Why EN 15437-2 Transforms European Rail Safety & Maintenance

EN 15437-2: On-Board Axlebox Temperature Monitoring Systems in Rail Applications

What is EN 15437-2?

EN 15437-2 is a European Standard that specifies the performance and design requirements for on-board axlebox temperature monitoring systems used in railway applications. This standard is crucial for ensuring the safety and reliability of rolling stock by providing a standardized framework for detecting bearing overheating, a primary cause of catastrophic axle failures and derailments.

The standard forms part of the EN 15437 series, which covers axlebox condition monitoring. While other parts may focus on different monitoring techniques (like vibration or acoustics), Part 2 is exclusively dedicated to temperature monitoring systems installed directly on the train, providing real-time data to the train’s control system and crew.

Core Objectives and Importance in the Rail Sector

The implementation of systems compliant with EN 15437-2 is driven by several key objectives that are fundamental to modern railway operations:

• Enhanced Safety: The primary goal is to prevent thermal runaway in axlebox bearings. By continuously monitoring temperatures and providing early warnings, the system allows for timely intervention before a critical failure occurs.
• Enabling Predictive Maintenance: Continuous data logging allows operators to identify trends in bearing temperature over time. A gradual increase in the operating temperature of a specific bearing can indicate wear or incipient failure, allowing maintenance to be scheduled proactively rather than reactively.
• Operational Efficiency: By reducing the risk of in-service failures, these systems minimize unplanned downtime, line blockages, and associated costs. They also provide a higher level of confidence in the health of the rolling stock.
• Interoperability: The standard provides a common technical language and set of requirements for manufacturers and operators across different European rail networks, ensuring that on-board systems perform to a consistent and reliable level.

Key Technical Requirements of EN 15437-2

The standard provides detailed technical specifications that a compliant on-board monitoring system must meet. These are broadly categorized into performance, design, and interface requirements.

Performance and Measurement Requirements

This section defines how well the system must perform its core function of temperature measurement and alerting.

• Measurement Accuracy: The system must measure temperatures within a specified tolerance across its entire operational range. This ensures that the data is reliable for both immediate alarm generation and long-term trend analysis.
• Operating Temperature Range: The sensors and electronics must function correctly within the wide range of ambient temperatures experienced by rolling stock, from extreme cold to high heat.
• Alarm Thresholds: EN 15437-2 defines the logic for setting alarm levels. This typically includes at least two stages:
  • Alert Level: An initial warning indicating an abnormal but not yet critical temperature rise. This prompts further investigation at the next opportunity.
  • Alarm Level: A critical warning indicating a dangerous temperature that requires immediate action, such as stopping the train.
• Response Time: The standard specifies the maximum time allowed from the moment a temperature threshold is crossed to when the alarm is communicated to the Train Control and Management System (TCMS) or the driver’s display.

Design and Construction Requirements

These requirements ensure the system is physically robust and reliable enough to withstand the harsh railway environment.

• Sensor Placement: The standard provides guidance on the optimal positioning of temperature sensors on the axlebox to ensure they capture a representative reading of the bearing’s thermal state.
• Environmental Resilience: The entire system, including sensors, cabling, and processing units, must be designed to withstand constant shock, vibration, humidity, and exposure to contaminants like brake dust and grease. This often involves adherence to other standards like EN 50155 (Electronic equipment used on rolling stock).
• Electromagnetic Compatibility (EMC): The system must not be affected by electromagnetic interference from other on-board systems (e.g., traction motors, converters) and must not emit interference that could affect them.
• Reliability and Maintainability: The system must be designed for a long service life with high reliability. Components should be easily accessible for inspection, maintenance, or replacement. The standard also addresses requirements for self-diagnostic capabilities to detect sensor or system faults.

Comparison: On-Board (EN 15437-2) vs. Trackside Monitoring

On-board axlebox temperature monitoring provides a fundamentally different approach compared to traditional trackside Hot Axle Box Detectors (HABDs). The following table compares the key characteristics of each system.

System Interfaces and Data Handling

A critical aspect of EN 15437-2 is defining how the monitoring system integrates with the wider train ecosystem. The system must provide clear, unambiguous information to the crew and log data for later analysis.

• Communication Interface: The system must typically interface with the Train Control and Management System (TCMS) via a standardized communication bus (e.g., CAN, Ethernet).
• Driver-Machine Interface (DMI): Alarms and system status must be clearly displayed to the driver, indicating the exact location of the problematic axle (e.g., car number, axle number).
• Data Logging: The system must have the capability to log temperature data and alarm events with timestamps. This data is invaluable for post-incident analysis and for feeding into predictive maintenance programs.

Conclusion: A Standard for Safety and Modern Maintenance

EN 15437-2 is more than just a technical specification; it is a foundational standard for enhancing the safety and efficiency of modern railways. By mandating a high level of performance and reliability for on-board axlebox temperature monitoring, it provides operators with a powerful tool to prevent critical failures. Furthermore, its emphasis on continuous data capture directly supports the industry’s shift from traditional time-based maintenance to more intelligent, condition-based, and predictive maintenance strategies, ultimately leading to safer, more reliable, and more cost-effective rail transport.