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Contenido archivado el 2024-05-28

Development of Novel Inspection Systems for Railway Wheelsets

Final Report Summary - SAFERAIL (Development of Novel Inspection Systems for Railway Wheelsets)

Executive Summary:
The aim of the SAFERAIL project is to develop a novel online system for the inspection of wheels and axles of moving trains (including tram, passenger and freight), and an ultrasonic-electromagnetic system for faster and more reliable inspection of the quality of new and old wheelsets during their production and maintenance. The SAFERAIL consortium has spent the last three years developing new inspection technology. This technology is intended to extend on the current state of the art for both trackside monitoring and manual inspection of rolling stock wheelsets in a bid to minimise wheelset failures, improve safety and reduce maintenance costs.

The SAFERAIL project has culminated with two fully working trackside inspection prototypes based on High Frequency Vibration Analysis (HFVA) monitoring installed at end user De Lijn sites in Belgium, and one prototype using Acoustic Emission (AE) based at end user EMEF site in Portugal. Both systems have detected wheel flats, out of roundness, and in addition suspension faults and rail break misalignments. The great advantage of the trackside inspection techniques is that detrimental defects can be picked up at an early stage before they have time to cause fatal consequences.

All of the trackside detection systems have the possibility to connect to a railway's computer network (Knowledge and Information System) to provide the train stakeholders with information they require on wheelset performance.

The trackside inspection systems can be placed at pre-chosen strategic points on the rail network, and will monitor faults in the wheels and axles of passing trains. It can look at a range of defects including flats in the wheels, defective wheelset bearings, significant cracks and wheel profile abnormalities. Using a special identification system, each wheelset is given a unique code. If a fault is identified on a wheelset, the system will automatically alert the signalling engineers who will then decide what action to take for that particular train, i.e. advise maintenance, reduce speed or stop it completely.

A trackside inspection system based on thermography has also been developed specifically for detection of hot spots in the wheel surface and axle bearing box. Although not as advanced in development as the HFVA and AE monitoring systems, it nevertheless does demonstrate proof of principle. The system was compared with a commercial hot box detector and it was found that the inspection results were comparable but realised with a much lower system cost.

Regarding manual inspection at the train workshop and maintenance depots, two manual inspection techniques and associated technologies have been developed. For Phased Array Ultrasonic Testing (PAUT) inspection, techniques for inspection of axles from the end face and neighbouring wheel seat areas have been developed. Four wheel inspection techniques have been developed to specifically meet the requirements of the end users. This included the inspection of cracking at web hole areas within the wheel and inspection for cracking at the wheel rim areas. The other inspection technology that has been developed is based on the Alternating Current Field Measurement (ACFM) technique. New and novel ACFM probes have been developed for inspection of both wheels and axles.

The successful implementation of the SAFERAIL deliverables and future commercialisation of the prototypes offers the rail industry several technical advantages, which will increase the reliability of rolling stock operations and help towards the optimisation of operation cost efficiency.

The consortium hopes that the technology can be taken down the path of full commercialisation. Some partners in SAFERAIL are more advanced than others in this respect, and have already enhanced their prototypes to a high degree of technology readiness. The partners also believe they can realise commercial solutions that will be far cheaper than those currently in the market.

Project Context and Objectives:
Today's European rail networks are getting busier with trains travelling at higher speeds, and carrying more passengers and heavier axle loads, than ever before. This combination of factors is putting considerable pressure on the existing infrastructure, leading to increased demands in inspection and maintenance of rail assets.

To maximise safety efficiency in rail travel the rail industry has applied a pro-active maintenance policy for wheelsets. This policy combines on-line monitoring and manual inspections during production and maintenance. Minimising wheelset failures not only improves safety but also helps reduce maintenance costs, and is a consideration for both train and light rail vehicle operators.

A European collaborative research project called SAFERAIL has spent the last three years developing new inspection technology. This technology is intended to extend on the current state of the art for both trackside monitoring and manual inspection of rolling stock wheelsets in a bid to minimise wheelset failures, improve safety and reduce maintenance costs.

Strategic objectives
The SAFERAIL project aims to fulfil the needs of industry by enabling online, reliable monitoring and improving the existing inspection methodologies of wheelsets during their production and maintenance. The associated increase in safety shall, in turn, increase public confidence in train travel. It also helps European rail industry to achieve its interoperability by rising up to the challenge of high standard safety and efficiency.

