1、BRITISH STANDARDBS EN 14994:2007Gas explosion venting protective systemsThe European Standard EN 14994:2007 has the status of a British StandardICS 13.230; 13.240g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g
2、44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g43g55g3g47g36g58BS EN 14994:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 29 June 2007 BSI 2007ISBN 978 0 580 54508 5National forewordThis British Standard was published by BSI. It is the UK
3、 implementation of EN 14994:2007.The UK participation in its preparation was entrusted to Technical Committee FSH/23, Fire precautions in industrial and chemical plant.A list of organizations represented on this committee can be obtained on request to its secretary.This publication does not purport
4、to include all the necessary provisions of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.Amendments issued since publicationAmd. No. Date CommentsEUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN 14994Fe
5、bruary 2007ICS 13.240English VersionGas explosion venting protective systemsSystmes de protection par vent contre les explosions degazSchutzsysteme zur Druckentlastung von GasexplosionenThis European Standard was approved by CEN on 15 December 2006.CEN members are bound to comply with the CEN/CENELE
6、C 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
7、 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 memb
8、ers 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, Sw
9、itzerland and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONCOMIT EUROPEN DE NORMALISATIONEUROPISCHES KOMITEE FR NORMUNGManagement Centre: rue de Stassart, 36 B-1050 Brussels 2007 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. E
10、N 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 5.1 General8 5.2 Venting of isolated compact enclosures.8 5.3 Situations outside the constraints of the basic
11、 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 5.3.5 Venting of enclosures containing turbulence inducing elements11 5.4 Elongated enclosures .11 5.4.1 Ge
12、neral11 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 ducts.16 6 Supplementary design aspects17 6.1 General17 6.2 Positioning and shape of explosion vents17 6.3
13、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 Marking .21 7.2 Accompanying documents.22 Annex A (informative) Assessment of the level of congestion in rooms co
14、ntaining 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 14994:2007 (E) 3 Figures Figure 1 Value of exponent as a function of AV/V2/3.10 Figure 2 Pressure reduction of par
15、tially 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 closed at one end .14 Figure 4 Vent spacing needed to keep pred from exceeding 0,2 bar for propane in pipes f
16、lowing 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 Correspondence between this European Standard and Directive 94/9/EC26 EN 14994:2007 (E) 4 Foreword This docu
17、ment (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. This European Standard shall be given the status of a national standard, either by publication of an identical
18、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 to CEN by the European Commission and the European Free Trade Association, and supports essential requiremen
19、ts 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, the national standards organizations of the following countries are bound to implement this European Standa
20、rd: 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. EN 14
21、994:2007 (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 14460 form a series of three standards which are used together. NOTE 1 These three standards together represen
22、t 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 applicable to: vent sizing to protect against the internal pressure effects of a gas explosion; flame and pressure e
23、ffects 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 against effects generated by detonation reactions or runaway exothermic reactions including decomposition in the g
24、as 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 buildings; design, construction and testing of explosion venting devices, which are used to achieve explosion vent
25、ing1); protection against overpressures caused by events such as overfilling, overpressurisation, fire engulfment, overheating etc. NOTE 3 Protection by venting against dust and hybrid explosions is specified in EN 14491. 2 Normative references The following referenced documents are indispensable fo
26、r 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 1127-1:1997, Explosive atmospheres Explosion prevention and protection Part 1: Basic concepts and met
27、hodology 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 EN 14797. EN 14994:2007 (E) 6 EN 13673-1, Determination of the maximum explosion pressure and the maximum ra
28、te 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 of gases and vapours Part 2: Determination of the maximum rate of explosion pressure rise EN 14797:2006, Expl
29、osion 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 conditions conditions of the surrounding medium where the atmospheric pressure can vary between 80 kPa and 110
30、 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 having a length (height) to diameter ratio of less than 2 EN 14373:2005, 3.14.1 NOTE The length L is calcul
31、ated 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 circle with the same area as the actual cross-sectional area. 3.4 elongated enclosures enclosures with length (he
32、ight) 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 perpendicular to this axis. For non-circular cross-sections, D is the diameter of a circle with the same area as
33、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 the main flow during the explosion, with D being the diameter measured perpendicular to this axis. For non-
34、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 by explosion venting EN 14797:2006, 3.4 NOTE Examples of such devices are: bursting discs, vent panels and
35、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 should be used in making up the vent area for explosion venting EN 14797:2006, 3.2 3.8 gas explosion consta
36、nt 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 vessel volume of 1 m3multiplied by V1/33.9 static activation pressure pstatdifferential pressure at which the ret
37、aining 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 Turbulence is a very effective transporter and mixer, and generally causing an overall increase of combustio
38、n 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 Efdimensionless number used to define the efficiency of the explosion venting device EN 14797:2006, 3.14 4 V
39、enting 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 early stage of the explosion, releasing un-burnt gas/vapour and combustion products from the opening so reduc
40、ing 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 enclosure. All parts of the enclosure e.g. valves, sight-glasses, man-holes and ducts, which are exposed to the expl
41、osion 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 pressure. Information required for calculation of the vent area includes the design pressure of the enclosure, the
42、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 and other characteristics of the venting device, and the condition of the explosive atmosphere inside the en
43、closure. 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 in practice accounted for. In a system consisting of two connected enclosures, a gas explosion ignited in one
44、 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 combination can enhance the violence of the secondary explosion (see 5.6). Turbulence inducing elements such as shelv
45、es 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 standard, more intricate methods may need to be applied. In the informative Annex A rules are given when to ap
46、ply 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 the informative Annex A together with requirements for the experimental validation of these methods. 5 Vent
47、ing 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 values of vent cover inertia and enclosure volume. Accurate sizing of vents is the most important aspect of ven
48、t 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 flam
49、mable gases shall be measured according to appropriate methodologies. In this European Standard the combustion characteristics gas explosion constant KGand maximum explosion pressure pmaxare used. The gas explosion constant is derived from the maximum rate of pressure rise (dp/dt)max. The latter characteristic and the maximum explosion pressure pmaxshall be determined according to EN 13673-2 and EN 13673-1 respectively. 5.2 Venting of isolated compact enclosures A method to size vent openings of compact enclosures is presen
