ASTM D3874-2012 Standard Test Method for Ignition of Materials by Hot Wire Sources《用电热丝法测量材料着火性的标准试验方法》.pdf

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1、Designation:D387410 Designation: D3874 12An American National StandardStandard Test Method forIgnition of Materials by Hot Wire Sources1This standard is issued under the fixed designation D3874; the number immediately following the designation indicates the year oforiginal adoption or, in the case o

2、f revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope*1.1 This test method is intended to differentiate, in a preliminary fashion, among materials with

3、 respect to their resistance toignition because of their proximity to electrically-heated wires and other heat sources.21.2 This test method applies to molded or sheet materials available in thicknesses ranging from 0.25 to 6.4 mm (0.010 to 0.25in.).1.3 This test method applies to materials that are

4、 rigid at normal room temperatures. That is, it applies to materials for whichthe specimen does not deform during preparation, especially during the wire-wrapping step described in 10.1. Examples ofdeformation that render this test method inapplicable include:1.3.1 Bowing, in either a transverse or

5、a longitudinal direction, or twisting of the specimen, during the wire-wrapping step, toa degree visible to the eye.1.3.2 Visible indentation of the wrapped wire into the specimen.1.4 The values stated in SI units are to be regarded as the standard. The inch-pound units given in parentheses are fori

6、nformation only. (See IEEE/ASTM SI-10 for further details.)1.5 This test method measures and describes the response or materials, products, or assemblies to heat and flame undercontrolled conditions, but does not by itself incorporate all factors required for fire hazard or fire risk assessment of t

7、he materials,products, or assemblies under actual fire conditions.1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the app

8、licability of regulatorylimitations prior to use.1.7 Fire testing is inherently hazardous. Adequate safeguards for personnel and property shall be employed in conducting thesetests.NOTE 1Although this test method and IEC 60695-2-20, differ in approach and in detail, data obtained using either are te

9、chnically equivalent.2. Referenced Documents2.1 ASTM Standards:3D1711 Terminology Relating to Electrical InsulationE176 Terminology of Fire StandardsIEEE/ASTM SI-10 International System of Units (SI) The Modernized Metric System2.2 IEC Standards:IEC 60695-2-20 Fire Hazard TestingSection 20: Glowing/

10、Hot-wire Based Test Methods, Hot-wire Coil Ignitability Test onMaterials4IEC 60695-4 Fire Hazard TestingPart 4: Terminology Concerning Fire Tests42.3 ISO StandardsISO 13943 Fire SafetyVocabulary51This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating

11、 Materials and is the direct responsibility of SubcommitteeD09.21 on Fire Performance Standards.Current edition approved MarchJan. 1, 2010.2012. Published April 2010.February 2012. Originally approved in 1988. Last previous edition approved in 20042010 asD387404.D387410. DOI: 10.1520/D3874-102.2K. N

12、. Mathes, Chapter 4, “Surface Failure Measurements”, Engineering Dielectrics, Vol. IIB, Electrical Properties of Solid Insulating Materials, MeasurementTechniques, R. Bartnikas, Editor, ASTM STP 926, ASTM, Philadelphia, 1987.3For referencedASTM standards, visit theASTM website, www.astm.org, or cont

13、actASTM Customer Service at serviceastm.org. ForAnnual Book ofASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.4Available from International Electrotechnical Commission (IEC), 3 rue de Varemb, Case postale 131, CH-1211, Geneva 20, Switzerland, http:/

14、www.iec.ch.5Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what chan

15、ges have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the offic

16、ial document.*A Summary of Changes section appears at the end of this standard.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3. Terminology3.1 Definitions:3.1.1 Use Terminology E176 and ISO 13943 and IEC 60695-4 for definitions of t

17、erms used in this test method and associatedwith fire issues. Where differences exist in definitions, those contained in Terminology E176 shall be used. Use Terminology D1711for definitions of terms used in this test method and associated with electrical insulation materials.3.2 Definitions of Terms

18、 Specific to This Standard:3.2.1 ignition, ninitiation of flaming produced by combustion in the gaseous phase that is accompanied by the emission oflight.4. Summary of Test Method4.1 In this test method, a rectangular bar-shaped test specimen, with the center portion wrapped with a coil of heater wi

19、re, issupported horizontally at both ends. The circuit is then energized by applying a fixed power density to the heater wire, whichrapidly heats up. The behavior of the test specimen is observed. until one of the following happens: (a) the material under testignites, (b) the material under test mel

