Railway Defect Detection Methods

The train transport is the one of the important methods of transportation that transfers passengers and goods on tracked vehicles running on rails. The railway track comprises various equipment, including but not limited to rail, sleeper, ballast, track bed and so on. Indeed, the railway equipment is the basis of rolling stock and train operations that bears the pressure from the wheels of rolling stock. In order to ensure that the train can operate at an uninterrupted maximum speed, and the railway authorities anticipate a complete passenger and freight transportation at desirable quality, the railway lines must be kept in standard conditions.

Considering, the continuous rolling of locomotives and long-term trainloads, which results is the track geometry of the railway line continues to deteriorate. Understandably the subgrade and ballast bed continue to produce deformed rails, couplings and sleepers, resulting in continuous changes in the technical status of the line equipment. In order to keep the railway line in standard conditions for a long period, regular maintenance and repair operations are required. Traditionally, the railway defect detection process, which is deemed difficult and dangerous, is done manually by the railway maintenance workers.

In the recent years, more sophisticated equipment such as portable detectors, track inspection trolleys, track comprehensive inspection vehicles, etc. had been developed. This article outlines two main modes of inspection, namely static and dynamic inspection, which are commonly used in the railway defect detection and maintenance work. Furthermore, the railway inspection equipment used by the major countries is summarized and the impact on railway inspection based on deep learning and artificial intelligence is appropriately predicted.

Track Static Inspection

Static inspection has changed from traditional manual inspection to new inspection methods, such as mechanical and electronic circuit inspectors and three-dimensional precision measurement systems. In the process of track static inspection, workers need to detect track gauge, track cross level, track alignment, etc.

Vibrations and the impact of high-speed trains are affecting track geometry to a huge scale. Besides heavy wear of the track, the track gauge, track cross level and track alignment are getting affected. The track geometry gauge is mainly used to measure the gauge and cross level (super elevation) of the line. Manual gauge is a traditional measure instrument. Manual gauge is usually used as measurement railway speeds of less than 160km/h.

During the measurement process, many aspects, such as the checking time, the judgment standard of the personnel, the position of the observation, the placement of the instrument, etc, can affect the accuracy of the values. Therefore, this method is not suitable for high-precision high-speed railway line detection, and if there are occurrence of combination factors, as discussed above, it may affect the line status of ordinary-speed railways.

Digital gauge is a new type of track geometry gauge. Comparing with the manual measuring methods, the digital gauge greatly improves the accuracy and eases the measurement work in track maintenance since it is equipped with records such as rapid numerical display, automatic temperature compensation, and an over-limit alarm. Therefore, in an environment where railway speeds continue to increase along with the work intensity, digital gauges provide easier and safer working environment. In daily maintenance, workers use the track geometry gauge to detect the gauge, track cross level, and super elevation. However, at present, the track geometry gauge can only complete some basic data detection, the workers need to consume a lot of physical energy, and the work efficiency is relatively low.

The geometric state detection of high-speed railway tracks is to detect the vertical and lateral deviations and irregularities of the track under the condition of no trainload, and the detection results are used as the main basis for track adjustment. It is a new technology to use the track inspection trolley to detect the geometric state of the track. It calculates the center mileage of the line by measuring the prism coordinates installed on the track inspection trolley. In the following, the railway  inspection  equipment  used  by  the  major  countries are  summarized  and  the impact  on railway inspection:

GEDO CE

The GEDO CE track inspection trolley produced by the German Sinning company, which has a mature and stable measuring system, is suitable for fine adjustment of double sleeper type ballastless track, turnout laying, long rail laying, joint adjustment and joint test, line maintenance, etc. GEDO has been widely used in the European railway industry. Its function into quickly collect line data, obtain the deviation between the design value and the measured value, and analyzing it through software. The data of the optimal starting amount and shifting amount are transmitted to the tamping machine in a digital way.

At the same time, the tamping operation plan is designed to guide the accurate operation of the tamping machine. The GEDO CE test shows that when the equipment is in a static and moving state, the error of the measurement point data is very small. When the equipment is in different speed states, it adopts automatic mode to collect, the result shows that the error is very small. In summary, it is shown that GEDO CE performs well under various conditions and the data is stable.

Amberg

Amberg GRP VMS adopts the relative measurement principle based on absolute control, which perfectly combines absolute measurement and relative measurement, and uses CPIII more efficiently, which can greatly improve the measurement efficiency while ensuring high accuracy. The system consists of a data collection car and a satellite car.

In addition to integrate mileage, super-elevation and gauge sensors, the data collection car is also equipped with a control point measuring instrument, which can measure the horizontal and vertical distances from the track to the control point. The product has been tested by the German market and has mature performance. A radio modem can be used for data communication between the computer and the total station. The equipment has a stable performance and high accuracy. It is currently used by many companies in China and has been used in railway construction in countries along the “Belt and Road”.

SOUTH

The SOUTH track inspection is made by China South Locomotive & Rolling Stock Corp. TGS FX standard hand-push type track inspection trolley assembled with sensors for track gauge measurement, track super elevation measurement and relative mileage measurement. It can automatically identify the target LEICA and other total stations, which can ensure the accuracy and reliability of the measurement. At the same time, the track inspection trolley has strong field operations and data processing capabilities. A radio modem can be used for data communication between the computer and the total station. The equipment has a stable performance and high accuracy. It is currently used by many companies in China and has been used in railway construction in countries along the “Belt and Road”.

Rail Defect Detector

With the development of ultrasonic testing technology, ultrasonic testing technology has become the main method of railway track defect detection. European countries and Japan and other developed railway countries have successively launched various forms of ultrasonic rail defect detection equipment, including “portable hand-push defect detectors”, “automatic rail defect detection vehicle”, and “special rail defect detection train”. For more information, you can also read “Train Wheel Inspection with Ultrasonic Measuring System”.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.