INTRO: To maintain high standards of ride on high speed lines with growing traffic, it is essential to improve monitoring of track components. SNCF has put in hand development of more powerful monitoring equipment, including a video rail surface inspection system in service since the start of this year. The case for a dedicated TGV infrastructure inspection train is stronger as further high speed routes near completion
BYLINE: André Le Bihan
Head of Maintenance Policy, Infrastructure Division, SNCF
IN the course of almost 20 years of commercial TGV operation at speeds up to 300 km/h, SNCF engineers have developed a comprehensive system for monitoring track condition on high speed lines and planning scheduled maintenance. A computer-based decision-support system is the main planning tool, supplied with a wide range of recording data gathered during periodic inspections and special visits.
The general principles of track monitoring and maintenance are the same for conventional and high speed lines, with the engineer striving to maintain the required standards of track geometry at the lowest possible cost. However, the higher dynamic forces experienced on high speed lines tend to accelerate the rate at which defects worsen. To maintain high safety and passenger comfort standards, SNCF has therefore developed a more intensive inspection programme for high speed routes (Table I).
Track geometry on high speed lines is monitored using Mauzin recording cars operating at speeds up to 200 km/h, which provide numerical and graphical data for the detection and short-term correction of short wave defects. These cars are also equipped to produce charts with an extended baseline so that long-wave defects can be analysed. It is vital that such defects are mastered if standards of ride quality are to be maintained at high speeds.
Work to correct and maintain track geometry is planned on a long-term basis using data provided by the recording cars. Longitudinal level, transverse level and alignment are calculated on board and fed into the database for the route in question. Further processing enables tamping operations to be planned to optimum effect.
Every two weeks, high speed lines are inspected for isolated defects by the test car Mélusine, which is marshalled in a service train and operates at line speed. Accelerometers installed in the car measure horizontal and vertical acceleration at bogie and car body level, and a recently-developed processing system provides automatic analysis of peak values with their location. Isolated defects are then corrected, mainly using multi-purpose tampers allocated to light maintenance work.
The ultimate development of the Mélusine concept would be a dedicated high-speed infrastructure inspection train, which as well as track geometry and ride quality would monitor the signalling and overhead electrification systems. As the French high speed network grows and traffic levels rise, the economic case for such a train becomes even stronger, and SNCF has decided to study a project to have such a train in service by 2005.
Inspection
Visual inspection of track components is undertaken every 10 weeks during a maintenance window, as it can be hard to verify the condition of components from the lineside or just using train-borne video equipment. Until now, TGV routes have been closed to traffic for around 90min during daylight hours to allow inspection work to take place, but commercial pressures mean that this traditional maintenance window is getting shorter.
To inspect plain line at night, we have been considering the introduction of specialised vehicles equipped with powerful spot lights. Although automatic monitoring systems are being installed on the high speed route between Paris and Marseille, sensitive and complex components such as the moving noses of switches and crossings will still require visual inspection in daylight, particularly if cracking is to be detected and monitored. The minimum time to allow for this task would appear to be 60min.
Most track maintenance work on a modern high speed line is generated by the interaction of wheel on rail, which has important consequences for rail life, track geometry and rolling noise. On the busiest sections of the high speed network, rail is inspected every six months using an ultrasonic testing car. Internal fatigue defects are rare due to the high quality of the rail steel employed and of the welds, as well as the maximum static axleload of 17 tonnes in force on the new lines. At a maximum speed of 70 km/h, the use of ultrasonic cars can hinder other maintenance work, and further acceleration of this inspection process would be welcome.
Although rail corrugation has never been observed on the French high speed network, probably due to the high rolling stability of TGV bogies and good elastic behaviour on the part of the track, surface defects resulting from rolling contact fatigue are a cause for concern. They are very difficult to detect by ultrasound and can cause multiple rail breaks (RG 12.00 p810). Having first appeared as squats on straight track, these defects are now giving rise to head checks on the running edge of the upper rail in large radius curves, including junctions and crossovers on high speed lines. A special programme of inspections must be followed to monitor the development of these defects, and new methods of preventative maintenance based on special grinding profiles are currently under development.
High speed video
The running surface geometry of the rail may be damaged locally by other phenomena, such as the crushing of ballast particles by ice falling from trains in winter. Since January 2001, a rail surface inspection system known as Ivoire has been in service at speeds up to 300 km/h, installed underneath the test car Mélusine. High speed routes will be inspected on a regular basis every three months, but additional inspections may take place if required.
Ivoire comprises a digital camera mounted above each rail, capable of processing up to 20million pixels each second. Defects as small as 1mm are clearly visible at 300 km/h, and there is sufficient memory for 2h 30min of continuous recording.
