1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS EN 14491:2012Dust explosion ventingprotective systemsBS EN 14491:2012 BRITISH STANDARDNational forewordThis British Standard is the UK implementation of EN 14491:2012. It supe
2、rsedes BS EN 14491:2006 which is withdrawn.BSI, as a member of CEN, is obliged to publish EN 14491:2012 as a British Standard. However, attention is drawn to the fact that during the development of this European Standard, the UK committee voted against its approval as a European Standard.The standar
3、d indicates that the calculation in equation 17, isconsidered valid for containers up to 10,000 m3. In the opinion ofthe committee, extrapolation of data to this extent introduces large uncertainties and may not be safe; use of this equation for vessels up to 100m3would be considered reasonable. In
4、any case, there is rarely a need to fit vent ducts to large vessels. Long standing advice from HSE recommends1 that silos and similar large vessels should be installed outside any building.Annex D (informative) considers the use of explosion venting toprotect buildings housing dust handling plants.
5、Large areas ofexplosion relief are often needed in such cases. The standard statesthat a lightweight roof may be considered sacrificial if its movementcan be tolerated. It also implies that wall panels may form elementsof explosion venting.Where elements of a building such as vent panels are placed
6、on the market with the intention that they will be used to provide explosion protection, the ATEX directive requires that they arethird party certified, and the relevant harmonized standard sets close limits on the opening pressure and other parameters. Lightweight building cladding or roofing panel
7、s may be placed on the market with no claimed intention that they will provide explosion protection. In some circumstances they may achieve the objective of an explosion vent, but users should be aware that national authorities might not accept the use of uncertified panels in this way.1 Refer to th
8、e HSE publication, Safe handling of combustible dusts: Precautions against explosions (2003), for advice on installing silos and similar large vessels.BS EN 14491:2012 BRITISH STANDARDThe UK participation in its preparation was entrusted to TechnicalCommittee EXL/23, Explosion and fire precautions i
9、n industrial andchemical plant.A list of organizations represented on this committee can beobtained on request to its secretary.This publication does not purport to include all the necessaryprovisions of a contract. Users are responsible for its correctapplication. The British Standards Institution
10、2012. Published by BSI StandardsLimited 2012ISBN 978 0 580 64622 5ICS 13.230Compliance with a British Standard cannot confer immunity fromlegal obligations.This British Standard was published under the authority of theStandards Policy and Strategy Committee on 31 August 2012.Amendments issued since
11、publicationDate T e x t a f f e c t e dEUROPEAN STANDARD NORME EUROPENNE EUROPISCHE NORM EN 14491 August 2012 ICS 13.230 Supersedes EN 14491:2006English Version Dust explosion venting protective systems Systmes de protection par vent contre les explosions de poussires Schutzsysteme zur Druckentlastu
12、ng von StaubexplosionenThis European Standard was approved by CEN on 30 June 2012. 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
13、 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 r
14、esponsibility 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, Former Yugoslav
15、 Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom. EUROPEAN COMMITTEE FOR STANDARDIZATION COMIT EUROPEN DE
16、NORMALISATION EUROPISCHES KOMITEE FR NORMUNG Management Centre: Avenue Marnix 17, B-1000 Brussels 2012 CEN All rights of exploitation in any form and by any means reserved worldwide for CEN national Members. Ref. No. EN 14491:2012: EBS EN 14491:2012EN 14491:2012 (E) 2 Contents Page Foreword 31 Scope
17、 42 Normative references 43 Terms and definitions .44 Venting of enclosures .65 Sizing of vent areas .75.1 General 75.2 Venting of isolated enclosures .85.3 Special dust cloud conditions 95.3.1 General 95.3.2 Pneumatic conveying of product with axial introduction into vessels and silos .95.3.3 Pneum
18、atic conveying of the product with tangential introduction into vessels and silos. 105.3.4 Free fall filling 115.4 Protection of interconnected enclosures . 115.5 Protection of pipes . 125.6 Influences of vent ducts . 135.7 Design of vent ducts 145.8 Hybrid mixtures . 156 Supplementary design consid
