ASTM D3874

ASTM D3874 – Standard Test Method for Ignition of Materials by Hot Wire Sources

Description:

Significance and Use

5.1 During operation of electrical equipment, including wires, resistors, and other conductors, it is possible for overheating to occur, under certain conditions of operation or when malfunctions occur. When this happens, a possible result is ignition of the insulation 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 method determines the average time, in seconds, required for material specimens to ignite under the specified conditions of test.

5.4 This method is suitable to characterize materials, subject to the appropriate limitations of an expected precision of ±15 %, to categorize materials.

5.5 In this procedure the specimens are subjected to one or more specific sets of laboratory conditions. If different test conditions are substituted or the end-use conditions are changed, it is not always possible by or from this test to predict changes in the fire-test-response characteristics measured. Therefore, the results are valid only for the fire test exposure conditions described in this procedure.

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.2

1.2 This test method applies to molded or sheet materials available in thicknesses up to and including 13.0 mm (0.51 in.).

1.3 This test method applies to materials that are rigid or flexible at normal room temperatures. It is important to minimize deformation during preparation, especially during the wire-wrapping step described in 10.1, by following the method outlined under Clause 10, Sample Preparation. Examples of deformation include bowing, in either a transverse or a longitudinal direction, twisting of the specimen, and indentation of the wire into the specimen during the wire-wrapping step, to a degree visible to the eye.

1.4 The values stated in SI units are to be regarded as standard. The values given in parentheses after SI units are provided for information only and are not considered standard. (See SI10 for further details.)

1.5 This test method measures and describes the response of materials, products, or assemblies to heat and flame under controlled 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 fire conditions.