1、| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | BRITISH STANDARD BS EN 50281-2-1:1999 Inco
2、rporating Amendment No. 1 The European Standard EN 50281-2-1:1998 has the status of a British Standard ICS 29.260.20 NO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAW Electrical apparatus for use in the presence of combustible dust Part 2-1: Test methods Methods of determining m
3、inimum ignition temperaturesThis British Standard, having been prepared under the direction of the Electrotechnical Sector Committee, was published under the authority of the Standards Committee and comes into effect on 15 May 1999 BSI 10-1999 ISBN 0 580 32398 6 BS EN 50281-2-1:1999 Amendments issue
4、d since publication Amd. No. Date Comments 10756 October 1999 Latest date of withdrawal of conflicting national standards changed National foreword This British Standard is the English language version of EN 50281-2-1:1998, including Corrigendum August 1999. The UK participation in its preparation w
5、as entrusted by Technical Committee GEL/31, Electrical apparatus for explosive atmospheres, to Subcommittee GEL/31/20, Apparatus for use in the presence of ignitable dust, which has the responsibility to: aid enquirers to understand the text; present to the responsible European committee any enquiri
6、es on the interpretation, or proposals for change, and keep the UK interests informed; monitor related international and European developments and promulgate them in the UK. A list of organizations represented on this committee can be obtained on request to its secretary. Cross-references The Britis
7、h Standards which implement international or European publications referred to in this document may be found in the BSI Standards Catalogue under the section entitled “International Standards Correspondence Index”, or by using the “Find” facility of the BSI Standards Electronic Catalogue. A British
8、Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct application. Compliance with a British Standard does not of itself confer immunity from legal obligations. Summary of pages This document comprises a front co
9、ver, an inside front cover, the EN title page, pages 2 to 24, an inside back cover and a back cover. The BSI copyright notice displayed in this document indicates when the document was last issued.CENELEC European Committee for Electrotechnical Standardization Comite Europe en de Normalisation Elect
10、rotechnique Europa isches Komitee fu r Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1050 Brussels 1998 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELEC Members. Ref. No. 50281-2-1:1998 E EUROPEAN STANDARD EN 50281-2-1 NORME EUROPE
11、 ENNE EUROPA ISCHE NORM September 1998 ICS 29.260.20 Incorporates Corrigendum August 1999 Descriptors: English version Electrical apparatus for use in the presence of combustible dust Part 2-1: Test methods Methods of determining minimum ignition temperatures Mate riels e lectriques destine sa e tre
12、 utilise se n pre sence de poussie res combustibles Partie 2-1: Me thodes dessai Me thodes de de termination de la tempe rature minimale dinflammation de la poussie re Elektrische Betriebsmittel zur Verwendung in Bereichen mit brennbarem Staub Teil 1-2: Untersuchungsverfahren Verfahren zur Bestimmun
13、g der Mindestzu ndtemperatur von Staub This European Standard was approved by CENELEC on 1998-09-01. CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration
14、. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the Central Secretariat or to any CENELEC member. This European Standard exists in three official versions (English, French, German). A version in any other language made by transla
15、tion under the responsibility of a CENELEC member into its own language and notified to the Central Secretariat has the same status as the official versions. CENELEC members are the national standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ire
16、land, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.Page 2 EN 50281-2-1:1998 BSI 10-1999 Foreword This European Standard was prepared by the Technical Committee CENELEC TC 31, Electrical apparatus for explosive atmospheres. The text of the draft was
17、submitted to the Unique Acceptance Procedure and was approved by CENELEC EN 50281-2-1 on 1998-09-01. This European Standard was prepared under a mandate given to CENELEC by the European Commission and the European Free Trade Association and supports the essential health and safety requirements of th
18、e EC Directive 94/9/EC. The following dates have been fixed: latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement (dop) 1999-09-01 latest date by which national standards conflicting with the EN have to be withdrawn (d
