Explosion venting devices

This European Standard specifies the requirements for venting devices used to protect enclosures against the major effects of internal explosions arising from the rapid burning of suspended dust, vapour or gas contained within. It includes the requirements for the design, inspection, testing, marking, documentation and packaging. This European Standard specifies explosion venting devices which are put on the market as autonomous protective systems.
Explosion venting devices are safety devices comprised of a pressure sensitive membrane fixed to and forming part of the structure that it protects, designed to intervene in the event of an explosion at a predetermined low pressure, to immediately open a vent area sufficient to ensure that the maximum pressure attained by the explosion within the enclosure does not exceed its designed resistance to pressure.
The application and specification of explosion venting devices is outlined for dust explosion protection in EN 14491 and for gas explosion protection in prEN 14994. The use of venting devices according to this European Standard on pipelines and on applications other than described in EN 14491 or prEN 14994 needs to be carefully evaluated and where appropriate their suitability needs to be confirmed by tests.
Flameless explosion venting devices avoid the breakthrough of flames into the surroundings. They are used to allow explosion venting in situations where the hazards of flames resulting from the venting action are not acceptable. Flameless explosion venting devices are treated in a separate standard.
This European Standard does not cover details for the avoidance of ignition sources from detection devices or other parts of the venting devices.

Einrichtungen zur Explosionsdruckentlastung

Diese Europäische Norm legt Anforderungen an Druckentlastungseinrichtungen fest, die zum Schutz von druckfesten Gehäusen gegen interne Explosionen angewendet werden. Erfasst werden Anforderungen an Herstellung, Inspektion, Prüfung, Kennzeichnung, Dokumentation und Verpackung. Einrichtungen zur Explosionsdruckentlastung werden als wesentliche Teile/Elemente von autonomen Schutzsystemen angewendet (z. B. Druckentlastungssysteme bei Gas- und Staub-Explosionen). Für andere Anwendungen als zur Explosionsdruckentlastung muss die jeweils zutreffende Europäische Norm angewendet werden. In der vorliegenden Norm werden keine Einzelheiten zur Vermeidung von Zündquellen an Detektoren oder anderen Teilen der Druckentlastungseinrichtungen erfasst.

Dispositifs de décharge d'explosion

La présente Norme européenne définit les exigences relatives aux dispositifs de décharge utilisés pour protéger des enceintes contre les principaux effets des explosions internes provenant de la combustion rapide des poussieres en suspension, des vapeurs ou des gaz qu’elles contiennent. Elle inclut les exigences relatives a la conception, a l’inspection, aux essais, au marquage, a la documentation et a l’emballage. Cette Norme européenne traite des dispositifs de décharge d’explosion commercialisés en tant que systemes de protection autonomes.
Les dispositifs de décharge d’explosion sont des dispositifs de sécurité constitués par une membrane sensible a la pression, fixée et intégrée a la structure qu’elle protege. Cette membrane est conçue pour s’ouvrir en cas d’explosion a une basse pression déterminée afin de libérer immédiatement une surface de décharge suffisante pour que la pression maximale atteinte par l’explosion a l’intérieure de l’enceinte n’excede pas sa capacité de résistance a la pression.
L’application et la spécification des dispositifs de décharge d’explosion est décrite dans l’EN 14491 pour la protection contre les explosions de poussieres et dans le prEN 14994 pour la protection contre les explosions de gaz. Il est nécessaire d’évaluer attentivement l’utilisation de dispositifs de décharge conformément a la présente Norme européenne pour les canalisations (L/D > 20) et pour des applications autres que celles décrites dans l’EN 14491 ou dans le prEN 14994. Le cas échéant, leur bonne adaptation doit etre confirmée par des essais.
Les dispositifs de décharge d’explosion sans flammes permettent d’éviter que la flamme de l’explosion sorte dans l’espace environnant. Ils sont utilisés pour permettre la décharge de l’explosion dans les situations ou les effets néfastes qui pourraient etre produits par la flamme résultant de cette décharge ne sont pas acceptables. Les dispositifs de décharge d’explosion sans flammes sont traités dans une norme séparée.

