ASTM D3874-97
(Test Method)Standard Test Method for Ignition of Materials by Hot Wire Sources
Standard Test Method for Ignition of Materials by Hot Wire Sources
SCOPE
1.1 This test method is intended to differentiate, in a preliminary fashion, among materials with respect to their resistance to ignition because of their proximity to electrically heated wires and other heat sources.
1.2 This test method applies to molded and sheet materials available in thicknesses of 0.25 mm (0.010 in.) to 6.4 mm (0.25 in.).
1.3 This test method applies to materials that are rigid at normal room temperatures. That is, the specimen does not deform during preparation including especially the wire-wrapping step described in 8.1. Examples of deformation that render this test method inapplicable include:
1.3.1 Bowing, in either transverse or longitudinal directions, or twisting of the specimen during the wire-wrapping step to a degree visible to the eye.
1.3.2 Visible indentation of the wrapped wire into the edges of 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 for information only.
1.5 This standard should be used to measure and describe the properties of materials, products, or assemblies in response to heat and flame under controlled laboratory conditions and should not be used to describe or appraise the fire hazard or fire risk of materials, products, or assemblies under actual fire conditions. However, results of this test may be used as elements of a fire risk assessment which takes into account all of the factors which are pertinent to an assessment of the fire hazard of a particular end use .
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
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NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
An American National Standard
Designation: D 3874 – 97
Standard Test Method for
Ignition of Materials by Hot Wire Sources
This standard is issued under the fixed designation D 3874; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This test method is intended to differentiate, in a 2.1 ASTM Standards:
preliminary fashion, among materials with respect to their D 1711 Terminology Relating to Electrical Insulation
resistance to ignition because of their proximity to electrically- E 176 Terminology of Fire Standards
heated wires and other heat sources. 2.2 IEC Standards:
1.2 This test method applies to molded or sheet materials IEC 695-2-1 Fire Hazard Testing. Part 2: Test Methods,
available in thicknesses ranging 0.25 to 6.4 mm (0.010 to 0.25 Section 20: Hot-Wire Coil Ignitability Test on Materials
in.). ISO/IEC Guide 52: Glossary of Fire Terms and Definitions
1.3 This test method applies to materials that are rigid at
3. Terminology
normal room temperatures. That is, it applies to materials for
which the specimen does not deform during preparation, 3.1 Definitions:
3.1.1 Use Terminology E 176 and ISO/IEC Guide 52 for
including especially during the wire-wrapping step described
in 9.1. Examples of deformation that render this test method definitions of terms used in this test method and associated
with fire issues. Where differences exist in definitions, those
inapplicable include:
1.3.1 Bowing, in either a transverse or a longitudinal direc- contained in Terminology E 176 shall be used. Use Terminol-
ogy D 1711 for definitions of terms used in this test method and
tion, or twisting of the specimen, during the wire-wrapping
step, to a degree visible to the eye. associated with electrical insulation materials.
3.2 Definitions of Terms Specific to This Standard:
1.3.2 Visible indentation of the wrapped wire into the
specimen. 3.2.1 ignition, n—initiation of flaming produced by com-
bustion in the gaseous phase that is accompanied by the
1.4 The values stated in SI units are to be regarded as the
standard. The inch-pound units given in parentheses are for emission of light.
information only.
4. Significance and Use
1.5 This test method measures and describes the response or
4.1 Under certain conditions of operation, or when malfunc-
materials, products, or assemblies to heat and flame under
tions occur, it is possible that electrical equipment including,
controlled conditions, but does not by itself incorporate all
but not limited to, wires, resistors, or other conductors, become
factors required for fire hazard or fire risk assessment of the
abnormally hot. When this happens, a possible result is ignition
materials, products, or assemblies under actual fire conditions.
of the insulation material.
