某船用柴油机排气波纹管故障分析与改进

Failure Analysis and Design Improvements on Exhaust Bellow of a Marine Diesel Engine

针对某船用柴油机的排气波纹管导流筒焊缝断裂和波纹管部分波与波之间严重贴合故障,对导流筒焊缝裂纹部位开展宏观、微观及理化失效分析。分析表明:导流筒焊缝断裂系焊缝晶间腐蚀疲劳所致。波纹管波纹段的设计补偿量与工作状态实测补偿量的对比,及平台疲劳寿命试验显示:波纹管严重贴合故障的原因为波纹段补偿量严重不足。据此提出了相应的改进方案:导流筒设计成一体成型翻边结构;更改涡前波纹管的设计轴向补偿量。试验表明:改进后的涡前波纹管未再出现类似故障。

A specific diesel engine that was equipped on a ship was found to have failures of a cracking weld seam on diversion tubes and severe bellow problem of too-close waves.Microscopic,macroscopic,and physicochemical failure analysis were carried out,and it showed that the cracking weld seam on diversion tubes was caused by the fatigue of intergranular corrosion.The design compensation value of the wave part of the bellow was compared with the actual compensation value in operation,and it showed that the cause of the severe bellow problem of too-close waves was seriously insufficient compensation.The improvement program was given accordingly.The diversion tubes was modified to the flanging structure of integrated modeling,and the designed shaft compensation of the bellow before turbo was modified.Similar failures didn′t happened during the test with the improved bellow.