Gate Valves,Gate Valve ,Slide Gate Valve,Sluice Gate Valve WENZHOU DIYE VALVE&FITTINGS CO.,LTD , https://www.diye-valve.com
Analysis and Research on a New Type of Anti-Slow Bolt in Preventing Bolt Activities
It is commonly thought that network-like cracks in the electroplated surface are influenced by the current intensity during plating and the temperature of the electrolyte. We have discussed this issue with the factory, but their explanations were not very convincing. In our view, this remains an unresolved technical challenge. Similar to the chrome-plated cylinder liners with a honeycomb structure, these patterns can help improve oil retention on the journal surface, especially during engine start-up and loading, where the oil film stored in the mesh pattern provides better protection for the crankshaft. However, the mesh grooves formed in the chrome plating of the cylinder liner are achieved through reverse plating, which differs from the iron plating layer’s mesh pattern on the journal. Practical experience has shown that cracks in damaged journals (typically over 2mm in length) tend to expand significantly after a mid-repair period, with the extent of expansion depending on the initial condition. At this stage, the crankshaft is no longer usable. Therefore, the presence of such reticular cracks limits the service life of the repaired crankshaft to just one mid-repair cycle, with very few being able to continue operating. If this issue can be resolved, non-etching iron plating technology could offer great potential for repairing high-volume, mass-produced diesel engine crankshafts. Otherwise, from an economic standpoint, the value of repairing damaged crankshafts in diesel locomotives becomes questionable.
To address this problem, we believe that new bolt anti-loosening technology must be introduced. Based on this understanding, we developed and manufactured a new type of anti-slip bolt. The key feature of this bolt is the use of a nylon sleeve, which is unthreaded. When the bolt is installed into the housing, the housing threads act as a die, forcing the nylon sleeve to extrude and create a tight interference fit. This is made possible by the elasticity of the nylon and its high coefficient of friction, which together provide effective anti-loosening performance. After implementing this new bolt design, we conducted a loading test on locomotive No. 4020 in May 2000. During the mid-repair period, the motor was replaced several times, yet none of the axle bolts loosened or failed. In total, we repaired 78 bolts, and only 6 showed signs of plastic deformation in the nylon thread. The integrity rate reached 92.13%, with 71.7% of the bolts remaining usable after replacing the nylon sleeves. This improvement significantly enhanced the reliability and cost-effectiveness of the repair process.