How to test the horizontal burning of fabric?

The Fabric horizontal burning tester is an instrument used to evaluate the horizontal burning characteristics of fabrics. It is primarily used to determine the horizontal burning performance of various textile fabrics, expressed as flame spread rate. It is suitable for determining the flame retardancy of clothing fabrics, decorative fabrics, tent fabrics, etc., which require flame retardancy. In safety-sensitive fields such as electronics, rail transportation, and building materials, the horizontal combustion spread characteristics of materials are a core indicator for assessing their fire risk. As a specialized device simulating the horizontal burning behavior of materials, the horizontal burning tester provides a scientific basis for classifying the flame retardancy performance of materials by accurately quantifying parameters such as flame spread rate and burning time.

Technical Principle:

Based on the quantitative analysis of heat conduction and flame spread

The horizontal burning tester is based on a physical model of "fire source contact - combustion spread," simulating the flame propagation behavior of materials on a horizontal plane by controlling the flame height, flame application time, and sample angle. Its core principles include:

Thermal radiation and flame contact: Using a Bunsen burner as the standard ignition source, a 20mm (50W) or 125mm (500W) flame conforming to standards such as UL94 and GB/T 2408 is generated by adjusting the gas flow rate and air ratio. The flame height error is controlled within ±1mm to ensure test repeatability.

Quantification of combustion spread: A high-precision timer records the time it takes for the flame front to spread from the ignition point to a preset mark (e.g., 25mm, 100mm), and the linear combustion rate (mm/min) is calculated based on the sample size. Some devices are equipped with an infrared thermal imager to monitor the temperature distribution and heat release rate during combustion in real time.

Dripping and melting behavior analysis: Degreased cotton or a metal mesh is placed under the sample to observe whether the burning drips ignite the underlying material, and the frequency and volume of molten material dripping are recorded to comprehensively assess the risk of secondary combustion of the material in a fire.

Operating Procedures:

Standardized Steps from Sample Installation to Result Determination

Sample Preparation:

Use a laser cutter to cut the material to standard dimensions, ensuring burr-free edges. For non-self-supporting materials, wrap them around a 12.7mm diameter metal rod, securing both ends to form a ring-shaped sample.

Mark 25mm and 100mm lines on the sample surface, with a line width ≤0.5mm to avoid affecting combustion behavior.

Equipment Calibration:

Use a flame height gauge to calibrate the Bunsen burner, ensuring the blue flame height is 20±1mm. Verify the 50W flame energy output through a copper block heating test.

Check the timer accuracy by comparing 10 timing results with a stopwatch; an error ≤0.1 seconds is considered acceptable.

Test Execution:

Hold the sample horizontally in the combustion chamber, with the lower surface 300mm from the degreased cotton. Ignite the Bunsen burner, tilting it at 45° to apply the flame to the free end of the sample for 30 seconds, ensuring the inner flame contacts the sample for 6mm.

After the flame extinguishes, record the position of the flame front and the amount of dripping. If the flame does not spread to the 100mm mark, the actual burning rate V = L/t (mm/min) needs to be calculated.

Result Judgment:

HB Grade Judgment: If the sample thickness is 3-13mm and the burning rate is ≤40mm/min, or the thickness is <3mm and the burning rate is ≤75mm/min, it is judged as HB grade.

Abnormal Handling: If the sample burns prematurely during the flame application process or the dripping material ignites the absorbent cotton, it needs to be resampled and tested, and the abnormal phenomenon recorded.

Industry Applications: Comprehensive Coverage from Consumer Electronics to New Energy

Consumer Electronics:

Mobile phone casings and charger cables must pass UL94 HB certification to ensure that a short circuit fire will not cause secondary disasters. Apple, Huawei, and other manufacturers have included horizontal burning tests in their supplier entry requirements.

New Energy Vehicles:

Battery pack insulation materials must meet FH-1 requirements to prevent the spread of flames in the event of thermal runaway. Tesla Model 3 battery modules use ceramicized silicone rubber, and their fire resistance integrity has been verified through horizontal burning tests.

Rail Transit:

High-speed rail seat fabrics must pass HB testing to ensure passengers have sufficient escape time in emergencies. CRRC requires suppliers to provide UL94 test reports as a mandatory bidding document.