The SAFERAIL project will support the effort of the rail industry in achieving better safety standards by developing novel methodologies and techniques for the inspection of wheelsets. Assuming a successful realisation of proof of principle prototypes, the project will help minimise wheelset failures and damage caused by faulty wheelsets to the rail tracks and rolling stock.

Technical objectives
Current inspection methodology for wheelsets fails to implement the reliability and efficiency targets set by the rail industry. Working together over a three year period, the SAFERAIL consortium is seeking to minimise wheelset failures in two separate ways.

a) Developing an on-line inspection system, that will be placed at pre-chosen strategic points on the rail network tracks, for inspection of faults in wheels and axles of passing trains. The system will be able to inspect passing trains for flats in the wheels, defective wheelset bearings, significant cracks and wheel profile abnormalities. The system will use an identification system for each passing train, and each wheelset will be given an identification code. If the SAFERAIL system identifies a wheelset fault on one of the passing trains, the system will automatically alert the signalling engineers. The engineers will then decide what action to take for that particular train, ie advise maintenance, reduce speed or stop it completely. In the case of a severe defect being discovered, the system will permit the signalling engineers to stop a particular train immediately in order to carry out emergency maintenance.

b) Developing a novel inspection system of new and in-service wheelsets based on ultrasonic phased arrays and ACFM probes. The consortium of this project will develop a novel ultrasonic phased array system, with higher resolution and speed of inspection operation, coupled with novel ACFM probes for the identification of surface breaking faults. Currently, ultrasonic phased arrays and other techniques in use to inspect wheelsets in-service have problems in finding small surface defects. The incorporation of ACFM probes will allow the accurate and fast inspection of wheelsets for any surface breaking faults.

The technical objectives of SAFERAIL include:

* Overcome the limitations of current on-line detectors by developing an integrated system based on high-frequency vibration analysis (HFVA), acoustic emission (AE) and thermography techniques for the accurate and reliable inspection of wheelsets of moving rolling stock.
* Develop an on-line HFVA module to be installed on railway tracks for the detection of shells, cracks and severe profile abnormalities in wheelsets.
* Develop an on-line novel AE module as part of the integrated on-line inspection system for detection of wheel flats and faulty wheelset bearings.
* Develop an on-line thermography module capable of inspecting the quality of wheelsets for cracks, defects in the braking mechanisms, and hot wheelset bearings
* Develop the required artificial intelligence, software and intelligent control unit to enable automatic analysis of the defects detected.
* Overcome the limitations of existing inspection methodologies during wheelset production and maintenance by developing a combined ultrasonic phased array/ACFM inspection system with the capability of automatically analysing the defects detected.
* Develop novel ultrasonic phased arrays for detection of deep buried defects in wheelsets during production and maintenance.
* Develop novel ACFM sensors for detection of surface-breaking defects on wheelsets during production and maintenance.
* Develop novel software that will enable the automated operation of the UT-ACFM system.

SAFERAIL is collaboration between the following organisations: Alfa Products & Technologies, EMEF SA, Envirocoustics A.B.E.E. Feldman Enterprises LTD, Instituto de Soldadura e Qualidade, Société Nationale des Chemins de fer Français (SNCF), Technical Software Consultants Ltd, TWI Ltd, University of Birmingham, Vlaamse Vervoermaatschappij De Lijn, VTG Rail UK Ltd. The project is co-ordinated and managed by TWI Ltd and is partly funded by the EC under the COLLABORATIVE Project ref: SCP7-GA-2008-218674. The project website address is:

Project Results:
New trackside monitoring and manual inspection prototype systems have been developed, trialled and demonstrated in a real environment.

Trackside monitoring
A key area of development in the project is the trackside inspection of passing rolling stock - be that freight or passenger trains or trams. Put simply, acoustic emission sensors and high-frequency vibration detectors are attached to the rail, and an associated data signal signature is acquired each time a rail wagon passes.

Two prototype trackside monitoring systems, using HFVA, were installed by APT and are up and running at De Lijn sites in Belgium. One system is at De Lijn's HQ in Antwerp and the other is at a site in Lombardsijde. The system has an optional excitation mechanism comprising a unique small impact hammer actuated by a push pull solenoid. A hard hammer tip ensures a short impact, thereby exciting the wheel up to very high frequencies, and gives the capability of detecting cracking in addition to ovality, flats and other wheelset issues. The sensors are microphones (with a high bandwidth) placed on the rail tracks, and are used to measure the response of the excitation. The data collection system contains novel software which is able to compute the collected HFVA data and alert of possible defects in the wheelsets

The inspection points were located close to the workshop which houses the trams when service is completed for the day. In this way all trams are monitored every day. Data results, including a digital camera image of the vehicle, are sent over the Ethernet to a server at APT. The data is sent after the measurement has been processed by the HFVA module. The results can be examined anywhere in the world via a password-protected internet browser. In addition, alerts can be automatically sent by email and text messaging on mobile phones.

