1、May 2007DEUTSCHE NORM English price group 13No part of this standard may be reproduced without prior permission ofDIN Deutsches Institut fr Normung e. V., Berlin. Beuth Verlag GmbH, 10772 Berlin, Germany,has the exclusive right of sale for German Standards (DIN-Normen).ICS 13.240!,xa-“9856210www.din
2、.deDDIN EN 14994Gas explosion venting protective systemsEnglish version of DIN EN 14994:2007-05Schutzsysteme zur Druckentlastung von GasexplosionenEnglische Fassung DIN EN 14994:2007-05www.beuth.deDocument comprises 29 pages 08.07DIN EN 14994:2007-05 2 National foreword This standard has been prepar
3、ed by CEN/TC 305 “Potentially explosive atmospheres Explosion prevention and protection”, Working Group WG 3 “Devices and systems for explosion prevention and protection” (Secretariat: DIN, Germany). The responsible German body involved in its preparation was the Normenausschuss Sicherheitstechnisch
4、e Grundstze (Safety Design Principles Standards Committee), Technical Committee NA 095-02-01 AA Explosionsschutzeinrichtungen (auer Flammendurchschlagsicherungen). The European Standards and draft Standards referred to in clause 2 and in the bibliography of this document correspond as follows: EN 11
5、27-1, EN 13237, EN 13637-1, EN 13637-2 and EN 14797 have been published as the corresponding DIN EN Standards with the same number. EN 14373, EN 14460 and EN 14491 referred to in the bibliography of this standard have been published as the corresponding DIN EN Standards and prEN 15089 as the corresp
6、onding DIN EN draft Standard with the same number. EUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN 14994February 2007ICS 13.240English VersionGas explosion venting protective systemsSystmes de protection par vent contre les explosions degazSchutzsysteme zur Druckentlastung von GasexplosionenThis E
7、uropean Standard was approved by CEN on 15 December 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
8、 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
9、 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, Lithua
10、nia, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2007 CEN A
11、ll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 14994:2007: EEN 14994:2007 (E) 2 Contents Page Foreword4 1 Scope 5 2 Normative references 5 3 Terms and definitions .6 4 Venting of enclosures .7 5 Venting of isolated compact enclosures.8 5
12、.1 General8 5.2 Venting of isolated compact enclosures.8 5.3 Situations outside the constraints of the basic method (turbulence inducing elements, partially filled enclosures) 9 5.3.1 General9 5.3.2 Elevated initial pressure .9 5.3.3 Effect of initial turbulence.10 5.3.4 Effect of partial filling 11
13、 5.3.5 Venting of enclosures containing turbulence inducing elements11 5.4 Elongated enclosures .11 5.4.1 General11 5.4.2 Venting of elongated enclosures vented at each end12 5.4.3 Venting of elongated enclosures vented along the enclosure .13 5.5 Pipes .14 5.6 Interconnected enclosures .16 5.7 Vent
14、 ducts.16 6 Supplementary design aspects17 6.1 General17 6.2 Positioning and shape of explosion vents17 6.3 Choice of venting device 17 6.4 External effects 18 6.4.1 General18 6.4.2 Flame effects18 6.4.3 Pressure effects.18 6.4.4 Deflectors .19 6.5 Recoil forces 20 7 Information for use 21 7.1 Marki
15、ng .21 7.2 Accompanying documents.22 Annex A (informative) Assessment of the level of congestion in rooms containing turbulence including elements 23 Annex ZA (informative) Relationship between this European Standard and the Essential Requirements of EU Directive 94/9/EC 26 Bibliography 27 EN 14994:
16、2007 (E) 3 Figures Figure 1 Value of exponent as a function of AV/V2/3.10 Figure 2 Pressure reduction of partially filled enclosures as a function of filling ratio.11 Figure 3 Maximum pressure developed during deflagration of propane-air mixtures flowing at 2 m/s or less in a smooth, straight pipe c
17、losed at one end .14 Figure 4 Vent spacing needed to keep pred from exceeding 0,2 bar for propane in pipes flowing at an initial velocity of between 2 m/s and 20 m/s .15 Figure 5 Design of a flame deflector plate (basic principles)20 Tables Table A.1 Values for the complexity factor c 24 Table ZA.1
18、Correspondence between this European Standard and Directive 94/9/EC26 EN 14994:2007 (E) 4 Foreword This document (EN 14994:2007) has been prepared by Technical Committee CEN/TC 305 “Potentially explosive atmospheres - Explosion prevention and protection”, the secretariat of which is held by DIN. Thi
