激光全焊接254SMO材质板式换热器失效及对策

Failure and Countermeasures of Laser All-welded 254SMO Plate Heat Exchanger

某公司Ⅰ套常减压蒸馏装置以加工中东高硫原油为主,在常顶首次使用了占地面积小、换热效率高和抗腐蚀性好的254SMO材质激光全焊接板式换热器。检修时观察到:该换热器油气入口侧发生腐蚀,通道内结垢堵塞较严重,立柱内表面存在点蚀,入口接管衬管存在裂纹。分析认为连多硫酸的生成形成了应力腐蚀的环境,常顶氯离子的存在不仅增加了不锈钢在连多硫酸环境中的应力腐蚀敏感性,还加速连多硫酸应力腐蚀破裂过程。通过工艺操作优化、材质升级为钛材和停工设备保护等措施抑制腐蚀的发生。

NO.1 atmospheric-vacuum distillation unit in SINOPEC Zhenhai Refining&Chemical Company mainly processed Middle East high-sulfur crude oil,which equipped with laser all-welded 254SOM plate heat exchanger with advantages of less land occupation,high heat transfer efficiency and excellent corrosion resistance.Some problems occurred during maintenance,including inlet erosion,channel fouling,pitting on inner column and cracks in entrance screened pipe.The analysis showed that stress corrosion environment was caused by the formation of polythionic acid,and the existence of chloride ion could not only increase stress corrosion susceptibility of stainless steel,but also accelerate corrosion cracking process of polythionic acid.Actions were carried out through upgrading material to titanium and implementing shutdown protection.