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1、BRITISH STANDARD BS 6746:1990 Incorporating Amendment No. 1 Specification for PVC insulation and sheath of electric cables BS 6746:1990 This British Standard, having been prepared under the direction of the Cables and Insulation Standards Policy Committee, was published under the authority of the Bo
2、ard of BSI and comes into effect on 31 August 1990 BSI 12-1998 First published August 1969 Second edition May 1976 Third edition December 1989 Fourth edition August 1990 The following BSI references relate to the work on this standard: Committee reference CIL/20 Draft for comment 89/24508 DC ISBN 0
3、580 18517 6 Committees responsible for this British Standard The preparation of this British Standard was entrusted by the Cables and Insulation Standards Policy Committee (CIL/-) to Technical Committee CIL/20, upon which the following bodies were represented: Aluminium Federation Association of Con
4、sulting Engineers Association of Manufacturers of Domestic Electrical Appliances British Approvals Service for Electric Cables British Cable Makers Confederation British Plastics Federation British Railways Board British Steel Industry British Telecommunications plc Department of the Environment (Pr
5、operty Services Agency) Department of Trade and Industry (Consumer Safety Unit, CA Division) ERA Technology Ltd. Electricity Supply Industry in England and Wales Engineering Equipment and Materials Users Association Institution of Electrical Engineers London Regional Transport The following bodies w
6、ere also represented in the drafting of the standard, through subcommittees and panels: Association of Supervisory and Executive Engineers British Rubber Manufacturers Association GAMBICA (BEAMA Ltd.) Queen Mary College Industrial Research Amendments issued since publication Amd. No.DateComments 693
7、8February 1992Indicated by a sideline in the margin BS 6746:1990 BSI 12-1998i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Definitions1 3Composition1 4Colours1 5Test requirements for physical and electrical properties1 Appendix A Method of test for insulation resistance
8、 constant (K value)5 Appendix B Method of test for colour fastness to daylight5 Appendix C Method of test for bleeding and blooming of colour5 Table 1 Types of insulation and sheath1 Table 2 Test requirements for compounds designated according to HD 212 Table 3 Test requirements for compounds design
9、ated according to this standard3 Publications referred toInside back cover BS 6746:1990 ii BSI 12-1998 Foreword This new edition of BS 6746 has been prepared under the direction of the Cables and Insulation Standards Policy Committee and it supersedes BS 6746:1984, which is withdrawn. This edition i
10、ntroduces technical changes but it does not reflect a full review or revision of the standard, which will be undertaken in due course. This standard should be read in conjunction with BS 6469 which describes the test methods common to various electric cable materials and is referred to in British St
11、andards for those materials. The second edition of this standard was prepared to take account of CENELEC1) Harmonization Document HD 21. The third edition agreed with HD 21.S2 dated October 1982. This edition incorporates amendments 1 and 2 (published September 1986 and February 1990) to BS 6746:198
12、4 and introduces compound TI 4 which appears in amendment No. 4 (dated January 1989) to HD 21.1 S2. Differences in the text between this edition and BS 6746:1984 are indicated by a line in the margin. Amendment No. 1 incorporates PVC type TI 3 compound to align with Amendment No. 2 to HD 21.1 S2. Th
13、e requirements for the various types of compound have been drafted such that compliance with them can be checked by testing samples taken from finished cables. Attention is drawn to the certification services of the British Approvals Service for Electric Cables (BASEC)2). These services include lice
14、nsing manufacturers to use BASEC certification trade marks as independent assurance that cables or cords have been designed and manufactured to appropriate British Standards. BASEC is a subscriber to an agreement in CENELEC whereby cables or cords coming within Harmonized Code Designations and manuf
15、actured under a BASEC licence can carry marks acceptable to other signatory countries (CENELEC “Common marking”). 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 Bri
16、tish 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, pages 1 to 6, an inside back cover and a back cover. This standard has been updated (see copyright date) and may have had amendments
17、 incorporated. This will be indicated in the amendment table on the inside front cover. 1) European Committee for Electrotechnical Standardization. 2) British Approvals Service for Electric Cables, Silbury Court, 360 Silbury Boulevard, Milton Keynes, Buckinghamshire MK9 2AF. BS 6746:1990 BSI 12-1998
