1、BRITISH STANDARDBS EN 15188:2007Determination of the spontaneous ignition behaviour of dust accumulationsICS 13.230g49g50g3g38g50g51g60g44g49g42g3g58g44g55g43g50g56g55g3g37g54g44g3g51g40g53g48g44g54g54g44g50g49g3g40g59g38g40g51g55g3g36g54g3g51g40g53g48g44g55g55g40g39g3g37g60g3g38g50g51g60g53g44g42g4
2、3g55g3g47g36g58BS EN 15188:2007This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 July 2008 BSI 2008ISBN 978 0 580 55237 3National forewordThis British Standard is the UK implementation of EN 15188:2007. It is identical with EN 15188.The UK p
3、articipation 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.EN 15188:2007 is concerned with the determination of the spontaneous igniti
4、on behaviour of dust accumulations. It prescribes test apparatus, the preparation of samples, an experimental procedure and discusses the analysis of results.The characterization of the self-ignition behaviour of dust deposits of different scale and of different bulk geometric shapes from tests on a
5、 number of differently sized samples can be obtained by plotting the logarithms of the volume/surface ratios versus the reciprocal of the self ignition temperature. EN 15188:2007 recognizes that the spread of the slope of the straight lines from this plot determined by different laboratories using d
6、ifferently constructed ovens is fairly large. Scale up of these results to industrial scale may lead to non-negligible differences in the values of ignition temperature.This should be taken into account when using this standard.This publication does not purport to include all the necessary provision
7、s of a contract. Users are responsible for its correct application.Compliance with a British Standard cannot confer immunity from legal obligations.Amendments/corrigenda issued since publicationDate CommentsEUROPEAN STANDARDNORME EUROPENNEEUROPISCHE NORMEN 15188August 2007ICS 13.230English VersionDe
8、termination of the spontaneous ignition behaviour of dustaccumulationsDtermination de laptitude lauto-inflammation desaccumulations de poussiresBestimmung des Selbstentzndungsverhaltens vonStaubschttungenThis European Standard was approved by CEN on 13 July 2007.CEN members are bound to comply with
9、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 CEN Management Centre
10、 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 CEN Management Centre has the same status as theofficial ver
11、sions.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, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal,Romania, Slovakia, Slovenia, Spa
12、in, 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 All rights of exploitation in any form and by any means reservedworldwide for CEN national Memb
13、ers.Ref. No. EN 15188:2007: EEN 15188:2007 (E) 2 Contents Page Foreword3 Introduction .4 1 Scope 5 2 Terms and definitions .5 3 Test apparatus .6 3.1 Sample baskets6 3.2 Oven 6 3.3 Thermocouples 6 3.4 Temperature recording equipment 6 4 Preparation of dust samples 6 5 Procedure .8 5.1 Experimental P
14、rocedure .8 5.2 Evaluation of tests.9 5.3 Calibration of thermocouples.10 6 Test report 11 Annex A (informative) Evaluation of experimental results for self-ignition temperatures 13 A.1 Introduction13 A.2 Methods based on the thermal explosion theory.13 A.3 Numerical solution of Fouriers equation .1
15、6 Annex ZA (informative) Relationship between this European Standard and the Essential Requirements of EU Directive 94/9/EC 20 Bibliography 21 BS EN 15188:2007EN 15188:2007 (E) 3 Foreword This document (EN 15188:2007) has been prepared by Technical Committee CEN/TC 305 “Potentially explosive atmosph
16、eres - 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 February 2008, and conflicting national standards shall be wit
17、hdrawn at the latest by February 2008. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN and/or CENELEC shall not be held responsible for identifying any or all such patent rights. This document has been prepared under a mandate
18、 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 94/9/EC, see informative Annex ZA, which is an integral part of this document. According to the CEN/CENELEC Internal Regul
19、ations, 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, Nethe
20、rlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and the United Kingdom. BS EN 15188:2007EN 15188:2007 (E) 4 Introduction The self-ignition behaviour of combustible dusts depends on their chemical composition as well as on related substance properties. It als
