00677390 PDF BRITISH STANDARD BS EN 61241 2 2 1996 Electrical apparatus for use in the presence of combustible dust — Part 2 Test methods — Section 2 2 Method for determining the electrical resistivit[.]
BRITISH STANDARD Electrical apparatus for use in the presence of combustible dust — Part 2: Test methods — Section 2.2 Method for determining the electrical resistivity of dust in layers The European Standard EN 61241-2-2:1995 has the status of a British Standard ICS 29.260.20 BS EN 61241-2-2:1996 BS EN 61241-2-2:1996 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee GEL/31, Electrical apparatus for explosive atmospheres, upon which the following bodies were represented: Association of British Mining Equipment Companies British Cables Makers Confederation British Electrical Systems Association (BEAMA Ltd.) British Gas plc British Lighting Association for the Preparation of Standards (Britlaps) Council for Electrical Equipment for Flammable Atmospheres (BEAMA Ltd.) Department of Trade and Industry (Standards Policy Unit) ERA Technology Ltd Electric Trace Heating Industrial Council (Ethic) Electrical Contractors Association Electroheat Manufacturers’ Association of BEAMA (EMAB) Energy Industries Council Engineering Equipment and Materials Users’ Association GAMBICA (BEAMA Ltd.) Gland Manufacturers Technical Committee Health and Safety Executive Institute of Petroleum Lighting Industry Federation Ltd Loss Prevention Council Marine Safety Agency Ministry of Defence National Inspection Council for Electrical Installation Contracting Rotating Electrical Machines Association (BEAMA Ltd.) Sira Limited Trades Union Congress United Kingdom Offshore Operators Association The following body was also represented in the drafting of the standard, through sub-committees and panels: This British Standard, having been prepared under the direction of the Electrotechnical Sector Board, was published under the authority of the Standards Board and comes into effect on 15 March 1996 © BSI 10-1999 The following BSI references relate to the work on this standard: Committee reference GEL/31 Draft for comment 90/32582 DC ISBN 580 25239 Department of the Environment (Building Research Establishment) Amendments issued since publication Amd No Date Comments BS EN 61241-2-2:1996 Contents Page Committees responsible Inside front cover National foreword ii Foreword Introduction Scope Normative references 3 Definitions Test apparatus Test sample Procedure Test report Annex ZA (normative) Normative references to international publications with their corresponding European publications Figure — Test cell Figure — Circuit diagram List of references Inside back cover © BSI 10-1999 i BS EN 61241-2-2:1996 National foreword This British Standard has been prepared by Technical Committee GEL/31 and is the English language version of EN 61241-2-2:1995 Electrical apparatus for use in the presence of combustible dust — Part 2: Test methods Section 2: Method for determining the electrical resistivity of dust in layers published by the European Committee for Electrotechnical Standardization (CENELEC) It is identical with IEC 1241-2-2:1993 incorporating corrigendum May 1994, published by the International Electrotechnical Commission (IEC), except that in EN 61241-1-1 “technical report” has been replaced by “standard” throughout the text Cross-reference Publication referred to Corresponding British Standard ISO 4225:1980 BS 6069 Characterization of air quality Part 2:1994 Glossary a a ISO 4225:1980 has been superseded by ISO 4225:1994 A British 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 cover, an inside front cover, pages i and ii, the EN title page, pages to 6, an inside back cover and a back cover This standard has been updated (see copyright date) and may have had amendments incorporated This will be indicated in the amendment table on the inside front cover ii © BSI 10-1999 EUROPEAN STANDARD EN 61241-2-2 NORME EUROPÉENNE August 1995 EUROPÄISCHE NORM ICS 29.260.20 Descriptors: Electric equipment, explosive atmosphere, explosion proofing, fire protection, dust, combustible dust, test, resistivity English version Electrical apparatus for use in the presence of combustible dust Part 2: Test methods Section 2: Method for determining the electrical resistivity of dust in layers (IEC 1241-2-2:1993 + corrigendum 1994) Matériels électriques destinés être utilisés en présence de poussières combustibles Partie 2: Méthodes d’essais Section 2: Méthode de détermination de la résistivité électrique des couches de poussières (CEI 1241-2-2:1993 + corrigendum 1994) Elektrische Betriebsmittel zur Verwendung in Bereichen mit brennbarem Staub Teil 2: Untersuchungsverfahren Hauptabschnitt 2: Verfahren zur Bestimmung des elektrischen Widerstandes von Staubschüttungen (IEC 1241-2-2:1993 + Corrigendum 1994) This European Standard was approved by CENELEC on 1995-03-06 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 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 translation 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 electrotechnical committees of Austria, Belgium, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom CENELEC European Committee for Electrotechnical Standardization Comité Européen de Normalisation Electrotechnique Europäisches Komitee für Elektrotechnische Normung Central Secretariat: rue de Stassart 35, B-1050 Brussels © 1995 Copyright reserved to CENELEC members Ref No EN 61241-2-2:1995 E EN 61241-2-2:1995 Foreword The text of the technical report IEC 1241-2-2:1993 with its corrigendum May 1994, prepared by SC 31H, Apparatus for use in the presence of ignitable dust, of IEC TC 31, Electrical apparatus for explosive atmospheres, was submitted to the formal vote and was approved by CENELEC as EN 61241-2-2 on 1995-03-06 without any modification The following dates were 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) 1996-03-01 — latest date by which the national standards conflicting with the EN have to be withdrawn (dow) 1996-03-01 Annexes designated “normative” are part of the body of the standard In this standard, Annex ZA is normative Annex ZA has been added by CENELEC © BSI 10-1999 EN 61241-2-2:1995 Introduction Definitions This standard is applicable to the determination of the electrical resistivity of dust in layers The test method is not suitable for use with recognized explosives, gunpowder, dynamite, or substances or mixtures of substances which may, under some circumstances, behave in a similar manner Where any doubt exists about the existence of a hazard due to explosive properties, an indication may be obtained by placing a very small quantity of the dust in question on the heated surface of the apparatus prescribed in IEC 1241-2-11), heated to 400 °C The test for explosivity will not always reveal the explosive nature of a dust so that a “fail to danger” situation could arise For the purpose of this standard the following definitions apply NOTE Precautions should be taken to safeguard the health of personnel conducting the tests against the risk of fire, explosion and/or the effects, including toxic effects, of combustion This test method is applicable to the construction and application of electrical apparatus for use in the presence of combustible dust Scope This standard specifies a method of test to determine, by application of a d.c voltage, the electrical resistivity of a layer of dust It is intended to be used in the design, construction, testing, and application of electrical apparatus for use in the presence of combustible dust The test method is not suitable for use with recognized explosives or substances having explosive properties Normative references The following normative documents contain provisions which, through reference in this text, constitute provisions of this standard At the time of publication, the editions indicated were valid All normative documents are subject to revision, and parties to agreements based on this standard are encouraged to investigate the possibility of applying the most recent editions of the normative documents indicated below Members of IEC and ISO maintain registers of currently valid International Standards ISO 565:1990, Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of openings ISO 4225:1980, Air quality — General aspects — Vocabulary 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 NOTE This definition includes what are defined in ISO 4225 as “dust” and “grit” 3.2 conductive dust dust with electrical resistivity equal to or less than 103 7.m 3.3 non-conductive dust dust with electrical resistivity greater than 103 7.m 3.4 electrical resistivity minimum value of the electrical resistance of a dust layer measured between electrodes spaced at unit distance apart, and each having unit area in contact with the dust NOTE For the purpose of this standard, electrical resistivity is measured in ohm metre Test apparatus Figure and Figure give details for the construction of the test apparatus The test cell (see Figure 1) is of open construction, and consists of two stainless steel bars with nominal dimensions: length (W) – 100 mm, height (H) – 10 mm, breadth (B) – 20 mm to 40 mm These bars are placed at a nominal distance apart of (L) – 10 mm on a base with a thickness between mm and 10 mm NOTE Glass or polytetrafluorethylene (PTFE) have been found to be suitable materials for the base Two glass bars, also with a nominal height of 10 mm, are placed across the ends of the electrodes to keep the dust layer in place Figure illustrates an example of a suitable electrical circuit for making the resistivity