Paragraph 1: Incident Overview
On October 30, 2023, a CN Rail freight train derailed near Dunsinane, New Brunswick, resulting in the spillage of approximately 2,000 liters of methanol. The derailment occurred as the train traversed a small bridge, triggering an emergency brake application initiated by the train itself. Upon inspection, the conductor discovered that the final four cars of the train had left the tracks. The spilled methanol and any affected soil were subsequently cleaned up. This incident highlighted the potential risks associated with undetected rail defects and the limitations of current inspection technologies.
Paragraph 2: Cause of Derailment
The Transportation Safety Board (TSB) investigation determined that the derailment was caused by a broken rail section beneath the train. This break was attributed to an internal fatigue defect that likely originated from fine surface cracks known as head checking. These microscopic cracks, while seemingly insignificant, compromised the structural integrity of the rail over time, ultimately leading to its failure under the weight of the train. The presence of head checking also interfered with the effectiveness of ultrasonic testing, a common method used for rail inspection.
Paragraph 3: Rail Inspection Procedures
Prior to the derailment, the affected rail section had undergone three separate ultrasonic rail flaw detection (RFD) tests within a five-month period. These tests were conducted by a third-party using a hi-rail vehicle, a specialized vehicle designed for rail inspections. However, each of these tests failed to produce valid results due to the presence of head checking on the rail surface. The operator then resorted to using a handheld ultrasonic tool, but this method also failed to identify the underlying internal defect.
Paragraph 4: Limitations of Ultrasonic Testing
The TSB investigation highlighted the limitations of ultrasonic testing in detecting internal rail defects when surface conditions, such as head checking, are present. The rough surface caused by head checking interferes with the transmission and reception of ultrasonic waves, making it difficult to accurately assess the internal structure of the rail. This can lead to false negatives, where defects are present but go undetected. The incident underscored the need for improved inspection methods that can effectively identify defects even in the presence of surface irregularities.
Paragraph 5: Regulatory Gaps and Safety Implications
Current regulations do not mandate the reporting of rail surface conditions that can compromise the reliability of ultrasonic testing. This regulatory gap allows potential internal rail defects to remain undetected, increasing the risk of derailments due to in-service rail failures. The TSB’s findings emphasized the need for stricter reporting requirements to ensure that railway operators are aware of any conditions that could hinder the effectiveness of inspection methods. This information would enable them to implement appropriate mitigation measures, such as more frequent inspections or rail replacement, to prevent future derailments.
Paragraph 6: Recommendations for Improved Rail Safety
The Dunsinane derailment serves as a stark reminder of the importance of robust rail inspection procedures and the need for continuous improvement in detection technologies. The TSB’s investigation highlighted the vulnerability of current ultrasonic testing methods to surface irregularities and advocated for more comprehensive reporting requirements to address this issue. Furthermore, there is a need for research and development of more advanced inspection techniques that can reliably detect internal defects even in the presence of surface conditions that might interfere with traditional methods. By addressing these gaps in inspection procedures and regulations, the rail industry can enhance safety and reduce the risk of future derailments caused by undetected rail flaws.
