氨合成系统废热锅炉管束焊接接头腐蚀原因分析及改进

Analysis of Causes for Corrosion of Tube Bundle Welded Joint of Waste Heat Boiler in Ammonia Synthesis System and Improvement

氨合成系统废热锅炉投运8个月后,其管束的气体进口端联箱管与换热管间的焊接接头出现连续点状腐蚀坑样缺陷,而管束的气体出口端相应位置没有出现此类缺陷,设备其他部位未见异常。通过对氨合成系统废热锅炉管束焊接接头腐蚀部位的宏观形貌、低倍形态、化学组分、扩展方向及金相组织等特征进行分析,判定腐蚀形态为电偶腐蚀。针对腐蚀形态,采取了相应的改进措施,取得了明显的效果。

8 months after putting into operation of the waste heat boiler in ammonia synthesis system, defects of continuous dotted etch pit appeared at welded joints between gas inlet connecting tube and heat exchange tube of tube bundle, while no such kind of defect found at relevant position of gas outlet of tube bundle, and there are no troubles seen in other parts of the equipment. Through analyzing features of micro profile, macroscopic appearance, chemical composition, extension direction and metallographic structure, etc. of corroded parts of the tube bundle welded joints of the waste heat boiler in ammonia synthesis system, it is determined that the corrosion form is galvanic corrosion. In connection with the corrosion form, relevant improvement measures are taken and significant effect is obtained.