18、1 1 Scope This British Standard specifies the physical and electrical requirements for the types of PVC insulation and sheath of electric cables given in Table 1. The relevant test methods for verification of compliance are given either in BS 6469 or in the appendices of this standard. NOTEThe title
19、s of the publications referred to in this standard are listed on the inside back cover. 2 Definitions For the purposes of this British Standard the following definitions apply. 2.1 median value when several test results have been obtained and ordered in an increasing or decreasing succession, the me
20、dian value is the middle value if the number of available values is odd, and is the mean of the two middle values if the number is even 2.2 variation the difference between the median value after ageing and the median value without ageing, expressed as a percentage of the latter 3 Composition The in
21、sulation or sheath shall consist of a compound based on one of the following materials, suitably compounded and processed to comply with this standard: a) polyvinyl chloride (PVC); or b) a copolymer of vinyl chloride; or c) a mixture of materials a) and b). 4 Colours Opaque insulation and sheath sha
22、ll be of a colour that reasonably matches one of the colours given in BS 6746C. NOTEThere is no requirement for the colour of transparent insulation and sheath. 5 Test requirements for physical and electrical properties 5.1 When tested by the methods specified in 5.2 and 5.3, the properties of the i
23、nsulation or sheath shall be in accordance with the requirements given in Table 2 or Table 3 for the particular type of material. Table 1 Types of insulation and sheath TypeMaximum operating temperature General application InsulationSheath C TI 170General purpose TM 170For use over cables operating
24、at a maximum conductor temperature of 80 C TI 270Flexible (including transparent) TM 270General purpose flexible TI 390Heat resistant TI 470For installation at low temperatures 270Hard 485FlexibleFlexible 585Hard 670General purpose 770Low temperature non-migratory for radio-frequency cables complyin
25、g with BS 2316 870Low temperature general purpose for radio-frequency cables complying with BS 2316 9For use over cables operating at a maximum conductor temperature of 90 C BS 6746:1990 2 BSI 12-1998 Table 2 Test requirements for compounds designated according to HD 21 TestRequirements InsulationSh
26、eath TI 1TI 2TI 3TI 4TM 1TM 2 Tensile properties of unaged test pieces Min. tensile strength, N/mm2 12.51015.012.512.510 Min. elongation at break, %125150150125125150 Low temperature bend test Temperature at which specimen shall not crack, C 15 2 15 2 15 2 40 2 15 2 15 2 Low temperature elongation t
27、est b Test temperature, C 15 2 15 2 15 2 40 2 15 2 15 2 Min. elongation, %202020202020 Low temperature impact test Temperature at which specimen shall not crack, C 15 2 15 2 40 2 15 2 15 2 Accelerated ageing for specified period at specified temperature followed by loss of mass test Max. loss of mas
28、s, mg/cm2, after ageing: 7 days at 80 2 C2.02.02.02.02.0 14 days at 115 2 C1.5 Accelerated ageing for specified period at specified temperature followed by tensile strength and elongation at break test Number of days ageing7714777 Ageing temperature, C80 280 2135 280 280 280 2 Tensile strength after
29、 ageing: min. value, N/mm2 12.5101512.512.510 max. variation, %202025202020 Elongation at break after ageing: min. value, %125150150125125150 max. variation, %202025202020 Pressure test at high temperature Test temperature, C80 270 290 280 280 270 2 Max. indentation, %a505050505050 Resistance to cra
30、cking Temperature at which specimen shall not crack, C 150 2150 2150 2150 2150 2150 2 Insulation resistance test Min. K value at 70 C, Mkm0.0370.0370.037 Min. K value at 90 C, Mkm0.037 Thermal stability test at 200 C Min. value, minutes240 NOTEA dash () indicates test not applicable. a The value of
31、50 % is inseparable from the underlying principle of the formula and is the same for all materials. The severity of the test can be changed by variation of the factor k only (see BS 6469) without altering the value of 50 %. b Currently only applicable to use of TI 3 on national types of cable with m
32、ean overall diameters exceeding 12.5 mm. BS 6746:1990 BSI 12-19983 Table 3 Test requirements for compounds designated according to this standard TestRequirements for insulation or sheath type: 2456789 Tensile strength and elongation at break test Min. tensile strength, N/mm2 18.57.512.567.57.512.5 M
33、in. elongation at break, %125150a125125125150150 Low temperature bend test Temperature at which specimen shall not crack, C 15 2 20 2 15 2 15 2 40 2 40 2 15 2 Low temperature elongation test Test temperature, C 15 2 20 2 15 2 15 2 40 2 40 2 15 2 Min. elongation, %20202020202020 Low temperature impac