Naprave za razbremenitev tlaka eksplozij

General Information

Status
Published
Publication Date
31-Mar-2007
Current Stage
6060 - National Implementation/Publication (Adopted Project)
Start Date
01-Apr-2007
Due Date
01-Apr-2007
Completion Date
01-Apr-2007

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2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Explosion venting devicesNaprave za razbremenitev tlaka eksplozijDispositifs de décharge d'explosionEinrichtungen zur ExplosionsdruckentlastungTa slovenski standard je istoveten z:EN 14797:2006SIST EN 14797:2007en13.230ICS:SLOVENSKI

STANDARDSIST EN 14797:200701-april-2007

EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 14797December 2006ICS 13.230 English VersionExplosion venting devicesDispositifs de décharge d'explosionEinrichtungen zur ExplosionsdruckentlastungThis European Standard was approved by CEN on 4 November 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 14797:2006: E

EN 14797:2006 (E) 2 Contents Page Foreword..............................................................................................................................................................4 1 Scope......................................................................................................................................................5 2 Normative references............................................................................................................................5 3 Terms and definitions...........................................................................................................................6 4 Design requirements.............................................................................................................................8 4.1 General....................................................................................................................................................8 4.2 Potential sources of ignition................................................................................................................9 5 Types of explosion venting devices....................................................................................................9 5.1 Explosion venting devices with reusable elements...........................................................................9 5.2 Explosion venting devices with non reusable elements...................................................................9 6 Back pressure supports........................................................................................................................9 6.1 General....................................................................................................................................................9 6.2 Opening back pressure supports......................................................................................................10 6.3 Non-opening back pressure supports...............................................................................................10 7 Testing of explosion venting devices................................................................................................10 7.1 General..................................................................................................................................................10 7.2 Static activation pressure...................................................................................................................10 7.3 Explosion testing.................................................................................................................................12 8 Information for use..............................................................................................................................16 9 Assembly, replacements or reusability.............................................................................................17 10 Marking.................................................................................................................................................17 10.1 General..................................................................................................................................................17 10.2 Explosion venting devices with reusable retaining elements........................................................17 10.3 Explosion venting devices with non-reusable retaining elements.................................................18 10.4 Omission of markings.........................................................................................................................18 11 Packaging.............................................................................................................................................19 11.1 General..................................................................................................................................................19 11.2 Marking.................................................................................................................................................19 Annex A (informative)

Examples for explosion venting devices.................................................................20 A.1 Re-closing explosion venting devices..............................................................................................20 A.2 Devices which require manual repositioning or replacement of the retaining element..............21 A.3 Devices with non reusable elements.................................................................................................23 Annex B (informative)

Service and maintenance...........................................................................................26 B.1 General..................................................................................................................................................26 B.2 Servicing...............................................................................................................................................26 Annex ZA (informative)

Relationship between this European Standard and the Essential Requirements of EU Directive 94/9/EC..............................................................................................27 Bibliography......................................................................................................................................................29 Figures Figure 1 — Direct comparison method..........................................................................................................14 Figure 2 — Example for direct comparison method....................................................................................15

EN 14797:2006 (E) 3 Figure A.1 — Example for an explosion door................................................................................................21 Figure A.2 — Example for a buckling-rod device..........................................................................................22 Figure A.3 — Example for a bursting panel device.......................................................................................23 Figure A.4 — Example for a restrained pop-out panel device.....................................................................24 Figure A.5 — Example for a back pressure support.....................................................................................25 Tables Table 1 — Symbols and their descriptions......................................................................................................8 Table 2 — Number of tests of explosion venting devices with non-reusable elements...........................12 Table ZA.1 — Correspondence between this European Standard and Directive 94/9/EC........................27

