Real-time monitoring of the longitudinal strain of Continuous Welded Rail for safety improvement

Continuous welded rail maintenance plays a significant role in ensuring high levels of rail traffic and safety. Temperature variations, excessive alignment defects, decreased fastening system resistance and train braking (always in the same stretches and in the same direction) may result in rail buckling or rail breaks. The current traditional monitoring systems and procedures for continuous welded rail consist of programmed discontinuous diagnostic surveys that require personnel intervention on site. Moreover, these traditional systems often imply destructive and invasive operations on the track that may lead to interruption of railway operations. This paper proposes a Rail Strain Monitoring System (RSMS) that performs a real-time rail strain monitoring and allows rail inspection without personnel on site. Using strain gauges and temperature sensors, placed on the rail in specific measurement points, the proposed Rail Strain Monitoring System performs a multi-parameter check by measuring, at the same time, the temperature, the rail strain and the neutral temperature of the rail. The paper describes the mode of operation of the Rail Strain Monitoring System, the calibration procedure and the results from the field, and highlights the advantages of this system in comparison to other traditional monitoring systems. The safety improvement that can be achieved with the application of the Rail Strain Monitoring System is analysed. In particular, the reliability of the system is evaluated and compared to the human error probability in the traditional manual inspections. Finally, the reduction of derailment risk and related economic damages is estimated.