SIST EN 14034-4:2005

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Determination of explosion characteristics of dust clouds - Part 4: Determination of the limiting oxygen concentration LOC of dust cloudsDétermination des caractéristiques d'explosion des nuages de poussieres - Partie 4 : Détermination de la concentration limite en oxygene CLO des nuages de poussiereBestimmung der Explosionskenngrößen von Staub/Luft-Gemischen - Teil 4: Bestimmung der Sauerstoffgrenzkonzentration SGK von Staub/Luft-Gemischen13.230Varstvo pred eksplozijoExplosion protectionICS:SIST EN 14034-4:2005enTa slovenski standard je istoveten z:EN 14034-4:200401-marec-2005SIST EN 14034-4:2005SLOVENSKI
STANDARD
EUROPEAN STANDARDNORME EUROPÉENNEEUROPÄISCHE NORMEN 14034-4September 2004ICS 13.230 English versionDetermination of explosion characteristics of dust clouds - Part4: Determination of the limiting oxygen concentration LOC ofdust cloudsDétermination des caractéristiques d'explosion des nuagesde poussières - Partie 4 : Détermination de la concentrationlimite en oxygène CLO des nuages de poussièresBestimmung der Explosionskenngrößen von Staub/Luft-Gemischen - Teil 4: Bestimmung derSauerstoffgrenzkonzentration SGK von Staub/Luft-GemischenThis European Standard was approved by CEN on 9 July 2004.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, 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© 2004 CENAll rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN 14034-4:2004: E

Electro pneumatic valve.16 Annex B (normative)
Dust disperser with 5 mm holes.19 Annex C (normative)
20 l sphere.22 C.1 General.22 C.2 Test apparatus.22 C.3 Test conditions.23 C.4 System to create the inert gas/air-mixture.24 C.5 Test procedure.24 Annex D (informative)
Examples of procedures to determine the LOC.25 Annex ZA (informative)
Relationship between this European Standard and the Essential Requirements of EU Directive 94/9.27 Bibliography.28

Annex II, Clause 1.0.1
1 Scope This document describes a test method for the determination of the limiting oxygen concentration 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, substances which do 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 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 14034-1:2004; Determination of explosion characteristics of dust clouds - Part 1: Determination of the maximum explosion pressure pmax of dust clouds. prEN 14034-2:2004; Determination of explosion characteristics of dust clouds - Part 2: Determination of the minimum rate of explosion pressure rise (dp/dt) max of dust clouds. prEN 14460, Explosion resistant equipment. 3 Terms and 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 maximum particle size will not exceed 500 µm. 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 ignition delay tv time between the initiation of the dust dispersion and the activation of the ignition source 3.4 inert gas non-flammable gas which will not support combustion and does not react to produce a flammable gas

Key 1 Pressure sensor 2 Chemical igniters 3 Inlet for purge air / inert gas 4 Dust disperser 5 Dust container 6 Fast acting valve 7 Connecting tube 8 Outlet for exhaust gas 9 Oxygen analyser Figure 1 — 1 m³ vessel (schematic)

4.2 Explosion vessel The standard explosion vessel is an explosion pressure resistant, spherical or cylindrical vessel having a volume of 1 m³ in accordance with prEN 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 that 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. 4.3 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 dm³. Its aspect ratio is 3:1. It is designed to withstand an overpressure of at least 20 bar (see Figure 2). The dust container 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 firing 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 between 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 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 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). For coarse, voluminous, fibrous or poorly flowing dust samples, it may not be possible 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 dust 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 these cases, additional safety measures should be employed, e.g. higher pressure resistance of the dust container.
1) (e.g. EN ISO 1127, DN 20, 3/4")

Key
1 6 mm hole 2 End cap with 6 mm hole Figure 3 — Location of the 6 mm holes in the dust disperser
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