Research on Design and Application of LISUN Horizontal and Vertical Combustion Tester Based on UL 94 Flammability Test

Abstract

The UL 94 flammability test is the most authoritative flammability grading evaluation system in the fields of electrical and electronic products and plastic materials worldwide, which directly determines whether materials can enter the core electrical product supply chain. The LISUN HVR-LS horizontal and vertical combustion tester is a special flammability testing equipment independently developed by LISUN for electrical equipment and plastic parts. It can accurately complete horizontal and vertical combustion tests and scientifically evaluate UL 94 flammability ratings including HB, V-0, V-1, V-2, 5VA and 5VB. Based on the requirements of the UL 94 flammability test, this paper expounds the design principle, technical parameters, test procedure and rating judgment of the instrument, verifies its reliability with measured data, and provides a standardized solution for flame retardant performance testing and quality control of materials.

Introduction

With the lightweight and integration trend of electrical and electronic products, the flame retardant safety of insulating materials, engineering plastics and structural components has become the key to product compliance and safe operation. As an internationally recognized standard for evaluating plastic combustion performance, the UL 94 flammability test quantifies core indicators such as self-extinguishing performance, anti-dripping performance and combustion rate by strictly controlling flame conditions, flame application duration and sample posture. It divides multiple flame retardant levels from HB to 5VA, providing a unified basis for product design, certification and quality inspection.

Traditional combustion testing equipment suffers from unstable flame control, insufficient timing accuracy and large posture adjustment errors, which cannot meet the stringent requirements of the UL 94 flammability test. Compliant with IEC 60695, GB/T 5169, UL 94 and other standards, the LISUN HVR-LS horizontal and vertical combustion tester adopts high-precision gas control, millisecond-level timing and modular attitude adjustment structure. It can stably output 50W (V-level) and 500W (5V-level) test flames to complete the full range of UL 94 flammability rating assessments. It is widely used in R&D, production and quality inspection of lighting, home appliances, low-voltage electrical appliances, power tools, electronic instruments and other industries.

Core Principle and Rating System of UL 94 Flammability Test

The UL 94 flammability test is divided into horizontal combustion and vertical combustion. It classifies solid combustible materials through standardized flame, flame application methods and judgment rules, and different test modes correspond to different application scenarios and safety requirements.

Horizontal Combustion (HB Rating)
It is applicable to general plastics with low flame retardant requirements. During the test, the sample is placed horizontally, and the burner applies flame at a specified angle to measure the combustion rate or confirm whether the flame extinguishes before the marked line. For materials with a thickness of 3–13 mm, the combustion rate shall not exceed 40 mm/min; for materials thinner than 3 mm, the combustion rate shall not exceed 75 mm/min. The material is qualified for HB rating if the flame extinguishes before the 100 mm mark.

Vertical Combustion (V-0/V-1/V-2/5VA/5VB)
The sample is clamped vertically with two test flame modes: 50W conventional V-level flame and 500W high-intensity 5V-level flame. The flame retardant rating is classified according to key indicators such as single afterflame time, total afterflame time, total afterflame plus afterglow time, whether high-temperature dripping ignites cotton below, and whether combustion spreads to the fixture.

Core Rating Criteria of UL 94

Data Source: UL 94 Standard and LISUN HVR-LS Product Manual

Design and Technical Parameters of LISUN HVR-LS Horizontal and Vertical Combustion Tester

The LISUN HVR-LS is a professional testing equipment specially developed to match the UL 94 flammability test. With high precision, high stability and standardized adaptation as the core design concept, it fully meets the flammability detection requirements for electrical equipment shells, insulating parts and plastic structural components.

Core Design Concept
First, the integrated dual-flame design supports both 50W conventional V-level test and 500W high-strength 5V-level test, fully covering the full range of UL 94 flame retardant grade testing requirements. Second, the sample posture is precisely adjustable with multiple combustion angles of 0°, 20° and 45°. The sample clamping structure ensures accurate positioning and unified flame application distance and angle to avoid manual operation errors. Third, the closed-loop gas flow control system is equipped with precision pressure regulating valves and flow meters to stably control gas flow and pressure, with continuously adjustable flame height to ensure constant flame conditions for the UL 94 flammability test. Fourth, it is equipped with a millisecond-level independent timing module to separately measure combustion, afterflame and afterglow time with an accuracy of 0.1s, fully meeting standard timing requirements. Fifth, the whole machine is equipped with a closed combustion chamber and exhaust structure with anti-flashback devices to improve the operational safety of laboratory tests.