EN 14797:2006 (E) 4 Foreword This document (EN 14797:2006) 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 June 2007, and conflicting national standards shall be withdrawn at the latest by June 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 requirements of EU Directive(s). For relationship with EU Directive(s), 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 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 14797:2006 (E) 5 1 Scope This European Standard specifies the requirements for venting devices used to protect enclosures against the major effects of internal explosions arising from the rapid burning of suspended dust, vapour or gas contained within. It includes the requirements for the design, inspection, testing, marking, documentation and packaging. This European Standard specifies explosion venting devices which are put on the market as autonomous protective systems. Explosion venting devices are safety devices comprised of a pressure sensitive membrane fixed to and forming part of the structure that it protects, designed to intervene in the event of an explosion at a predetermined low pressure, to immediately open a vent area sufficient to ensure that the maximum pressure attained by the explosion within the enclosure does not exceed its designed resistance to pressure. The application and specification of explosion venting devices is outlined for dust explosion protection in EN 14491 and for gas explosion protection in prEN 14994. The use of venting devices according to this European Standard on pipelines and on applications other than described in EN 14491 or prEN 14994 needs to be carefully evaluated and where appropriate their suitability needs to be confirmed by tests. Flameless explosion venting devices avoid the breakthrough of flames into the surroundings. They are used to allow explosion venting in situations where the hazards of flames resulting from the venting action are not acceptable. Flameless explosion venting devices are treated in a separate standard. This European Standard does not cover details for the avoidance of ignition sources from detection devices or other parts of the venting devices. 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 13237:2003, Potentially explosive atmospheres — Terms and definitions for equipment and protective systems intended for use in potentially explosive atmospheres EN 13463-1, Non-electrical equipment for potentially explosive atmospheres — Part 1: Basic method and requirements EN 14491, Dust explosion venting protective systems prEN 14994:2005, Gas explosion venting protective systems EN 60079-0, Electrical apparatus for explosive gas atmospheres — Part 0: General requirements

(IEC 60079-0:2004) prEN 61241-0, IEC 61241-0, Ed. 1: Electrical apparatus for use in the presence of combustible dust — Part 0: General requirements

EN 14797:2006 (E) 6 3 Terms and definitions For the purposes of this document, the terms and definitions given in EN 13237:2003 and the following apply. 3.1 batch quantity of non-reusable retaining elements made as a single group of the same type, size, materials and specified static activation pressure requirements when the non-reusable retaining elements are manufactured from the same lot of material 3.2 effective vent area AE product of the geometric vent area Ad and the venting efficiency Ef for the venting device NOTE It is the effective vent area that should be used in making up the vent area for explosion venting. 3.3 explosion venting protective measure which will prevent the explosion pressure in a vessel or other closed volume from exceeding the vessel design strength by exhausting the explosion through an explosion venting device in the vessel walls 3.4 explosion venting device device which protects a vessel or other closed volume by explosion venting 3.5 gas explosion constant KG maximum value of the pressure rise per unit time (dp/dt)max during the explosion of a specific explosive atmosphere in a closed vessel under specific test conditions normalized to a vessel volume of 1 m3 multiplied by V1/3 [prEN 14994:2005, 3.8] 3.6 dust explosion constant Kst maximum value of explosion pressure rise per unit of time (dp/dt)max in a volume of 1 m3 multiplied by V1/3 3.7 retaining element part or parts of the explosion venting device that determines the activation pressure NOTE It may or may not be re-useable. 3.8 reduced explosion pressure pred overpressure generated by an explosion of an explosive atmosphere in an enclosure protected by explosion venting 3.9 restraining element parts of some explosion venting devices that prevent components or objects from becoming dangerous missiles

EN 14797:2006 (E) 7 NOTE They may or may not be reusable. 3.10 specific mass total mass per unit area (Ad) of the venting element. The specific mass is used in determining the effect of inertia 3.11 static activation pressure pstat differential pressure at which the retaining element activates such that the venting element is able to open 3.12 static activation pressure tolerance range range of differential pressure between the specified maximum static activation pressure and the specified minimum static activation pressure or the range of differential pressure in positive and negative percentages or quantities which is related to the specified static activation pressure 3.13 vent area Ad geometric vent area of an explosion venting device.

