输气管道阴极保护电绝缘装置失效检测与预防——以中国石油西南油气田公司金山输气站绝缘装置为例

电绝缘装置的作用是保障有限长管道上阴极保护的电流密度充分有效，同时隔断与其他相连的金属设备或构筑物的电连接。实际生产中，管道输送的气质中容易包含卤水及沉积物，它们会吸附在管道金属内表面，形成导电介质，造成绝缘装置失效，致使阴极保护效率降低。为此，对中国石油西南油气田公司金山输气站所辖的4条管线的绝缘装置电性能进行了检测，分析了造成管道阴极保护绝缘失效的原因，发现绝缘装置失效后的危害是可能造成管道阴极保护低效和管道腐蚀。进而提出了控制腐蚀的方法：从设计上将绝缘接头放在不易积水的位置、施工安装要避开低洼积水段、定期清管排污以防止管道电连接短路等。上述对策解决了长期困扰输气生产的技术难题。

Inspection and countermeasures for the failures of electrical insulation device by cathodic protection: A case study in the Jinshan Gas Transmission Station operated by the PetroChina Southwest Company

Insulation devices like flanges or joints play an important role in assuring the efficacy of cathodic protection(CP) current density on a limited section of a long-distance pipeline,meanwhile isolating its possible electrical connection with the attached metallic equipments or structures.Because the brine and deposits contained in the transmitted gas in the pipeline easily adhere to the inner surface of metal pipes to form a conducting medium,resulting in the failure of insulation devices and poor performance of cathodic protection.In view of this,a case study is conducted of four pipelines operated by the Jinshan Transmission Station of the PetroChina Southwest Oil & Gasfield Company.Through the inspection of electrical properties of the insulation device there,the reasons for the CP insulation failure of pipes are analyzed,meanwhile it is concluded that the hazards after that failure are the main reason for low CP efficacy and steel pipe corrosion.Additionally,some corrosion control methods are suggested as follows:(1) The insulation joints should be put in the position where water is difficultly accumulated;(2) The low-lying area with water easily accumulated should be avoided by operation and installation;(3) Pigging should be done regularly to prevent the occurrence of short circuit in the electrical connection of pipes.All these above countermeasures will solve the bottlenecking technical problem of CP insulation failures in the gas transmission work.