34、t test Temperature at which specimen shall not crack, C 15 2 Accelerated ageing for specified period at specified temperature followed by loss of mass test Max. loss of mass, mg/cm2, after ageing: 7 days at 80 2 C2.02.02.02.0 7 days at 100 2 C1.5 10 days at 115 2 C1.5 Accelerated ageing for specifie
35、d period at specified temperature followed by tensile strength and elongation at break test Number of days ageing7107 Ageing temperature, C135 2135 2100 2 Tensile strength after ageing: min. value, N/mm212.512.5 max. variation. %2525 Elongation at break after ageing: min. percentage of unaged value,
36、 %65 min. value, %125150 max. variation from unaged value, %2525 Pressure test at high temperature Test temperature, C80 290 295 280 260 260 290 2 Max. indentation, %b50505050505050 BS 6746:1990 4 BSI 12-1998 Table 3 Test requirements for compounds designated according to this standard 5.2 The tests
37、 for insulation and sheath designated according to HD 21.S2 shall be those printed in italic type in Table 2; the tests for insulation and sheath designated according to this standard shall be those printed in italic type in Table 3; the conditions of temperature, test duration, etc. shall be as spe
38、cified in the appropriate table and the methods of sampling and of testing shall be as described in the appropriate clause of BS 6469:1990 or appendix of this standard, as stated below. NOTEAttention is drawn to the fact that additional test to those called up in this standard may be required by cab
39、le specifications. 5.3 Unless otherwise stated in the British Standard for the particular cable, the tests on insulation shall be made on samples from each core if the cable has one, two or three cores, and on samples from three cores (of different colours, if any) if the cable has more than three c
40、ores. The tests shall be carried out not less than 16 h after extrusion. TestRequirements for insulation or sheath type: 2456789 Hot deformation test Max. deformation, %30c65c30c65c65c65c40c Resistance to cracking Temperature at which specimen shall not crack, C 150 2150 2150 2150 2100 2120 2150 2 I
41、nsulation resistance constant test Min. K value at 20 C, Mkm3500.351800.00350.00350.00350.0035 Colour fastness to daylightdThe perceived colour change shall not be poorer than grey scale 4 of method AO2C of BS 1006. Bleeding and blooming of colourdNo appreciable staining of PVC film or filter paper
42、NOTEA dash () denotes test not applicable. a 125 % for specified radial thickness up to and including 0.4 mm. b The value of 50 % is inseparable from the underlying principle of the formula and is the same for all materials. The severity of the test can be changed by variation of the factor k only (
43、see BS 6469), without altering the value of 50 %. c Applicable only for specified radial thickness less than 0.4 mm. d These tests apply only when requested by the purchaser. It is essential therefore for the purchaser to state at the time of enquiry or order he requires this testing to be done. Tes
44、tMethod Tensile properties: tensile strength and elongation at break 2.2 of BS 6469:1990 Low temperature bend, elongation and impact tests 4.3 of BS 6469:1990 Accelerated ageing2.3 of BS 6469:1990 Loss of mass4.1 of BS 6469:1990 Pressure test at high temperature 4.2 of BS 6469:1990 Hot deformation t
45、est4.5 of BS 6469:1990 Resistance to cracking4.4 of BS 6469:1990 (Heat shock test) Insulation resistance constant (K value) Appendix A of this standard Colour fastness to daylightAppendix B of this standard Bleeding and blooming of colour Appendix C of this standard Thermal stability test4.6 of BS 6
46、469:1990 BS 6746:1990 BSI 12-19985 Appendix A Method of test for insulation resistance constant (K value) A.1 Test on core for compounds types TI 1, TI 2, TI 3 and TI 4 Remove the sheath and any other covering or filling from a length of 5 m, taking care not to damage the insulation. Immerse the cor
47、e in water for 2 h at a temperature of 70 2 C, 90 2 C for TI 3 a length of about 250 mm at each end of the core projecting above the water. Apply a voltage between 300 V and 500 V d.c. between the conductor and the water. Measure the insulation resistance 1 min after the application of the voltage.
48、Calculate the insulation resistance constant (K value) from the equation: where A.2 Test on core for compounds types 2 and 4 Proceed as described in A.1, except: a) immerse the core for at least 12 h in water at a temperature of 20 5 C, and b) maintain the water temperature at 20 1 C for the 30 min immediately preceeding the test. Calculate the insulation resistance constant (K value) from the equation given in A.1. A.3 Test on sheath For the test piece use a sheet 1.00 0.15 mm thick and large enough to accommodate the electrodes, mou