20、ts, (c) 120 s of exposure have gone by without ignition or melting. The time to ignition andthe time to melt through, as applicable, are recorded.5. Significance and Use5.1 During operation of electrical equipment, including wires, resistors, and other conductors, it is possible for overheating tooc

21、cur, under certain conditions of operation, or when malfunctions occur. When this happens, a possible result is ignition of theinsulation material.5.2 This test method assesses the relative resistance of electrical insulating materials to ignition by the effect of hot wire sources.5.3 This test meth

22、od determines the average time, in seconds, required for material specimens to ignite under the specifiedconditions of test.5.4 This method is suitable to characterize materials, subject to the appropriate limitations of an expected precision of 615 %,to categorize materials.5.5 In this procedure th

23、e specimens are subjected to one or more specific sets of laboratory conditions. If different test conditionsare substituted or the end-use conditions are changed, it is not always possible by or from this test to predict changes in thefire-test-response characteristics measured. Therefore, the resu

24、lts are valid only for the fire test exposure conditions described inthis procedure.6. Apparatus6.1 Heater WireThe heater wire shall be a No. 24AWG, Nichrome (Nickel-Chrome) wire, that is iron free, with the followingnominal properties: a wire composition of 20 % chromium-80 % nickel, a diameter of

25、0.050.5 mm (0.020 in.), a nominal coldresistance of 5.28 V/m (1.61V/ft), and a length-to-mass ratio of 580 m/kg (864 ft/lb).6.2 Calibrate each spool of test wire for energized resistance, in accordance with the method outlined in Annex A1. Suchcalibration is necessary due to the typical variability

26、of wire lots in composition, processing, sizing, and metallurgy.6.3 Supply CircuitThe supply circuit, which is a means for electrically energizing the heater wire, shall comply with6.3.1-6.3.4.6.3.1 The supply circuit capacity shall be sufficient to maintain a continuous linear 50 to 60 Hz power den

27、sity of at least 0.31W/mm (8.0 W/in.) over the length of the heater wire at or near unity power factor. The power density of the supply circuit at 60A and 1.5 V shall approximate 0.3 W/mm.6.3.2 The supply circuit shall have a means of voltage adjustment to achieve the desired current as determined f

28、rom Annex A1.Such means of voltage adjustment shall provide a smooth and continuous adjustment of the power level.6.3.3 The supply circuit shall have a means of voltage adjustment of measuring the power to within 62%.6.3.4 The test circuit shall be provided with an easily actuated on-off switch for

29、the test power, and with timers to record theduration of the application of test power.6.4 Test ChamberUse as a test chamber a draft-free closed chamber having a volume of at least 0.3 m3(10.5 ft3). The ratiobetween any two transverse dimensions of the chamber shall not exceed 2.5. The test chamber

30、shall be positively vented to theoutside of the test facility before and after the test, but it shall remain closed and unvented during the test. The chamber shall beequipped with an observation window.6.5 Test FixtureTwo supporting posts shall be positioned 70 mm (234 in.) apart to support the spec

31、imen in a horizontalposition, at a height of 60 mm (238 in.) above the bottom of the test chamber, in the approximate center of the test chamber.6.6 Specimen-Winding FixtureA fixture shall be provided to uniformly position the wire, with a spacing of 6.35 6 0.05 mm(0.250 6 0.002 in.) between turns a

32、nd with a winding tension of 5.4 6 0.02 N (1.21 6 0.0045 lbf).7. Safety Precautions7.1 It is possible that fumes and products of incomplete combustion are liberated from the specimen when conducting this test.Avoid the inhalation of such fumes and products of combustion and exhaust them from the tes

33、t chamber after each run.7.2 Take precautions to safeguard the health of personnel against the risk of explosion or fire, the inhalation of smoke, or otherD3874 122products of combustion, or the exposure to the residues potentially remaining on the specimen after testing.8. Test Specimens8.1 The tes

34、t specimen shall consist of a bar measuring 12.5 6 0.2 by 125 6 5mm(12 by 5 in.) and of the thickness to be tested.9. Conditioning9.1 Condition the specimens and heater wire as follows:9.1.1 Sample ConditioningPrior to testing, maintain the samples in a dry condition. If this is not practical, dry t

