected malfunctions in the time span between there being an outbreak of gas and the equipment being de-energized
426-01-18
EPL Ga
equipment for explosive gas atmospheres, having a "very high" Level of Protection, which is not a source of ignition in normal operation, during expected malfunctions or during rare malfunctions
426-01-19
EPL Gb
equipment for explosive gas atmospheres, having a "high" Level of Protection, which is not a source of ignition in normal operation or during expected malfunctions
426-01-20
EPL Gc
equipment for explosive gas atmospheres, having an "enhanced" Level of Protection, which is not a source of ignition in normal operation and which can have some additional protection to ensure that it remains inactive as an ignition source in the case of regular expected occurrences (for example failure of a lamp)
426-01-21
EPL Da
equipment for explosive dust atmospheres, having a "very high" Level of Protection, which is not a source of ignition in normal operation, during expected malfunctions, or during rare malfunctions
426-01-22
EPL Db
equipment for explosive dust atmospheres, having a "high" Level of Protection, which is not a source of ignition in normal operation or during expected malfunctions
426-01-23
EPL Dc
equipment for explosive dust atmospheres, having an "enhanced" Level of Protection, which is not a source of ignition in normal operation and which can have some additional protection to ensure that it remains inactive as an ignition source in the case of regular expected occurrences (for example failure of a lamp)
426-01-24
Level of Protection
subdivision of a Type of Protection, correlating with the Equipment Protection Level, that differentiates the likelihood of the equipment becoming a source of ignition
Note: For example, Type of Protection intrinsic safety "i" is subdivided into Levels of Protection "ia", "ib", and "ic", which correlate with EPL Ga, EPL Gb, and EPL Gc (for explosive gas atmospheres).
426-02 Physical and chemical phenomena
426-02-01
auto-ignition temperature; AIT
lowest temperature (of a hot surface) at which, under specified conditions, an ignition of a flammable gas or vapour in mixture with air/inert gas occurs
Note: The conditions are specified in ISO/IEC 80079-20-1.
426-02-05
explosive test mixture
specified explosive mixture used for the testing of equipment for explosive gas atmospheres
426-02-09
lower flammable limit; LFL
concentration of flammable gas or vapour in air, below which an explosive gas atmosphere does not form
Note 1: For the purposes of Ex Equipment, this was previously referred to as the lower explosive limit (LEL).
Note 2: The concentration can be expressed as either a volume fraction or a mass per unit volume.
