1、Designation: D3874 13D3874 18Standard 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 of revision, the year of last revision. A
2、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 respect to their resistance toignition b
3、ecause 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 rigid at normal room temperatures. That
4、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 a longitudinal direction, or twisting of
5、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 forinformation only. (See SI10 for further de
6、tails.)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 the materials,products, or assemblies under actual fi
7、re 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 safety, health, and healthenvironmental practices and determine theapplicability of regulatory
8、 limitations 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property shall be employed in conducting thesetests.NOTE 1Although this test method and IEC 60695-2-20, TS 60695-2-20 (withdrawn), differ in approach and in detail, data obtained using either ar
9、etechnically equivalent.1.8 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Principles for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization
10、Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:3D1711 Terminology Relating to Electrical InsulationD6194 Test Method for Glow-Wire Ignition of MaterialsE176 Terminology of Fire StandardsE3020 Practice for Ignition SourcesIEEE/ASTM SI-10 American National Standa
11、rd for Metric Practice1 This test method is under the jurisdiction of ASTM Committee D09 on Electrical and Electronic Insulating Materials and is the direct responsibility of SubcommitteeD09.17 on Fire and Thermal Properties.Current edition approved Nov. 1, 2013Nov. 1, 2018. Published December 2013N
12、ovember 2018. Originally approved in 1988. Last previous edition approved in 20122013as D3874 12.D3874 13. DOI: 10.1520/D3874-13.10.1520/D3874-18.2 K. N. Mathes, Chapter 4, “Surface Failure Measurements”, Engineering Dielectrics, Vol. IIB, Electrical Properties of Solid Insulating Materials, Measure
13、mentTechniques, R. Bartnikas, Editor, ASTM STP 926, ASTM, Philadelphia, 1987.3 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. ForAnnual Book ofASTM Standardsvolume information, refer to the standards Document Summary page on the
14、 ASTM website.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users con
15、sult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken
16、, PA 19428-2959. United States12.2 IEC Standards:IEC TS 60695-2-20 Fire Hazard TestingSection 20: Glowing/Hot-wire Based Test Methods, Hot-wire Coil Ignitability Teston Materials (withdrawn)4IEC 60695-4 Fire Hazard TestingPart 4: Terminology Concerning Fire Tests for Electrotechnical Products42.3 IS
17、O StandardsISO 13943 Fire SafetyVocabulary53. Terminology3.1 Definitions:3.1.1 Use Terminology E176 and ISO 13943 and IEC 60695-4 for definitions of terms used in this test method and associatedwith fire issues.Where differences exist in definitions, those contained inTerminology E176 shall be used.
18、 UseTerminology D1711for definitions of terms used in this test method and associated with electrical insulation materials.3.2 Definitions of Terms 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
19、.the initiation of combustion. E1763.2.1.1 DiscussionThe combustion may be evidenced by glow, flame, detonation, or explosion. The combustion may be sustained or transient (seeTerminology E176).4. Summary of Test Method4.1 In this test method, a rectangular bar-shaped test specimen, with the center
20、portion wrapped with a coil of heater wire, 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 test
21、ignites, (b) the material under test melts, (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 conduct
22、ors, it is possible for overheating tooccur, 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 effec
23、t of hot wire sources.5.3 This test method 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 categ
24、orize materials.5.5 In this procedure the 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 chara
25、cteristics measured. Therefore, the results 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 2
26、0 % chromium-80 % nickel, a diameter of 0.5 mm (0.020 in.), a nominal cold resistanceof 5.28 /m (1.61/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 necessa
27、ry due to the typical variability 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 with 6.3.1 6.3.4.6.3.1 The supply circuit capacity shall be sufficient to maintain a cont
28、inuous linear 50 to 60 Hz power density 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.4 Available from International Electrotechnical Commission (IEC), 3 rue de Va
29、remb, Case postale 131, CH-1211, Geneva 20, Switzerland, http:/www.iec.ch.5 Available from International Organization for Standardization (ISO), 1, ch. de la Voie-Creuse, Case postale 56, CH-1211, Geneva 20, Switzerland, http:/www.iso.ch.D3874 1826.3.2 The supply circuit shall have a means of voltag
30、e adjustment to achieve the desired current as determined from AnnexA1.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 s
31、hall be provided with an easily actuated on-off switch for 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 dimen
32、sions of the chamber shall not exceed 2.5. The test chamber 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 s
33、hall be positioned 70 mm (234 in.) apart to support the specimen 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
34、spacing of 6.35 6 0.05 mm0.05 mm (0.250 6 0.002 in.) between turns and 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
35、 such fumes and products of combustion and exhaust them from the test 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 otherproducts of combustion, or the exposure to the residues potentially remaining
36、 on the specimen after testing.8. Test Specimens8.1 The test specimen shall consist of a bar measuring 12.560.2 by 12565 mm (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 sa
37、mples in a dry condition. If this is not practical, dry the 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 % r
38、elative humidity.Maintain the test facilities at 50 6 5 % 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
39、dissipate 0.26 W/mm oflength (6.5W/in. of length) for 8 to 12 s to relieve the internal stresses within the wire. Calibrate the wire in accordance with AnnexA1 to determine the correct current level.10. Procedure10.1 Wrap the center portion of the test specimen with a test wire, conditioned in accor
40、dance with 9.1.2, using the windingfixture as specified in 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
41、 the free ends ofthe wire to the test circuit. The connection 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.) thro
42、ugh the nickel-chrome wire. The 0.26 W/mmshall be maintained 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 me
43、lt through the wire without ignition,discontinue the test 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 appr
44、opriate.11. Report11.1 Report the following information:11.1.1 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,D3874 18311.1.4 Thickness of specimens tested,11.1.5 Time to ignition f
45、or each specimen or the time at which the wire turns no longer contact 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 tes
46、t method, the average determined will fall within615 % of the valueobtained 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. Keywords
47、13.1 hot wire; ignition; resistance to ignitionANNEX(Mandatory Information)A1. 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 mathematic
48、al relationship is developed between current and power dissipation,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
49、. It has been found thatthe variation of electrical resistance 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 the hotwire ignition equipment (see Fig. A1.1). Place an ammeter in the circuit. Fit a voltmeter with small voltage-measuring probes formeasuring 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 connect
