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Broken rails can kill – as the beleaguered rail industry in the UK knows to its cost. US-based Harsco Track Technologies is patenting a technique (US 6 515 249) that avoids the problems that arise when faulty rail sections are cut out and the gap filled with a repair strip. The aim is to preserve the “neutral rail temperature” – the ambient temperature at which the rail was installed and set under tension. Filling a gap with a new piece of rail introduces a different NRT, leading to mismatched expansion and contraction on hot and cold days. Harsco’s answer is to cut out the bare minimum length of rail necessary to remove a defect, shape the two severed rail ends so they’ll fit together, then use a 300-tonne rail-puller to stretch the rails until they fill the gap. A single weld then secures the joint, with little or no change in the NRT.