What is the operating procedure for the Single Wire Cable Burning Tester?

In modern society, wires and cables are used virtually everywhere. With continuous technological advancement, the safety of wires and cables has become an increasingly important issue that cannot be overlooked. The single wire and cable vertical flame tester is a core testing instrument for evaluating the flame-retardant performance of wires and cables. It is primarily used to determine the vertical burning characteristics of a single insulated wire or cable under specified flame conditions.By simulating a localized ignition source in a real fire scenario, this instrument scientifically evaluates whether a material can resist flame propagation. It provides essential data support for production quality control, product research and development, and third-party certification of wires and cables.

Working Principle and Structural Components of the Single Wire and Cable Vertical Flame Tester

The fundamental operating principle of the single wire and cable vertical flame tester is to vertically secure a specimen of specified length inside a test chamber and apply a standardized flame to its lower end using a standard Bunsen burner positioned at an angle of 45°.

By precisely controlling the gas flow rate, flame height, and flame application duration, the instrument enables operators to observe and record key parameters, including the flaming time after removal of the ignition source, afterglow time, charred length, and whether flaming droplets ignite the underlying bedding material.

The instrument mainly consists of the following components:

Combustion Test Chamber

The chamber is typically manufactured from stainless steel or electrostatically powder-coated steel. Its internal dimensions are precisely designed to minimize interference from external airflow. It is also equipped with an observation window and an illumination system.

Burner System

The system uses a standard Bunsen burner with an internal diameter of approximately 9.5 mm and propane or liquefied petroleum gas (LPG) as fuel.

A precision flowmeter is provided to regulate the gas and air mixture ratio, ensuring that the flame power remains stable at approximately 1 kW.

Specimen Fixing Device

An adjustable metal support ensures that the specimen is vertically suspended and allows the distance between the specimen and the burner to be adjusted according to the specimen diameter.

Automatic Control and Detection System

Modern instruments generally use a PLC programmable controller combined with a touchscreen interface to achieve automatic ignition, automatic timing, automatic test data recording, and test result generation.

The system features high-precision timing capabilities and can accurately record flame application duration and afterflame time.

Safety Protection System

The safety system includes gas leakage alarms, automatic gas shut-off valves, automatic extinguishing devices for residual flames after testing, and an efficient exhaust ventilation system.

These features protect operators and facilitate the removal of toxic combustion gases.

Operating Procedures for the Single Wire and Cable Vertical Flame Tester

The single wire and cable vertical flame test shall be conducted in accordance with the applicable standards. Specimen preparation, equipment calibration, flame application, and test result recording must be properly standardized to ensure accurate and reliable results.

1.Preparation Before Testing

Specimen Preparation

Select wire or cable specimens that meet the applicable standard requirements and cut them to the specified length.

Remove surface dust, oil, and other contaminants. Inspect the insulation and sheath for integrity, and perform any necessary stripping or preparation according to the test requirements.

Mark the designated flame application position on the specimen.

Equipment Inspection and Calibration

Inspect the gas and air supply systems, pipeline connections, and exhaust system to ensure normal operation and the absence of leakage.

Calibrate the burner flame height, temperature, and gas flow rate according to the applicable standard requirements.

Check the timer, vertical alignment of the specimen fixture, and airflow conditions inside the combustion chamber.

Confirmation of Environmental Conditions

Confirm that the ambient temperature and humidity meet the standard requirements and prevent external airflow from interfering with the combustion process.

Clean the combustion chamber and place absorbent cotton beneath the specimen as required by the applicable standard to determine whether flaming droplets ignite the underlying material.

2.Specimen Installation

Secure the specimen vertically in the fixture of the flame tester, ensuring that it remains upright without noticeable bending.

Apply the specified tension or install the required weight according to the standard.

Adjust the burner position so that the nozzle is aligned with the designated flame application point on the specimen.

Close the combustion chamber door and activate the exhaust system to maintain stable testing conditions.

3.Combustion Testing Procedure

Ignition and Flame Stabilization

Ignite the burner and adjust the gas and air flow rates until the flame height, temperature, and shape meet the requirements specified in the applicable standard.

Allow the flame to stabilize before conducting the test.

Flame Application

Apply the flame to the specimen at the specified position and for the prescribed duration in accordance with the applicable standard.

Record the flame application time.

During testing, observe the specimen's combustion behavior, flame propagation, and flaming droplets. Check whether the absorbent cotton beneath the specimen is ignited.

Flame Removal and Combustion Observation

After the specified flame application period, remove the burner and record the specimen's afterflame time and afterglow time.

Observe whether the flame propagates into the specified region and record the presence of flaming droplets and whether they cause ignition.

Test Data Recording

Record the following parameters:

Flame application duration

Afterflame time

Afterglow time

Flame propagation distance

Ignition of absorbent cotton by flaming droplets

Changes in the specimen's appearance after combustion

4.Post-Test Handling

After the specimen has completely cooled, remove it from the fixture.

Observe and measure the remaining specimen length after combustion, and inspect the insulation and sheath for charring, cracking, or other damage.

Clean the ash and residual materials from the combustion chamber and replace the absorbent cotton.

Finally, shut off the gas supply and power to the instrument, and organize the complete test records.

5.Test Result Evaluation

Evaluate the combustion performance of the specimen comprehensively according to the requirements of the applicable standard.

The principal evaluation criteria include:

Afterflame Time: Whether the afterflame time complies with the specified limits of the applicable standard.

Afterglow Time: Whether the afterglow time meets the prescribed requirements.

Flame Propagation: Whether the flame propagation distance exceeds the specified limit or reaches the restricted upper region defined by the standard.

Ignition by Flaming Droplets: Whether flaming droplets ignite the absorbent cotton beneath the specimen.

Specimen Condition: The remaining specimen length after combustion and the extent of damage to the insulation and sheath.

A specimen can be considered to have passed the applicable flame performance test only when all relevant evaluation criteria comply with the requirements of the corresponding standard.

6.Testing Precautions

Testing must be conducted using the specimen quantity and repetition frequency specified by the applicable standard to ensure good repeatability of the results.

Operators should wear protective gloves and safety goggles to avoid contact with high-temperature components and inhalation of combustion smoke.

Throughout the entire testing process, operators must strictly comply with the instrument operating procedures and relevant safety requirements.

Conclusion

The single wire and cable vertical flame tester is not only a critical instrument for ensuring cable safety but also an important tool for promoting technological advancement in the industry.In the future, with continuous technological development, vertical flame testers will continue to play an indispensable role in the safety assessment of wires and cables, providing reliable technical support for flame-retardant performance evaluation, product quality assurance, and fire safety improvement.