考虑广域地形条件的油气管道阴极保护电位分布特性研究

Study on cathodic protection potential distribution of oil and gas pipelines under broad area topography condition

为了研究在山区丘陵等广域地形条件下牺牲阳极法对埋地油气碳钢管道的保护特性,对法兰无防腐层及法兰带防腐层而管道防腐层局部破损两种工况分别建立了有限元模型,分析了阳极布置方式与运行时间、土壤电阻率及管道防腐层破损面积对管道腐蚀与阴极保护电位分布的影响。仿真结果表明:在上述两种工况下,缩减阳极间距和增加阳极长度均可使法兰与管体部分的保护电位及泄漏电流密度降低,而阳极与管道的水平距离基本无影响;阳极运行时间越长,阳极表面沉淀越厚,阳极腐蚀速率越低且与其所处地势条件相关,而阴极保护电位基本不变;随着土壤电阻率的增大,阴极保护电位升高,法兰和防腐层破损区域管道的腐蚀加剧;随着管道防腐层破损面积增大,所有防腐层破损处的管道电位均升高且变化规律一致。

To study the protection characteristics of sacrificial anode method for buried oil and gas carbon steel pipelines under broad area topography conditions such as mountains and hills,two finite element models were established,one for the unprotected insulating flange and the other for the locally damaged pipeline when the insulating flanges are well protected.The effects of anode arrangement,system operation time,resistivity of soil,and damaged area of the protective layer on the corrosion of pipeline and the distribution of cathodic protection potential were analyzed.The simulation results showed that under the two working conditions,the protection potential and leakage current density on the unprotected flange and exposed pipeline could be reduced by reducing the inter-anode spacing or increasing the length of anode,but slightly affected by the horizontal distance between the anode and pipeline.The longer the cathodic protection system runs,the thicker the precipitate forms on the surface of anode,and the lower the corrosion rate of anode is,which is related to the geographical conditions.However,the cathodic protection potential is scarcely changed.The increase of the resistivity of soil makes the cathodic protection potential shift positively,and aggravates the corrosion of the unprotected flange and exposed pipeline.With the increasing of the damaged area of protective layer on pipeline,the potentials at the damaged area all shift positively in a similar trend.