Introduction to the Glow Wire Test
The Glow Wire Test (GWT) is a critical flammability assessment method used to evaluate the fire resistance of materials and components in electrical and electronic equipment. This test simulates thermal stress caused by overheating components or electrical faults, ensuring compliance with international safety standards such as IEC 60695-2-10, IEC 60695-2-11, and UL 746A. The test measures a material’s ability to resist ignition, limit flame spread, and prevent dripping of molten particles that could propagate fire.
Industries such as household appliances, automotive electronics, and telecommunications rely on GWT to mitigate fire hazards in high-risk environments. The LISUN ZRS-3H Glow-wire Test Apparatus is a precision instrument designed to conduct these evaluations with repeatability and accuracy, meeting stringent regulatory requirements.
Principles of the Glow Wire Test
The GWT involves heating a standardized Nichrome (80% nickel, 20% chromium) wire to a predetermined temperature, typically between 550°C and 960°C, using an electrically controlled system. The glowing wire is then applied to the test specimen under a specified force (1.0 N ± 0.2 N) for 30 seconds. Post-application, the specimen is observed for ignition, flame duration, and afterglow.
Key parameters assessed include:
- Ignition Time: Duration before sustained flaming occurs.
- Flame Extinguishment Time: Time taken for flames to self-extinguish.
- Material Dripping: Whether molten droplets ignite surrounding materials.
The LISUN ZRS-3H automates these measurements, incorporating a high-resolution thermocouple and digital temperature control (±2°C accuracy) to ensure consistency.
Regulatory Standards and Compliance
Compliance with GWT is mandatory for products sold in regions governed by IECEE CB Scheme, EU Directives (e.g., Low Voltage Directive), and North American safety certifications (UL, CSA). Specific standards include:
| Standard | Application Scope | Test Temperature Range |
|---|---|---|
| IEC 60695-2-10 | Basic testing methodology | 550°C – 960°C |
| IEC 60695-2-11 | End-product flammability assessment | 750°C – 850°C |
| UL 746A | Polymeric materials in electrical devices | Varies by material |
Non-compliance risks product recalls, legal liabilities, and safety failures. The LISUN ZRS-3H is pre-configured to execute tests per these standards, reducing calibration overhead.
Applications Across Industries
Electrical and Electronic Equipment
Circuit boards, connectors, and insulating materials must resist ignition from faulty components. The LISUN ZRS-3H verifies flame-retardant properties in enclosures and internal assemblies.
Household Appliances
Components in washing machines, microwaves, and refrigerators undergo GWT to prevent fires from electrical shorts. For example, thermoplastic housing in power switches is tested at 750°C.
Automotive Electronics
With increasing electrification, GWT ensures battery management systems, wiring harnesses, and infotainment units meet ISO 20653 (IP6K9K) for thermal safety.
Lighting Fixtures
LED drivers and plastic diffusers are tested to avoid ignition from prolonged overheating. The LISUN ZRS-3H’s adjustable temperature range accommodates varied material thresholds.
Medical Devices
Critical equipment like ventilators and MRI machines must prevent fire propagation. GWT certifies biocompatible polymers used in casings and cable insulation.
Technical Specifications of the LISUN ZRS-3H
- Temperature Range: 100°C – 1000°C (±2°C stability)
- Wire Dimensions: 4.0 mm diameter Nichrome, per IEC 60695-2-10
- Test Duration: Programmable (1–999 seconds)
- Force Application: 1.0 N ± 0.2 N via calibrated weights
- Data Logging: Integrated software records ignition times, temperature curves, and flame durations
- Safety Features: Overheat protection, emergency stop, and fume extraction compatibility
Competitive Advantages
- Precision Engineering: Closed-loop PID temperature control minimizes drift.
- Modular Design: Supports additional fixtures for needle-flame or hot-wire tests.
- Regulatory Readiness: Pre-loaded test protocols for IEC, UL, and GB standards.
- Durability: Industrial-grade stainless steel construction resists oxidation.
Case Study: GWT in Industrial Control Systems
A manufacturer of programmable logic controllers (PLCs) used the LISUN ZRS-3H to test polycarbonate enclosures. At 850°C, the material exhibited no ignition, achieving IEC 60730-1 compliance. The apparatus’s repeatability (<5% variance) facilitated batch certification.
Future Trends in Flammability Testing
Emerging materials like halogen-free flame retardants (HFFR) require dynamic testing conditions. The LISUN ZRS-3H’s firmware-upgradable design adapts to evolving standards such as IEC 62368-1 for AV/IT equipment.
FAQ
Q1: What is the maximum sample thickness the LISUN ZRS-3H can test?
A: The apparatus accommodates specimens up to 25 mm thick, per IEC 60695-2-10 requirements.
Q2: How often should the glow wire be replaced?
A: Replace after 50 tests or if oxidation reduces diameter below 3.8 mm.
Q3: Can the LISUN ZRS-3H test vertically oriented samples?
A: Yes, an optional fixture allows vertical mounting for assessing dripping behavior.
Q4: Is the system compatible with third-party data analysis software?
A: CSV export enables integration with LabVIEW or MATLAB for advanced analytics.
Q5: What industries mandate GWT compliance?
A: Aerospace (DO-160), automotive (ISO 16750), and consumer electronics (IEC 62368) are key sectors.
