What is a laboratory needle flame tester?

The laboratory needle flame tester is a specialized testing instrument used to evaluate the combustion behavior of materials or products under flame exposure. It is commonly applied in industries such as electrical and electronic products, insulation materials, and engineering plastics. By simulating small flame ignition sources that may occur during actual use, it determines material flammability characteristics and fire hazard, providing scientific data and support for product design, quality control, and safety certification.

Basic Definition

The needle flame tester, also referred to as a Needle Flame Test Apparatus, is designed and manufactured according to specific international or domestic standards. The device uses a slender small burner—a needle-shaped flame source—to generate a controlled, standardized flame that is applied to the specimen. This allows for the assessment of the material’s flame resistance and fire behavior.

The apparatus is primarily used to evaluate whether a material is easily ignitable by a small flame, the duration of sustained burning after ignition, and the extent of flame spread. Tests are conducted under standardized conditions of height, angle, and exposure time to ensure reproducibility and comparability of results, enabling accurate determination of whether a material’s combustion performance meets safety requirements.

Principle and Working Method

The principle of the needle flame tester is to produce a stable, small flame from the needle-shaped burner and apply it to the specimen under strictly controlled angles, exposure times, and temperatures. The burner is typically installed inside a test chamber and fueled by gases such as butane, with a regulator to control the flow. The relative position of the burner to the specimen, the flame angle, and the exposure duration are all set according to standard requirements.

During testing, the burner is positioned at a specified angle—often 45°—to the specimen to produce a small flame on its surface. The flame height, duration, and whether the specimen ignites and sustains combustion are recorded to assess fire hazard. Materials that do not ignite easily or burn weakly are considered to have good flame retardancy, while those that ignite readily or sustain burning indicate higher fire risk.

The device is usually equipped with a ruler, thermocouples, timing devices, and gas flow control systems to precisely regulate test conditions and record key metrics. Thermocouples monitor flame temperature to ensure compliance with standard requirements, and timers control the duration of flame exposure and record the combustion process.

Applicable Standards

The needle flame test is a standardized test method referenced by multiple international and national standards, including:

IEC 60695-11-5: Fire hazard testing – Needle flame test methods – Apparatus and guidance

IEC 60695-2-2: Specifications for test apparatus, verification methods, and guidelines for needle flame testing

National or regional standards such as GB/T 5169.5-2020. GB 4706.1. and UL 94 also reference needle flame testing

These standards specify requirements for specimen preparation, test conditions, burner parameters, flame height, flame angle, timing procedures, and evaluation criteria. Standardized testing ensures that results are consistent, comparable, and reproducible across laboratories and testing environments.

Structure and Components of the Needle Flame Tester

Although designs vary slightly among manufacturers, the core components of a needle flame tester typically include:

Needle-shaped burner: A fine, elongated metal tube or nozzle with a small internal diameter (approximately 0.5–0.9 mm) that produces a standardized small flame.

Gas supply system: Provides fuel such as butane, with regulators and valves to control gas flow, ensuring a stable flame at the required temperature.

Test chamber: Creates a controlled environment that minimizes airflow interference, and may include smoke extraction and observation windows.

Control and recording system: Includes timers, temperature sensors, and a touchscreen or software controller for setting test parameters, controlling the process, and recording data.

Specimen fixtures and support: Secure the test sample in the correct position and maintain the prescribed geometric relationship between the flame and the specimen.

These components work together to achieve precise flame application and strict process control, yielding reliable combustion performance data.

Testing Procedure

The standard procedure for needle flame testing generally includes the following steps:

Specimen Preparation

Before testing, specimens are preconditioned according to standard requirements, such as storage under specified temperature and humidity to ensure stability.

Specimen Installation

Specimens are mounted vertically or in a specified position on the apparatus fixture, ensuring that the distance and angle relative to the burner comply with the standard.

Test Parameter Setting

Test parameters such as flame height, exposure time, and gas flow rate are set through the control system to meet standard conditions. For example, certain standards specify a flame height of approximately 12 mm and a fixed exposure duration.

Flame Application

The gas burner is ignited, and the flame is applied to the specimen at the prescribed angle. Timing and temperature monitoring are conducted throughout the exposure.

Observation and Recording

The specimen’s response is observed, including ignition occurrence, duration of burning, and flame spread. Temperature changes and elapsed time are recorded.

Result Evaluation

Based on the standard’s evaluation criteria, the test data are analyzed to determine whether the material’s combustion performance meets safety requirements, including whether sustained burning or flame propagation occurs.

Applications and Scope

The needle flame tester is widely used in several fields, including:

Electrical and electronic device safety testing: Evaluates the fire performance of structural materials and components in electrical devices to assess fire risk under faults such as short circuits or overheating.

Insulation material evaluation: Assesses flame retardancy of wires, cables, insulating sleeves, and other electrical insulation materials to ensure system safety.

Engineering plastics and combustible materials testing: Determines combustion behavior and fire hazard of engineering plastics and other flammable materials, aiding in material selection and improvement.

Product development and quality control: Identifies potential fire hazards in new product development and serves as a critical inspection step in production quality control.

Value in Laboratory Safety Systems

The needle flame tester provides important contributions to modern laboratory safety systems:

Scientific data support: Standardized combustion testing provides reliable, comparable data for R&D and safety engineering decisions, enabling informed material usage and safety design strategies.

Compliance and certification support: Needle flame testing is a key requirement for products needing international or national safety certification.

Fire risk reduction: Evaluating material performance under small flame exposure allows early identification of potential fire hazards, enhancing overall product safety.

In summary, the laboratory needle flame tester is a professional instrument for evaluating material and product combustion behavior under small flame exposure. Through standardized testing methods, precise experimental control, and scientific procedures, it provides reliable data for safety assessment, regulatory compliance, and quality assurance. As product safety requirements continue to rise, needle flame testing has become an indispensable method in industries such as electrical and electronic products, insulation materials, and engineering plastics.