19、ow) 2003-06-30 Annexes designated “normative” are part of the body of the standard. In this standard, annexes A and B are normative. Contents Page Foreword 2 Introduction 3 1 Scope 3 2 Normative references 3 3 Definitions 3 4 Method A: dust layer on a heated surface at a constant temperature 4 4.1 P
20、reparation of dust sample 4 4.2 Test apparatus 4 4.3 Procedure 5 4.4 Test acceptance criteria 6 4.5 Reporting of results 6 4.6 Application of results 6 5 Method B: dust cloud in a furnace at a constant temperatue 6 5.1 Preparation of dust sample 6 5.2 Test apparatus 7 5.3 Procedure 7 5.4 Air pressur
21、e 7 5.5 Criterion for ignition 7 5.6 Minimum ignition temperature of a dust cloud 7 5.7 Reporting of results 7 Annex A (normative) Method A: Construction of a heated surface and measurement of temperature distribution on the surface 8 Annex B (normative) Costruction of a constant temperature furnace
22、 14Page 3 EN 50281-2-1:1998 BSI 10-1999 Introduction This European Standard describes methods for determining the minimum ignition temperature of dust for the purpose of selecting electrical apparatus. These are: Method A: Dust layer on a heated surface at a constant temperature (clause 4); Method B
23、: Dust cloud in a furnace at a constant temperature (clause 5). Method A determines the minimum ignition temperature of a dust layer on a prescribed heated surface. Method B determines the minimum ignition temperature of a dust cloud within a prescribed heated furnace. The test methods are of a gene
24、ral nature, and may be used for purposes of comparison, but in certain industrial situations further tests may be necessary. The methods for determining the minimum ignition temperatures are not suitable for use with recognized explosives, for example, gunpowder, dynamite, or mixtures of substances
25、which may, under some circumstances, behave similarly. Where there is doubt, an indication of the existence of a hazard due to explosive properties may be obtained by testing a very small quantity of the dust on a surface at 4008C or higher, located remotely from the operator. 1 Scope This European
26、Standard specifies two test methods for determining the minimum ignition temperatures of dust for the purpose of selecting electrical apparatus for use in the presence of combustible dust in accordance with EN 50281-1-2:1998 and constructed in accordance with EN 50281-1-1:1998. These methods are not
27、 suitable for use with substances having explosive properties. Method A (clause 4) is applicable to the determination of the minimum temperature of a prescribed hot surface which will result in the decomposition and/or ignition of a layer of dust of a specified thickness deposited on it. The method
28、is particularly relevant to industrial equipment with which dusts are present on hot surfaces in thin layers exposed to the atmosphere. Method B (clause 5) is applicable to the determination of the minimum temperature of a prescribed hot surface which will result in the ignition of a cloud of given
29、sample of dust or other particulate solid. The test is intended to be carried out as a complementary test after determining the minimum ignition temperature of a dust layer by method A of this European Standard. NOTE 1 Concerning method B: because the method of operation of the furnace gives short r
30、esidence times for dust particles within it, this method of test is applicable to industrial equipment where dust is present as a cloud for a short time. This method of test is of small scale and the results are not necessarily representative of all industrial conditions. NOTE 2 Concerning method B:
31、 the method is not applicable to dusts which may, over a longer period of time than provided for in the test method, produce gasses from deposits generated during pyrolysis or smouldering. 2 Normative references EN 50281-1-1, Electrical apparatus for use in the presence of combustible dust Part 1-1:
32、 Electrical apparatus protected by enclosures Construction and testing. EN 50281-1-2, Electrical apparatus for use in the presence of combustible dust Part 1-2: Electrical apparatus protected by enclosures Selection, installation and maintenance. ISO 565, Test sieves Metal wire cloth, perforated met
33、al plate and electroformed sheet Nominal sizes of openings. ISO 4225, Air Quality General aspects Vocabulary. 3 Definitions For the purpose of this European Standard the following definitions apply. 3.1 dust small solid particles that settle out under their own weight but that may remain suspended i
34、n air for some time in the atmosphere (includes dust and grit as defined in ISO 4225) 3.2 ignition of a dust layer ignition shall be considered to have occurred if glowing or flaming is initiated in the material, or a temperature of 4508C or more, or a temperature rise of 250 K or more above the tem
