基于内外检测数据对齐的管道腐蚀原因分析

Analysis of Pipeline Corrosion Causes Based on Alignment of Internal and External Inspection Data

长庆油田某原油管道经漏磁内检测后对典型的外部腐蚀进行开挖,发现保温管下大面积腐蚀。基于管道内外检测数据对比,阴极保护、土壤电阻率及交/直流杂散电流干扰检测,结合直接开挖结果,研究原油管道腐蚀原因。研究结果表明:基于外检测时,对阴极保护、土壤电阻率及交/直流杂散电流干扰进行检测,当无交/直流干扰,管道本体无腐蚀产生;基于内检测后,检测信号显示部分管道存在大量外部腐蚀缺陷,选取一处典型大面积腐蚀缺陷进行直接开挖,对该处缺陷进行交/直流干扰检测,检测无干扰,发现保温层出现渗水,保温层下管道本体出现浮锈,环氧煤沥青出现老化并与管道本体发生剥离,腐蚀产物和保温层发泡材料出现粘结。内外检测数据对齐能研究管道外部环境对管道本体安全和腐蚀的影响,可进一步完善管道完整性评价体系。

After magnetic flux leakage testing,a crude oil pipeline in Changqing Oilfield is excavated for typical external corrosion,and it is found that there is extensive corrosion under the insulation pipe.Based on the comparison of pipeline internal/external detection data,cathodic protection,soil resistivity,and AC/DC stray current interference detection,combined with direct excavation results,the causes of corrosion in crude oil pipelines are studied.The results show that cathodic protection,soil resistivity,and AC/DC stray current interference are tested in external detection.When there is no AC/DC interference,there is no corrosion on the pipeline body.After internal detection,the detection signal shows that there are a large number of external corrosion defects in some pipelines.A typical large-area corrosion defect is selected for direct excavation,and AC/DC interference testing is conducted on this defect.The test shows no interference,and it is found that there is water seepage in the insulation layer,floating rust in the pipeline body below the insulation layer,aging of epoxy coal tar and peeling off from the pipeline body,and bonding between the corrosion products and the foaming material of the insulation layer.The alignment of internal/external detection data can study the impact of the external environment of pipelines on the safety and corrosion of pipeline bodies,and can further improve the pipeline integrity evaluation system.