基于层次分析和FAD图的管道环焊缝适用性评价方法

焊缝缺陷是导致管道失效的主要原因之一,因此在役长输管道在进行升压前或复产前,应对管道全线环焊缝进行适用性评价,以排除管道隐患并确定合适的压力范围。由于管道的敷设位置大多位于地下,焊缝处的载荷参数难以准确获取,现有的环焊缝适用性评价多是仅仅基于管道内压进行评价,忽略附加载荷的影响,导致评价结果不准确。针对上述情况,本文以某天然气长输管道环焊缝开挖后的无损检测结果为基础数据,建立待评价焊缝处附加载荷的层次分析风险因素模型,改进了API 579中失效评估图（failure assessment diagram,FAD）传统评价方法,实现管道环焊缝的精准适用性评价,为管道安全提供决策支持。该方法与准则对在役长输管道全线路环焊缝适用性评价工程实践具有借鉴意义。

FITNESS-FOR-SERVICE ASSESSMENT OF GIRTH WELDS OF PIPELINE BASED ON ANALYTIC HIERARCHY PROCESS AND FAILURE ASSESSMENT DIAGRAM

Weld defect is one of the main reasons leading to the failure of pipelines. Therefore, the fitness-for-service assessment of girth welds along the whole pipeline should be carried out before pipeline boosting or resuming production, so as to eliminate the hidden danger and determine the appropriate pressure range of it. Due to the fact that most pipeline laying locations are underground, it is difficult to accurately obtain the load parameters at the welds. The existing fitness-for-service assessment of girth welds is mainly based on the internal pressure of pipelines and ignores the influence of additional load, which results in inaccurate evaluation results. In this paper, the fitness-for-service assessment of girth welds along a long-distance natural gas pipeline was carried out using the results of non - destructive testing after the excavation of girth weld as the basic data, using the failure assessment diagram in standardized API579 as the evaluation method, and determining the additional load at the welds through AHP, providing decision support for pipeline safety. The method and criterion can be used for reference in the engineering practice of girth weld fitness-for-service assessment for the whole pipeline of long distance pipeline in service.