EN 1127-1:2007

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Explosive atmospheres - Explosion prevention and protection - Part 1: Basic concepts and methodologyAtmospheres explosives - Prévention de l'explosion et protection contre l'explosion - Partie 1 : Notions fondamentales et méthodologieExplosionsfähige Atmosphären - Explosionsschutz - Teil 1: Grundlagen und MethodikTa slovenski standard je istoveten z:EN 1127-1:2007SIST EN 1127-1:2008en,fr,de13.230Varstvo pred eksplozijoExplosion protectionICS:SLOVENSKI
STANDARDSIST EN 1127-1:200801-februar-2008

EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 1127-1November 2007ICS 29.260.20Supersedes EN 1127-1:1997
English VersionExplosive atmospheres - Explosion prevention and protection -Part 1: Basic concepts and methodologyAtmosphères explosives - Prévention de l'explosion etprotection contre l'explosion - Partie 1: Notionsfondamentales et méthodologieExplosionsfähige Atmosphären - Explosionsschutz - Teil 1:Grundlagen und MethodikThis European Standard was approved by CEN on 21 October 2007.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this EuropeanStandard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such nationalstandards may be obtained on application to the CEN Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translationunder the responsibility of a CEN member into its own language and notified to the CEN Management Centre has the same status as theofficial versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland,France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMITÉ EUROPÉEN DE NORMALISATIONEUROPÄISCHES KOMITEE FÜR NORMUNGManagement Centre: rue de Stassart, 36
B-1050 Brussels© 2007 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 1127-1:2007: E

Information for the use of tools in potentially explosive atmospheres.37 Annex B (informative)
Classification of zones for gases/vapours and for dusts.38 Annex C (informative)
Relation between categories and zones.40 Annex D (informative)
Concepts for the use of measuring and control systems to avoid effective ignition sources.41 Annex ZA (informative)
Relationship between this European Standard and the Essential Requirements of EU Directive 94/9/EC.42 Annex ZB (informative)
Relationship between this European Standard and the Essential Requirements of EU Directive 98/37/EC.43 Annex ZC (informative)
Relationship between this European Standard and the Essential Requirements of EU Directive 2006/42/EC.44 Bibliography.45

Tables Table C.1 — Relation between categories and zones.40 Table C.2 — Applicable equipment in the different zones.40 Table D.1 — Additional measuring and control systems necessary to avoid effective ignition sources.41 Table ZA — Correspondence between this European Standard and Directive 94/9/EC.42

Flammable and/or combustible substances shall be considered as materials which can form an explosive atmosphere unless an investigation of their properties has shown that in mixtures with air they are incapable of self-sustained propagation of an explosion.
This potential hazard associated with explosive atmosphere is released when ignited by an effective ignition source. The safety data listed in 4.2, 4.3 and 4.4 describe safety relevant properties of substances. They can be obtained by laboratory experiments and in a few cases also by calculation methods1). The safety data obtained are used for the identification of the hazard. It is necessary to bear in mind that such safety data are not physical constants but depend for instance on the techniques used for their measurement. Also, for dusts, tabulated safety data are for guidance only because the values depend on particle size and shape, moisture content and the presence of additives even in trace concentrations. For a specific application, samples of the dust to be present in the equipment should be tested and the data obtained used in the identification of the hazard.
4.2 Combustion properties Since in this context it is not the material itself that represents the potential hazard but its contact or mixing with the air, the properties of the mixture of the flammable substance with air shall be determined. These properties give information about a substance's burning behaviour and whether it could give rise to fire or explosions. Relevant data are e.g. a) flash point; b) explosion limits (LEL, UEL); c) limiting oxygen concentration (LOC).
1) Appropriate standards have been or are being developed by CEN and CENELEC, see also Bibliography.

Shock waves are generated, for example, during the sudden relief of high-pressure gases into pipelines. In this process the shock waves are propagated into regions of lower pressure faster than the speed of sound. When they are diffracted or reflected by pipe bends, constrictions, connection flanges, closed valves etc., very high temperatures can occur. NOTE 2 Equipment, protective systems and components containing highly oxidizing gases, e.g. pure oxygen or gas atmospheres with a high oxygen concentration, can become an effective ignition source under the action of adiabatic compression, shock waves or even pure flow because lubricants, gaskets and even construction materials can be ignited. If this leads to destruction of the equipment, protective systems and components, parts of it will ignite a surrounding explosive atmosphere. For protective measures against ignition hazards due to adiabatic compression and shock waves, see 6.4.13. 5.3.14 Exothermic reactions, including self-ignition of dusts Exothermic reactions can act as an ignition source when the rate of heat generation exceeds the rate of heat loss to the surroundings. Many chemical reactions are exothermic. Whether a reaction can reach a high temperature is dependent, among other parameters, on the volume/surface ratio of the reacting system, the ambient temperature and the residence time. These high temperatures can lead to ignition of explosive atmospheres and also the initiation of smouldering and/or burning. Such reactions include those of pyrophoric substances with air, alkali metals with water, self-ignition of combustible dusts2), self-heating of feed-stuffs, induced by biological processes, the decomposition of organic peroxides, or polymerization reactions. Catalysts can also induce energy-producing reactions (e.g. hydrogen/air atmospheres and platinum).
2) For determination of the spontaneous ignition behaviour of dust accumulations see EN 15188.
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