Train travel is one of the safest modes of transport. For it to remain so, regular inspection and maintenance of train axles is vital to ensuring the structural integrity of wheelsets. The EU-funded AXLEINSPECT project has developed new ultrasonic inspection technology that makes check-ups both easier and more reliable than conventional methods.
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Between 1995 and 2010, train axle failure – which can lead to derailments and other issues – could have caused 33 deaths and 48 injuries in Europe alone Regular inspection and maintenance of axles can help to prevent such incidents by detecting signs of material stress and fatigue before they can have fatal results, says the AXLEINSPECT team.
The project developed a novel approach using ultrasonic phased-array technology to provide train operators with methods for frequent, yet speedy inspections that require a minimum of disassembly and cause little downtime. Thanks to the phased-array technology, it is now technically possible to cover all the critical areas of the axle with only one ultrasonic probe, with the beam manipulated electronically.
Disassembly of the wheelsets, probe changes and manual movement, which are currently still the standard in manual testing and visual inspection, are no longer required with the new technology. As a result, the process becomes much less time-consuming, complicated and expensive.
One fits all
Due to the axles’ complex geometry, conventional testing calls for a number of sensors to be used; in some cases up to 10 different ones that may have different characteristics and thus need to be calibrated and recalibrated multiple times.
AXLEINSPECT combines a phased-array probe with a scanner mounted on the train, which can record the signs of potential defects.
“The variety of axle geometries and train designs in Europe alone is unbelievable,” says project coordinator Dimos Liaptsis of engineering consultancy company TWI Limited. “In order for us to make the system as affordable to the operators as possible, we went for a modular design. Therefore, if we have to inspect a different train design, we only need to change a small part of the scanner instead of the whole system.”
The team put the system to the test on a real train, examining an axle with all the wheels, gear boxes and brake disks attached. The quality of the results was broadly comparable with those obtained using conventional methods. In some instances, the AXLEINPSECT system even provided more information than the standard technique.
Eliminating potential sources of error
Repeated dis- and reassembly can itself cause wear and tear on the axles being examined. And the fact that much of the inspection, including the placement of sensors, has to be done manually, creates additional room for error. Both issues could be avoided with the AXLEINSPECT technology.
“But for me, the main thing is that there is currently no audit trail,” explains Liaptsis. “You assume that the operator has followed the same inspection procedure and has performed the tests in the appropriate way. However, at the moment no data is being captured regarding how the sensor calibration or testing was done. If something happens, how can you prove that the inspection has been carried out correctly?”
The data acquired during testing with the AXLEINSPECT system can be saved and used for further analysis and comparison with new data from the next inspection.
On the home stretch
In the inspection industry, there are nine technology readiness levels (TRLs) from ‘0’ (infant stages of a technology) to ‘9’ (fully commercial product). “At the end of the project, we were probably between technology readiness levels 6 and 7: we had developed a system and demonstrated it in a relevant environment,” says Liaptsis. “Now, we need to make sure that the system works correctly at a price that operators are willing to pay, and we also have to go through the relevant regulatory bodies to fully qualify the system for use in the railway industry.”
Currently, the AXLEINSPECT consortium is looking for backing to take the technology the final mile, with the goal of presenting a full commercial system at the beginning of 2019.