Taking a different line

Network Rail and London Underground are supporting a project to build an ultrasonic device for inspecting cracks in rails, which could be fitted to conventional passenger trains.

Researchers at Warwick, Birmingham and Bristol universities will build and test the device in a three-year project, due to begin this summer.

Unlike conventional train-mounted ultrasound devices, the technology is not limited to speeds of up to 30–35mph, which will allow it to be fitted to ordinary passenger trains, dramatically increasing the number of inspections that can be carried out, said Dr Steve Dixon, leader of Warwick University’s ultrasound group.

Conventional systems are limited in speed because they are based on a transducer that both generates and receives the ultrasound waves. This means the transducer must move no more than 1mm in the time it takes the wave to travel down into the rail, bounce off the defect and travel back to the transducer. Even with waves travelling at 3,000 or 6,000m/sec, this means the train carrying the device cannot travel very fast.