Trolley rack, rail clips , spreader, guide plate, brakes, cable reels electric control cabinet and other equipments on port cranes are under tremendous vibration load at work, especially the front and the back girder joints are full load on lifting moment, withstanding enormous impact and strong vibration. The engineers of Shanghai Zhenhua Heavy Industries previously used the combination lock fastening method of nylon nut + strength bolts + spring washer + stopper washer + glue, but failure cases of the combination of fastener still occur. Using 30° variable tooth type locknut not only reduces the amount of use of auxiliary fasteners, but also radically solves the technical problems. Zhenhua Heavy Industries now uses 30° variable tooth type locking threaded fasteners on the key parts of crane equipment which is easy to loose in poor and vibration condition, which ensures the safe operation of the crane equipment.