measurement It contains a 10 k7 resistor to restrict the breakdown current to a maximum value of 0,2 A at a maximum supply voltage of 000 V d.c Other circuits with comparable characteristics and accuracy may be used 1) IEC 1241-2-1:1993, Electrical apparatus for use in the presence of combustible dust — Part 2: Test methods — Section (under consideration) © BSI 10-1999 EN 61241-2-2:1995 The current-to-voltage converter has six ranges to deal with the various values of supply voltage and dust resistivity A voltage inverter is present to provide a positive output All resistors are %, 0,5 W high-stability carbon-film type Test sample The test sample shall be homogeneous and representative of the dust received for testing When dust is received, it should be put in a closed vessel until tested, or it should be conditioned, or it should be tested directly, and the moisture content measured at the same time and reported The sample of dust 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 aperture of 71 4m (supplementary size, see ISO 565) If it is required to test coarser dust, a test sieve with a nominal size of aperture up to 500 4m may be used State the nominal size of aperture of the sieve used in the report of the test State the moisture content of the dust sample as tested in the report of the test, and describe the method of measurement State in the test report any apparent changes in the properties of the dust, for example moisture content or particle shape, resulting from the preparation of the test sample, for example in sieving Measure the resistance of the filled test cell Rs with the following values of d.c voltage applied: 110, 220, 300, 500, 000, 500, 000 V Apply each value of voltage for at least 10 s, and longer if polarization is evident The same sample of dust in the test cell may be used for all the tests at any one of the values of voltage 6.3 Calculation of resistivity Generally, Ro is greater than 10 Rs, and the resistivity of the dust is calculated from the equation @ = 0,001 Rs [H × W/L] If Ro is less than 10 Rs, the resistivity is calculated from the equation @ = 0,001 Rs × Ro/[Ro – Rs] × H × W/L where @ is the resistivity in 7.m Ro is the resistance of empty test cell in 7; Rs is the resistance of the filled test cell in 7; H is the height of the electrode in mm; W is the length of the electrode in mm; L is the space between electrodes in mm Calculate the resistivity for each value of the applied voltage Procedure Test report 6.1 Preliminary measurement The test report shall include the results of the measurements, the name, source and chemical description (if not implicit in the name) of the dust tested, the particle size and moisture content of the test sample, and the date and identification number of the test Report the mass of the dust in the test cell, and the ambient temperature at the time of the test The report shall state that the determination of electrical resistivity of the dust has been carried out in accordance with this standard Measure the resistance Ro of the empty test cell with the two glass bars in position 6.2 Measurement of resistance Pour a weighed quantity of the test sample into the test cell Remove excess dust by running a straight-edge along the top of the stainless steel electrodes Collect and weigh the excess Calculate the mass of dust in the test cell © BSI 10-1999 EN 61241-2-2:1995 Figure — Test cell Figure — Circuit diagram © BSI 10-1999 EN 61241-2-2:1995 Annex ZA (normative) Normative references to international publications with their corresponding European publications This European Standard incorporates by dated or undated reference, provisions from other publications These normative references are cited at the appropriate places in the text and the publications are listed hereafter For dated references, subsequent amendments to or revisions of any of these publications apply to this European Standard only when incorporated in it by amendment or revision For undated references the latest edition of the publication referred to applies (including amendments) NOTE When the international publication has been modified by CENELEC common modifications, indicated by (mod), the relevant EN/HD applies Publication Year Title ISO 565 1990 ISO 4225 1980 Test sieves — Metal wire cloth, perforated metal plate and electroformed sheet — Nominal sizes of openings Air quality — General aspects — Vocabulary EN/HD Year — — © BSI 10-1999 BS EN 61241-2-2:1996 List of references See national foreword © BSI 10-1999 BS EN 61241-2-2:1996 BSI — British Standards Institution BSI is the independent national body responsible for preparing British Standards It presents the UK view on standards in Europe and at the international level It is incorporated by 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