长输管道辅助牺牲阳极阴极保护影响因素研究及效果分析

Study on Influencing Factors of Auxiliary Cathodic Protection of Long-distance Pipelines by Sacrificing Anode and Analysis of Its Effect

长输管道运行多年后局部防腐层会出现明显劣化,外加电流阴极保护系统已不能对全管段进行有效保护,需要在欠保护区域追加牺牲阳极辅助保护。本文通过仿真计算手段研究了涂层破损率、土壤电阻率和并行管道对牺牲阳极辅助保护措施效果的影响,并以镁合金牺牲阳极进行了现场验证。结果表明:在相同的牺牲阳极保护方案下,当防腐层破损率从0.05%增加到10%时,管道的保护效果逐渐降低,且当长输管道防腐层破损率超过5%时,添加牺牲阳极的辅助阴极保护方法效果不佳,应考虑修补或更换防腐层;随着土壤电阻率的增大,牺牲阳极保护的管道距离缩短,且当土壤电阻率超过30Ω·m左右时,需考虑在欠保护管段部位添置外加电流防腐站的方法,以保证管道的安全运行;当目标管道涂层破损率和土壤电阻率较小时,存在防腐层质量不高的并行管道可以提高目标管道的防护效果。现场试验同样表明:镁合金牺牲阳极可为涂层破损率和土壤电阻率较小的目标管道提供有效防护,且防腐层质量不高的并行管道提高了牺牲阳极保护效果。

After years of operation of long-distance pipeline,there will be significant local deterioration of its anti-corrosion layer,and the impressed current cathodic protection system can no longer effectively protect the entire pipeline section.The auxiliary protection of sacrificing anode needs to be added in the under-protection areas.The effects of coating damage rate,soil resistivity,and parallel pipelines on the effectiveness of anode sacrificing auxiliary protection measures were studied through simulation calculations,and on-site verification was conducted by sacrificing Mg alloy anode.The results show that under the same sacrificial anode protection scheme,when the damage ratio of the anti-corrosion layer increases from 0.05%to 10%,the protection effect of the auxiliary cathodic protection method to the pipeline gradually decreases.Moreover,when the damage ratio of the anti-corrosion layer in long-distance pipelines exceeds 5%,the auxiliary cathodic protection method of adding sacrificial anodes has poor effect,and repair or replacement of the anti-corrosion layer should be considered.As the soil resistivity increases,the length of pipeline protected by sacrificing anode decreases.When the soil resistivity exceeds about 30Ω·m,it is necessary to consider adding an external current anti-corrosion station in the under-protection pipeline section to ensure the safe operation of the pipeline.When the damage ratio of the target pipeline's anti-corrosion coating and soil resistivity are low,the presence of parallel pipelines with low quality anti-corrosion coating can improve the protection effect of the target pipeline.On site experiments also indicate that sacrificed anode Mg alloy can provide effective protection for target pipelines with low corrosion damage ratio and soil resistivity,and the presence of parallel pipelines with low quality corrosion protection layers can improve the effectiveness of sacrificial anode protection.