35、he samplesin an air-circulating oven at 70 6 2C (158 6 3.5F) for seven days and cool over a desiccant, such as silica gel, for a minimumof 4 h. Prior to testing, condition the dry samples for at least 40 h at 23 6 2C (73 6 3.5F) and 50 6 5 % relative humidity.Maintain the test facilities at 50 6 5 %

36、 relative humidity and 23C.9.1.2 Heater Wire Conditioning and CalibrationFor each test, use a length of previously calibrated wire measuringapproximately 250 mm (10 in.). Prior to testing, anneal each straight length by energizing the wire to dissipate 0.26 W/mm oflength (6.5 W/in. of length) for 8

37、to 12 s to relieve the internal stresses within the wire. Calibrate the wire in accordance withAnnexA1 to determine the correct current level.10. Procedure10.1 Wrap the center portion of the test specimen with a test wire, conditioned in accordance with 9.1.2, using the windingfixture as specified i

38、n 6.6 and a winding force of 5.4 6 0.02 N (1.21 6 0.0045 lbf). Apply five complete turns spaced 6.35 6 0.05mm (14 in.) between turns.10.2 Position the specimen on the test fixture such that the length and width are horizontal. Securely connect the free ends ofthe wire to the test circuit. The connec

39、tion is to be capable of transmitting the test power without significant losses, and insofaras possible, not mechanically affect the specimen during the test.10.3 Start the test by energizing the circuit to dissipate 0.26 W/mm (6.5 W/in.) through the nickel-chrome wire. The 0.26 W/mmshall be maintai

40、ned during the test.10.4 Continue heating until the test specimen ignites (see 3.2.1). When ignition occurs, shut off the power and record the timeto ignition. Discontinue the test if ignition does not occur within 120 s. For specimens that melt through the wire without ignition,discontinue the test

41、 when the specimen is no longer in intimate contact with all five turns of the heater wire.10.5 Note the following observations:10.5.1 The time to ignition of each specimen, and10.5.2 The time for each specimen to melt through the wire if appropriate.11. Report11.1 Report the following information:1

42、1.1.1 Complete identification of the material tested including type, source, and manufacturers code number,11.1.2 Testing room conditions,11.1.3 Number of specimens tested,11.1.4 Thickness of specimens tested,11.1.5 Time to ignition for each specimen or the time at which the wire turns no longer con

43、tact the specimen,11.1.6 Calculation and record of the average time for ignition,11.1.7 Calibrated test current, and11.1.8 Geometry of test chamber.12. Precision and Bias12.1 It is likely that, when care is taken to adhere to this test method, the average determined will fall within 615 % of the val

44、ueobtained by an interlaboratory evaluation.12.2 A statement of bias for this test method is not practicable since there is no standard reference material available with aknown characteristic of true resistance to ignition.13. Keywords13.1 hot wire; ignition; resistance to ignitionANNEX(Mandatory In

45、formation)D3874 123A1. TEST WIRE CALIBRATIONA1.1 GeneralA1.1.1 Due to normal variations in metals, it is essential that each spool of test wire be calibrated with respect to energizedresistance according to the following procedure. A mathematical relationship is developed between current and power d

46、issipation,based on performance under the calibration experiment. Essentially, the voltage over a carefully measured length of wire, and thecurrent through the wire are measured over a range of values to establish the power-current relationship. It has been found thatthe variation of electrical resi

47、stance of the test wire within the spool is not significant.A1.2 Apparatus and EquipmentA1.2.1 Position approximately 250 mm (10 in.) of test wire as a horizontal open loop connected to the supply contacts of thehot wire ignition equipment (see Fig. A1.1). Place an ammeter in the circuit. Fit a volt

48、meter with small voltage-measuring probesfor measuring voltage across a measured length of the wire.A1.3 ProcedureA1.3.1 Position the voltmeter probes near the ends of the test wire prior to connecting the wire, with the wire in a horizontalstraight position. Carefully measure and record the length

49、of the wire between the contact points of the clips. Connect the wire tothe test apparatus and energize to current levels, from 1 to 8 A in increments of 1 A. Record current and voltage at each level.A1.4 CalculationA1.4.1 For each measurement, calculate the linear power density as follows:W 5EILwhere:W = linear power density, W/mm (or W/in.),E = measured voltage, V,I = measured current, A, andL = measured length between voltage clips, mm (or in.).A1.4.2 Construct a calibration curve of current as a function of linear power density. The desired calibrate