含多局部减薄缺陷压力管道的安全评定方法讨论

Discussion on Safety Assessment of Pressure Pipe with Multiple Local Wall Thinning Defects

局部减薄是压力管道常见的一种体积型缺陷,在管道的服役过程中不仅会出现单个局部减薄缺陷,甚至会有多个局部减薄缺陷。通过有限元方法模拟内压作用下含双局部减薄缺陷管道获得其极限载荷,讨论了在不同的轴向和环向排列方式以及不同的局部减薄相对深度下,两局部减薄缺陷间的距离对压力管道极限载荷影响程度的差异。然后对所计算模型应用API 579-1 ASMEFFS-1—2007《适合服役》与GB/T19624—2004《在用含缺陷压力容器安全评定》中对多局部减薄(凹坑)处理方法进行评定,并与有限元得到的结果进行比较,发现两评定规范既存在着保守性,也存在着不安全性。最后对两评定规范所论述的方法进行修正,提出了一种新的用于内压作用下含多局部减薄缺陷管道的多局部减薄处理方法。

The local wall thinning defect is a common volume defect in pressure pipes.In service of pressure pipes,there is not only single local wall thinning defect,but also multiple local wall thinning defects.The limit load of pipes with double wall thinning defects under pressure by finite element method was obtained.The influence of the distance of double local wall thinning to the pipes′ limit load was discussed when defects located at axial and circle arrangement respectively at different relative depth.Then all the computational models were assessed with the processing method of multiple local wall thinning defects in API 579-1ASME FFS-1—2007 Fitness-For-Service and GB/T 19624—2004 In-Service Pressure Vessels Containing Defects,and compared with the results of the finite element computation.It′s showed that processing methods of two standards are both of conservative and unreliable aspects.At last,the processing method of two standards was modified,and a new processing method of multiple local wall thinning defects of pipes under pressure was proposed.