Abstract: Analysis of samples taken from the cracking area of the multilayered urea reactors verified the existence of stress corrosion cracking (SCC) cracks. The influence factors of SCC in multilayered urea reactors were investigated. The results show that the leak detection steam may condense in the interlayer clearances, which would cause alkaline medium concentration at the heavy weld. It was the initiation and propagation of micro-cracks under alkaline environment and local high stress concentrations that lead to the SCC of heavy girth weld urea of the multilayered reactors. The results can give beneficial directions to avoid SCC of layers and catastrophic ruptures of multilayered urea reactors.

Key words: Urea reactor, Stress corrosion cracking , Clearance； Finite element analysis； Heavy girth weld

摘要： 对多层包扎尿素合成塔开裂部位进行了取样分析,确认为应力腐蚀裂纹。并对应力腐蚀的影响因素
进行了分析,结果表明检漏蒸汽会在深环焊缝的层板间隙处冷凝,产生碱性介质浓缩。深环焊缝部位在碱性环境和
局部较高应力下萌生裂纹并扩展,是导致多层包扎尿素合成塔应力腐蚀开裂的原因。分析的结果为多层包扎尿素
合成塔避免层板开裂和灾难性爆炸事故指明了方向。

关键词: 尿素合成塔  ,  应力腐蚀开裂 ,  ,  间隙 , 有限元分析 ,  深环焊缝