NOTE The vent area is the minimum cross-sectional flow area of the explosion venting device taking into consideration the possible reduction of the cross section, e.g. by back pressure support, restraining devices and parts of the explosion venting device which remain after venting 3.14 venting efficiency Ef dimensionless number used to define the efficiency of the explosion venting device as determined in 7.3.4 3.15 venting element part of the explosion venting device that covers the vent area and opens under explosion conditions NOTE It may or may not incorporate the retaining element - it may or may not be reusable.

EN 14797:2006 (E) 8 Table 1 — Symbols and their descriptions Symbol Description Units A Required vent area m2 AE Effective vent area m2 Ad Geometric vent area m2 Ef Venting efficiency - pstat Static activation pressure bar pred Reduced explosion pressure bar pred, baseline Reduced explosion pressure measured using an explosion venting device with a specific mass < 0,5 kg m-2 bar pred, test device

Reduced explosion pressure measured using an explosion venting device under investigation bar KG Gas explosion constant bar m s-1 Kst Dust explosion constant bar m s-1 V Volume of vessel to be protected by explosion venting m3 4 Design requirements 4.1 General Explosion venting devices shall be designed so that they open when subjected to pressure exceeding their static activation pressure (within a stated static activation pressure tolerance range). Any part not designed to rupture shall not rupture. Venting elements shall be designed so that they shall not fragment to produce dangerous missiles. These requirements may be proved by explosion testing, but other methods e.g. calculation, may be used if their validity has been verified from representative explosion tests. Explosion venting devices shall employ re-usable elements or non re-usable elements (see Clause 5). Explosion venting devices may be provided with back pressure supports (see Clause 6). The performance capability of an explosion venting device is defined by the following parameters:  the static activation pressure pstat and its tolerance;  the maximum KG/Kst values specified by the manufacturer;  the maximum reduced pressure pred specified by the manufacturer;  the minimum venting efficiency Ef of the device. Tests to determine or prove these parameters are given in Clause 7. Explosion venting devices shall be designed to maintain their specified performance taking into account environmental and process conditions. Build-up or addition of any substance on external surfaces of the device (e.g. snow and ice) and the build-up of product on the internal surfaces of the device may affect the correct operation of the device, so particular attention shall be given to preventing such effects. Material used for the parts of explosion venting devices shall be selected on the basis of their suitability with regard to the chemical and physical conditions to which they will be subjected in service.

EN 14797:2006 (E) 9 It is common practice to use electrical detection devices to sense vent function, to operate an alarm or shut plant down. Such detection devices shall meet the requirements of EN 13463-1, EN 60079-0 and prEN 61241-0. Explosion venting devices can incorporate thermal insulation on the internal or external or both sides to prevent heat loss and/or condensation. Gaskets or seals forming part of an explosion venting device, shall be as specified by the manufacturer and shall be compatible with the chemical, thermal, mechanical and environmental demands of the application. 4.2 Potential sources of ignition Due consideration shall be given to potential sources of ignition in the design and material specification of venting devices, e.g. static electricity, heating and detection devices. Requirements for potential sources of ignition in electrical and non-electrical equipment apply, as stated in EN 13463-1. 5 Types of explosion venting devices 5.1 Explosion venting devices with reusable elements Explosion venting devices with re-usable elements shall be distinguished as follows: a) normally automatically re-closing devices; b) devices which require manual re-positioning of the retaining elements. For examples see Annex A. 5.2 Explosion venting devices with non reusable elements Explosion venting devices with non reusable elements describe all devices which after having functioned can not be reused without the replacement of an individual element or a number of elements. For examples see Annex A. NOTE Flameless explosion venting devices are treated in a separate standard. 6 Back pressure supports 6.1 General When the pressure external to the explosion venting device is greater than the pressure inside the protected vessel, unless the device is capable of withstanding this pressure difference, a back pressure support shall be fitted which prevents damage to the venting element. The back pressure support shall be either permanently attached to the venting element or it shall form part of the explosion venting device that ensures it is fitted to the correct side of the venting element. The back pressure support shall not cause the explosion venting device to perform incorrectly. When back pressure supports are used consideration shall be given to the effects of the back pressure support on the vent area and venting efficiency.

