1、BRITISH STANDARDBS EN 14034-3:2006Determination of explosion characteristics of dust clouds Part 3: Determination of the lower explosion limit LEL of dust cloudsICS 13.230g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g
2、40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58+A1:2011National forewordThis British Standard is the UK implementation of EN 14034-3:2006+A1:2011. It supersedes BS EN 14034-3:2006, which is withdrawn.The start and finish of text introduced or altered by amendment is in-dicate
3、d in the text by tags. Tags indicating changes to CEN text carry the number of the CEN amendment. For example, text altered by CEN amendment A1 is indicated by !“.The UK participation in its preparation was entrusted to Technical Committee FSH/23, Fire precautions in industrial and chemical plant.A
4、list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliancewith a British Standard cannot confer immunity from leg
5、al obligations.BS EN 14034-3:2006+A1:2011This British Standard was published under the authority of the Standards Policy and Strategy Committee on 30 June 2006 BSI 2011Amendments/corrigenda issued since publicationDate Comments 30 August 2011 Implementation of CEN amendment A1:2011ISBN 978 0 580 735
6、82 0EUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 14034-3:2006+A1 January 2011 ICS 13.230 Supersedes EN 14034-3:2006English Version Determination of explosion characteristics of dust clouds - Part 3: Determination of the lower explosion limit LEL of dust cloudsDtermination des caractristiques
7、 dexplosion des nuages de poussire - Partie 3: Dtermination de la limite infrieure dexplosivit LIE des nuages de poussire Bestimmung der Explosionskenngren von Staub/Luft-Gemischen - Teil 3: Bestimmung der unteren Explosionsgrenze UEG von Staub/Luft-Gemischen This European Standard was approved by C
8、EN on 20 April 2006 and includes Amendment 1 approved by CEN on 13 November 2010. CEN 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
9、bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC 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 translation under the re
10、sponsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions. CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany,
11、 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 STANDARDIZATION COMIT EUROPEN DE NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Man
12、agement Centre: Avenue Marnix 17, B-1000 Brussels 2011 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 14034-3:2006+A1:2011: EEN 14034-3:2006+A1:2011 (E) 2 Contents Page Foreword 4Introduction .51 Scope 62 Normative references 63 T
13、erms and definitions .64 Test apparatus .74.1 General 74.2 Explosion vessel 74.3 Dust dispersion system (dust container, fast acting valve, connecting tube, dust disperser) 94.4 Ignition source 124.5 Control unit 124.6 Pressure measuring system 125 Dust sample . 126 Test procedure 127 Calibration an
14、d verification . 157.1 Calibration . 157.2 Verification 158 Safety precautions/instructions 169 Alternative test equipment/procedures 1610 Test report . 16Annex A (normative) Electro Pneumatic Valve . 18Annex B (normative) Dust disperser with 5 mm holes . 20Annex C (normative) 20 l sphere 23C.1 Gene
15、ral . 23C.2 Test apparatus 23C.3 Test conditions . 24C.4 Test procedure 24Annex ZA (informative) !Relationship between this European Standard and the Essential Requirements of EU Directive 94/9/EC“ 26Bibliography . 27Figures Figure 1 1 m vessel (schematic) . 8Figure 2 Dust container with blasting ca
16、p activated valve as commonly used for explosion suppression (schematic; it is commercially available) 9Figure 3 Location of the 6 mm holes in the dust disperser 11Figure 4 Dust dispersion and pressure-time curve . 14Figure 5 Determination of the lower explosion limit LEL . 15Figure A.1 Electro Pneu
17、matic Valve (schematic) . 18Figure A.2 Discharge characteristic of dust dispersers (without dust) 19BS EN 14034-3:2006+A1:2011EN 14034-3:2006+A1:2011 (E) 3 Figure B.1 Location of the 5 mm holes in the dust disperser . 21Figure B.2 Rebound nozzle . 22Figure B.3 Dispersion cup 22Figure C.1 Test equipm
18、ent 20 l sphere (schematic) . 24BS EN 14034-3:2006+A1:2011EN 14034-3:2006+A1:2011 (E) 4 Foreword This document (EN 14034-3:2006+A1:2011) has been prepared by Technical Committee CEN/TC 305 “Potentially explosive atmospheres Explosion prevention and protection”, the secretariat of which is held by DI
19、N. 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 July 2011, and conflicting national standards shall be withdrawn at the latest by July 2011. Attention is drawn to the possibility that some of t
20、he elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document includes Amendment 1, approved by CEN on 2010-11-13. This document supersedes EN 14034-3:2006. The start and finish of text
21、introduced or altered by amendment is indicated in the text by tags !“. 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/E
22、C, 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 pmaxof dust clouds; Part 2: De
23、termination of the maximum rate of explosion pressure rise (dp/dt)maxof 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 s
24、tandards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norwa
25、y, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. BS EN 14034-3:2006+A1:2011EN 14034-3:2006+A1:2011 (E) 5 Introduction This European Standard specifies a method for experimental determination of the lower explosion limit of dust clouds. The lower explos
26、ion 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. !deleted text“ BS EN 14034-3:2006+A1:2011EN 14034-3:2006+A1:2011 (E) 6 1 Scop
27、e 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
28、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 Th
29、e 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
30、 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 max
31、imum particle size will not exceed 500 m. 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 clos
32、ed 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 tvtime between the initi
33、ation of the dust dispersion and the activation of the ignition source BS EN 14034-3:2006+A1:2011EN 14034-3:2006+A1:2011 (E) 7 3.6 initial pressure pipressure in the explosion vessel at the moment of ignition 3.7 initial temperature Ti temperature in the explosion vessel at the moment of ignition 3.
34、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 m, as used for the d
35、etermination 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
36、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 m in accordance with
37、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 t
38、hat 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. BS EN 14
39、034-3:2006+A1:2011EN 14034-3:2006+A1:2011 (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 m vessel (schematic) BS EN 14034-3:2006+A1:2011EN 14034-3:2006+A1:2011 (E) 9 4.3
40、 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 dm. Its aspect ratio is 3:1. It is designed to withstand an overpressure of at least 20 bar (see Figure 2). The dust container
41、 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 f
42、iring 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 betw
43、een 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
44、 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
45、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“) BS EN 14034-3:2006+A1:2011EN 14034-3:2006+A1:2011 (E) 10 For coarse, voluminous, fibrous or poorly flowing dust samples, it may not be possible
46、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 du
47、st 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 this case, additional safety measures should be employed, e. g. higher pressure resistance of the dust container. BS EN 1403
48、4-3:2006+A1:2011EN 14034-3:2006+A1:2011 (E) 11 Dimensions in millimeters Key 1 6 mm hole 2 end cap with 6 mm hole Figure 3 Location of the 6 mm holes in the dust disperser BS EN 14034-3:2006+A1:2011EN 14034-3:2006+A1:2011 (E) 12 4.4 Ignition source !The ignition source comprises two electrically act
49、ivated pyrotechnical igniters, each having an ignition energy of 5 kJ. This is the nominal calorimetric energy based on the mass of pyrotechnic powder in the igniters. When activated, the igniters shall release a dense cloud of very hot particles with little gas. The igniters are fired by electrical fuse heads. The power supply circuit for the igniters shall be capable of firing the fuse heads in less than 10 ms. The