35、perature of the prescribed hot surface, is measured in the test 3.3 minimum ignition temperature of a dust layer the lowest temperature of a hot surface at which ignition occurs in a dust layer of specified thickness on this hot surface NOTE 1 Because of the wide range of processes in industry, the
36、ignition of dust layers may be dependent upon local conditions. This method of test is not necessarily representative of all industrial conditions, where account may need to be taken of such factors as the presence of thick layers of dust and of the distribution of temperature in the environment. NO
37、TE 2 When carrying out this test, it is essential that all necessary precautions be taken to safeguard the health of personnel, for example, against the risk of fire, explosion, inhalation of smoke and any toxic products of combustion.Page 4 EN 50281-2-1:1998 BSI 10-1999 3.4 ignition of a dust cloud
38、 the initiation of an explosion by the transfer of energy to a dust cloud in air 3.5 ignition temperature of a dust cloud the lowest temperature of the hot inner wall of a furnace at which ignition occurs in a dust cloud in air contained therein NOTE When carrying out this test, it is essential that
39、 all necessary precautions be taken to safeguard the health of personnel, for example, against the risk of fire, explosion, inhalation of smoke and any toxic products of combustion. 4 Method A: dust layer on a heated surface at a constant temperature 4.1 Preparation of dust sample The sample shall b
40、e prepared so as to be homogeneous and representative of the dust received for consideration. The dust sample to be tested shall, in general, be able to pass through a woven metal wire cloth or a square hole perforated plate test sieve with a nominal size of aperture of 200mm (supplementary sizes, I
41、SO 565). If it is necessary to test a coarser dust, passing a test sieve with a nominal size of aperture up to 500mm, the fact shall be stated in the report of the test. Any apparent changes noted in the properties of the dust during preparation of the sample, for example, by sieving or owing to tem
42、perature or humidity conditions, shall be stated in the report of the test. 4.2 Test apparatus The apparatus is shown schematically in Figure A.1. Essential details and performance requirements are given in the following clauses. Methods of construction to enable these requirements to be met are des
43、cribed in annex A. 4.2.1 Heated surface The heated surface shall consist of a metal plate and shall provide a working area of at least 200 mm in diameter, and be not less than 20 mm in thickness. The plate shall be heated electrically and its temperature shall be controlled by a device for which the
44、 sensing element is a thermocouple mounted in the plate near the centre and with its junction within 1 0,5 mm of the upper surface and in good thermal contact with the plate. A similar thermocouple shall be mounted near the control thermocouple in a similar manner, and shall be connected to a temper
45、ature recorder to record the temperature of the surface during a test. The heated surface and its control device shall satisfy the following performance requirements: a) The heated surface shall be capable of attaining a maximum temperature of 4008C without a dust layer in position. b) The temperatu
46、re of the heated surface shall be constant to within 5 K throughout the period of a test. c) When the heated surface has reached a steady state, the temperature across the surface shall be uniform to within 5 K when measured across two diameters at right angles, by the procedure in annex A. This req
47、uirement shall be satisfied at nominal surface temperatures of 2008C and 3508C. d) The temperature control shall be such that the recorded surface temperature does not change by more than 5 K during the placing of the dust layer, and it shall be restored to within 2 K of the previous value within 5
48、min of placing the dust layer. e) Temperature control and measurement devices shall be calibrated and shall have limits of inaccuracy of 3K . 4.2.2 Dust layer thermocouple A fine thermocouple (0,20 mm to 0,25 mm diameter) of chromel-alumel or other suitable material shall be stretched across the hea
49、ted surface, and parallel to it, at a height of between 2 mm and 3 mm from it with the junction over the centre of the plate. This thermocouple shall be connected to a temperature recorder in order to determine the behaviour of the dust layer during the test. 4.2.3 Temperature measurements Temperature measurements using thermocouples shall be made either relative to a fixed reference junction or with automatic cold junction compensation. In either case, calibration shall satisfy the requirements of