19、erations 166.1 General . 166.2 Explosion effects external to the vent 166.2.1 General . 166.2.2 Flame effects . 166.2.3 Pressure effects 176.2.4 Effects of flameless explosion venting devices 186.2.5 Recoil forces . 186.2.6 Vacuum breakers 197 Marking 208 Information for use . 20Annex A (informative
20、) Explosion venting of dust filters 21Annex B (informative) Explosion venting of cyclones . 23Annex C (informative) Estimating the L/D ratio when calculating vent areas for elongated enclosures . 24Annex D (informative) Protection of buildings 31D.1 General . 31D.2 Calculating the vent area . 31D.3
21、Calculation of internal surface area 32Annex E (informative) Deflectors 33Annex F (informative) Significant changes between this European Standard and EN 14491:2006 35Annex ZA (informative) Relationship between this European Standard and the Essential Requirements of EU Directive 94/9/EC . 38Bibliog
22、raphy . 39BS EN 14491:2012 EN 14491:2012 (E) 3 Foreword This document (EN 14491:2012) 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
23、 of a national standard, either by publication of an identical text or by endorsement, at the latest by February 2013, and conflicting national standards shall be withdrawn at the latest by February 2013. Attention is drawn to the possibility that some of the elements of this document may be the sub
24、ject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document supersedes EN 14491:2006. Annex F provides details of significant technical changes between this European Standard and the previous edition. This document has been pre
25、pared under a mandate given to CEN by the European Commission and the European Free Trade Association, and supports essential requirements of EU Directive 94/9/EC. For relationship with EU Directive(s), see informative Annex ZA, which is an integral part of this document. According to the CEN/CENELE
26、C Internal Regulations, the national standards organisations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Icel
27、and, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. BS EN 14491:2012EN 14491:2012 (E) 4 1 Scope This European Standard specifies the basic requirements of design for
28、the selection of a dust explosion venting protective system. This European Standard is one of a series including EN 14797, Explosion venting devices and EN 14460, Explosion resistant equipment. The three standards together represent the concept of dust explosion venting. To avoid transfer of explosi
29、ons to other communicating equipment, one should also consider applying EN 15089 Explosion Isolation Systems. This European Standard covers: vent sizing to protect an enclosure against the internal pressure effects of a dust explosion; flame and pressure effects outside the enclosure; recoil forces;
30、 influence of vent ducts; hybrid mixtures. This European Standard is not intended to provide design and application rules against effects generated by detonation reactions or runaway exothermic reactions. This European Standard does not cover fire risks arising from materials either processed, used
31、or released by the equipment or from materials that make up equipment and buildings. This European Standard does not cover the design, construction, testing and certification of explosion venting devices that are used to achieve explosion venting1). 2 Normative references The following documents, in
32、 whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. EN 13237:2003, Potentially explosi
33、ve atmospheres Terms and definitions for equipment and protective systems intended for use in potentially explosive atmospheres EN 14460:2006, Explosion resistant equipment EN 14797:2006, Explosion venting devices EN 15089, Explosion isolation systems 3 Terms and definitions For the purposes of this
34、 document, the terms and definitions given in EN 13237:2003, EN 14460:2006 and the following apply. 3.1 building enclosed, roofed space that contains a working environment that may include process plant, offices and personnel, either separately or together, but is not, in itself, an item of process
35、plant 1) This is covered in EN 14797. BS EN 14491:2012 EN 14491:2012 (E) 5 3.2 enclosure vessel that forms a distinct and identifiable part of a process plant and to which explosion protection by explosion venting can be applied as described in this European Standard 3.3 hybrid mixture mixture of fl
