The bolts originally used in the railway hump are easy to loosen, and the railway section maintenance team needs to tighten and maintain half a day a week; After the bolts are loosened and tightened for many times, the threads will be damaged and scrapped. The bolts need to be replaced as a whole every six months to one year. All bolts are scrapped. The maintenance team of the railway section needs one day to replace the scrapped bolts.

      The new generation of spherical self tightening nuts developed by Zhejiang self tightening Wang Machinery Co., Ltd. through the application of mechanical principle and self tightening principle can effectively solve this problem. Dozens of heavy-duty trains enter the station every day on the track of the main test section, and the self tightening bolts are not loose, completely avoiding daily inspection and weekly personnel maintenance.