脱硫化氢汽提塔T5001塔底油抽出线弯头开裂失效分析

Cracking Failure Analysis of Bottom Oil Extraction Elbow of Hydrogen Sulfide Stripping Tower T5001

针对氢精制装置脱硫化氢汽提塔T5001塔底油抽出线弯头出现的裂纹进行失效分析,为同类弯头的开裂失效控制提供理论依据。通过材料化学成分分析、力学性能试验、裂纹形貌观察、断面能谱分析、金相试验分析和弯头应力有限元分析的多学科分析方法,确定了造成弯头开裂失效的多种因素。结果表明:该弯头的力学性能、化学成分均符合304L标准;裂纹形貌照片、断面能谱结果和金相试验分析显示弯头内壁存在腐蚀且断面存在硫离子和氯离子,裂纹从内壁到外壁扩展;弯头应力有限元分析显示弯头在工作状态下弯头内弧侧应力水平最高,为24.8 MPa。弯头工作环境中存在氯离子、硫离子且受到周向和轴向应力双重作用,导致弯头从内壁先发生应力腐蚀开裂。建议严控保温材料的氯离子含量,增加弯头及其连接的管道系统定期清洗工作,将管线的工作温度和压力控制在适宜范围内,防止类似事故的发生。

Failure analysis was carried out for crack in the bottom oil extraction line elbow of hydrogen sulfide stripping tower T5001 in hydrorefining unit,which can provide theoretical basis for cracking failure control of similar elbows.By multi-disciplinary analysis methods of material chemical composition analysis,mechanical property test,crack morphology observation,cross section energy spectrum analysis,metallographic test analysis and bending stress finite element analysis,the various factors that cause bending cracking failure were determined.The results show that the mechanical properties and chemical composition of the elbow meet the standards of 304L.The results of fracture morphology,cross section energy spectrum and metallographic test show that there is corrosion in the inner wall of the elbow and S element and Cl element exsit in the cross section,and the crack extends from the inner wall to the outer wall.The finite element analysis of elbow stress shows that the stress level on the inner arc side of the elbow is highest when the elbow is working,which is 24.8 MPa.The double action of circumferential stress,axial stress and Cl-,Si-in the working environment of elbow leads to stress corrosion cracking from inner wall.It is suggested to strictly control the chloride ion content of insulation materials,increase the regular cleaning work of elbow and the connected pipeline system and control the working temperature and pressure of the pipeline within the appropriate range to prevent the similar accidents.