The system has successfully detected wheel flats and out-of-roundness. In addition, it has also detected suspension faults and rail brake misalignments. De Lijn actually operate trams rather than trains, but the inspection techniques used apply to trains too, and this has been tested with VTG's freight wagons at its Long Marston site in the UK.

Another trackside monitoring system, developed by partners Feldman, Envirocoustics, and University of Birmingham, is installed at EMEF's site in Lisbon, Portugal. This system is based on AE sensing. AE data post-processing is carried out by the system, and alerting of possible defects is made by software referencing critical Key Performance Indexes (KPIs), a sentencing process unique to SAFERAIL and developed by Feldman.

For vehicle wheelset condition follow up, and damage pattern recognition, each train and vehicle is identified with radio frequency identification (RFID) technology. A beacon exchanges data with passing trains, and searches in a database of fitted bogies and wheelset types. Alerts from the network sensors' grid can be programmed to warn of a major problem that can occur in the bogies\wheelsets. EMEF also record all the results from their regular workshop inspections of each wagon. This data is stored in a database and the knowledge of bogie and wheelset maintenance helps to give a clearer picture of the different types of defects that can be expected to occur in-service.

Independently, ISQ has been investigating thermography technology and have been developing a trackside inspection prototype based on infrared thermography sensors. The system detects hot spots of passing rolling stock (wheels and axle boxes) using an array of thermopile sensors. REFER (Rede Ferroviária Nacional) made available a section of public track, where it was already using a commercially available hot box detector from another provider, so that ISQ could perform comparative studies. At passing train speeds of 53km/h, the temperature data acquisition was comparable to the commercially available hot box detector but implemented with lower cost sensors, and in hardware one tenth of the price. The results are promising and the system useful for a preliminary assessment of temperature condition of wheels and axles.

Manual Inspection
SAFERAIL has developed new inspection techniques based on alternative current field measurement (ACFM) and phased array ultrasonic testing (PAUT). Despite the fact that ultrasonic phased arrays are faster, and much more reliable, than traditionally used NDE equipment, they can still miss surface-breaking defects. This means that wheelsets also need to be inspected using either eddy current probes or, more commonly, magnetic particle inspection (MPI).

Ultrasonic phased arrays have the capability of emitting ultrasonic shear waves under different angles by steering the ultrasound beam. TWI and ISQ have jointly been investigating this feature and, through modelling and trials at VTG, SNCF and EMEF, have developed new inspection procedures for the inspection of axles and wheels. Crucially, ISQ and TWI were able to perform inspections of axles using PAUT from the axle end face. This avoids having to disassemble the axle from the wheelset and saves a lot of down time.

Ultrasonic inspection does have a dead zone and, significantly, a crack present in the first few millimetres of surface cannot normally be detected. Also using ACFM to inspect ensures a greater defect detection capability.

ACFM is an electromagnetic inspection technique, used to detect and size surface breaking cracks in metals. It is typically used to replace MPI, as ACFM can work through paint and dirt and measures the depth of the defect. It works by inducing a current in the surface of the piece to be inspected. Any defects in the component will change the direction of these sub-surface currents; these changes are detected by small sensors, and are used to compute the length and depth of the defect.

ACFM offers the possibility of allowing quicker inspection than that delivered by MPI, and PAUT will allow more extensive information to be gathered faster than with conventional ultrasonic inspection.

As the inventors of ACFM, TSC is leading the development and commercialisation of the ACFM inspection system. The University of Birmingham have also been investigating ACFM through modelling and experiments in the project in order to better understand the ACFM signals, especially those relating to multiple rolling contact fatigue wheel surface defects. TSC is working to improve the speed of data collection and analysis, plus the development of algorithms to improve the accuracy of depth sizing typical defects. TSC have developed new novel ACFM probes for both axle and wheel profile inspection.