Key Technical Parameters
Timing range: 0–999.9s, adjustment accuracy: 0.1s; Standard combustion angle: 0°, 20°, 45°; Flame height adjustment range: 20–175mm; Gas flow range: 0–1L/min, working air pressure: 0–0.25MPa; Equipped with standard Bunsen burner, inner tube size: 9.5±0.3mm, tube length: 100±10mm; Standard 50W copper block temperature calibration component, optional 500W high-temperature test kit; Compliant with mainstream flame retardant testing specifications including UL 94, GB/T 2408, GB/T 5169 and IEC 60695.

Test Procedure Based on UL 94 Flammability Test

The operation process of the UL 94 flammability test with LISUN HVR-LS horizontal and vertical combustion tester is standardized and clear, ensuring the repeatability and accuracy of test results. Firstly, prepare samples by cutting specimens strictly in accordance with UL 94 standards and completing constant temperature and humidity pretreatment to eliminate environmental interference. Secondly, calibrate the instrument in advance, including flame height, gas flow, timing system and temperature module, to ensure all parameters meet standard requirements. Then, clamp and position the sample, select horizontal or vertical clamping mode according to test type, and accurately adjust flame application distance and combustion angle. After that, start the test, control flame application times and duration according to corresponding flame retardant grade requirements, and observe the sample combustion state in real time. After the test, fully record key data such as afterflame time, afterglow time, combustion spreading length, dripping shedding and cotton ignition status. Finally, combine with the rating criteria to comprehensively analyze test data and complete the evaluation of material UL 94 flammability rating.

Instrument Advantages and Industry Applications

 Core Advantages Compared with Traditional Equipment
This equipment can meet multiple standard tests of UL, national standards and IEC in one stop, completing multi-system certification tests with a single device and reducing enterprise procurement costs. The overall structure and control logic are fully aligned with UL 94 flammability test specifications. With superior flame stability, timing accuracy and clamping positioning precision compared with ordinary simple combustion testers, the test data is authoritative and valid for third-party testing and export certification. The equipment has a sturdy and durable structure with stable gas control components, maintaining good data consistency under long-term continuous testing. The human-machine interface is intuitive with visualized parameter adjustment, easy for new operators to master, suitable for both laboratory R&D testing and mass production sampling inspection.

 Main Application Scenarios
The LISUN HVR-LS horizontal and vertical combustion tester is widely used in lighting fixtures, household appliances, low-voltage power distribution equipment, new energy electrical appliances, power tools, automotive electronics, electronic connectors, insulating plastic materials and other fields. It serves as the core testing equipment for incoming material inspection, product R&D improvement, UL certification application and daily quality management, providing strong technical support for the overall fire safety and compliant production of electrical products.

Conclusion and Prospect

The UL 94 flammability test is a core testing item for the global fire safety access of electrical and plastic materials. The flame retardant rating is directly related to product safety and market access qualifications. Tailored for the combustion characteristic detection needs of electrical equipment and plastic parts, the LISUN HVR-LS horizontal and vertical combustion tester can stably complete horizontal and vertical combustion tests, output accurate test data, and scientifically evaluate the UL 94 flammability rating of various materials through reasonable structural design, precise control system and standardized configuration parameters.

With the rapid development of the new energy industry and smart electronic devices, the application scenarios of various flame retardant polymer materials continue to expand, and the industry’s requirements for material flame retardant testing are becoming increasingly stringent. In the future, LISUN will continue to optimize and upgrade the intelligent functions of horizontal and vertical combustion testers, add automatic data recording, data storage and one-click report export functions, further improve the detection efficiency and intelligence level of the UL 94 flammability test, and provide more professional, efficient and reliable overall combustion testing solutions for global customers.