19、s 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 August 2007, and conflicting national standards shall be withdrawn at the latest by August 2007. This document has been prepared under a mandate given
20、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 94/9/EC, see informative Annex ZA, which is an integral part of this document. According to the CEN/CENELEC Internal Regulations,
21、 the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands,
22、 Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom. EN 14994:2007 (E) 5 1 Scope This European Standard specifies the basic design requirements for the selection of a gas explosion venting protective system. This European Standard, EN 14797 and EN 14
23、460 form a series of three standards which are used together. NOTE 1 These three standards together represent the concept of gas explosion venting. NOTE 2 To avoid transfer of explosions to other communicating equipment one should also consider applying prEN 15089. This European Standard is applicab
24、le to: vent sizing to protect against the internal pressure effects of a gas explosion; flame and pressure effects outside the enclosure; recoil forces; influence of vent ducts; influence of initial temperature and pressure. This European Standard does not provide design and application rules agains
25、t effects generated by detonation reactions or runaway exothermic reactions including decomposition in the gas phase. This European Standard is not applicable to: fire risks arising either from materials processed, used or released by the equipment or from materials that make up equipment and buildi
26、ngs; design, construction and testing of explosion venting devices, which are used to achieve explosion venting1); protection against overpressures caused by events such as overfilling, overpressurisation, fire engulfment, overheating etc. NOTE 3 Protection by venting against dust and hybrid explosi
27、ons is specified in EN 14491. 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) appli
28、es. EN 1127-1:1997, Explosive atmospheres Explosion prevention and protection Part 1: Basic concepts and methodology EN 13237:2003, Potentially explosive atmospheres Terms and definitions for equipment and protective systems intended for use in potentially explosive atmospheres 1)This is covered by
29、EN 14797. EN 14994:2007 (E) 6 EN 13673-1, Determination of the maximum explosion pressure and the maximum rate of pressure rise of gases and vapours Part 1: Determination of the maximum explosion pressure EN 13673-2, Determination of maximum explosion pressure and the maximum rate of pressure rise o
30、f gases and vapours Part 2: Determination of the maximum rate of explosion pressure rise EN 14797:2006, Explosion venting devices 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 1127-1:1997 and EN 13237:2003 and the following apply. 3.1 atmospheric co
31、nditions conditions of the surrounding medium where the atmospheric pressure can vary between 80 kPa and 110 kPa and the temperature between 20 C and 60 C 3.2 gas for the purpose of this European Standard, gas, vapour or any mixture thereof at atmospheric conditions 3.3 compact enclosures enclosures
32、 having a length (height) to diameter ratio of less than 2 EN 14373:2005, 3.14.1 NOTE The length L is calculated along the axis parallel to the main flow during the explosion, with D being the diameter measured perpendicular to this axis. For non-circular cross-sections, D is the diameter of a circl
33、e with the same area as the actual cross-sectional area. 3.4 elongated enclosures enclosures with length (height) to diameter ratio of 2 to 10 EN 14373:2005, 3.14.2 NOTE The length L is calculated along the axis parallel to the main flow during the explosion, with D being the diameter measured perpe
34、ndicular to this axis. For non-circular cross-sections, D is the diameter of a circle with the same area as the actual cross-sectional area. 3.5 pipe construction with a ratio length (height) to diameter greater than 10 EN 14373:2005, 3.14.3 NOTE The length L is calculated along the axis parallel to
35、 the main flow during the explosion, with D being the diameter measured perpendicular to this axis. For non-circular cross-sections, D is the diameter of a circle with the same area as the actual cross-sectional area. 3.6 explosion venting device device which protects a vessel or other closed volume
