In the safety protection system of electrical equipment, fire testing is always a core link. The needle flame test can accurately simulate the "small fire source risk", so it becomes a key technology to block the source of electrical fires. Unlike fire-extinguishing performance tests for large-scale combustion, it focuses on small flames caused by internal component failures, overloads and other scenarios of equipment. Through standardized tests, workers can verify the fire resistance of materials and structures—it serves as a "front-line defense" to protect personal and property safety. From test principles to industrial applications, from standard specifications to technological evolution, the needle flame test has formed a complete technical system, which profoundly influences the design, production and market access of electrical products.

1. Test Principle: Accurately Simulate "Small Fire Source" Risks

The core logic of the needle flame test is to reproduce the "local small fire source" scenario that may occur inside electrical equipment. Such fire sources mostly come from component failures (e.g., capacitor breakdown, resistor overload), poor contact (e.g., loose terminal blocks) or insulation aging. They are characterized by "moderate temperature, small size and easy neglect"—the temperature is usually between 500℃ and 900℃, and the flame height is only a few millimeters. Workers build a standardized fire source through special devices to verify whether the equipment can block the spread of the fire source and prevent "small fires from becoming major disasters".

2. Key Test Parameters of Needle Flame Test

The international standard IEC 60695-11-5 and domestic standard GB/T 5169.16-2022 require strict control of core parameters:

Flame shape: A needle-shaped flame is used, with a height of 5mm±0.5mm. Workers must monitor in real time via a thermocouple to ensure the flame tip temperature remains stable between 750℃ and 950℃;

Flame application method: Apply the flame vertically or horizontally at a 45° angle to key parts of the sample (e.g., shell, insulation layer, component pins) and burn continuously for 30 seconds (adjustable to 60 seconds for special scenarios);

Judgment indicators: After the test, the "Three No Requirements" must be met—no sustained combustion of the sample (afterflame time ≤30 seconds, ≤15 seconds for medical equipment), no ignition of the underlying layer (e.g., tissue paper, absorbent cotton) by flame drippings, and no structural burn-through exposing internal circuits.

3. Composition of Needle Flame Tester

A complete set of needle flame test equipment includes five core modules:

Gas supply system: Provides propane or butane gas; workers can control the flame size via a regulating valve;

Needle-shaped burner: Uses a metal tube with an inner diameter of 0.5mm-0.8mm to ensure the flame is needle-shaped;

Temperature control system: Links thermocouple and temperature controller to maintain stable flame tip temperature;

Sample fixing device: Adjustable in angle and position to simulate the actual installation state of the equipment;

Observation and recording system: Equipped with an observation window and timer to record the combustion process and afterflame time.

4. Technical Value

The value of the needle flame test lies in advancing the "defense line" of electrical fire prevention. It does not seek fire-extinguishing solutions only after a fire occurs; instead, it blocks the fire chain from the source by simulating risks and verifying performance during the product design stage. From the daily safety of mobile phone chargers, to the life protection of surgical equipment, and to the large-scale risk prevention of energy storage stations, the needle flame test always takes "small flames" as the test object and guards the huge electrical safety system. With continuous technological upgrading, it will more accurately adapt to the needs of new electrical equipment, become a "cornerstone technology" for the safe development of the electrical industry, and continue to protect the safety of human production and life.