根据铁道部有关文件规定 ,正线列车运行过岔时速≥ 1 2 0 km/h时 ,必须在道岔上设置外锁闭装置。而对于工务部门而言 ,列车运行时速的提高 ,又要求将钢轨进行无缝焊接。日前 ,通过对北京局已上道可动心轨外锁闭装置的调研 ,发现可动心轨辙岔外锁闭装置 ,由于心轨根端焊接加大其 According to the relevant documents of the Ministry of Railways, an external locking device must be provided on the switch when the speed of the positive train crosses over 120 km / h. For the public works department, the increase of train running speed also requires that the rails be welded seamlessly. A few days ago, the Beijing Bureau has been on the road can be moving outside the locking device research and found that movable outside the heart rut locking device, because the heart of the root end welding increases its