SIST EN 14034-3:2006
(Main)Determination of explosion characteristics of dust clouds - Part 3: Determination of the lower explosion limit LEL of dust clouds
Determination of explosion characteristics of dust clouds - Part 3: Determination of the lower explosion limit LEL of dust clouds
This standard describes a test method for the determination of the lower explosion limit of dust clouds in a closed vessel under defined initial conditions of pressure and temperature.
This method is not suitable for use with recognised explosives, like gunpowder and dynamite, explosives which do not require oxygen for combustion, pyrophoric substances, or substances or mixtures of substances which may under some circumstances behave in a similar manner. Where any doubt exists about the existence of hazard due to explosive properties, expert advice should be sought.
Bestimmung der Explosionskenngrößen von Staub/Luft-Gemischen - Teil 3: Bestimmung der unteren Explosionsgrenze UEG von Staub/Luft-Gemischen
Diese Norm legt ein Prüfverfahren fest für die Bestimmung der unteren Explosionsgrenze von Staubwolken in
einem geschlossenen Behälter unter definierten Anfangsbedingungen von Druck und Temperatur.
Dieses Verfahren ist nicht geeignet für Sprengstoffe, wie Schießpulver und Dynamit sowie Stoffe, die ohne
Sauerstoff verbrennen, pyrophore Stoffe oder Stoffe bzw. Stoffgemische, die sich unter bestimmten
Umständen ähnlich verhalten. Wenn Zweifel über eventuell vorhandene Gefährdungen durch die
Explosionswirkung bestehen, sollten Fachleute zu Rate gezogen werden.
Détermination des caractéristiques d'explosion des nuages de poussiere - Partie 3: Détermination de la limite inférieure d'explosivité LIE des nuages de poussiere
La présente Norme spécifie une méthode d’essai pour déterminer la limite inférieure d’explosivité des nuages de
poussiere dans un récipient fermé, dans des conditions initiales de pression et de températures définies.
Cette méthode ne convient pas aux explosifs reconnus comme tels, comme la poudre et la dynamite, aux explosifs
dont la combustion ne nécessite pas d’oxygene, aux substances pyrophoriques ou aux substances et mélanges de
substances pouvant, dans certaines circonstances, se comporter de maniere similaire. Lorsqu’il existe un doute sur
l’existence d’un phénomene dangereux en raison de propriétés explosives, il convient de faire appel a l’avis
d’experts.
Ugotavljanje eksplozijskih značilnosti oblakov prahu – 3. del: Ugotavljanje spodnje meje eksplozivnosti SME oblakov prahu
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Standards Content (Sample)
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Determination of explosion characteristics of dust clouds - Part 3: Determination of the lower explosion limit LEL of dust cloudsDétermination des caractéristiques d'explosion des nuages de poussiere - Partie 3: Détermination de la limite inférieure d'explosivité LIE des nuages de poussiereBestimmung der Explosionskenngrößen von Staub/Luft-Gemischen - Teil 3: Bestimmung der unteren Explosionsgrenze UEG von Staub/Luft-GemischenTa slovenski standard je istoveten z:EN 14034-3:2006SIST EN 14034-3:2006en13.230ICS:SLOVENSKI
STANDARDSIST EN 14034-3:200601-september-2006
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 14034-3May 2006ICS 13.230 English VersionDetermination of explosion characteristics of dust clouds - Part3: Determination of the lower explosion limit LEL of dust cloudsDétermination des caractéristiques d'explosion des nuagesde poussière - Partie 3: Détermination de la limite inférieured'explosivité LIE des nuages de poussièreBestimmung der Explosionskenngrößen von Staub/Luft-Gemischen - Teil 3: Bestimmung der unterenExplosionsgrenze UEG von Staub/Luft-GemischenThis European Standard was approved by CEN on 20 April 2006.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 Central Secretariat 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 Central Secretariat has the same status as the officialversions.CEN members are the national standards bodies of Austria, Belgium, 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© 2006 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 14034-3:2006: E