36、 by explosion venting EN 14797:2006, 3.4 NOTE Examples of such devices are: bursting discs, vent panels and explosion doors. EN 14994:2007 (E) 7 3.7 effective vent area AEproduct of the geometric vent area Adand the venting efficiency Effor the venting device. NOTE It is the effective vent area that
37、 should be used in making up the vent area for explosion venting EN 14797:2006, 3.2 3.8 gas explosion constant KGmaximum value of the pressure rise per unit time (dp/dt)maxduring the explosion of a specific explosive atmosphere in a closed vessel under specified test conditions normalised to a vesse
38、l volume of 1 m3multiplied by V1/33.9 static activation pressure pstatdifferential pressure at which the retaining element activates such that the venting element is able to open EN 14797:2006, 3.11 3.10 turbulence motion of a fluid having local velocities and pressures that fluctuate randomly NOTE
39、Turbulence is a very effective transporter and mixer, and generally causing an overall increase of combustion rates. 3.11 turbulence inducing elements obstructions inside protected enclosures at which during an explosion turbulence is generated increasing the combustion rate 3.12 venting efficiency
40、Efdimensionless number used to define the efficiency of the explosion venting device EN 14797:2006, 3.14 4 Venting of enclosures Explosion venting is a protective measure preventing unacceptable high explosion pressure build-up inside enclosures. Weak areas in the walls of the enclosure open at an e
41、arly stage of the explosion, releasing un-burnt gas/vapour and combustion products from the opening so reducing the overpressure inside the enclosure. Normally the explosion venting is applied such that the maximum reduced explosion pressure shall not exceed the known design pressure of the enclosur
42、e. All parts of the enclosure e.g. valves, sight-glasses, man-holes and ducts, which are exposed to the explosion pressure shall be taken into account when estimating the design pressure of the enclosure. The vent area is the most important factor in determining the maximum reduced explosion pressur
43、e. Information required for calculation of the vent area includes the design pressure of the enclosure, the explosion characteristics of the gas, the shape and size of the enclosure, presence of turbulence inducing elements (including congestion) inside the enclosure, the static activation pressure
44、and other characteristics of the venting device, and the condition of the explosive atmosphere inside the enclosure. EN 14994:2007 (E) 8 Venting does not prevent an explosion, it limits the explosion pressure. Flame and pressure effects outside the enclosure and flying debris shall be expected and i
45、n practice accounted for. In a system consisting of two connected enclosures, a gas explosion ignited in one can propagate into the second. The propagation of this explosion generates turbulence, can cause pre-compression and can act as a large ignition source in the second enclosure. This combinati
46、on can enhance the violence of the secondary explosion (see 5.6). Turbulence inducing elements such as shelves in a drying oven may cause considerably more violent gas explosions. This will increase the venting requirements. As this mechanism is not covered by the general method presented in this st
47、andard, more intricate methods may need to be applied. In the informative Annex A rules are given when to apply the general method of the present standard and when one shall use more intricate methods if turbulence inducing elements are present. A general description of intricate methods is given in
48、 the informative Annex A together with requirements for the experimental validation of these methods. 5 Venting of isolated compact enclosures 5.1 General Venting devices shall comply with the requirements of EN 14797. Two principle venting device parameters are pstatand Ef, which is affected by val
49、ues of vent cover inertia and enclosure volume. Accurate sizing of vents is the most important aspect of vent design. Venting requirements depend in practice on the combustion characteristics of the gas, the state of the flammable mixture (concentration, turbulence, distribution), and the geometry of the enclosure (including the presence of turbulence inducing elements). Combustion characteristics of flammable gases shall be measured according to appropriate methodologies. In this European Standard the combustion char
