The significance of fire hazard testing
Common safety issues in the field of consumer electronics are often caused by dangers such as internal component failure or fire in and around the casing. In order to evaluate the fire risk of electrical and electronic products, it is necessary to conduct flame retardant tests on the components and materials of electronic and electrical products. Common flame retardant tests include needle flame test, glow wire test, and horizontal and vertical burning tests.
In the field of electrotechnical products, the risk of fire are often caused by internal component failure, like the product shell fires and the surrounding material fires. So, in order to evaluate the fire risk , it is necessary to conduct flame retardant tests on the components and material of electrotechnical products. Normally, the fire hazard testing includes needle flame test, glow wire test, and horizontal and vertical flame test.
Standards involved
The needle-flame test is to simulate the effect of a small flame which may result from fault conditions in accordance with standard IEC60695-11-5. And the glow / hot – wire test simulate the effects of thermal stresses which may be produced by heat sources with a flameless ignition test procedure in accordance with standard IEC60695-2-10 to IEC60695-2-13. And the horizontal and vertical flame test is conducted with a apparatus which can produce 50W and 500W test flames to assess the flammability properties of materials in accordance with standards IEC60695-11-4, IEC60695-11-3 and UL94.
Needle Flame Test
The Needle Flame Tester consists of a dia.0.9mm needle burner that tilts to 45 degree from the vertical and is fueled with butane gas. The fire hazard of the specimen is assessed by measuring the burning duration of the specimen, and any ignition of the wrapping tissue and white pine board below the specimen. Needle flame apparatus simulates the effect of a small flame which may result from fault conditions, such as fault leakage current, components overheating and poor contact, the failures may cause a small flame and spread to surrounding parts. The needle flame test is to assess the fire risk of small parts or components of electrotechnical products under failure conditions. When the test procedures of glow wire test and horizontal and vertical combustion test are not applicable, the needle flame test procedure can be applied.
Glow wire test
The glow wire tester integrated with a specific material ( Ni/Cr(80/20)) and sharp heating wire, the glow-wire loop is heated to specific temperature (550 ℃~960 ℃) for 1 min by max current, then vertical burns the sample with certain pressure (0.95N) for 30s, then check if the test specimen and bedding material are burning, and count the burning time to judge the dangerousness of the specimen. The glow-wire apparatus simulates the effects of thermal stresses which may be produced by heating sources such as glowing elements or overloaded resistor, for short periods, in order to assess the fire hazard by a simulation technique. The test procedures applied to end products, solid electrical insulating materials or other solid combustible materials. If a sample ignites during a glow wire test, a needle flame test is required to evaluate its combustion hazard.
Horizontal and vertical flame test
The horizontal and vertical flame tester uses a bunsen burner of a specified size and specified gas source (methane or natural gas) to ignite the horizontal or vertical specimen for several times in a certain flame height and a certain flame angle. And the fire hazard is evaluated by burning rate, after glow time, after flame time and damage length of the specimen. The horizontal and vertical flame apparatus is to simulate the early fire hazard situations in the environment around electrotechnical products. The fire hazard is assess by a simulation technique. When fire occurs around the product, care should be taken to prevent the spread of fire. The horizontal vertical flame test is applied to test the parts and components of electrotechnical products and household appliance, such as insulating shells, switch panels, printed boards and insulating materials of household appliances.
