91色情片

Broken rails can kill 鈥� 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 鈥渘eutral rail temperature鈥� 鈥� 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鈥檚 answer is to cut out the bare minimum length of rail necessary to remove a defect, shape the two severed rail ends so they鈥檒l 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.