Our highways and overpasses are already congested with vehicles, necessitating a shift to an alternative transportation solution: rail. This shift has played a significant role in driving improvements in the rail industry's infrastructure and maintenance processes. Consequently, approximately 25% to 35% of train operating costs are spent on track maintenance. What's needed is a cost-effective rail solution.
The need for solutions to optimize operations in the railway industry is becoming increasingly important. These solutions will help identify defects early in the development process, enabling operators to fix them before they become severe. Understanding the extent and severity of damage is beneficial when rolling stock is scheduled for maintenance or overhaul, reducing operational problems, optimizing fleet availability, and minimizing overall losses and downtime costs.
Mechanical sensors
One solution implemented was mechanical sensors. These sensors were used to measure track geometry parameters. Before the introduction of ultrasonic transducers into railway inspection in 1953, electromagnetic technology was one of the primary tools for detecting internal defects in high-speed rail networks. Since then, various inspection methods have been used to monitor the health of railway infrastructure or as a preventative measure against railway malfunctions.
Rail bearings and wheels are essential components of trains; any defects can have serious consequences. Premature failure of railcar axle bearings can significantly increase train operating costs and potentially affect train safety. Healthy bearings produce a certain level of vibration and noise, but defective bearings can generate considerably higher levels of vibration and noise. Similarly, wheel defects on railcars have been identified as a significant source of damage to railway infrastructure and rolling stock. They also contribute to noise and vibration emissions, the cost of which is substantial.
Defects in railway vehicle wheels directly contribute to increased wear and damage to railway infrastructure. This leads to additional maintenance and repair costs, thus shortening the lifespan and availability of locomotives and rolling stock. Early detection of train wheel defects plays a crucial role in providing train operators with timely information for necessary repairs, preventing further wheel deterioration and damage to railway infrastructure.
Over the past few decades, with the help of data-driven railways, there has been a growing focus on the quality of measurement technologies used to support decision-making in the railway sector. Traditionally, high-precision inspections according to established standards, or periodic actions when inspections are impractical, have supported safety-based decisions within the railway system. While safety remains a top priority, maintenance decisions have gained increasing attention. Condition monitoring systems are designed to identify the condition of assets and inform the decision-making process. This, in turn, helps reduce the incidence of urgent and costly unplanned interventions, thereby improving performance and safety.
Sensing technology
Different sensing technologies monitor axle box bearings and wheels, such as vibration/acceleration, microphone/sound measurement, acoustic emission/ultrasound, and heat. Vibration, sound measurement, and ultrasonic technologies are used to detect early defects. On the other hand, thermal sensors are based on detecting the heat generated by bearings and wheels with serious defects.
Railway operators have raised the demand for more cost-effective and environmentally friendly solutions. This has led to the integration of many technologies into the sensors themselves to reduce additional costs. For example, new sensors on the market are based on vibration energy harvesting technology within piezoelectric PVDF materials, a technology that is both environmentally friendly and cost-effective. This technology, combined with the sensor design, utilizes the piezoelectric PVDF material to convert vibration into electrical energy. This technology is based on a cantilever structure; when the cantilever vibrates, the electrical energy it generates is stored in a supercapacitor. The electricity from the capacitor is then transferred to the sensor.
In summary, the current market places specific demands on the railway industry, leading to increased demand for cost-effective and safety-oriented solutions. Track axle bearings and wheel sensors play a crucial role in detecting early defects that could have serious consequences. Energy harvesting technologies also contribute to cost savings and environmental benefits.
