EN 50281-3:2002
(Main)Equipment for use in the presence of combustible dust - Part 3: Classification of areas where combustible dusts are or may be present
Equipment for use in the presence of combustible dust - Part 3: Classification of areas where combustible dusts are or may be present
Superseded by EN 61241-10:2004
Betriebsmittel zur Verwendung in Bereichen mit brennbarem Staub - Teil 3: Einteilung von staubexplosionsgefährdeten Bereichen
Appareils pour utilisation en présence de poussières combustibles - Partie 3: Classement des emplacements où des poussières combustibles sont ou peuvent être présentes
Električne naprave za uporabo ob prisotnosti gorljivega prahu - 3. del: Razdelitev območij, v katerih je ali je lahko prisoten gorljiv prah
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Standards Content (Sample)
SLOVENSKI SIST EN 50281-3:2003
STANDARD
marec 2003
Električne naprave za uporabo ob prisotnosti gorljivega prahu - 3. del:
Razdelitev območij, v katerih je ali je lahko prisoten gorljiv prah
Equipment for use in the presence of combustible dust -- Part 3: Classification of
areas where combustible dusts are or may be present
ICS 29.260.20 Referenčna številka
© Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno
EUROPEAN STANDARD EN 50281-3
NORME EUROPÉENNE
EUROPÄISCHE NORM September 2002
ICS 29.100.01
English version
Equipment for use in the presence of combustible dust
Part 3: Classification of areas where combustible dusts
are or may be present
Appareils pour utilisation en présence Betriebsmittel zur Verwendung in
de poussières combustibles Bereichen mit brennbarem Staub
Partie 3: Classement des emplacements Teil 3: Einteilung von
où des poussières combustibles sont staubexplosionsgefährdeten Bereichen
ou peuvent être présentes
This European Standard was approved by CENELEC on 2002-03-05. CENELEC members are bound to
comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European
Standard the status of a national standard without any alteration.
Up-to-date lists and bibliographical references concerning such national standards may be obtained on
application to the Central Secretariat or to any CENELEC member.
This European Standard exists in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CENELEC member into its own language and
notified to the Central Secretariat has the same status as the official versions.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Czech Republic,
Denmark, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Luxembourg, Malta,
Netherlands, Norway, Portugal, Slovakia, Spain, Sweden, Switzerland and United Kingdom.
CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung
Central Secretariat: rue de Stassart 35, B - 1050 Brussels
© 2002 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. EN 50281-3:2002 E
Foreword
This European Standard was prepared by a joint Working Group (JWG 17) from CENELEC TC 31,
Electrical apparatus for explosive atmospheres - General requirements, and CEN TC 305.
The text of the draft was submitted to the Unique Acceptance Procedure and was approved by
CENELEC as EN 50281-3 on 2002-03-05.
This European Standard was prepared under a mandate given to CENELEC by the European
Commission and the European Free Trade Association and supports the essential safety
requirements of the EC Directive 94/9/EC.
The following dates were fixed:
- latest date by which the EN has to be implemented
at national level by publication of an identical
national standard or by endorsement (dop) 2003-03-01
- latest date by which the national standards conflicting
with the EN have to be withdrawn (dow) 2005-03-01
Annexes designated "informative" are given for information only.
In this standard, annexes A to C are informative.
__________
- 3 - EN 50281-3:2002
Contents
Introduction.4
1 Scope.5
2 Normative references.5
3 Definitions.6
4 Area classification for combustible dusts.7
5 Sources of release for explosive dust atmospheres.9
6 Zones for explosive dust atmospheres.10
7 Dust layer hazard .13
8 Documentation.13
Annex A (informative) Examples of area classification .16
Annex B (informative) Risk of fire from hot surface ignition of dust layer .20
Annex C (informative) Housekeeping.23
Figure 1 – Identification of zones on drawings .15
Figure A.1 – Area classification for a bag emptying station within a building and without
exhaust ventilation .16
Figure A.2 – Area classification for a bag emptying station within a building and with exhaust
ventilation.17
Figure A.3 – Area classification for cyclone and filter with clean outlet outside building .18
Figure A.4 – Area classification for a drum tipper within a building without exhaust
ventilation.19
Figure B.1 – Reduction in the maximum permissible surface temperature of
apparatus for increasing depth of dust layers.21
Table 1 - Designation of zones depending on presence of combustible dust.10
Introduction
Combustible dusts are hazardous because when they are dispersed in air by any means they form
potentially explosive atmospheres. Further, layers of combustible dust may ignite and act as ignition
sources for an explosive atmosphere.
Therefore, equipment placed in an environment where dust clouds can form should be dust ignition
protected and have a surface temperature limitation below the temperature at which a dust cloud or
layer will ignite.
This standard gives guidance on the identification of areas where hazards from combustible dust can
arise. The purpose is to permit selection of appropriate equipment for use in such areas. General and
special criteria are given, with examples, for the procedure used to identify areas.
By exercising ingenuity in the layout of equipment, it is frequently possible to locate much of the
equipment in less hazardous or in non-hazardous locations and thus, to reduce the amount of special
equipment required.
This standard contains an informative annex giving practical examples for classifying areas.
- 5 - EN 50281-3:2002
1 Scope
This standard is concerned with the classification of areas where explosive dust/air mixtures and
combustible dust layers are present, in order to permit the proper selection of equipment for use in
such areas.