Data captured during recording runs is processed by a separate facility, and is presented in two formats. The number of defects per km can be presented in graphical form, with each defect classified into one of four categories depending on its magnitude. For each defect falling into Category 4, the most serious, a separate file is produced containing an image of the fault an its exact location. This enables the most appropriate course of action to be taken.
Mélusine is now also capable of measuring rolling noise in the 1000 to 5000Hz spectrum, by means of microphones mounted under the bogies. Rail defects have their particular noise signature, with the frequency of the sound inversely proportional to the wavelength of the fault that generated it. Correlated with very precise measurement of the rail head, these measurements enable a map of rolling noise to be produced, which will be developed to guide grinding operations.
Since the opening of the first section of the Paris - Lyon route in 1981, a track geometry database has been maintained for high speed lines, expanding with the development of the TGV network. In addition, specialised software has been developed to manage maintenance tasks, such as Timon for tamping and grinding, or Defrail for rail maintenance. The track monitoring system for TGV routes is not in itself revolutionary, but through collating considerable amounts of physical data and improving methods and tools continually, we have been able to provide high track quality at low cost. n
IN the course of almost 20 years of commercial TGV operation at speeds up to 300 km/h, SNCF engineers have developed a comprehensive system for monitoring track condition on high speed lines and planning scheduled maintenance. A computer-based decision-support system is the main planning tool, supplied with a wide range of recording data gathered during periodic inspections and special visits.
The general principles of track monitoring and maintenance are the same for conventional and high speed lines, with the engineer striving to maintain the required standards of track geometry at the lowest possible cost. However, the higher dynamic forces experienced on high speed lines tend to accelerate the rate at which defects worsen. To maintain high safety and passenger comfort standards, SNCF has therefore developed a more intensive inspection programme for high speed routes (Table I).
Track geometry on high speed lines is monitored using Mauzin recording cars operating at speeds up to 200 km/h, which provide numerical and graphical data for the detection and short-term correction of short wave defects. These cars are also equipped to produce charts with an extended baseline so that long-wave defects can be analysed. It is vital that such defects are mastered if standards of ride quality are to be maintained at high speeds.
Work to correct and maintain track geometry is planned on a long-term basis using data provided by the recording cars. Longitudinal level, transverse level and alignment are calculated on board and fed into the database for the route in question. Further processing enables tamping operations to be planned to optimum effect.
Every two weeks, high speed lines are inspected for isolated defects by the test car Mélusine, which is marshalled in a service train and operates at line speed. Accelerometers installed in the car measure horizontal and vertical acceleration at bogie and car body level, and a recently-developed processing system provides automatic analysis of peak values with their location. Isolated defects are then corrected, mainly using multi-purpose tampers allocated to light maintenance work.
The ultimate development of the Mélusine concept would be a dedicated high-speed infrastructure inspection train, which as well as track geometry and ride quality would monitor the signalling and overhead electrification systems. As the French high speed network grows and traffic levels rise, the economic case for such a train becomes even stronger, and SNCF has decided to study a project to have such a train in service by 2005.
Inspection
Visual inspection of track components is undertaken every 10 weeks during a maintenance window, as it can be hard to verify the condition of components from the lineside or just using train-borne video equipment. Until now, TGV routes have been closed to traffic for around 90min during daylight hours to allow inspection work to take place, but commercial pressures mean that this traditional maintenance window is getting shorter.
To inspect plain line at night, we have been considering the introduction of specialised vehicles equipped with powerful spot lights. Although automatic monitoring systems are being installed on the high speed route between Paris and Marseille, sensitive and complex components such as the moving noses of switches and crossings will still require visual inspection in daylight, particularly if cracking is to be detected and monitored. The minimum time to allow for this task would appear to be 60min.
Most track maintenance work on a modern high speed line is generated by the interaction of wheel on rail, which has important consequences for rail life, track geometry and rolling noise. On the busiest sections of the high speed network, rail is inspected every six months using an ultrasonic testing car. Internal fatigue defects are rare due to the high quality of the rail steel employed and of the welds, as well as the maximum static axleload of 17 tonnes in force on the new lines. At a maximum speed of 70 km/h, the use of ultrasonic cars can hinder other maintenance work, and further acceleration of this inspection process would be welcome.
Although rail corrugation has never been observed on the French high speed network, probably due to the high rolling stability of TGV bogies and good elastic behaviour on the part of the track, surface defects resulting from rolling contact fatigue are a cause for concern. They are very difficult to detect by ultrasound and can cause multiple rail breaks (RG 12.00 p810). Having first appeared as squats on straight track, these defects are now giving rise to head checks on the running edge of the upper rail in large radius curves, including junctions and crossovers on high speed lines. A special programme of inspections must be followed to monitor the development of these defects, and new methods of preventative maintenance based on special grinding profiles are currently under development.
