What are the upgrades in the railway vehicle materials from the UL94 V0 standard to the new EN 45545-2:2020+A1:2023 standard?
Created on 2025.09.28
The transition of the railway material flame retardant system from the UL94 V0 standard to the EN 45545-2:2020+A1:2023 standard represents a fundamental shift in the fire safety requirements for railway vehicle materials from a single combustion performance to a multidimensional risk management approach. The following is an in-depth analysis of the core upgrade points:
1. Comprehensive Reform of the Testing System
1. Fine classification of fire risk levels
The new standard abandons the single level of UL94 V0 and categorizes materials into three levels: HL1 (low risk), HL2 (medium risk), and HL3 (high risk) based on the risk level of the vehicle's operating environment (such as tunnel running time and passenger density). Taking HL3 as an example, its core indicator requirements are as follows:
- Heat Release Rate (ISO 5660-1)
- Smoke Toxicity (EN 17084)
- Flame Spread (ISO 5658)
2. Expansion and Deepening of Testing Dimensions
Unlike UL94 V0, which focuses solely on vertical burning performance, EN 45545-2:2020+A1:2023 establishes a comprehensive assessment system that integrates combustion, smoke, toxicity, and heat release.
- Heat Release Test
- Smoke Density Test
- Toxic Gas Testing
II. Accurate Matching of Material Classification and Application Scenarios
1. Systematic Expansion of Material Classification
The new standard categorizes materials into R1-R28, a total of 28 categories, covering a full range from structural materials to electronic components:
- Add Category
- Scene Segmentation
2. Mandatory Requirements for System Integration Performance
Unlike UL94 V0, which tests single materials, EN 45545-2:2020+A1:2023 emphasizes the synergistic effects of material combinations:
- Component-level testing
- Composite Material Assessment
3. Improvement of the Scientific Validity and Authenticity of Testing Methods
1. Introduction of Dynamic Testing Scenarios
The A1 revised version adds dynamic testing conditions that simulate train operation:
- Airflow Impact
- Temperature gradient
2. Upgrade of Testing Equipment
- High-precision instruments
- Automated Analysis
Four, the integration of environmental protection and sustainability requirements
1. Halogen-free and low-toxicity trend
The new standard encourages the use of halogen-free flame retardant materials, such as HL3 level cables that must use low smoke halogen-free (LSOH) materials, with a halogen content of ≤50ppm, while UL94 V0 allows the use of halogen-containing flame retardants.
2. Circular Economy Considerations
A1 Revision clearly requires the recyclability of materials throughout their entire lifecycle:
- Material Identification
- Life Cycle Assessment (LCA)
V. Strengthening Certification and Compliance Management
1. Mandatory third-party certification
All railway vehicle materials must be certified by a Notified Body in the European Union to obtain the CE mark, and the product manual must indicate the applicable HL level and testing standards.
2. Full Process Traceability System
The new standard requires the establishment of a complete traceability chain from raw material procurement to finished product delivery, including:
- Material Batch Management
- Aging Test
6. Comparison of Typical Material Properties
Performance Indicators | UL94 V0 (typical value) | EN 45545-2 HL3 (R1 class materials) |
Burning Droplets | Allow non-flammable dripping | Completely prohibited from dripping |
Heat Release Rate (kW/m²) | Not specified | MARHE≤30 |
Smoke Density (Ds) | Not specified | ≤100 |
Toxicity Index (CIT) | Not specified | The content you provided appears to be incomplete or not properly formatted for translation. Please provide the full text or clarify the content you would like to have translated. |
Oxygen Index (LOI) | ≥25% | ≥32% |
Seven, the core differences between HL2 and HL3.
Indicator | HL2 (Medium Risk) | HL3 (High Risk) |
Peak Heat Release Rate (PHRR) | ≤60kW/m² | ≤30kW/m² |
Smoke Density (Ds) | ≤300 (Light transmittance ≥ 67%) | ≤100 (Light transmittance ≥ 80%) |
Toxicity Index (CIT) | ≤0.9 | ≤1 (but the test is stricter) |
Critical Radiation Flux (CFE) | ≥12kW/m² | ≥20kW/m² |
Droplet Behavior | Allow a small amount of molten droplets (ignition time ≥ 5 seconds) | Completely prohibit droplet formation |
Applicable Scenarios | Ground / Elevated Line, Evacuation Time 5-10 Minutes | Long tunnel, deep-buried section of the subway, evacuation time > 20 minutes |
VIII. Implementation Cases and Industry Trends
1. Double-decker train material upgrade
- Case: A certain European double-decker train uses R1 class phenolic resin wall panels (CFE=15kW/m²) and R21 class flame-retardant mattresses (CIT=0.8), meeting the HL2 requirements.
- Cost Comparison: The material cost of HL2 is 15%-20% higher than HL1, but 30% lower than HL3.
Summary
EN 45545-2:2020+A1:2023 has established a more scientific and stringent fire safety standard for railway vehicle materials than UL94 V0 by introducing a multi-dimensional risk assessment system, dynamic testing methods, and full lifecycle management requirements. This upgrade is reflected not only in the enhancement of technical indicators but also in the shift from "passive fire protection" to "active safety" concepts. EN 45545-2 HL2 achieves a balance between safety and economy through moderate fire protection requirements, making it suitable for most conventional railway scenarios. For material manufacturers, systematic upgrades in flame retardant formulation design, testing method innovation, and supply chain management are necessary to meet the new standards' comprehensive requirements for safety, environmental protection, and sustainability, promoting the development of fire protection technology in rail transit towards intelligence and systematization.
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