Difference Between Needle Flame Test and Glow Wire Test

What is a needle flame test?
The full name of IEC 60695-2-2 is Fire hazard testing Part 2: Test methods – Section 2 Needle-flame test. It was prepared by IEC technical committee 89: Fire hazard testing. The following is the related introduction of IEC 60695-2-2 Scope.

This section of IEC 60695-2-2 specifies a needle-flame test to simulate effect of small flames which may result from fault conditions within equipment, in order to assess by a simulation technique the fire hazard.It is applicable to electrotechnical equipment, its sub-assemblies and components and to solid electrical insulating material or other combustible materials.

ZY-3 Needle flame test 

Definition of difference:
The needle flame test is used to determine that the test flame will not ignite the part under specified conditions, or that the test flame ignites the combustible part, but the part’s burning duration or burning length is limited, and the flame or from the test sample. Falling burning or scorching particles will not spread the fire.

The glow-wire test is to test the stability of electrical and electronic products at work. The glow wire itself is actually a resistance wire ring with a fixed specification. During the test, it should be heated to a specified temperature, so that the tip of the glow wire contacts the sample for the standard required time, and then observe and measure its state. The test range depends on the specific test procedure.

Test principle difference:
The needle flame test is to ignite a needle-shaped burner of a specified size (Φ0.9mm) with a specific gas (butane) at an angle of 45° and directionally ignite the sample, and observe whether the sample is ignited and the burning time and burning length. Evaluate the fire hazard of the equipment due to small flames caused by fault conditions.

The glow-wire test is to heat the nickel-chromium wire (U-shaped glow-wire tip) with a specified material of Φ4 mm to the specified temperature (300 ℃ ~ 1000 ℃) with a large current, and then burn the test sample at the specified pressure (1.0N) level for 30s , whether the test items and beddings ignite or hold burning time to determine the fire hazard of the finished electrical and electronic equipment; after the test is completed, record the glowing time, ignition time (Ti), flame extinction time (Te), flammability index (GWFI) ).

Difference in sample size
In the needle flame test, the test sample can be a finished sample without special requirements, and the size of the plane of the test sample in the glow wire test should be: length ≥ 60mm; width (inside of the fixture) ≥ 60mm; thickness: 0.75±0.1mm, 1.5 ±0.1mm or 3.0±0.2mm.

Differences in the evaluation of test results
The needle flame test is evaluated according to the requirements of the product standard. If the product standard does not require it, one of the following requirements is met:
 1) The test sample does not produce flame and burning phenomenon, and the packaging silk paper does not ignite or the white pine board does not carbonize.
2) After the needle flame is removed, the flame or burning duration of the test sample, surrounding parts and the bottom layer is less than 30s, the parts around the test sample and the bottom layer will not continue to burn, the packaging silk paper will not ignite, and the white pine board will not burn. Not carbonized.

Evaluation of glow wire test results
1. Evaluation of Glow Wire Flammability Index (GWFI) Results
The test sample is considered to have withstood the test if it does not ignite or if both of the following conditions are met:
a) If the flame or glow wire of the test sample is extinguished within 30 s after removing the glow wire
b) The wrapping silk paper did not ignite
If either or both of the above conditions are not met, choose a lower test temperature and repeat the test with a new test sample. If both of the above conditions are met, repeat the test with a new test sample at a higher test temperature. The test shall be repeated at the highest test temperature at which the test sample meets conditions a) and b). The GWFI to be determined is the highest test temperature at which conditions a) and b) are satisfied for three consecutive tests.

Evaluation of Glow Wire Ignition Temperature (GWIT) Results
The light-off temperature of the test sample during application of the glow-wire shall be determined, and the test temperature shall be recorded 25K (30K between 900°C and 960°C) higher than the maximum temperature at the top of the glow-wire that did not cause the test sample to ignite for three consecutive tests for GWIT. Test related equipment: ZRS-3H  glow wire tester;  Zy-3 needle flame tester.

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