High speed video
The running surface geometry of the rail may be damaged locally by other phenomena, such as the crushing of ballast particles by ice falling from trains in winter. Since January 2001, a rail surface inspection system known as Ivoire has been in service at speeds up to 300 km/h, installed underneath the test car Mélusine. High speed routes will be inspected on a regular basis every three months, but additional inspections may take place if required.
Ivoire comprises a digital camera mounted above each rail, capable of processing up to 20million pixels each second. Defects as small as 1mm are clearly visible at 300 km/h, and there is sufficient memory for 2h 30min of continuous recording.
Data captured during recording runs is processed by a separate facility, and is presented in two formats. The number of defects per km can be presented in graphical form, with each defect classified into one of four categories depending on its magnitude. For each defect falling into Category 4, the most serious, a separate file is produced containing an image of the fault an its exact location. This enables the most appropriate course of action to be taken.
Mélusine is now also capable of measuring rolling noise in the 1000 to 5000Hz spectrum, by means of microphones mounted under the bogies. Rail defects have their particular noise signature, with the frequency of the sound inversely proportional to the wavelength of the fault that generated it. Correlated with very precise measurement of the rail head, these measurements enable a map of rolling noise to be produced, which will be developed to guide grinding operations.
Since the opening of the first section of the Paris - Lyon route in 1981, a track geometry database has been maintained for high speed lines, expanding with the development of the TGV network. In addition, specialised software has been developed to manage maintenance tasks, such as Timon for tamping and grinding, or Defrail for rail maintenance. The track monitoring system for TGV routes is not in itself revolutionary, but through collating considerable amounts of physical data and improving methods and tools continually, we have been able to provide high track quality at low cost. n
Table I. Frequency of track inspection
TABLE: Type Conventional routes, High speed lines, max speed 160 to 220 km/h max speed 300 km/h
On-foot inspection 2 weeks Plain line 1 10 weeks
by gang foreman Switches & crossings 5 weeks
Formation/structures 2 5 weeks
General inspection by district manager
On foot 2 months 1 month
From train cab 2 weeks 2 weeks
Special inspection Daily on line opening, at 160 km/h
Track recording car 6 months 3 months 3
Accelerometer recordings 6 months 4 2 weeks 5
Ultrasonic rail inspection 12 months 6 months
1. Undertaken during daylight maintenance windows, or at night on foot or from inspection trolleys2. Inspection of fencing, ditches, earthworks and other structures undertaken in daylight from outside the right of way3. Using an extended baseline to analyse long wave defects4. Using a portable device5. Using test car Mélusine
CAPTION: Top: Monitoring heads for the Ivoire equipment are mounted in protective cases below the Mélusine recording car
CAPTION: Still photograph of a rail surface defect (left) and an image from the Ivoire video system taken at 300 km/h
CAPTION: Fig 1. Analysis of track faults by category as recorded by Ivoire during a run on TGV Nord in December 2000
Track monitoring on the TGV network
To ensure high standards of ride and comfort on high speed lines with growing traffic, French National Railways is improving its monitoring and track measurement techniques. These include a video rail surface inspection system able to operate at up to 300 km/h that has been in use since January. Plans are now advancing for a dedicated high speed inspection train that would enter service in 2005
Surveillance continue de la voie sur le réseau TGV
Afin de s’assurer d’un haut niveau de roulement et de confort sur les lignes à grande vitesse dont le trafic s’accroît, la SNCF améliore ses techniques de surveillance et de mesure de la voie. Parmi elles, on note un système vidéo d’inspection de la surface des rails pouvant fonctionner jusqu’à 300 km/h, employé depuis janvier. Les projets avancent désormais vers la création d’une rame d’inspection spécialisée, à grande vitesse, qui entrerait en service en 2005
Gleisüberwachung auf dem TGV-Netz
Zur Sicherstellung eines guten Fahrverhaltens und des Komforts auf den Hochgeschwindigkeitsstrecken bei zunehmenden Verkehr verbessert die SNCF Überwachungs- und Gleismessverfahren. Dies umfasst unter Anderem ein Video-Schienen-Prüfsystem, welches mit Geschwindigkeiten bis zu 300 km/h eingesetzt werden kann, und sich seit Januar im Einsatz befindet. Es bestehen Pläne, einen Hochgeschwindigkeitsmesszug zu bauen, welcher 2005 in Betrieb kommen k