1.6 This standard does not purport to address all of the
4.2 This test method assesses the relative resistance of
safety concerns, if any, associated with its use. It is the
electrical insulating materials to ignition by the effect of hot
responsibility of the user of this standard to establish appro-
wire sources.
priate safety and health practices and determine the applica-
4.3 This test method determines the average time, in sec-
bility of regulatory limitations prior to use.
onds, required for material specimens to ignite under the
NOTE 1—Although this test method and IEC 695-2-20, differ in
conditions of test.
approach and in detail, data obtained using either are technically equiva-
4.4 Subject to limitations in precision and bias, this test
lent.
method can be used to categorize materials.
This test method is under the jurisdiction of ASTM Committee D09 on
Electrical and Electronic Insulating Materials and is the direct responsibility of
Subcommittee D09.21 on Fire Performance Standards.
Current edition approved Sept. 10, 1997. Published November 1997. Originally
approved in 1988. Last previous edition approved in 1990 as D 3874 – 90a. Annual Book of ASTM Standards, Vol 10.01.
2 4
K. N. Mathes, Chapter 4, “Surface Failure Measurements”, Engineering Annual Book of ASTM Standards, Vol 04.07.
Dielectrics, Vol. IIB, Electrical Properties of Solid Insulating Materials, Measure- Available from International Electrotechnical Commission (IEC), 3 Rue de
ment Techniques, R. Bartnikas, Editor, ASTM STP 926, ASTM, Philadelphia, 1987. Varembe, Geneva, Switzerland.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
NOTICE: This standard has either been superceded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
D3874–97
5. Apparatus 8. Conditioning
5.1 Heater Wire—No. 24 AWG, Nickel-Chrome wire, that 8.1 Condition the specimens and heater wire as follows:
is iron free having the following nominal properties: the wire 8.1.1 Sample Conditioning—Prior to testing, maintain the
has a composition of 20 % chromium-80 % nickel, measures samples in a dry condition. If this is not practical, dry the
0.05 mm (0.020 in.) in diameter, has a nominal cold resistance samples in an air-circulating oven at 70 6 2°C (158 63.5°F)
of 5.28 V/m (1.61V/ ft), and has a length-to-mass ratio of 580 for seven days and cool over a desiccant, such as silica gel, for
m/kg (864 ft/lb). a minimum of 4 h. Prior to testing, condition the dry samples
for at least 40 h at 236 2°C (73 6 3.5°F) and 50 6 5 % relative
5.2 Due to normal variations in composition, processing,
sizing, and metallurgy between wire lots, it is necessary that humidity. Maintain the test facilities at 50 6 5 % relative
humidity and 23°C.
each spool of test wire be calibrated for energized resistance in
accordance with the method outlined in Annex A1. 8.1.2 Heater Wire Conditioning and Calibration—For each
test, use a length of previously calibrated wire measuring
5.3 Supply Circuit—A means for electrically energizing the
approximately 250 mm (10 in.). Prior to testing, anneal each
heater wire. The supply circuit shall have the following
straight length by energizing the wire to dissipate 0.26 W/mm
capabilities:
of length (6.5 W/in. of length) for 8 to 12 s to relieve the
5.3.1 Sufficient capacity to maintain a continuous linear 50
internal stresses within the wire. Calibrate the wire in accor-
to 60 Hz power density of at least 0.31 W/mm (8.0 W/in.) over
dance with Annex A1 to determine the correct current level.
the length of the heater wire at or near unity power factor.
Conditions of the supply circuit at 60 A and 1.5 V should result
9. Procedure
in power density approximating 0.3 W/mm.
5.3.2 A means for adjustment of voltage to achieve the
9.1 Wrap the center portion of the test specimen with a test
desired current as determined from Annex A1. Such means for
wire, conditioned in accordance with 8.1.2, using the winding
adjustment shall provide a smooth and continuous adjustment
fixture as specified in 4.6 and a winding force of 5.4 6 0.02 N
of the power level.
(1.216 0.0045 lbf). Apply five complete turns spaced 6.35 6
5.3.3 A means of measuring the power to within 62%.
0.05 mm ( ⁄4 in.) between turns.
5.3.4 The test circuit shall be provided with an easily
9.2 Position the specimen on the test fixture such that the
actuated on-off switch for the test power, and timers to record length and width are horizontal. Secure
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