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1、BRITISH STANDARDCommon test methods for cables under fire conditions Measurement of smoke density of cables burning under defined conditions Part 2: ProcedureThe European Standard EN 50268-2:1999 has the status of aBritish StandardICS 13.220.40; 29.060.20| BS EN50268-2:2000|NO COPYING WITHOUT BSI PE
2、RMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBS EN 50268-2:2000National forewordThis British Standard is the official English language version of EN 50268-2:1999. It supersedes BS 7622-2:1993 which is withdrawn.The UK participation in its preparation was entrusted by Technical Committee GEL/20, Elec
3、tric cables, to Subcommittee GEL/20/3, Insulation and sheath, which has the responsibility to: aid enquirers to understand the text; present to the responsible international/European committee any enquiries on the interpretation, or proposals for change, and keep the UK interests informed; monitor r
4、elated international and European developments and promulgate them in the UK.A list of organizations represented on this subcommittee can be obtained on request to its secretary.Cross-referencesThe British Standards which implement international or European publications referred to in this document
5、may be found in the BSI Standards Catalogue under the section entitled International Standards Correspondence Index, or by using theFind facility of the BSI Standards Electronic Catalogue.A British Standard does not purport to include all the necessary provisions of a contract. Users of British Stan
6、dards are responsible for their correct application.Compliance with a British Standard does not of itself confer immunity from legal obligations.Summary of pagesThis document comprises a front cover, an inside front cover, the EN title page, pages 2 to 6, an inside back cover and a back cover.The BS
7、I copyright notice displayed in this document indicates when the document was last issued.Amd. No.DateCommentsThis British Standard, having been prepared under the direction of the ElectrotechnicalSector Committee, was published under the authority of the Standards Committee and comes into effect on
8、 15 April 2000BSI 04-2000ISBN 0 580 34493 0Amendments issued since publicationEUROPEAN STANDARDEN 50268-2NORME EUROPE ENNEEUROPA ISCHE NORMSeptember 1999ICS 13.220.40; 29.060.20Supersedes HD 606.2 S1:1992English versionCommon test methods for cables under fire conditions Measurement of smoke density
9、 of cables burning under defined conditions Part 2: ProcedureMe thodes dessai communes aux ca bles soumis au feu Mesure de la densite de fume es de gage espar des ca bles bru lant dans des conditions de finies Partie 2: Proce dureAllgemeine Pru fverfahren fu r das Verhalten von Kabeln und isolierten
10、 Leitungen im Brandfall Messung der Rauchdichte von Kabeln und isolierten Leitungen beim Brennen unter definierten Bedingungen Teil 2: Pru fverfahrenThis European Standard was approved by CENELEC on 1999-04-01.CENELEC members are bound to comply with the CEN/CENELEC Internal Regulations which stipul
11、ate 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 e
12、xists 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 ele
13、ctrotechnical standards bodies of Austria, Belgium, Czech Republic, Denmark, Finland, France, Germany, Greece, Iceland, Ireland, Italy, Luxembourg, Netherlands, Norway, Portugal, Spain, Sweden, Switzerland and United Kingdom.CENELECEuropean Committee for Electrotechnical Standardization Comite Europ
14、e en de Normalisation Electrotechnique Europa isches Komitee fu r Elektrotechnische NormungCentral Secretariat: rue de Stassart 35, B-1050 Brussels1999 CENELEC All rights of exploitation in any form and by any means reserved worldwide for CENELECmembers.Ref. No. EN 50268-2:1999 EPage 5EN 50268-2:199
15、9BSI 04-2000ForewordThis European Standard was prepared by the TechnicalCommittee CENELEC TC20, Electric cables, andContentsPageagreed at its Dublin meeting (April 1997).The text of the draft was submitted to the Unique Acceptance Procedure and approved by CENELEC as EN 50268-1 on 1999-04-01.This Eu
16、ropean Standard supersedes HD 606.2 Sl:1992The following dates were fixed:Foreword 21Scope 32Normative references 33Definitions 34Test apparatus 35Test assembly 3 latest date by which the EN has to be implemented at national level by publication of an identical national standard or by endorsement la
17、test date by which national standards conflicting with the EN have to be withdrawn(dop) 2000-04-01(dow) 2001-04-015.1Cable test pieces 35.2Cable selection and assembly 35.3Positioning of test pieces 36Test procedure 47Evaluation of test results 48Retest procedure 4Annex A (informative) Guidance onAn
18、nexes designated informative are given for information only. In this standard annexes A and B are informative.calculation of absorbance 6Annex B (informative) Recommendedperformance requirement 61 ScopeEN 50268 specifies a method of test for measurement of smoke density of cables burning under defin
19、ed conditions. It is suitable for electric insulated conductor or cable, or optical cables. Part 1 specifies the apparatus and part 2 specifies procedure. This standard includes an informative annex of recommended requirements for compliance.NOTE Experience has shown that the test protocol is not su
20、itable for some cables that exceed 70 mm overall diameter. In such cases the manufacturer should be consulted.2 Normative referencesThis European Standard incorporates by dated or undated reference, provisions from other publications. These normative references are cited at the appropriate places in
21、 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 onlywhen incorporated in it by amendment or revision. For undated references the latest edition of the publication referred to
22、 applies.EN 50268-1, Common test methods for cables under fire conditions Measurement of smoke density of cables burning under defined conditions Part 1: Apparatus.EN 60695-4, Fire hazard testing Part 4: Terminology concerning fire tests.NOTE IEC 60695 is in the course of re-numbering its parts and
