A New Rapid Automated Railhead Inspection System

The FP7-funded RIFLEX project has produced a system that is capable of non-destructively inspecting a larger cross-section of a railhead and automatically logging defects at speeds up to 70mph.
A New Rapid Automated Railhead Inspection System © Ian Nicholson
During routine vehicle operation, rails are subjected to intense bending and shear stresses, plastic deformation and wear, leading to the degradation of their structural integrity over time. Defects form in the rail head, web or foot, but are most prevalent in the railhead. Defects caused by wheelslip, squats, shelling and rolling contact fatigue need to be identified.

One of the main problems in the current methods of inspecting railheads is the need for the sensing device to be in contact with the railhead itself, which inherently limits the speed of inspection. The current methods of eddy current inspection, alternating current field measurement, conventional ultrasonic testing and magnetic flux leakage have all proved inadequate for the envisaged resource efficient rail transport system of the future with their slow inspection speeds and limited defect detection.

Eddy current inspection, the most widely used method, and alternating current field measurement can only be applied at walking speed and are limited to detecting surface breaking defects only. Ultrasonic testing is also a walking speed technology where the orientation of defects greatly affects the likelihood of detection and is unable to detect surface defects. Magnetic flux leakage inspection does allow a faster inspection rate, up to 35 km/hr, but it cannot detect defects below 4mm in size.

The RIFLEX consortium has developed a system that can inspect the entire contour of the railhead using multiple, flexible electromagnetic acoustic transducers (EMATs) that conform to the shape of the railhead. Two devices are used in a complimentary configuration; the first generating an acoustic wave across a short distance on the railhead and the second collecting the resulting signal, providing greater coverage of the railhead. An optical focussing system ensures that a minimum gap between the rail and transducer is maintained and that the transducer remains coupled to the railhead.

The system has been fully trialed at Quinton Rail Technology Centre, UK. Hosted by RIFLEX project partner Rail Alliance, the facility provided the optimum indoor and outdoor location for demonstrating the RIFLEX prototype. The indoor hangar facility containing embedded track connected to the outdoor rail track loop ensured that the prototype setup could proceed despite the rain! Fortunately the weather on the second day improved and helped facilitate a successful outdoor demonstration. Demonstrations included manual track inspection (deployment of the prototype by operator pushing the trolley on rail), deployment by locomotive, and a demonstration of the sensor technology and signal data acquisition.

The RIFLEX system can:
- Inspect at speeds of over 70mph
- Increase railhead inspection coverage of over 50%
- Automatically and instantly warns at the presence of a defect
- Be deployed on a cart based system for manual or locomotive operation

The RIFLEX system provides:
- Increase in infrastructure availability, through reduced possession times and personnel exposure time leading to improved operational safety
- Increased efficiency by removing requirement for repeated inspection to verify results
- Increased detection due to greater rail head coverage
- Optimising maintenance scheduling, leading to efficient maintenance activities

Source: http://cordis.europa.eu/news/rcn/134576_en.html?isPermaLink=true?WT.mc_i...