The wheelprobe has been designed to inspect the surface of the wheel that comes into contact with the rail. As the wheel is worn down, the profile of the wheel changes. To accommodate for this change in profile, the individual sensor coils are mounted in spring loaded pistons, that can move up and down independently. The wheelprobe consists of twenty channels with three sensor coils each (one for each orthogonal direction). It also contains orthogonal field generation coils, allowing it to detect and accurately size surface breaking defects in any orientation. This sophisticated design is the most complex probe TSC have designed, and represents a step-change in their technology. Previous probes of this complexity have been created, but have not had either the twin excitation field or the design for the complex shaped profile - they have been created for flat steel plates. The axleprobe is used to inspect the axle; the axle consists of three parts, two curved shoulders with straight sections between the two.

TSC used a variety of numerical models and verification methods to ensure the probes' electromagnetic field suited the complex geometries of the wheelsets.

Potential Impact:
*Socio-economic impact

There can be no sustainable transport in Europe without a safe and efficient railway system. However, safety and efficiency in the modern European railway system depends on the implementation of the rail research agenda set by the Commission. The successful implementation and commercialisation of the systems developed within SAFERAIL will assist the European rail industry to significantly improve its safety record by delivering the technology required to eliminate wheelset failures and derailments that result from them. The number of fatalities and injuries associated with wheelset related accidents is grossly underestimated as the contribution of defective wheelsets to the damage of the rail network infrastructure and rolling stock cannot be calculated easily. By removing the deleterious effects of defective wheelsets the rail industry can eliminate associated fatalities and injuries, substantially improve its maintenance strategies, minimise operating costs, improve its efficiency, increase public confidence in train travel, reduce train delays and use the financial resources that will be saved through the reduction of maintenance costs in improving rail infrastructure across Europe.

SAFERAIL will allow several environmental benefits to be drawn by supporting the growth of the rail industry. It will assist in the minimisation of damage in wheelsets and wheelset related damage to the rail network and rolling stock, thus extending the operational lifetime of assets and reducing the need for new components which contribute to the depletion of valuable natural resources. The successful implementation and commercialisation of the SAFERAIL systems should potentially eliminate wheelset related derailments of freight trains carrying hazardous substances which can cause significant pollution in the surrounding area where the derailment occurred.

The on-line inspection is primarily realised through the HFVA and the AE modules. The data collecting equipment has already been used successfully in trials. Remaining activities focus on the optimisation and development of the defect detection and recognition algorithms and testing to evaluate the design in terms of ruggedness and durability. It is still expected that development of the thermography module for trackside inspection will also be of benefit. The aim of the dual application of the UT-ACFM system is to be capable of inspecting wheelsets for both deeply buried and surface-breaking defects simultaneously, without the need for complementary inspection using eddy current probes or MPI. It is expected that the SAFERAIL consortium will be successful in this aim.

For the trackside inspection depending on the configuration of the wheelsets, the number of axles passing over the monitoring system and the current maintenance intervals, the pay-back period is expected to range between 11 to 18 months after installation. For example, the life expectancy of wheels is mainly determined by the maximum amount of metal that can be removed during wheel truing. Up till now, wheel truing was conducted at fixed km intervals. The new SAFERAIL trackside inspection systems enable a switch to condition based wheel truing, which results in significant savings. By keeping vehicles without wheel defects running, the truing intervals are significantly increased. Moreover, the early detection of wheel flats and out-of-roundness results in a reduction of the metal removed during wheel truing and thus offers an increased life expectancy.

The technology developed in SAFERAIL will contribute to the innovative research that is concerned with novel wheelset and vehicle designs for improving the efficiency of train travel. By supporting the strong growth of the European rail industry, SAFERAIL assists the general economic growth in the EU which is interconnected with the transport growth.

The successful implementation and commercialisation of the SAFERAIL deliverables will offer to the rail industry several technical advantages which will increase the reliability of rolling stock operations, and will help towards the optimisation of operational cost efficiency. The partners believe that the full commercialisation of the SAFERAIL technology is feasible, either as individual modules or as a complete system.

Better services would give rail transport a big competitive edge, making it the best way to combine short travel time with easy accessibility to leisure and professional hubs, and with minimal environmental impact. The challenge for Europe is to improve the safety of the rail systems in a way that is financially viable, ecologically sound, efficient and accessible to all EU countries.

*Dissemination activities:
The SAFERAIL consortium has been very active in their dissemination activities throughout the three year project duration. The project attracted the interest of a number of different high quality engineering and scientific magazines. A number of articles have been published in those magazines, and the work was presented at a number of NDT conferences. The project partners will continue with the dissemination activities after the project end to promote the project results.

Of significant note are the following activities:

A dedicated five paper session for SAFERAIL was organised for the CM2010 Seventh International Conference on Condition Monitoring and Machinery Failure Prevention Technologies which was held in the UK in June 2010.

