在役低硬度P91管道寿命评估及运行策略制定

Life assessment and operation strategy formulation of low-hardness P91 pipe in service

某火电机组P91主蒸汽管道局部硬度偏低,现场对该部位进行了无损检测、壁厚测量、布氏硬度检测及金相组织检验,结合机组检修、运行资料分析了硬度偏低的原因,并对其进行了非破坏性剩余寿命评估和运行策略制定。结果表明,低硬度区金相组织粗大,马氏体特征不明显;焊缝热处理工艺制定或执行不当是造成管道局部低硬度的主要原因之一;按照1.5的安全系数,低硬度区域剩余寿命较短,如果进一步降低安全系数,相应剩余寿命有所增加,但是也增加了继续运行的安全风险性;为保证后续运行的安全性,应采取降参数运行的方式。

There was low local hardness of P91 main steam pipe in one thermal power unit.The non-destructive testing,thickness measurement,Brinell hardness testing and metallographic examination were conducted on site.The reasons for the low hardness were analyzed by combining with the unit maintenance and operation data.Moreover,the non-destructive life assessment and operation strategy formulation were performed.The results showed that the metallographic structure of the low hardness region was coarse,and the characteristic of martensite was nonobvious.One of the main causes was the improper preparation or execution of heat treatment procedures for welding line.According to the safety factor of 1.5,the residual life of the low hardness region was short.If the safety factor was further reduced,the corresponding residual life would increase,but the safety risk of continuous operation was also increased.It was necessary to reduce the operation parameters to ensure the safety of subsequent operation.