23、sections. This will also affect the equivalent ENs.3 DefinitionsFor the purposes of this part 2 of EN 50268 the definitions in EN 60695-4 apply.4 Test apparatusThe test procedure defined in this part 2 of EN 50268 shall be carried out using the test apparatus, i.e. test enclosure, photometric system
24、 and standard fire source, given in EN 50268-1.5 Test assembly5.1 Cable test piecesThese shall consist of one or more samples of cable1,00 m 0,05 m long which shall be carefully straightened and then conditioned for at least 16 h at23 8C5 8C.5.2 Cable selection and assembly5.2.1 Selection of number
25、of test piecesOverall diameter of the cable (D)mmNumber of test piecesCablesBundlesdD 4020 D # 4010 D # 205 D # 101 # D # 5123a, c N2b, c45Db N = 45 bundles23 Dc The value of N1 and N2 shall be rounded downwards to the integer to give the number of cables or bundles.d Each bundle shall consist of se
26、ven cables twisted together with a lay between 20 D and 30 D and bound with two turns of approximately 0,5 mm diameter wire in the centre and at every100 mm each side from the centre (see Figure 1)N1a N1 = cables5.2.2 Assembly of test piecesThe test pieces shall remain in situ during the test as fol
27、lows: cables or bundles shall be bound together at the ends, and at 300 mm from each end, at which place they shall be clamped to the support by means of wire binders.NOTE Depending upon construction, small cables and flexible cables may be subject to movement during the test. In these cases it is a
28、lso recommended that the cables or bundles are bound with two turns of approximately 0,5 mm diameter wire in the centreand at every 100 mm each side from the centre. Alternatively, the cables or bundles may be tensioned at one or both ends by means of an appropriate device, for example spring or wei
29、ght.5.3 Positioning of test piecesThe tray containing the alcohol shall be supported above the ground surface to permit air circulation around and beneath the tray. The test pieces (cables or bundles) shall be laid touching in a horizontal position and centred above the tray so that the distance bet
30、ween the underneath of the test pieces and the bottom of the tray is 150 mm 5 mm (see Figure 2).6 Test procedureNOTE Before each test it may be necessary to clean the windows of the photometric system to regain 100 % light transmission after stabilization of the voltage (see also clause A.2 of annex
31、 A of EN 50268-1).6.1 Immediately before commencing a test, the temperature within the cube shall be in the range of25 8C5 8C when measured at the internal doorsurface at a height of 1,5 m to 2,0 m and a minimum of0,2 m from the walls.6.2 Before a test, carry out one blank test as defined in EN 5026
32、8-1, clause 8 to preheat the test enclosure if necessary.6.3 For the test, the fire source shall be as defined inEN 50268-1, clause 6.6.4 With the test samples supported above the tray, start the air circulation and ignite the alcohol. Make sure that all the persons leave the cube immediately, and t
33、hat the door is closed.6.5 The test is considered as ended when there is no decrease in light transmittance for 5 min after the fire source has extinguished or when the test duration reaches 40 min.6.6 Record the minimum light transmittance.NOTE If it is required to use information on smoke density
34、for wider hazard evaluation or fire safety engineering purposes, it may be necessary to calculate absorbance levels. Guidance on such calculations is given in annex A.6.7 Extract the combustion products at the end of each test.7 Evaluation of test resultsThe requirement shall be as given in the rele
35、vant cable specification.NOTE If no value is given in the relevant cable specification it is recommended that the recommendation in annex B be adopted as a minimum.8 Retest procedureIn case of dispute a further two tests shall be undertaken using similar cables.Both of these test results shall compl
36、y with the requirements of clause 7.Key:1. Wire binder2. Centre3. Number of test pieces = 7Dimensions in millimetresFigure 1 Method of binding for cable bundlesKey:A. Side view1. Support4. Back wallB. Plan view2. Metal tray5. Floor3. Test pieceDimensions in millimetresFigure 2 Method of support of t
37、est piecesAnnex A (informative)Guidance on calculation of absorbanceThe absorbance (Ao), i.e. the absorbance produced across the opposite faces of a cube of side 1 m when one unit of material is burned, is calculated from the expression.AmVAo = nlwhereAm is the measured absorbance as calculated in E
38、N 50268-1, 10.5 using the minimum light transmittance (lt) recorded by the photocell in 6.6 of this part 2;Vis the measured volume of the cube (in m3);n is the total number of samples of cable in the test assembly;NOTE Where bundles are tested n is the number of bundles multiplied by the number of c
39、able samples in each bundle.lis the measured length of the optical path(in m).The absorbance value obtained is of significance if the system involves different cables/products and an overall assessment of smoke density level is required.Annex B (informative)Recommended performance requirementThe per
40、formance requirements for a particular type or class of insulated conductor or cable should preferably be given in the individual cable standard. In the absence of any given requirement it is recommended that a value of 60 % light transmittance is adopted as a minimum for any cable tested against th
41、is standard.blankBS EN|50268-2:2000BSI389 Chiswick High RoadLondonW4 4AL| 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 Royal
42、Charter.| Revisions| British Standards are updated by amendment or revision. Users of British Standards| should make sure that they possess the latest amendments or editions.| It is the constant aim of BSI to improve the quality of our products and services. We| would be grateful if anyone finding an inaccuracy or ambiguity while using this| British Standard would inform t