Remote detection of heat-related track defects: a new approach

With the European summer hopefully just around the corner, engineers must consider how best to manage the risk of heat-related track buckle. Established measures include targeted (and disruptive) speed reductions and (expensive) human observation of the track to detect and report lateral movement. They also include localised temperature monitoring, but this is usually based on measurement of air temperature, which can be up to 20 degrees different to the steel rails and does not relate directly to movement.

The search is on for an automated and effective monitoring solution to detect lateral movement that can be applied over extended lengths of track.

Wireless remote monitoring is one of the principal technologies in the spotlight. Track temperature sensors can be incorporated into a wireless platform, bringing the advantages of constant, unattended data collection and automated alerting – but extreme rail temperatures do not always correspond with movement.

The use of wireless tilt sensors on track and structures has become widespread over the last two decades but, while they are effective at detecting parameters such as changes in cant and twist that include an element of rotational movement, they will not detect a purely translational sideways shift. Similarly, wireless instruments to measure rail stress have been around for a while – but again they only indicate the risk of track buckle, because stress levels can vary widely without manifesting in lateral movement.

What is needed is a solution that directly measures lateral movement of the rails and does so in a continuous manner, with automated alerts sent to remote users.

That’s why Senceive monitoring experts have been working with track engineers to explore new options. In a pioneering research project with Network Rail, a testbed has been set up to evaluate a number of approaches. This comprises a length of continuously welded track and a series of hydraulic rams that can push and pull the track sideways in a controlled way. In this regulated environment, it has been possible to show that the Senceive Optical Displacement Sensor (ODS) can detect lateral movement to millimetre precision with updates sent via the cellular network every few minutes.

While various deployment options are possible, the most straightforward is to fix the sensor to a solid object that is unconnected to the track, such as a gantry or retaining wall, and direct the laser at the web of the rail. Where no suitable structure can be found, metal stakes can be used. Alternatively, the sensor can be fixed to the sleeper and directed at a solid object, ideally within about 20 metres of the track.

The next step in this process will be wider rollout of this approach to more sites that have been identified as being at-risk. These deployments could involve a multi-sensor approach to measure rail temperature and stress, alongside the measurement of displacement measured by the ODS. They will also include sophisticated cameras capable of enabling remote users to see up to 50 metres of track in any light condition. A feature that makes this solution especially effective is compatibility with Senceive’s smart InfraGuard solution which can be configured so that defects automatically trigger increased sampling, alerts and photography. In this way track, engineers can learn what’s happening on site long before they can get boots on he ballast.

As this smart IoT approach becomes more widely adopted, the days of depending on the vigilant watchman or tolerating disruptive speed restrictions could be drawing to a close.

Image credit: Sencieve