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复合管海底管道在铺设过程中发生破断后,316L/625衬管暴露于海水或含有泥沙的海水中,可能发生腐蚀破坏。根据316L/625材料的腐蚀速率、管壁厚度和允许的最大点蚀深度来预估复合管允许的浸泡期限。如果破损的管道能在允许的浸泡期限内完成修复作业,则该管道可视为累积损耗而非失效,修复后仍可继续服役。修复方法为,切除破损管段后,排出海底管道内的海水,用含(300—500)×10-6除氧剂、杀菌剂和缓蚀剂的淡水清洗316L/625管壁上残留的氯化物和溶解氧,清洗淡水的Cl-浓度宜小于200×10-6。并根据腐蚀与污损情况确定是否需要进行酸液清洗。
After the submarine pipe of the composite pipe is broken during laying, the 316L / 625 liner may be exposed to seawater or seawater containing sediment, which may cause corrosion damage. The allowable immersion period of the composite pipe is estimated based on the corrosion rate of the 316L / 625 material, the wall thickness and the maximum allowable pitting depth. If the damaged pipe can be repaired within the allowable immersion period, the pipe can be regarded as a cumulative loss rather than a failure and can continue to be serviced after the repair. The repair method is as follows: after removing the damaged pipe section, the seawater in the submarine pipeline is drained; the residual chloride on the 316L / 625 pipe wall is washed with fresh water containing (300-500) × 10-6 oxygen scavenger, bactericide and corrosion inhibitor; and Dissolved oxygen, Cl - concentration of fresh water should be less than 200 × 10-6. And according to the corrosion and defacement determine whether the need for acid cleaning.