EN 14034-3:2006 (E) 2 Contents Page Foreword.4 Introduction.5 1 Scope.6 2 Normative references.6 3 Terms and definitions.6 4 Test apparatus.7 4.1 General.7 4.2 Explosion vessel.7 4.3 Dust dispersion system (dust container, fast acting valve, connecting tube, dust disperser).9 4.4 Ignition source.12 4.5 Control unit.12 4.6 Pressure measuring system.12 5 Dust sample.12 6 Test procedure.12 7 Calibration and verification.14 7.1 Calibration.14 7.2 Verification.14 8 Safety precautions/instructions.15 9 Alternative test equipment/procedures.15 10 Test report.15 Annex A (normative)
Electro Pneumatic Valve.17 Annex B (normative)
Dust disperser with 5 mm holes.19 Annex C (normative)
20 l sphere.22 C.1 General.22 C.2 Test apparatus.22 C.3 Test conditions.23 C.4 Test procedure.23 Annex ZA (informative)
Relationship between this European Standard and the Essential Requirements of EU Directive 94/9/EC.25 Bibliography.26 Figures Figure 1 — 1 m³ vessel (schematic).8 Figure 2 — Dust container with blasting cap activated valve as commonly used for explosion suppression (schematic; it is commercially available).9 Figure 3 — Location of the 6 mm holes in the dust disperser.11 Figure 4 — Dust dispersion and pressure-time curve.13 Figure 5 — Determination of the lower explosion limit LEL.14 Figure A.1 — Electro Pneumatic Valve (schematic).17 Figure A.2 — Discharge characteristic of dust dispersers (without dust).18
EN 14034-3:2006 (E) 3 Figure B.1 — Location of the 5 mm holes in the dust disperser.20 Figure B.2 — Rebound nozzle.21 Figure B.3 — Dispersion cup.21 Figure C.1 — Test equipment 20 l sphere (schematic).23 Tables Table ZA.1 — Correspondence between this European Standard and Directive 94/9/EC.25
EN 14034-3:2006 (E) 4 Foreword This document (EN 14034-3:2006) has been prepared by Technical Committee CEN/TC 305 “Potentially explosive atmospheres – Explosion prevention and protection”, the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by November 2006, and conflicting national standards shall be withdrawn at the latest by November 2006. This document has been prepared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directives. For relationship with the EU Directive 94/9/EC, see informative Annex ZA, which is an integral part of this document. This European Standard is one of a series of standards as listed below: EN 14034 "Determination of explosion characteristics of dust clouds" – Part 1: Determination of the maximum explosion pressure pmax of dust clouds; – Part 2: Determination of the maximum rate of explosion pressure rise (dp/dt)max of dust clouds; – Part 3: Determination of the lower explosion limit LEL of dust clouds; – Part 4: Determination of the limiting oxygen concentration LOC of dust clouds. According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, 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.
EN 14034-3:2006 (E) 5 Introduction This European Standard specifies a method for experimental determination of the lower explosion limit of dust clouds. The lower explosion limit is the lowest concentration of a combustible dust in mixture with air at which an explosion occurs. The measurement of the lower explosion limit forms the basis for hazard identification and explosion prevention. Therefore this document gives added values to the following clauses of the EU directives: Directive 94/9/EC of the European Parliament and the Council of March 23, 1994 on the approximation of the laws of the member states concerning equipment and protective systems intended for use in potentially explosive atmospheres.
Annex II, Clause 1.0.1 Directive 98/37/EC of the European Parliament and the Council of June 22, 1998 on the approximation of the laws of the member states relating to machinery Annex I, Clause 1.5.7
EN 14034-3:2006 (E) 6 1 Scope This standard describes a test method for the determination of the lower explosion limit of dust clouds in a closed vessel under defined initial conditions of pressure and temperature.