Presentations at QNDE 2010, EWGAE 2010, CM2011, CM2011, BINDT2010, BINDT2011 conferences

Publication of papers in three peer reviewed journals:

‘Acoustic Emission Inspection of Rail Wheels’
Author(s): K. Bollas, D. Papasalouros, D. Kourousis, A. Anastasopoulos
Journal of Acoustic Emission, Vol. 28, April 2010, p. 215-228

‘Recent research and development activities in electromagnetic sensor technologies’
Author(s): B Blakeley; M Lugg,
Insight - Non-Destructive Testing and Condition Monitoring, Vol.53 Number 3, March 2011

‘Modelling of the response of an ACFM sensor to rail and rail wheel RCF cracks’
Author(s): G. Nicholson and C.L Davis
Journal of NDT&E International, Accepted October 2011

Video demonstrating the trackside HFVA monitoring system.

Training videos giving overviews of the technologies used in SAFERAIL have been developed and are available for public access at the SAFERAIL website.

Published articles in technology magazines including:
Railway Gazette International, September 2009.
The Parliament Magazine's Regional, October 2009.
Projects, Issue 25, 2011.
European Railway Review, Issue 6, 2011.

There have also been press releases and articles too numerous to mention here.

*Exploitation of the results
The SAFERAIL project has delivered a suite of trackside and manual inspection techniques. The aim of the project was to produce a working prototype, overcome any technical issues with the hardware, and enable the development and investigation of software control and inspection algorithms.

The successful implementation of the SAFERAIL deliverables offers the rail industry several technical advantages, which will increase the reliability of rolling stock operations and help towards the optimisation of operation cost efficiency.

The consortium hopes that the technology can be taken down the path of full commercialisation. Some partners in SAFERAIL are more advanced than others in this respect, and have enhanced their prototypes to a high degree of technology readiness. The route to full commercialisation will require further work involving aesthetics and production engineering to satisfy cost, standards and quality criteria. The partners believe they can realise commercial solutions that will be far cheaper than those currently in the market.

All partners have demonstrators. APT, Feldman and Envac have trackside inspection system prototypes already integrated with the end user telemetry infrastructure. It is intended to have these systems operating for at least a year after the SAFERAIL project close. They have the full agreement of the end users that demonstrations to other railway stake holders can take place. Already APT and Feldman have demonstrated to other railway stake holders.

The manual inspection systems require further testing to evaluate the design in terms of ruggedness and durability, to identify areas of robustness and potential weakness. The data from this testing must be fed into a design review that should also incorporate modification for production engineering, as well as a compliance review to ensure that the system meets the operation requirements of a workshop environment.

TSC will keep a wheelset setup at its premises and will actively seek exploitation routes for the new probe technology. The wheelprobe also has application for other inspection industries.

The aim is to market the systems and technology to a number of potential end users.

List of Websites:
A project website was set up to act as a communication port between the partners and disseminate the project:

For general enquires regarding the SAFERAIL project please contact at TWI Ltd, Granta Park, Great Abington, Cambridge, CB21 6AL, UK.
Tel: +44 (0)1639 873100 Website:

Contact details according to the specific technologies developed in SAFERAIL are listed below:

High Frequency Vibration Analysis (HFVA) - Alfa Products and Technologies (APT), Mechelseveest 18/0301, 3000 Leuven, Belgium. Tel: 0032 1623 2040. Website:

Acoustic Emission (AE) - Feldman Enterprises Ltd, 15 Agiou Palvlou St, Ledra House, 1105 Nicosia, Cyprus. Tel: 0030 694 57 27217. Website:

and Envirocoustics SA, El. Venizelou 7 & Delfon, Metamophosis, 14452 Athens, Greece. Tel: 0030 210 284 6801. Website:

Thermography - Instituto de Soldadura e Qualidade (ISQ), Av. Prof. Dr. Cavaco Silva, Nº 33, Taguspark - Oeiras, 2740-120 Porto Salvo, Portugal. Tel: +351 (21) 422 90 44. Website:

Phased array ultrasound testing (PAUT) - TWI Ltd, Granta Park, Great Abington, Cambridge, CB21 6AL, UK. Tel: +44 (0)1639 873100 Website:

Alternating current field measurement (ACFM) - Technical Software Consultants Ltd (TSC), 6 Mill Square, Featherstone Road, Wolverton Mill, Milton Keynes, MK12 5RB, UK. Tel: +44 (0) 1908 317 444 Website: