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1、BRITISH STANDARD BS 7447:1991 Method of test for Determination of the ignitability of solid electrical insulating materials when exposed to an electrically heated wire source (Implementation of CENELEC HD 541 S1) Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 1
2、0:43:55 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7447:1991 This British Standard, having been prepared under the direction of the General Electroctechnical Standards Policy Committee, was published under the authority of the Standards Board and comes into effect on 30 September 1991 BSI 01-2000
3、 The following BSI references relate to the work on this standard: Committee reference GEL/89 Draft for comment 88/31660 DC ISBN 0 580 19745 X Committees responsible for this British Standard The preparation of this British Standard was entrusted by the General Electrotechnical Standards Policy Comm
4、ittee (GEL/-) to Technical Committee GEL/89, upon which the following bodies were represented: Association of Manufacturers of Domestic Electrical Appliances British Cable Makers Confederation British Electrical Systems Association (BEAMA Ltd.) British Plastics Federation British Telecommunications
5、plc EEA (the Association of Electronics, Telecommunications and Business Equipment Industries) Electrical Installation Equipment Manufacturers Association (BEAMA Ltd.) Electricity Supply Industry in United Kingdom Electronic Components Industry Federation ERA Technology Ltd. Home Office Lighting Ind
6、ustry Federation Ltd. Ministry of Defence National Supervising Inspectorate Telecommunication Engineering and Manufacturing Association Amendments issued since publication Amd. No.DateComments Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:43:55 GMT+00:00 20
7、06, Uncontrolled Copy, (c) BSI BS 7447:1991 BSI 01-2000i Contents Page Committees responsibleInside front cover Forewordii 1Scope1 2Significance of testing1 3Test specimens1 4Conditioning1 5Test chamber1 6Glow-wire ignition1 7Test report2 Figure 1 Glow-wire and position of the thermocouple3 Figure 2
8、 Test apparatus (example)4 Table 1 Glow-wire temperature2 Publication(s) referred toInside back cover Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:43:55 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7447:1991 ii BSI 01-2000 Foreword This British Standard h
9、as been prepared under the direction of the General Electrotechnical Standards Policy Committee and implements CENELEC Harmonization Document HD 541 S1. The method described is identical to Method A in IEC 829:1988 “Methods of test for the determination of the ignitability of solid electrical insula
10、ting materials when exposed to electrically heated wire sources”, published by the International Electrotechnical Commission (IEC). When IEC 829 was considered for endorsement by CENELEC it was agreed not to include Method B of IEC 829 in the CENELEC HD. Attention is drawn to BS 6334, identical with
11、 IEC 707, which describes a method for checking the consistency of characteristics of a material for comparison and classification purposes. A British Standard does not purport to include all the necessary provisions of a contract. Users of British Standards are responsible for their correct applica
12、tion. 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, pages 1 to 4, an inside back cover and a back cover. This standard has been updated (see copyright date)
13、and may have had amendments incorporated. This will be indicated in the amendment table on the inside front cover. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:43:55 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7447:1991 BSI 01-20001 1 Scope The test meth
14、od of this standard is applicable to solid electrical insulating materials and is intended to serve as an indication of their ignitability when using an electrically heated wire as an igniting source. The results make it possible to provide a relative comparison of various materials according to the
15、 temperature at which the test specimen ignites during the application of the igniting source. This test method is not valid for determining the ignition behaviour of complete items of equipment, since the dimensions of the insulating systems, the design and heat transfer to adjacent metallic parts,
16、 etc. greatly influence the ignitability of the electrical insulating materials used therein. In addition to this, it is not valid for determining fire behaviour and fire hazard of equipment. 2 Significance of testing The ignitability is a measure of the ease with which a test specimen can be ignite
17、d due to the influence of an external heat source and is identified by the combination of heat input and temperature required to start ignition of the specimen under test. The tests are carried out on test specimens of fixed dimensions and under definite assessment criteria with a specified igniting
18、 source. The significant feature of the test is the determination of the minimum temperature measured at the tip of the glow-wire as igniting source, causing ignition of the test specimen. Thus the temperature measured is dependent on the specific conditions of the test method. Other tests and ignit
19、ion sources may give different results with regard to the ignitability of materials under test. 3 Test specimens Test specimens shall have the following dimensions: The test specimens can be manufactured for example by compression moulding, transfer moulding, injection moulding, casting or be machin
20、ed from sheets or parts having large enough plane sections. The test specimens may be rectangular or round plane plates. A set of at least 10 test specimens will in general be adequate for conducting the tests. NOTEThe ignitability will usually vary depending on the thickness of the material. Theref
21、ore, in addition to the thickness specified, it may be helpful to obtain results for thicknesses of about 0.8 mm, 1.6 mm and 6.0 mm commonly encountered in practice. 4 Conditioning Before testing, the test specimens shall be conditioned for 48 h at standard atmosphere B (48 h/23 C/50 % r.h.) in acco
22、rdance with BS 2844. 5 Test chamber The chamber shall be draught-free, with a capacity of approximately 1 m3, and shall permit observation. For safety and convenience, it is desirable that this enclosure (which can be completely closed) be fitted with a device, such as an exhaust fan, to remove prod
