Difference between needle flame test, glow wire test and horizontal and vertical burning test

In order to evaluate the fire hazard of electrical and electronic products, it is necessary to conduct flame hazard tests on the components and materials of electronic and electrical products. The common flame hazard tests include needle flame test, glow wire test, and horizontal and vertical flame test, so what’s the difference between them?

1. Standard

1) The needle flame test is designed according to IEC60695-11-5 <<Test flames -Needle flame test method - Apparatus, confirmatory test arrangement and guidance>>.

2) The glow wire test is carried out in accordance with IEC60695-2-10 <<Glowing/hot-wire based test methods - Glow-wire apparatus and common test procedure>>.

3) The horizontal and vertical flame test is carried out according to UL94, IEC60695-11-10 <<Test flames - 50W horizontal and vertical flame test methods>>.

2. Testing method

1) Test method of Needle flame test

The needle flame test is to use a needle burner with a specified size ( at least 35mm long with a bore of 0.5mm±0.1mm and an outer diameter not exceeding 0.9mm) to ignite the sample with butane or propane gas (purity at least 95%) at an angle of 45°, and observe whether the sample is ignited and the burning time and flame length to evaluate the fire hazard of equipment due to small flames caused by fault conditions.

2) Test method of glow wire test

The glow-wire test is to heat the nickel/chromium(>77%Ni/20±1%Cr) wire with an overall diameter of 4.0 mm±0.07 (before bending) to the 960℃ temperature with a large current, and then burn the specimen with a 0.95N±0.1N for 30 seconds, and observe whether the specimen and the wrapping tissue are ignited or the ignite time to determine the fire hazard of the finished electrical and electronic equipment.

3) Test method of horizontal and vertical flame test

It is suitable for the laboratory test procedures intended to compare the burning behaviour of different materials used in electrotechnical products when vertically or horizontally oriented test bar specimens are exposed to a small flame ignition source with a norminal thermal power of 50W. It determines either the linear burning rate or the self-extinguishing properities of materials. There are two methods as below:

Method A is horizontal burning test (HB) and is intended to determine the liner burning rate of materials under specific test conditions. The specimen is in a horizontal position, is suitable for evaluating the extent of burning and/or the rate of flame spread, such as linear burning rate.

Method B is a vertical burning test (V) and is intended to determine whether materials self-extinguish under specific test conditions. The sample is in a vertical position, suitable for evaluating the degree of combustion after the test flame is removed.

3. Application scene

1) Needle flame test

Both the needle flame test and the glow wire test are used in the electrical and electronic product industry to determine the flame retardancy of electronic products. Compared with the glow wire test, the needle flame test is a fire and the effect is more direct. Due to the leakage path fault current, components in the product Fault conditions such as overheating of components or poor contact may cause flames and spread to nearby components.

The needle flame test is to simulate a small flame generated under product failure conditions, and use simulation technology to evaluate the risk of fire. When the glow wire test and the horizontal and vertical burning test methods of small parts (or components) are not suitable, the needle flame test method can be used for the test.

If the sample ignites in the glow wire test, the needle flame test is required to assess its combustion hazard.

2) Glow wire test

Under the fault or overload conditions, electrical components or parts may reach excessive temperatures or ignite nearby components. The glow wire test simulates the thermal stress caused by a heat source or ignition source such as a glowing element or an overload resistor in a short period of time, and uses simulation techniques to assess the fire risk.

The glow wire test is suitable for electrical and electronic products, plastics and their non-metallic insulating material parts, such as switch housings, relay sockets, etc.

3) Horizontal and vertical flame test

The horizontal and vertical burning test is to simulate the early situation of fire hazard in the surrounding environment of electronic and electrical products, and use simulation technology to evaluate the fire hazard. When a fire occurs around the product, it should be ensured that the spread of fire will not be caused.

The horizontal and vertical flame test is applicable to components, parts and components of electrical and electronic products, household appliances, such as insulating casings, switch panels, printed boards and insulating materials of household appliances.

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