21、o depends on the size and geometry of the body of material, and, last but not least on the ambient temperature. The reason behind self-heating (or possibly self-ignition) is that the surface molecules of combustible dust particles undergo exothermic reactions with the oxygen in air transported into
22、the void volume between the particles even at normal temperatures. Any heat then released will cause the temperature of the reactive dust-air system to rise, thus accelerating the reaction of additional dust molecules with oxygen, etc. A heat balance involving the heat produced inside the bulk (quan
23、tity and surface of reactive surface molecules, specific heat producing rate) and the heat loss to the surroundings (heat conductivity and dimension of the bulk, heat transfer coefficient on the outside surface of the bulk and the size of the latter) is decisive as to whether a steady state temperat
24、ure is reached at a slightly higher temperature level (the heat loss terms are larger than the heat production term), or whether temperatures in the bulk will continue to rise up to self-ignition of the dust, if heat transport away from the system is insufficient (in this case the heat production te
25、rm is larger than all heat losses). The experimental basis for describing the self-ignition behaviour of a given dust is the determination of the self-ignition temperatures (TSI) of differently-sized bulk volumes of the dust by isoperibol hot storage experiments (storage at constant oven temperature
26、s) in commercially available ovens. The results thus measured reflect the dependence of self-ignition temperatures upon dust volume. Plotting the logarithms of the volume/surface ratios lg (V/A) of differently sized dust deposits versus the reciprocal values of the respective self-ignition temperatu
27、res 1/TSIin K-1 or following other evaluation procedures described in Annex A one produces straight lines, allowing interpolation, to characterise the self-ignition behaviour of dust deposits of a different scale and of a different bulk geometric shapes (see 5.1). Experience has shown that the sprea
28、d of slopes of such straight lines determined by different laboratories using differently constructed ovens is fairly large. This is the reason why scale up of those results to industrial scale will lead to non-negligible errors in TSI. Experience has shown, that it seems necessary to prescribe the
29、installation of a unique inner chamber into the oven, surrounding the dust samples and the thermocouples, with an also prescribed air flow through this chamber. In this way the spread of results should be minimised. Decisions on the design of this inner chamber and on the amount of air flow respecti
30、vely other test setups leading to comparable results have to be carried out later on. If it is possible based on suitable thermo analytic test procedures (adiabatic, isothermal or dynamic tests) to derive a reliable formal kinetic model, which describes the heat production of the substance as a func
31、tion of temperature, then the volume dependency of the self-ignition temperature may be calculated according to the methods described in Annex A. BS EN 15188:2007EN 15188:2007 (E) 5 1 Scope This European Standard specifies analysis and evaluation procedures for determining self-ignition temperatures
32、 (TSI) of combustible dusts or granular materials as a function of volume by hot storage experiments in ovens of constant temperature. The specified test method is applicable to any solid material for which the linear correlation of lg (V/A) versus the reciprocal self-ignition temperature 1/TSI(with
33、 TSIin K) holds (i.e. not limited to only oxidatively unstable materials). This European Standard is not applicable to the ignition of dust layers or bulk solids under aerated conditions (e.g. as in fluid bed dryer). This European Standard should not be applied to dusts like recognised explosives th
34、at do not require atmospheric oxygen for combustion, nor to pyrophoric materials. NOTE Because of regulatory and safety reasons “recognised explosives” are not in the scope of this European Standard. In spite of that, substances which undergo thermal decomposition reactions and which are not “recogn
35、ised explosives” but behave very similarly to self-ignition processes when they decompose are in the scope. If there are any doubts as to whether the dust is an explosive or not, experts should be consulted. 2 Terms and definitions For the purposes of this document, the following terms and definitio