This method is not suitable for use with recognised explosives, like gunpowder and dynamite, explosives which do not require oxygen for combustion, pyrophoric substances, or substances or mixtures of substances which may under some circumstances behave in a similar manner. Where any doubt exists about the existence of hazard due to explosive properties, expert advice should be sought. 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. EN 14460, Explosion resistant equipment 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. 3.1 dust small solid particles 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) NOTE Generally maximum particle size will not exceed 500 µm. 3.2 combustible dust dust able to undergo an exothermic reaction with air when ignited NOTE The terms “flammable” and “combustible” are used synonymously. 3.3 explosion pressure pex highest overpressure occurring during an explosion of a dust cloud in a closed vessel 3.4 explosive atmosphere mixture with air, under atmospheric conditions, of flammable (combustible) substances in the form of gases, vapours, mists or dusts, in which, after ignition has occurred, combustion spreads to the entire unburned mixture 3.5 ignition delay tv time between the initiation of the dust dispersion and the activation of the ignition source 3.6 initial pressure pi pressure in the explosion vessel at the moment of ignition
EN 14034-3:2006 (E) 7 3.7 initial temperature Ti temperature in the explosion vessel at the moment of ignition 3.8 lower explosion limit (LEL) lowest concentration of a combustible dust in mixture with air at which an explosion occurs 4 Test apparatus 4.1 General The standard test apparatus to determine the lower explosion limit of dust clouds is an explosion pressure resistant vessel of 1 m³, as used for the determination of the maximum explosion pressure and the maximum rate of explosion pressure rise of dust clouds as well as the limiting oxygen concentration of dust/air/inert gas mixtures. The main components of the test apparatus are explosion vessel; dust dispersion system; ignition source; control unit; pressure measuring system. NOTE The 20 l sphere apparatus is an alternative explosion vessel for these determinations (see Annex C). 4.2 Explosion vessel The standard explosion vessel is an explosion pressure resistant, spherical or cylindrical vessel having a volume of 1 m³ in accordance with EN 14460. The aspect ratio of the cylindrical vessel shall be 1:1 ± 10 % (see Figure 1). NOTE It is recommended that the explosion vessel be designed to withstand an overpressure of at least 20 bar. The apparatus shall be fitted with electrical and/or mechanical cut-offs as far as possible to ensure that any openings in the vessel (e.g. main door, instrument ports, inlet or outlet) are properly closed before a test procedure can start. The apparatus shall also be equipped as far as possible to ensure that any residual pressure inside the vessel is vented before the vessel can be opened.
EN 14034-3:2006 (E) 8
Key 1 pressure sensor
5 dust container 2 chemical igniters
6 fast acting valve 3 inlet for purge air
7 connecting tube 4 dust disperser
8 outlet for exhaust gas Figure 1 — 1 m³ vessel (schematic)
EN 14034-3:2006 (E) 9 4.3 Dust dispersion system (dust container, fast acting valve, connecting tube, dust disperser) The dust to be dispersed is charged into a dust container having a volume of 5,4 dm³. Its aspect ratio is 3:1. It is designed to withstand an overpressure of at least 20 bar (see Figure 2). The dust container has an outlet at the base, through which the dust leaves the container. This outlet is closed by a fast acting valve activated by a blasting cap. The valve has a mushroom-shaped seal. The seal is held in position against the pressure in the dust container by a small ring. The ring is destroyed by firing a blasting cap and the valve opens due to the pressure inside the dust container (see Figure 2). The valve shall be designed so that it opens in less than 10 ms. For alternative valves see Annex A. The fast acting valve is connected to the side of the explosion vessel. The connecting tube between the fast acting valve and the dust disperser shall be not longer than 350 mm (see Figure 1).
Key 1 dust container
5 protective hood 2 mushroom shaped seal
6 protective hood 3 seal housing
7 blasting cap 4 support ring
8 connecting tube Figure 2 — Dust container with blasting cap activated valve as commonly used for explosion suppression (schematic; it is commercially available)
For dispersing the dust, a perforated semicircular spray pipe (dust disperser) is mounted inside the explosion vessel, concentric with its wall. The spray pipe, with an internal diameter of 21,7 mm1) is fitted with 13 holes of a diameter of 6 mm (incl. one hole in each end cap) which are located as shown in Figure 3 (see also Figure 1).
1) (e.g. EN ISO 1127, DN 20, 3/4")
EN 14034-3:2006 (E) 10 For coarse, voluminous, fibrous or poorly flowing dust samples, it may not be possible to properly discharge the dust through the dust dispersers detailed in Figures 3 and B.1. It may, therefore, be necessary to use special dust dispersers, examples of which are given in Figures B.2 and B.3. In such cases, the dust disperser used shall be described in the test report. NOTE If other dust dispersing systems than those described in this standard are used, a propagation of the explosion from the explosion vessel into the dust container, cannot be excluded. For
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