Building Materials:

Fire-stopping materials must pass FH-2 testing to verify their fire-retardant performance in cable penetration holes. Companies such as 3M and Hilti have reduced the burning rate by more than 30% through optimized material formulations.

Maintenance and Repair

I. Daily Pre-Operation Routine Inspections

Gas System Safety Check

Leak Detection: Apply soapy water to the gas source interface and observe for bubbles. In one laboratory, the lack of leak detection led to a slow gas leak, causing a sudden flame explosion during testing and damaging the sample holder.

Pressure Confirmation: The gas pressure must be stable between 0.05MPa and 0.1MPa, which can be checked using the instrument's built-in pressure gauge. Insufficient pressure will result in insufficient flame height (e.g., a setting of 20mm but actual height of only 15mm), while excessive pressure may cause backfire.

Electrical System Functionality Check

Touchscreen Response: Click each function button to ensure a response time ≤0.5s. If lag occurs, clear the cache or restart the instrument. In one case, the touchscreen delay reached 2s, leading to misjudgment of the flame application time.

II. Weekly In-Depth Maintenance Items

Bunsen Lamp Cleaning and Calibration

Carbon Deposits Cleaning: Use a fine copper wire brush to clean the burner's inner diameter to prevent carbon buildup from affecting the flame shape. When the carbon buildup thickness exceeds 0.2mm, the flame height may decrease by 10%~15%.

Inner Diameter Calibration: Use a dedicated gauge (9.5mm±0.5mm) for inspection. If the gauge fails to pass through, the Bunsen lamp must be replaced. In one instrument, the inner diameter of the Bunsen lamp was worn down to 9.0mm, resulting in a 7% reduction in flame heat radiation.

Sample Clamping Mechanism Lubrication

Adjusting the Track: Apply high-temperature resistant grease (temperature resistance ≥200℃) to ensure smooth up/down and left/right movement. A dry track can cause sample positioning deviation. In one test, due to track jamming, the distance between the sample and the flame deviated by 10mm, resulting in a combustion rate test value error of ±8%.

III. Monthly Performance Verification

Timing System Calibration

Comparative Test: Record the 60s flame application time simultaneously using a stopwatch and the instrument. The error should be ≤ ±0.2s. If the deviation exceeds 0.5s, the PLC program needs to be checked or the timing module replaced.

Flame Height Consistency Test

Multi-point Measurement: Take three points (top, middle, and bottom) in the vertical direction of the flame. The height difference should be ≤ 2mm. One instrument experienced flame height fluctuations of up to 5mm due to unstable gas flow, resulting in a 12% difference in combustion rate at different locations on the same sample.

IV. Annual Professional Calibration Project

Full Parameter System Calibration

Contracted to a third-party organization: Calibration includes Bunsen burner inner diameter, flame temperature (heating time 44s±2s from 100℃ to 700℃), and flow accuracy (error ≤ ±4.8ml/min). One company had not calibrated for three years, resulting in a flow error of ±8ml/min, leading to customer questioning of the test data.

Safety Function Test

Gas Alarm: Simulate a leak scenario; the alarm response time should be ≤ 10s. An instrument's alarm delay reaches 30 seconds, posing a significant safety hazard.

Exhaust System: Wind speed testing requires ≥0.5 m/s to ensure timely exhaust of smoke. Insufficient wind speed will lead to a decrease in oxygen concentration inside the chamber, affecting combustion.

The textile horizontal combustion testing machine is a core piece of equipment for assessing the fire risk of materials. Its accuracy and reliability directly affect the credibility of product safety certification. From routine gas leak detection and track lubrication maintenance to annual full-parameter calibration and safety function verification, strict control at every stage is the cornerstone of ensuring the scientific validity of test data. With the rapid development of new energy vehicles, rail transportation, and other fields, the requirements for the flame retardant performance of materials are becoming increasingly stringent. The maintenance of the testing machine has been upgraded from basic operation to a key aspect of technical management. Only through a systematic maintenance process and professional calibration methods can the equipment be ensured to always be in optimal working condition, providing the industry with reliable combustion performance data and contributing to the continuous upgrading of safety standards.

2025-11-27 14:58