What apparatus is used for a flame test?

The Needle Flame Tester is a flammability testing device used to evaluate the ignition hazard of solid materials—such as electrical and electronic equipment, insulating materials, and engineering plastics—when exposed to a small flame simulating internal fault conditions.

Its primary purposes include:

Simulating small flames generated by internal product faults (such as leakage currents or poor electrical contacts);

Assessing the flame-retardant performance and ignition risk of materials or components;

Providing a suitable method for products that cannot be effectively evaluated by the Glow Wire Test or horizontal/vertical burning tests (UL 94).

Working Principle

The core working principle is based on applying a standardized small flame to the specimen and observing its combustion behavior.

Flame Generation

Butane (or propane) gas with a purity of ≥95% is discharged through a stainless-steel needle burner with an internal diameter of 0.5 mm ± 0.1 mm and ignited to produce a stable, controllable needle-shaped flame.

Flame Parameter Control

Flame height: 12 mm ± 1 mm

Flame tip temperature: 800°C ± 10°C

Gas pressure: 20 kPa ± 2 kPa

These parameters ensure flame stability and repeatability.

Flame Application

The flame is applied to the specimen at a 45° angle for a specified duration (typically 10 s or 30 s, depending on the standard).

Result Evaluation

Material flame-retardant performance is assessed by observing and recording:

Whether ignition occurs

Afterflame time

Burning length or extinction behavior

This test is conducted in accordance with IEC 60695-11-5 and other relevant standards, and is widely used in electronics, automotive, and construction industries to evaluate fire hazards under simulated internal fault conditions.

Function and Significance

The Needle Flame Test is a critical method for evaluating flame resistance under small-flame ignition risk. Its advantages include:

Accurately simulating micro-flames generated by internal faults in electrical and electronic equipment;

Assessing ignition characteristics of high-risk small components such as insulating materials and connectors;

Quantifying ignition resistance, flame spread, and self-extinguishing performance;

Ensuring compliance with IEC 60695 and other international safety standards.

This enables manufacturers to identify and improve flammable weaknesses during product design, enhance safety and compliance, and reduce fire risks and liability.

Operating Procedure of the Laboratory Needle Flame Tester

The procedure is primarily based on IEC 60695-11-5 and GB/T 5169.5-2008.

1. Pre-Operation Preparation

Equipment Calibration

Annual calibration by a qualified institution;

Daily inspection after startup;

Temperature response from 100°C to 700°C must be ≤23.5 ± 1 s;

Flame height must meet 12 ± 1 mm.

Gas Supply Connection

Use butane gas with purity ≥95%;

Check airtightness;

Ensure stable gas pressure.

Environmental Requirements

Well-ventilated test room without strong airflow interference;

A 10 mm white pine board covered with tissue paper is placed 200 ± 5 mm below the specimen.

2. Standard Operating Steps

Specimen Installation

Mount the specimen vertically in the holder;

Ensure unobstructed test surface;

Adjust the burner position so the flame tip is 8 mm from the bottom or 5 mm from the side of the specimen.

Flame Calibration and Adjustment

Ignite burner (purge air before first use);

Adjust gas flow to produce a stable blue conical flame (12 ± 1 mm);

Set burner angle to 45° during testing (vertical during calibration).

Parameter Setting

Typical flame application time: 30 s (adjustable 0–999.9 s);

Select underlay status (with or without) as required.

Start Test

Move burner to contact specimen and start timing;

Observe ignition behavior, afterflame duration, and whether molten droplets ignite the tissue paper.

Completion and Recording

Record afterflame time (tb), defined as the time from flame removal until complete extinction;

If tb ≤ 30 s and the underlay does not ignite or char, the specimen is typically considered compliant.

Shutdown and Cleaning

Close gas valve and power supply;

Activate exhaust system;

Clean residue after cooling.

Evaluation Criteria

Pass Criteria (unless otherwise specified):

Afterflame time ≤ 30 s;

Underlay does not ignite or char;

No sustained burning or flame spread beyond test area.

Classification

Some systems support classification such as V-0. V-1. V-2. or HB (according to UL 94).

Safety Precautions

Do not open the chamber door during testing;

In case of gas leakage, press emergency stop and close main valve;

Use CO₂ or dry powder extinguishers (never water-based);

Test alarm system sensitivity weekly.

Maintenance and Management

Proper maintenance ensures stable operation, accurate results, and laboratory safety compliance.

1. Routine Maintenance

Cleaning Before and After Testing

Clean combustion chamber residues after each test (power and gas off);

Remove specimens only after cooling to room temperature.

Burner Maintenance

After cooling, remove nozzle and clean with a fine wire to remove carbon deposits;

For stubborn contamination, soak in neutral detergent;

Ensure ignition electrode spacing is 5–10 mm.

Gas Line Inspection

Check hose connections and aging;

Adjust flame control valve to minimum before ignition.

2. Calibration and Verification

Flame Height: 12 ± 1 mm

Burner Angle: 45° ± 2°

Timing System Error: ≤ ±0.5 s (at 10 s, 30 s, 60 s, 120 s checkpoints)

Temperature Response: 100°C to 700°C within 23.5 ± 1 s

Temperature Indication Error: Calibrated with platinum resistance thermometer and dry-block furnace at 100°C and 700°C.

3. Safety Management

Personal Protection

Operators must wear flame-retardant clothing, heat-resistant gloves, goggles, and face shields. Tie back long hair and remove flammable items.

Environmental Safety

Establish a 1-meter safety perimeter;

Use fire-resistant laboratory surfaces;

Ensure proper ventilation to remove toxic gases such as CO and HCN.

Emergency Measures

In case of gas leakage, close gas source immediately and ventilate;

If fire spreads, use nearby extinguisher and cut off power and fuel;

For burns, rinse with cold water and seek medical care if necessary.

Operational Discipline

Confirm no gas leakage before ignition;

After testing, close gas supply first, burn off residual gas, then cut power;

Ensure equipment temperature drops below 50°C before next test.

The Needle Flame Tester is a widely used flammability evaluation instrument that simulates real fire conditions to assess material combustion performance.Correct operating procedures and strict compliance with standards ensure the accuracy and repeatability of test results. At the same time, comprehensive safety precautions are essential to prevent fire hazards and other accidents during testing.