23、ucts of combustion which may be toxic. However, it is important to note that the device shall be turned off during the actual test and started again immediately after the test to remove the products of combustion. WARNING NOTE. It is essential that precautions are taken to safeguard the health of pe
24、rsonnel conducting tests against: the risk of fire; the inhalation of smoke and/or toxic products; the toxic residues. 6 Glow-wire ignition 6.1 Igniting source The igniting source shall be a glow-wire in accordance with BS 6458-2.1. The thermocouple and its arrangement in the tip of the glow-wire sh
25、all be in accordance with BS 6458-2.1 (see Figure 1). 6.2 Calibration of the igniting source The calibration of the thermocouple and the measuring instrument shall be in accordance with BS 6458-2.1. 6.3 Test apparatus An example of the test apparatus is given in BS 6458-2.1 (see Figure 2). 6.4 Test
26、procedure 6.4.1 General Mount or clamp the test specimen so that heat losses due to the supporting or fixing means are insignificant. Provide a free surface area at least 40 mm in diameter inside the clamps. Arrange the specimen so that: the plane surface in contact with the tip of the glow-wire is
27、vertical; Length (mm):60; Width (mm):60; Thickness (mm):3.0 0.2. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:43:55 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7447:1991 2 BSI 01-2000 the tip of the glow-wire is applied to the centre of the free surface
28、area of the test specimen. Electrically heat the glow-wire to one of the temperatures in Table 1 which is considered just sufficiently high enough to cause ignition. Measure the temperature by means of the calibrated thermocouple. Ensure that, before starting the test, this temperature and the heati
29、ng current are constant for a period of at least 60 s and that heat radiation does not influence the test specimen during this period or during the calibration, for example by providing adequate distance or by using an appropriate screen. Before each test clean any residue of the previously tested m
30、aterial from the tip of the glow-wire, for example by means of a brush. Bring the tip of the glow-wire into contact with the test specimen with an applied force of 0.8 N to 1.2 N for 30 1 s. Maintain the heating current constant during this period. Mechanically limit the movement of the tip of the g
31、low-wire into the test specimen during the test to 7 mm. During the application of the glow-wire observe the test specimen in subdued light and note if ignition occurs within the specified time of application. Table 1 Glow-wire temperature Ignition means that a flame is visible for more than 5 s and
32、/or a tissue paper placed underneath the apparatus is ignited by particles falling from the test specimen. NOTENeither ignition of the tissue paper nor scorching of the pine wood board by “flaming drops” or “flaming debris” from the glow-wire after its removal from the test specimen is a criterion f
33、or failure of the test. 6.4.2 Procedure to identify the glow-wire ignition temperature index If ignition occurs during the time of application of the glow-wire, repeat the test with a new test specimen at a temperature preferably 50 K lower than that used during the first test. Should ignition not o
34、ccur during the time of application of the glow-wire repeat the test with a new test specimen at a temperature preferably 50 K higher than that used during the first test. Repeat the tests with new specimens each time and reduce the interval of test temperature to 25 K in the final approach to deter
35、mine the maximum test temperature which will not cause ignition during three subsequent tests. 6.5 Evaluation of results: glow-wire ignition temperature The temperature reported to be the glow-wire ignition temperature shall be that which is 25 K higher than the temperature of the tip of the glow-wi
36、re which does not cause ignition in the three subsequent tests of 6.4. Example: 850/3.0 (test temperature 850 C, 3.0 mm thickness of test specimens). 7 Test report The test report shall include the following information: a) the method of test used (glow-wire ignition) and reference to this standard;
37、 b) complete identification of the tested material, including type and manufacturer; c) description of the method used for the preparation of the test specimens (see clause 3); d) thickness of the test specimens (see clause 3); e) results of the test (see 6.5); f) whether the test specimens melt wit
38、hout burning, release burning droplets or show any unusual behaviour; g) the penetration of the tip of the glow-wire into the test specimen; h) any deviation from the specified conditions. Test temperatureTolerance CC 500 550 600 650 700 750 10 800 850 900 960 15 Licensed Copy: London South Bank Uni
39、versity, London South Bank University, Fri Dec 08 10:43:55 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7447:1991 BSI 01-20003 Key 1 Glow-wire hard-soldered at 3 2 Thermocouple 3 Stud All dimensions are in millimetres Figure 1 Glow-wire and position of the thermocouple Licensed Copy: London South B
40、ank University, London South Bank University, Fri Dec 08 10:43:55 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7447:1991 4 BSI 01-2000 Key 1 Positioning clamp 2 Carriage 3 Tensioning cord 4 Base plate 5 Weight 6 Stop 7 Scale for measure of flame 8 Scale for penetration 9 Glow-wire (Figure 1) 10 Bre
41、ak-through in base plate for particles falling from the test specimen Figure 2 Test apparatus (example) Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:43:55 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7447:1991 BSI 01-2000 Publication(s) referred to BS 284
42、4, Memorandum on conditioning of solid electrical insulating materials prior to and during testing. BS 6334, Methods of test for the determination of the flammability of solid electrical insulating materials when exposed to an igniting source1). BS 6458, Fire hazard testing for electrotechnical prod
43、ucts. BS 6458-2, Methods of test. BS 6458-2.1, Glow-wire test. 1) Referred to in the foreword only. Licensed Copy: London South Bank University, London South Bank University, Fri Dec 08 10:43:55 GMT+00:00 2006, Uncontrolled Copy, (c) BSI BS 7447:1991 BSI 389 Chiswick High Road London W4 4AL BSI Brit
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