Needle Flame Test Procedure
Before the needle flame test, you need to condition the test specimen and the wooden board covered with a layer of the tissue in an environment of temperature between 15℃ and 35℃ and relative humidity between 45% and 75% for not less than 24 hours. The test specimens shall be tested within 1 hour once they are taken out from the conditioning atmosphere.
Turn on the lights inside the chamber, and open the chamber door to clamp the specimen. You need to ensure that the specimen is arranged in a normal use position such that ignition is most likely to occur during the test.
Place a layer of the material or components usually surrounding or situated underneath the specimen, maintaining a distance the same as that in the application. If the surrounding materials and distances are unknown, you need to place a piece of a flat smooth wooden board with 10 mm in thickness covered with a single layer of wrapping tissue below the flame application point on the specimen at a distance of (200 ± 5) mm.
- Burner Position Presetting
The carriage inside the chamber is activated to automatically move to a position near the underside of the specimen. You are required to adjust the vertical burner tube to tilt 45 degrees.
With the provided gauges, a spacing between the center of the top of the burner and the remaining portion of the test specimen during the test shall be maintained at (8 ± 1) mm (applicable when the specimen is vertically above the test flame) or (5 ± 1) mm (applicable when the specimen is located horizontally from the test flame) by adjusting the specimen up, down, left or right.
When the position of applying flame is determined, adjust the proximity switch of the carriage to the matching position. During the test, the carriage will automatically stop after moving to the specified position.
Reset the carriage to the initial position and restore the burner tube to the vertical state. Turn on the gas supply switch to ensure that the specified gas flows in the burner tube. You can light the test flame with an ignition device such as a lighter, then turn off the light inside the chamber to provide a dark background to calibrate the flame height. The flame height is controlled by rotating the gas source control valve to adjust the gas flow rate.
We will configure a unique gauge with the instrument to assist in this step. The required overall height of the test flame has to be maintained at (12±1) mm. Wait for a minimum of 5 min to allow the burner conditions to reach equilibrium.
- Flame Temperature Measurement
Before the test, we need to test whether the temperature of the flame reaches the specified standard. Slide the temperature measuring assembly on the top inside the test chamber to the appropriate position. Manually place the copper block with built-in temperature sensing element K-type thermocouple in the flame, turn on the temperature test switch, and the digital screen will automatically start to display its real-time temperature.
When the temperature reaches 100 degrees, the timer starts to count automatically and stops when it reaches 700 degrees. The time not more than (23.5 ± 1) seconds for the copper block to hear up from (100 ± 5) degrees Celsius to (700 ± 3) degrees Celsius is qualified. For more detailed flame temperature test methods, please refer to Annex A of the IEC 60695-11-5.
Set the necessary parameters on the operation panel and start the test. Rotate the burner so that the burner tube is positioned at 45 degrees from the vertical. Turn on the automatic displacement switch of the carriage, and the carriage will automatically move to the flame application point just set to start applying flame to the specimen.
After the specified flame-application time arrives, the carriage will automatically return to the starting point. The instrument will automatically start recording the self-sustaining burning time when the test flame is removed.
When the flame is completely extinguished, or glowing combustion is invisible, press the timer pause button to get the burning duration of the needle flame test. Test other samples are in the same way. Usually, the test is performed on three test specimens.
- Observations and Measurements
You are required to measure and record the duration of burning from the moment the test flame is removed from the specimen until the last flames have extinguished and the glowing combustion of the specimen, the specified layer, and/or the surrounding parts is no longer visible.
- Evaluation of Test Results
A sample passes the needle flame test as long as either of the following two conditions is satisfied:
- No ignition of the specified layer, no flame, and no glowing of the specimen after the removal of the needle flame.
- Flames or glowing of the test specimen and the surrounding parts extinguish within 30 seconds after the removal of the test flame. Also, the surrounding parts have not burnt away entirely, and there has been no ignition of the specified layer.