A £1.2 million, European funded project managed by TWI Ltd has developed, produced and demonstrated a novel ‘clamp on’ prototype device for swift inspection of aluminothermic (AT) welds in rail track. With 1.5 million AT welds in the UK alone and a further 65,000 welds being added annually, the RAILECT consortium responded to the need to develop inspection approaches that can confirm the structure of a joint with minimal track possession time.
The new semi-automated technology is able to provide a full volumetric inspection in 15 minutes, saving both time and resources. The system works through the application of newly developed phased array probes that are able to detect any faults within the AT weld. The system can be used to identify and prevent breakages and is able to provide a better analysis of welds when compared to the previous method of visual inspection.
Although the use of AT welds is well established, they are nevertheless critical safety components in the European rail infrastructure; an increase of rail speed, density of rail traffic and greater freight or passenger train weight can cause an increasing number of rail breaks across the European rail network. The types of defects that are found in AT welds are those normally associated with gravity feed castings, shrinkage, hot tears, ‘lack of fusion’ and porosity. The main two types of weld failure is a vertical fracture associated with centre-line shrinkage and split-web fracture resulting from the cyclic nature of stress in the rail web on bends in the track. Adopting inspection techniques that assure the track owner that no damaging defects are present is essential. The system developed by the RAILECT team offers new confidence and efficiency to an advancing European industry sector.