In this standard, 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 the hazard of dust layer ignition is described.
The standard assumes effective housekeeping based on a system of cleaning for the plant.
The principles of the standard can also be followed when combustible fibres or flyings may cause a
hazard.
This standard is intended to be applied where there can be a risk due to the presence of explosive
dust/air mixtures or combustible dust layers under normal atmospheric conditions. It does not apply to
� underground mining areas,
� areas where a risk can arise due to the presence of hybrid mixtures,
� dusts of explosives which do not require atmospheric oxygen for combustion, or to pyrophoric
substances,
� catastrophic failures, which are beyond the concept of abnormality dealt with in this standard (see
NOTE 1),
� any risk arising from an emission of flammable or toxic gas from the dust.
This standard does not take into account the effects of consequential damage following a fire or an
explosion.
NOTE 1 Catastrophic failure in this context is applied, for example, to the rupture of a storage silo or a pneumatic conveyor.
NOTE 2 In any process plant, irrespective of size, there can be numerous sources of ignition apart from those associated with
equipment. Appropriate precautions will be necessary to ensure safety in this context, but these are outside the scope of this
standard.
2 Normative references
This European Standard incorporates by dated or undated reference, provisions from other
publications. These normative references are cited at the appropriate places in the text and the
publications are listed hereafter. For dated references, subsequent amendments to or revisions of any
of these publications apply to this European Standard only when incorporated in it by amendment or
revision. For undated references the latest edition of the publication referred to applies (including
amendments).
EN 1127-1 Explosive atmospheres - Explosion prevention and protection
Part 1: Basic concepts and methodology
1)
EN 13237-1 Potentially explosive atmosphere – Terms and definitions for equipment and protective
systems intended for use in potentially explosive atmospheres
EN 50281-1-1 Electrical apparatus for use in the presence of combustible dust
Part 1-1: Electrical apparatus protected by enclosures - Construction and testing
———————
1)
At draft stage.
EN 50281-1-2 Electrical apparatus for use in the presence of combustible dust
Part 1-2: Electrical apparatus protected by enclosures - Selection, installation and
maintenance
EN 50281-2-1 Electrical apparatus for use in the presence of combustible dust
Part 2-1: Test methods - Methods for determining the minimum ignition temperatures
of dust
IEC 61241-3 Electrical apparatus for use in the presence of combustible dust
Part 3: Classification of areas where combustible dusts are or may be present.
ISO 4225 Air quality - General aspects – Vocabulary
3 Definitions
For the purpose of this standard the following definitions apply.
3.1
area
a three-dimensional region or space
3.2
atmospheric conditions (surrounding conditions)
conditions that include variations in pressure and temperature above and below reference levels of
101,3 kPa (1 013 mbar) and 20 °C (293 K), provided that the variations have a negligible effect on the
explosive properties of the combustible dust (IEC 61241-3)
3.3
hybrid mixture
mixture of flammable substances in different physical states, with air (EN 1127-1)
NOTE An example of a hybrid mixture is a mixture of methane, coal dust and air.
3.4
dust
small solid particles including fibres and flyings in the atmosphere which settle out under their own
weight, but which may remain suspended in air for some time (includes dust and grit as defined in
ISO 4225)
3.5
explosive dust atmosphere
a mixture with air, under atmospheric conditions, of flammable substances in the form of dust or fibres
in which, after ignition, combustion spreads throughout the unconsumed mixture (IEV 426-02-04)
3.6
combustible dust
dust that can burn or glow in air and could form explosive mixtures with air at atmospheric pressure
and normal temperatures
3.7
hazardous area (dust)
area in which combustible dust in cloud form is, or can be expected to be, present in quantities such
as to require special precautions for the construction, installation and use of equipment in order to
prevent ignition of an explosive dust/air mixture. Hazardous areas are divided into zones based upon
the frequency and duration of the occurrence of explosive dust/air mixture
- 7 - EN 50281-3:2002
3.8
non-hazardous area (dust)
area in which combustible dust in cloud form is not expected to be present in quantities such as to
require special precautions for the construction, installation and use of apparatus
3.9
dust containment
those parts of the process equipment inside which materials are handled, processed, transported or
stored e.g. to prevent the release of dust to the surrounding atmosphere
3.10
source of dust release
a point or location from which combustible dust can be released to the atmosphere. This can be either
from a dust containment or a dust layer.
Sources of release will be divided into the following grades depending on the order of decreasing
severity:
� 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;
� primary grade of release: A source can be expected to release combustible dust in normal
operation occasionally;
� secondary grade of release: A source which is not expected to release combustible dust during
normal operation but if it releases, is likely to do so only infrequently and for short periods only
3.11
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
3.12
normal operation
the situation when the process equipment is operating within its design parameters. Minor releases of
dust which may form a cloud or layer (e.g. releases from filters) can be part of normal operation
3.13
abnormal operation
expected process linked malfunctions that can occur infrequently
3.14
equipment
machines, apparatus, fixed or mobile devices, control components and instrumentation thereof and
detection or prevention systems which, separately or jointly, are intended for the generation, transfer,
storage, measurement, control and conversion of energy or the processing of material and which are
capable of causing an explosion through their own potential sources of ignition
4 Area classification for combustible dusts
4.1 General
This standard adopts the concept, similar to that used fo
...
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