EN 14797:2006 (E) 10 6.2 Opening back pressure supports The opening back pressure support shall give adequate support to the venting element. The support shall be of a design such that the pressure in the system is transmitted to the venting element. When the explosion venting device is activated, the back pressure support shall open simultaneously with the venting element. The effect of the specific mass of the opening back pressure supports shall be considered in the determination of the efficiency of an explosion venting device. 6.3 Non-opening back pressure supports The non-opening back pressure support shall give adequate support to the venting element. The support shall be of a design such that the pressure in the system is transmitted to the venting element. The effect of non-opening back pressure supports shall be considered when determining the effective vent area. 7 Testing of explosion venting devices 7.1 General Each design of explosion venting device shall be subject to type tests and design assessments to assure: a) function and mechanical integrity (type testing only); b) efficiency, where required (type testing only); c) static activation pressure. The static activation pressure and the mechanical strength of the explosion venting device shall be proven. 7.2 Static activation pressure 7.2.1 General All explosion venting devices shall be tested for static activation pressure. The number of tests required shall be in accordance with 7.2.5. Depending on the explosion venting device type, the static activation pressure can be measured using either a pressure test method or a mechanical test method. The observed static activation pressure shall be recorded. The static activation pressure test shall have starting conditions where inside and outside pressure conditions are equal. The static activation pressure is observed:  when discharge begins;  when the venting element releases from the retaining element.

EN 14797:2006 (E) 11 7.2.2 Pressure test method The retaining elements and where applicable the venting elements shall be tested in an appropriate arrangement where they are assembled and mounted according to the manufacturer's instructions. The test arrangement shall be equipped with calibrated measuring instruments suitable for the testing of the explosion venting device. The pressure measuring device shall be located as near as practicable to the explosion venting device and connected in such a way as to minimize pressure drop. The pressure shall be increased to 90 % of the expected minimum static activation pressure in a time not less than 5 s and thereafter the pressure shall be increased at a linear rate which allows accurate reading or recording of the pressure measurement system but in not more than 120 s. Appropriate safety measures shall be observed when carrying out the tests. 7.2.3 Mechanical test method The retaining element and where applicable the venting element shall be tested in an appropriate arrangement where they are assembled and mounted according to the manufacturer's instructions. The test arrangement shall be equipped with calibrated measuring instruments suitable for the test. By applying continuously increasing mechanical forces on the venting element, the activation of an explosion venting device is effected. The direction of the force shall be normal to the venting element. The point of application of the force shall depend on the design of the explosion venting device. Mechanical forces shall be applied almost statically (10 kN m-2 min-1). Appropriate safety measures shall be observed when carrying out the tests. 7.2.4 Influence of temperature The static activation pressure shall normally be determined at a temperature in the range of 15 °C to 25 °C. If there is a temperature dependence of the static activation pressure, this dependence shall be determined for the temperature range in which the device will be used. 7.2.5 Number of tests 7.2.5.1 Devices with non reusable elements A number of explosion venting devices with non-reusable elements shall be selected at random from each batch (see Table 2) and be tested in accordance with 7.2.1 in order to verify that the static activation pressure meets the specified requirements. Static activation tests carried out during the manufacture of the batch of explosion venting devices i.e. discarded or trial tests shall not be considered part of the batch testing procedure.

