加氢裂化装置高压换热器腐蚀开裂原因分析及对策

CAUSE ANALYSIS ON THE CORROSION CRACKING OF HIGH-PRESSURE HEAT EXCHANGER IN HYDROCRACKING UNIT AND THE COUNTERMEASURES

某厂加氢裂化装置在运行过程中,热高分气与混氢换热器壳体环焊缝出现三处穿透性裂纹,装置被迫紧急停车进行设备返修,在返修时发现壳体内壁存在严重的腐蚀。通过无损检验、理化检验、垢样分析、工艺分析等手段,得出焊缝硬度超标在湿硫化氢环境中发生应力腐蚀开裂是根本原因。焊缝的开裂是多方因素造成的,文章从设计、工艺、设备和监检测等方面进行了深入的分析和探讨,并提出控制和预防对策,为避免换热器再次开裂及类似故障的发生提供建议。

During the operation process of a hydrocracking unit in certain factory,three penetrating cracks of the shell girth welding of the hot high-pressure separator gas and hydrogen mixing heat exchanger occurred,resulting in an emergency shutdown of the unit.In the repair period,serious corrosion was found on the inner wall of the shell.Through non-destructive testing,physical and chemical test,scale sample analysis,process analysis and so on,it is concluded that the root cause was that the hardness of the weld exceeded the standard and stress corrosion cracking occurred in wet hydrogen sulfide environment.Weld cracking was caused by various factors.This paper makes an in-depth analysis and discussion from such aspects as design,process,equipment and inspection.It then brings forward the prevention and control countermeasures.The paper also presents some suggestions to avoid future cracking and similar faults of the heat exchangers.