Europe's railway networks have dedicated teams devoted to checking track safety, inspecting the metal for any cracks or defects that could cause problems. If a track needs fixing, it is often welded on-site. But for all their expertise, the track inspectors have few tools to check whether the resulting welds are strong enough. Now, however, researchers have built a new tool to provide an easy yet reliable ultrasonic test of track welds, adding a much-needed layer of safety to the rail network.
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The project, named Railect, has built a testing device that clamps on to the rail. Ultrasonic transducers then effectively inspect the weld, while the defect detection software crunches the data to seek deep, internal volumetric defects that cannot be seen with the naked eye.
“The system does a full volumetric inspection of the rail weld in less than 15 minutes and is very easy to operate because most of the operations are automated,” says Railect’s project coordinator Tamara Colombier, from TWI, a Cambridge-based research organisation. “Because it gives an accurate position of the size and location of any weld defects, it could also reduce the very high rejection rate given by the visual inspection.”
Although they fix flaws on the rails, the welds themselves can suffer shrinkage, hot tears, slag inclusions, failure to fuse, and porosity. Weld joint failures account for 20% of all rail failures, but because of the welds’ complex structure, geometry and thickness, it is difficult to check their strength and integrity of the volume beneath the surface. Indeed, because most checks are made with the human eye, a large number of welds with surface cracks are rejected even though they might be deeper inside.
There are an estimated 11 million welds on the European rail network, with around a thousand new ones added daily. But unless new tools become available, the rise in rail speeds, denser rail traffic, and heavier freight train weights are all likely to create more rail breaks across the European network. “Now that the high speed network is expanding within Europe, the frequency of the inspection and maintenance has to be increased,” says Colombier. “Having a reliable, advanced and innovative system of inspection such as the Railect system will contribute to the establishment of a safer European railway network.”
Backed by a €1.1 million grant from the European Commission, Railect’s partners – five from Britain, plus one each from Poland, France and Lithuania – have patented the technologies, and are working to bring it to market. Network Rail, the authority responsible for the United Kingdom's railway network, has already indicated it will buy 40 Railect units.
Colombier says that beyond the obvious benefits for safety, the technology will also reduce maintenance costs on Europe's rail network, costs associated with the high rejection rates. And by boosting the overall weld quality, it will ensure a smoother ride on passenger trains. “Railect could radically improve safety standards all over Europe,” Colombier says. “And that can only be good for Europe’s railways.”