Railway Defect Detection Methods (part2)
2- Track Dynamic Inspection
Track dynamic inspection is the geometric state detection of the line by the train at a constant speed. At present, track dynamic inspection has formed a detection system with comprehensive inspection cars and track inspection cars as the main part, supplemented by vehicle-mounted line checkers and portable line detectors.
2.1 France Iris 320 High-Speed Inspection Vehicle
At the end of 2006, the SNCF4530 train was transformed into an “Iris320” measuring train, making it possible to have a complete locomotive dedicated to monitoring high-speed lines in France and Belgium. The Iris320 high-speed inspection vehicle simplifies the infrastructures inspection work for high-speed railways and some existing railways, and the total length of the railway lines that have been inspected has reached 7,500km. This new type of inspection vehicle can only complete the inspection of various functions at the highest line speed, but also provide commercial services on the line. One advantage of using this new type of inspection vehicle is that it is no longer necessary to inspect high-speed railways during the maintenance period. More frequent and rigorous inspections of tracks, electrical equipment, signals and telecommunications systems are also conducive to improving maintenance efficiency, changing the way of passive maintenance of line infrastructure, and developing to preventive maintenance.
2.2 CIT
CIT (comprehensive inspection train) is a series of the railway’s comprehensive inspection of EMU trains for high-speed railway infrastructure with speeds of over 200 km/h that implement regular inspections, comprehensive inspections and high-speed inspections. CIT includes important technical and basic equipment, such as pantograph contact network, communication signal, etc.
2.3 GeoRail-Xpress
The German GBMWiebe Rail Engineering Machinery Company, Bennlec Systemtechnik Joint Stock Company and Deutsche Bahn developed the inspection vehicle that can inspect visible and invisible parts of the line through digitalized measurement, while collecting and analyzing at 100km/h.
The main equipment of the GeoRail-Xpress comprehensive inspection vehicle includes:
1- Geological survey equipment, consisting of a radar system equipped with four antennas, with a maximum detection depth of 4m.
2- Tunnel inspection equipment, consisting of a side wall equipped with four antennas and a top detection radar system.
3- Line and environment detection device, composed of four-dimensional orbit environmental cameras.
4- Track detection device, composed of six laser sensors and two digital line scan cameras.
5- Sleepers and a ballastless track detection device are composed of four digital line scan cameras for detecting concrete cracks.
6- The rail head detection device is composed of two high resolution line scan cameras for detecting the condition of the rail head.
7- Satellite positioning synchronization device.
2.4 Archimede
The Archimede high-speed comprehensive inspection vehicle of the Italian Road Network Company (RFI) is manufactured by MerMec and consists of a dual-stream E402B series locomotive, four trailers and one driving car. Archimede is used to measure track geometry, rail cross-section and wear, and running quality, and to detect contact wire geometry, wear and pantograph-net contact, including video inspection of track and catenary. It can also detect signals and communication equipment.
2.5 Locomotive Vehicle-Mounted Track Dynamic Monitoring System
The locomotive vehicle-mounted track dynamic monitoring system consists of a monitoring device installed on the locomotive and a ground receiving system. It measures the smoothness of the line according to the locomotive vibration level caused by the uneven line during the operate of the train, and the magnitude of the acceleration in the two vertical directions.
The system can identify the deviation level according to the deviation standard and generate guidance line maintenance through computer processing. It has the characteristics of a short detection cycle, strong continuity, uniform standards, no human factor, and clear disease search.
3- Comparison of Different Detection Methods
The detection methods of track static detection and track dynamic detection are summarized in this article and the “Railway Defect Detection Methods (part1)” article. By enumerating the testing equipment in different railway countries, it can be concluded that there are corresponding testing tools for static testing and dynamic testing.
3.1 Principle
- Track static inspection: In GPS positioning, it is considered that position of the receiver antenna remains unchanged relative to the earth throughout the observation process, and in data processing, position of the receiver is regarded as a non-time-varying quantity.
- Track dynamic inspection: Every 300 mm forward of the vehicle, the computer collects data for each monitoring project once. When the acquisition amount of a data breaks the minimum limit value for three consecutive times, it is counted as an initial defect. The maximum acquisition value of the defect is the amplitude of the overrun defect, and the minimum defect starting point is the length of the defect.
3.2 Detection method
- Track static inspection: The track detector or track gauge is used to detect the track irregularity. Although the speed is slow, the track gauge can get the absolute coordinates of the track. In this method by combining the obtained data with the design data can be got, deviation of the track position, the absolute deviation of the elevation, the ultra-high deviation and deviation of the track distance, which are used to guide the fine change of the high-speed railway.
- Track dynamic inspection: High-speed inspection vehicle can quickly reflect the track statue, such as gauge, level, height, cross-level, etc. The maximum detection speed is determined by the different countries’ inspection vehicle.
4- Railway Detection Methods in the Future
Through the analysis of the railway inspection methods and equipment in the fast-developing countries in the world, it is concluded that the railway department should establish a complete railway line dynamic and static inspection, maintenance and management system. Continuous optimization of inspection equipment has several advantages, including meeting the safety requirements of high-speed trains, and improving inspecting speed, and reducing overall maintenance cost, and further realize the scientific development concept of low carbon, and environmental protection. Railway detect detection methods will be safer and economical based on cloud computing, Internet of Things, big data, artificial intelligence, robotics, next-generation communications, satellite navigation, and other new technologies.
For the part of detection, more and more companies use the detection machines that apply the deep learning. The technology not only can use the big data to detect the railway structure damage, but also it can record the data efficiently. Besides that, using the artificial intelligence also can achieve the intelligent monitor to reduce the labor strength.
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