36、ns apply. 2.1 self-ignition temperature TSIhighest temperature at which a given volume of dust just does not ignite NOTE Self-ignition temperature is expressed in C. 2.2 oven temperature arithmetic mean of the measured values of two thermocouples, both freely installed in an oven at half the distanc
37、e between the wall and the surface of the dust sample NOTE Oven temperature is expressed in C. 2.3 sample temperature temperature measured at the centre of the dust sample using a thermocouple NOTE Sample temperature is expressed in C. 2.4 induction time interval of time between reaching the storage
38、 temperature and an ignition NOTE Induction time is expressed in h. 2.5 ignition initiation of combustion EN 13478:2001, 3.20 BS EN 15188:2007EN 15188:2007 (E) 6 3 Test apparatus 3.1 Sample baskets The samples have to be loosely filled into mesh wire baskets of different volumes. The baskets have to
39、 be open at the top and closed at the bottom. They consist of a narrow-meshed wire net, made of e.g. stainless steel. The width of the mesh has to be chosen in such a way that the dust cannot fall through the mesh, but the diffusion of oxygen from the oven air into the dust sample is not hindered. R
40、ecommended shapes of the mesh wire baskets are that of a cylinder with a height to diameter ratio of 1 or that of a cube. To allow an assessment of the self-ignition behaviour of dust accumulations of larger sizes than the laboratory-scale at least three mesh wire baskets of different volumes have t
41、o be used for the tests. NOTE 1 A higher level of certainty is achieved with four different sample volumes. The smallest volume should normally be in the order of 10 cm3and the largest should normally not be smaller than approximately 1 l. If only a limited amount of sample material is available, ev
42、en smaller baskets may be used. However it has to be assured that the volume of the basket following in a series exceeds that of the previous one by a factor of 2 at a minimum. NOTE 2 For the sake of comparing products with respect to their self-ignition behaviour in devices or apparatus, where the
43、sizes of the dust accumulations are limited for the reason of a specific design, often the determination of the self-ignition temperature for a basket of 400 cm3or 1 000 cm3is sufficient. 3.2 Oven Commercially available ovens can be used. They shall have an air inlet opening in the lower section and
44、 an air outlet opening in the upper section (see schematic drawing in Figure 1). They should have a useful volume of about 120 l (enabling the installation of an inner chamber into the oven, surrounding the dust samples and the thermocouples, being equipped with an upstream heat exchanger consisting
45、 of copper tube coils) and be controllable in a temperature range from 35 C to 300 C. This construction enables a prescribed air flow through this chamber. The oven temperature shall be stable within a range of 1 % of the respective oven temperature. Alternative test arrangements can be used to prov
46、ide the specified test conditions. For example, the test basket can be shielded by placing it inside an additional mesh wire basket. Mechanically ventilated ovens can also be used provided the test basket is shielded (e.g. by using an inner chamber or an additional mesh wire basket). 3.3 Thermocoupl
47、es Both for measuring the sample temperature as well as for measuring the oven temperature, sheathed thermocouples with an external diameter of e.g. 1 mm are recommended. 3.4 Temperature recording equipment Appropriate data acquisition may be used for measuring and recording signals of the thermocou
48、ples. 4 Preparation of dust samples To investigate situations occurring in practice a representative sample should be used (produced by the operating conditions of the process). The sample characteristics shall be recorded in the test report. The bulk density of the dust for each experiment is deter
49、mined by weighing the baskets as well as the moisture content of the dust before and after filling. BS EN 15188:2007EN 15188:2007 (E) 7 Key 1 heating oven 5 thermocouple for measuring sample temperature 2 inner chamber (volume 50 l) 6 wire gauze cylinder with dust sample 3 air outlet, diameter 10 mm 7 deflector 4 thermocouple for measuring oven temperature 8 air inlet (preheated air, adjustable flow rate), diameter 8 mm Figure 1 Suggested experimental setup for hot storage tests If the results are required to compare different dusts with each other
