Difference between the Operating Procedure of Needle Flame Test Apparatus in IEC 60695-11-5:2004 and GB/T 5169.5-2008

The Needle Flame Test is the main test item for testing whether electronic products and materials are inflammable. It simulates the flame generated by overheating of electronic products and components under fault or overload conditions, thus realistically reproducing the existing situation and evaluating the fire hazard of the product by simulation technology. This paper analyzes the requirements of the use of the Needle Flame Tester in accordance with IEC 60695-11-5:2004 and GB/T 5169.5-2008, the requirements of the equipment, and the confirmation method of the main technical index calibration results, and summarizes the precautions in the process of the needle flame test.

According to IEC60695-2-2, IEC60695-11-5 and GB/T-5169.5, ZY-3/ZY-3S needle flame test equipment is applied in the production and quality control department of lighting products, hyperpiesia electrical apparatus, domestic appliance, machine electric appliance, electrical machine, power tool, electronic instrument, electrician instrument and technical equipment. Also, the apparatus is suitable for the industry of insulation material, engineering plastics and solid combustible material.

I. Main Differences Between Old and New Standards
1.1 Expansion of Applicable Scope
The GB/T 5169.5-2008 standard expands the scope of application. The needle flame test not only considers the risk of ignition caused by failure of internal components or parts of the product, but also considers the risk of ignition caused by overheating caused by other equipment from the external environment. Through simulation technology, the internal and external ignition performance are evaluated in order to more comprehensively detect the reaction characteristics of the entire product, components or materials to heat and flame.

1.2 Requirements for Needle Flame Testing Equipment
1) For the Test Box: The GB/T 5169.5-1997 standard does not specify the volume of the test box, while the new standard clearly stipulates that the volume of the laboratory ventilation cabinet/test box should be at least 0.5m3, and the color of the box surface should be dark. The needle flame test should be conducted in an environment without ventilation. The standard stipulates the size of the test box in order to prevent the loss of oxygen caused by air convection during the test and affect the test results.

2) For Burners and Flames: The new standard specifies the use of gaseous gases with a purity not less than 95%| and large alkanes. Butane is a flammable, odorless, easily liquefied and stored gas, and most experiments often choose butane gas. At the same time, for the requirements of the flame height during the needle flame test, the device and procedure specified in Annex A of the standard should be adopted to confirm.

1.3 Addition of Sample Requirements
The GB/T 5169.5-2008 new standard adds sample descriptions, which requires that the test sample should be a complete device, component or part. If necessary, it can be properly cut and disassembled, and the test conditions should be ensured without significant difference from the normal use of the product. The addition of this stipulation is to more realistically simulate the ignition effect of the product when it ignites.

1.4 Modification of Test Results Evaluation
How to judge whether the test sample can withstand the needle flame test, the new GB/T5169.5-2008 standard stipulation is stricter than the old standard. The new standard stipulates that after the needle flame is removed, the flame or heat from the test sample and the surrounding parts should be extinguished within 30s, and the burning of the base layer or packaging paper caused by the burning of the test sample should not be allowed. It can be judged that the test sample does not meet the requirements. Such a regulation is to prevent secondary ignition caused by the flame from the falling of the product.

1.5 Addition of Test Report
The GB/T 5169.5-2008 new standard adds the content of the test report, mainly including: type and description of the test sample, preparation method, all pretreatment of the test sample, number of test samples, subcool level, surface to be tested and points of needle flame, regulations on the base layer affected by burning or hot particles falling from the test sample, whether more than one point is tested on the same test sample, test results.

II. Experimental Process and Procedure
1)The needle flame test is generally carried out on three specimens (except those specified otherwise).

2)The test sample should be placed in the position most easily ignited in normal use and fix the test sample without affecting the application of test flame or flame spread. The test flame should be applied at the surface of the specimen which is most easily affected by the flame. Keep the flame tip in contact with the surface of the sample, adjust the flame height to 12mm ±1mm, and the time from the temperature of 100℃ ±2 °℃ to 700 °℃ ±3 °℃ is 23.5s ±1.0s.
3)During the test, molten material may be dropped into the combustion tube from the burning of the test sample, which may eventually block the air inlet channel and affect the test results. In order to avoid this situation, the new standard stipulates that the combustion chamber can be inclined at 45° angle. At the same time, the center of the top of the combustion chamber should maintain a distance of 8mm ±1mm from the bottom of the remaining part of the sample or a distance of 5mm ±1mm from the side.
4)Wrap a sheet of thin paper on a smooth wooden board about 10mm thick and place it 200mm ±5mm below the test sample undergoing needle flame.
5)When the temperature of the flame reaches, start the test switch to conduct the test. Observe the test sample, surrounding components and base layer, and record the burning duration (tb) from the moment the test flame leaves to the moment the flame is completely extinguished and the test sample, the specified base layer or nearby components cannot be seen hot.