EN 14797:2006 (E) 12 Table 2 — Number of tests of explosion venting devices with non-reusable elements Total number in a batch Number to be tested Less than 10 2 10 to 15 3 16 to 30 4 31 to 100 6 101 to 250 4 % but not less than 8 251 to 1 000 3 % but not less than 10

All the test results shall fall in the tolerance range for the static activation pressure specified by the manufacturer. Otherwise the batch shall be deemed to have failed the test. 7.2.5.2 Devices with reusable elements The static activation pressure of explosion venting devices with reusable elements shall be determined in at least three tests per device. All the test results shall fall in the tolerance range for the static activation pressure specified by the manufacturer. Otherwise the device shall be deemed to have failed the test. 7.3 Explosion testing 7.3.1 General Mechanical strength and venting efficiency of explosion venting devices shall be determined. The manufacturer shall specify the range of nominal sizes of the venting device, pstat-value of the venting device, the maximum Kst/KG and pmax-value at which the device can be used, and the maximum pred-value for which the device is designed. For type testing of a range of explosion venting devices of an identical design, but a defined range of nominal sizes, testing shall be carried out on a representative selection of nominal sizes from this range. Tests shall be performed on the smallest and largest sizes in this range and if there are more than five different sizes also tests shall be performed with at least one intermediate size. The explosion venting devices shall be mounted on the test apparatus either directly or with an appropriate adapter. The area of the explosion venting device shall not be greater than the opening in the test apparatus. 7.3.2 Explosion testing for function and mechanical integrity The mechanical integrity of the venting device shall be assessed by an explosion test using an explosion with a Kst or KG-value not less than that provided by the manufacturer as the maximum value for which the device is designed (see 7.3.1) and a reduced explosion pressure not less than 1,1 × the maximum value that the device is designed to withstand (see 7.3.1). The volume of the test vessel shall satisfy the testing requirement of 7.3.1. A minimum of at least 2 explosion tests shall be carried out. The mechanical integrity shall be such that any part not designed to fail shall not fail and that no dangerous missiles are produced. All tests shall be documented.

EN 14797:2006 (E) 13 7.3.3 Effect of specific mass on venting efficiency 7.3.3.1 Specific mass smaller or equal to 0,5 kg m-2 Explosion venting devices which are almost inertia-free (with a specific mass less than 0,5 kg m-2) do not impede the venting process to any great extent. For the determination of the venting efficiency of such explosion venting devices explosion testing is therefore not required and the venting efficiency shall be 1. 7.3.3.2 Specific mass greater than 0,5 kg m-2 and smaller or equal to 10 kg m-2 Explosion venting devices with venting elements with a mass per unit area greater than 0,5 kg m-2 can influence the venting process by their opening and release behavior. Experiments have shown that explosion venting devices with an inertia greater than 0,5 kg m-2 and smaller or equal to 10 kg m-2 can have a venting efficiency < 1,0 depending on application. NOTE According to EN 14491 where: A / V0,753 < 0,07. The venting efficiency Ef = 1,0. This is valid for pstat

≤ 0,1 bar and 0,1 bar < pred < 2 bar. For all other conditions the efficiency has to be determined by tests (see 7.3.4.1). 7.3.3.3 Specific mass greater than 10 kg m-2 This influence shall be determined by comparing the venting efficiency to that of an explosion venting device (with a specific mass less than 0,5 kg m-2 e.g. a bursting foil) regarded as being inertia-free as described in 7.3.4. 7.3.4 Determination of venting efficiency by direct comparison method The venting efficiency shall be determined by explosion tests. The complete venting device, including all added elements, shall be compared to a venting device with a specific mass < 0,5 kg m-2 (e.g. bursting foil) of same size, static activation pressure pstat and geometry without any obstructions. In addition to the tests at the maximum KG, Kst values specified by the manufacturer, tests shall also be done at lower KG, Kst values. Three to five KG, Kst values are sufficient, as evenly distributed as is practicable between KG, Kst = 50 bar m s-1 and the maximum values specified by the manufacturer. More tests shall be performed if no single relationship is found between KG, Kst value and pred. In the case of temperature dependence on performance of the venting device, the test shall be carried out with the test conditions resulting in the highest pred. The effective venting efficiency shall be calculated by t

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