管道内腐蚀直接评估技术与实践应用

Internal corrosion direct assessment technology and applications for pipelines

内腐蚀的直接评估(Internal Corrosion Direct Assessment,ICDA)技术是用于评价通常输送干气、但可能短期接触湿气或游离水(或其他电解液)的输气管道完整性的系统方法,适用于不能开展内检测的管道。其包括4个步骤:预评价、间接检测、直接检测、后评价。ICDA评估管道水聚集和内腐蚀的可能性,从而找出首个最有可能的腐蚀区域位置,如果这个区域位置通过验证没有发现腐蚀,则其他下游部位出现水聚集或腐蚀的可能性很小。本文提出了ICDA的步骤和方法,对陕京天然气管道一线陕西段神森站至府谷压气站段进行了ICDA评估,评价管道全长52.09 km,按照冬夏季天然气输送量不同,计算得出了管道水积聚析出的临界角冬季1月份为6.17°,夏季7月份为为1.97°。分析沿线高程数据,得出全线高程倾角分布图,选择多个倾角(大于临界角)较大的高风险区域位置开挖,发现管道无明显壁厚减薄,管道状况良好。通过内腐蚀评估可进一步确定管道的内部状况,对于不能实施内检测的管道安全状况评估具有重要意义。

ICDA(Internal Corrosion Direct Assessment)technology is used for evaluation of the integrity of pipeline systems which are transporting dry gas with exposure to moisture or free water(or other electrolyte)in short-term,especially for pipelines on which ILI(In Line Inspection)cannot be carried out. There are four steps: pre-assessment,indirect detection and direct detection and post assessment. Through ICDA,the potential of water accumulation and internal corrosion in pipelines can be evaluated to identify the most probable corrosion area. If no corrosion is found in this area,it is unlikely that water will accumulate at other downstream sites. In this thesis,the method and steps of ICDA are presented and it was carried out on the pipeline section between Shenmu to Fugu valve of the Shan-Jing natural gas pipeline in Shaanxi Province. The total length of the pipeline is 52.09 km. According to different natural gas transportation modes in winter and summer,the critical angle for water accumulation in the pipeline is 6.17° in January and 1.97° in July. The data of the elevation along the pipeline is analyzed,and the elevation angle profile is obtained. Through the excavation of the high risk area with bigger inclination(larger than critical angle),there is no significant wall thinning and the pipeline is in good condition. The internal condition of the pipeline can be further determined by ICDA,which is significant for assessment of the pipeline safety status where it is not possible to carry out the ILI and in unpiggable pipelines.