III. Method of Confirming Calibration Results of Equipment
The main performance parameters of needle flame tester include box size, burner size and inclination angle, timer, flame height, temperature calibration:
1)Box size. Clear requirements have been made for the volume of the test box. The volume of the test box shall not be less than 0.5m3. The test box should be dark enough. In case of dispute, 20Lux illuminance should be used to facilitate the experimenter to adjust the flame height more accurately and observe the burning of the sample.

2)Burner size and tilt angle. Use calipers to measure the hole diameter of the burner, requiring the hole diameter to be 0.5mm ±0.1mm. Use vernier calipers to measure the length and outer diameter of the burner tube, requiring length ≥35mm and outer diameter ≤0.9mm to meet the requirements. Use universal angle ruler to measure the tilt angle of the burner. The standard stipulates that “the burner can be inclined 45° to the vertical to prevent the material from falling into the combustion tube”. Therefore, the tilt angle of the burner should be able to reach 45° to meet the requirements.

3)Timer. Electronic stopwatch is used to calibrate the time point of flame application, sustained flame time point and temperature rise time point. The error of the timer shall be ±0.5s, which meets the standard requirements.
4)Flame height. During the needle flame test, vernier calipers can be used to measure the flame height, which is 12mm ±1mm, which meets the standard requirements.

5)Temperature calibration. The new standard specifies the material for the temperature-sensing copper block used for flame confirmation test as CU-ETP UNS C11000, the diameter of the copper block as 4mm ±0.01mm, and the mass as 0.58g ±0.01g. The requirements on the copper block are not only conducive to the repeatability and comparability of the test, but also conducive to improving the accuracy of the test results. After inserting the thermocouple into the whole depth of the hole, squeeze the copper block to fix the thermocouple, but do not damage the thermocouple, and put it into the heating pot, respectively set at 100℃ and 700℃, read the three temperature display values on the temperature meter, take the average value as the actual temperature display value, and consider it valid when the temperature test results are between 100℃+5℃ and 700℃+3℃.

IV. Precautions for Needle Flame Test
1)The test equipment should meet the size requirements of GB/T 5169.5-2008 standard. When carrying out the test, the test box should be locked to avoid the loss of oxygen due to air flow, thus affecting the test results.
2)When the gas source changes, the flame temperature will undoubtedly be affected, so confirmation of the flame test must be conducted when changing the gas source.
3)Before the test, the test sample and the base layer (board and filter paper) used should be pre-treated in accordance with the temperature and humidity requirements specified in the standard, generally requiring placement in the environment for at least 24 hours.
4)When multiple tests are required on the same sample, it is necessary to ensure that the deterioration caused by the previous tests will not affect the results of the tests to be conducted.
5)Pay attention to keep the interior of the equipment clean, and clean up after the experiment; check the needle holes of the burner before each test to avoid blocking by molten droplets, thus affecting the full combustion of the flame.

V. Conclusion
Needle Flame Test is a relatively important test item for testing the fire risk of electrical and electronic products and materials. Test personnel should have a deep understanding of the standards, understand the differences between old and new standards, and master the operation methods skillfully, so as to avoid and reduce the factors affecting the test results, so as to improve the accuracy of needle flame test conclusions. This not only helps to improve the quality of enterprise products, but also helps to effectively control enterprise costs, thus more effectively improving the overall quality of electrical and electronic products.

Lisun Instruments Limited was found by LISUN GROUP in 2003. LISUN quality system has been strictly certified by ISO9001:2015. As a CIE Membership, LISUN products are designed based on CIE, IEC and other international or national standards. All products passed CE certificate and authenticated by the third party lab.

Our main products are Goniophotometer, Integrating Sphere, Spectroradiometer, Surge Generator, ESD Simulator Guns, EMI Receiver, EMC Test Equipment, Electrical Safety Tester, Environmental Chamber, Temperature Chamber, Climate Chamber, Thermal Chamber, Salt Spray Test, Dust Test Chamber, Waterproof Test, RoHS Test (EDXRF), Glow Wire Test and Needle Flame Test.

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