36、ammable substances with air in different physical states SOURCE: EN 13237:2003 3.4 dust explosion constant KStmaximum value of the pressure rise per unit time (dp/dt)maxduring the explosion of a specific explosive atmosphere involving dust in a closed vessel under specified test conditions normalise
37、d to a vessel volume of 1 m3multiplied by V1/3Note 1 to entry: See EN 14034-2. 3.5 gas explosion constant KGmaximum value of the pressure rise per unit time (dp/dt)maxduring the explosion of a specific explosive atmosphere involving gas or vapour in a closed vessel under specified test conditions no
38、rmalised to a vessel volume of 1 m3multiplied by V1/3SOURCE: EN 14994:2007, 3.8, modified 3.6 geometric vent area Avratio of required vent area A and venting efficiency Effor the venting device Note 1 to entry: The geometric vent area is the minimum cross-sectional flow area of the vent opening, tak
39、ing into consideration the possible reduction of the cross section, e.g. by back pressure supports, retaining devices and parts of the explosion venting device which remain after bursting or venting. 3.7 required vent area A vent area required for the explosion venting assuming optimum venting effic
40、iency 3.8 overpressure required vent area pressure above ambient pressure 3.9 maximum explosion overpressure pmaxmaximum overpressure occurring in a closed vessel during the explosion of an explosive atmosphere and determined under specified test conditions Note 1 to entry: See EN 14034-1. BS EN 144
41、91:2012EN 14491:2012 (E) 6 3.10 pipe connection between two or more enclosures Note 1 to entry: A pipe cannot be explosion protected by the explosion venting methods for enclosures described in this European Standard. 3.11 explosive atmosphere mixture with air, under atmospheric conditions, of flamm
42、able (combustible) substances in the form of gases, vapours, mists or dusts, in which, after ignition has occurred, combustion spreads to the entire unburned mixture 3.12 maximum reduced explosion overpressure pred,maxresulting maximum overpressure generated by an explosion of an explosive atmospher
43、e in a vessel at optimum fuel concentration, after effective explosion venting or explosion suppression 3.13 maximum rate of explosion pressure rise (dp/dt)maxmaximum value of the pressure rise per unit time during explosions of all explosive atmospheres in the explosion range of a combustible subst
44、ance in a closed vessel determined under specified test conditions Note 1 to entry: This parameter is numerically identical with the parameter KSt, if the test vessel is 1 m3in volume, but the unit of the latter is barms1whereas the unit of the (dp/dt)maxis bars1. Note 2 to entry: See EN 14034-2. 3.
45、14 maximum external overpressure pext,maxexternal maximum value of the overpressure generated by vented dust explosion 3.15 static activation overpressure pstatdifferential pressure at which the retaining element activates such that the venting element is able to open SOURCE: EN 14797:2006, 3.11 3.1
46、6 vacuum breaker device which prevents damage to a vessel when the internal pressure falls below atmospheric pressure 4 Venting of enclosures Explosion venting is a protective measure for enclosures by which unacceptably high internal explosion overpressures are prevented. Weak areas in the walls of
47、 the enclosure open at an early stage of the explosion, burning and/or un-burnt material and combustion products are released and the overpressure inside the enclosure is reduced. Information required for calculation of the vent area includes the explosion resistance of the enclosure, the explosion
48、characteristics of the dust, the shape and size of the enclosure, the static activation overpressure and other characteristics of the vent closure, and the condition of the dust cloud inside the enclosure. Explosion venting shall not be performed if unacceptable amounts of materials that are classif
49、ied as poisonous, corrosive, irritant, carcinogenic, teratogenic or mutagenic can be released. Either the dust or the BS EN 14491:2012 EN 14491:2012 (E) 7 combustion products can present a hazard to the immediate environment. If there is no alternative to explosion venting, an endangered area shall be specified. NOTE 1 There is no direct guidance for estimating an endangered area for toxic or other harmful emissions, but the safe discharge area for external fla
