Rail safety, related to train wheel sets, looks certain to improve throughout Europe as three years of work on a collaborative European research project draws to an end.
Dubbed SAFERAIL the 11 partner-led project has culminated in the manufacture of actual working prototypes that are ready to be commercialised. Wheel set defects have been associated with rail accidents, damage to the network, delays and unnecessary costs for many years.
This has led to the implementation of rules on the maximum acceptable length and depth of wheel set defects that may stay in service. Extensive experimental results have however shown, that some non-condemnable wheel set defects can still cause damage to the rails.
The objective of SAFERAIL was to develop techniques to identify faults in wheel sets before they were big enough to cause a breach of safety criteria. Development followed two distinct paths, firstly the development of trackside on-line systems for the inspection of wheels and axles of a moving train. For this modules using high frequency vibration analysis, acoustic emission and thermography techniques were implemented. Secondly manual inspection systems were developed whereby inspection probes were moved over the wheelsets, to detect flaws. For these phased array ultrasonic and alternating current field measurement techniques were implemented.
What has been achieved? A key area of development in the project was the trackside inspection of passing rolling stock, namely freight trains, passenger trains or trams. Three working trackside inspection systems for data collection and possible wheel set flaw notification are in full time use now by operators De Lijn and EMEF.
In May 2011 the SAFERAIL consortium invited selected guests from the rail industry to see at first hand the recent developments of the consortium. This was followed by a site visit to Belem train station on REFER's Cascais line in Lisbon. A live demonstration was given of the acoustic emission based track side inspection system. Included guests were Mr António Mendonça, the Minister for Public Works, Transport and Communications (Portugal) and Transport secretary Correia da Fonseca.
This system based on acoustic emission sensing allows for vehicle wheel set condition follow up and damage pattern recognition. To do this each train and vehicle is identified with RFID technology. A beacon exchanges data with passing trains and searches in a database for fitted bogies and wheel-set type. Alerts from the network sensors grid can be programmed for anticipated warning of a major problem that could occur in the bogies or wheel-sets.
EMEF also records all the results from the regular workshop manual inspections eg one such measurement is a basic wheel thickness measurement, and this data is used to improve the trackside early fault detection sentencing reliability.
Two prototype trackside monitoring systems, using high-frequency vibration analysis (HFVA) were installed by APT and are up and running at De Lijn sites in Belgium. Data results are sent over the ethernet to servers at APT and De Lijn headquarters. The data is sent after the measurement has been processed by the HFVA module.
The results can be examined via a password-protected internet browser anywhere in the world. In addition, alerts can be sent automatically by email and text messaging on mobile phones. So far the system has successfully detected wheel flats and out-of-roundness. In addition, it has also detected suspension faults and rail brake misalignments.
More recently trials and demonstrations of the manual inspection techniques have been undertaken at SNCF headquarters in Nevers. Both phased array ultrasonic testing and alternating current field measurement techniques were used on an assortment of wheel set samples selected by SNCF in order to trial the equipment.
What is next? Usually these types of project still require a lot of further development before commercialisation. However, the trackside inspection systems are already being successfully used and, with some minor modifications to improve product robustness, are ready for commercialisation now. The use of such systems by the rail industry means that unacceptable defects can be picked up at an early stage before a catastrophe ensues.
The manual inspection techniques provide a proof in principle and still require some refinement in order to transform the laboratory equipment into robust workshop equipment. In addition it has been concluded that instead of moving the probe around the wheel set by the operator, mechanics should be implemented to automate the wheel set handling. In this way operator error is reduced. TWI is developing the techniques further and hopes to trial at other end user sites.
