The insulation of the anticorrosion layer acts as a barrier to effectively isolate the pipeline from the corrosive environment, and its quality directly affects the effectiveness of the anticorrosion system. The anti-corrosion technology statistics of pipelines a and b are obtained based on the comprehensive test results. Among them, the insulation performance of the anti-corrosion layer adopts the insulation resistivity as the evaluation index, the test technology adopts the multi-frequency tube current method, and the polarization of the anti-corrosion layer is determined according to the technical regulations for the overhaul of the asphalt anti-corrosion layer of the buried steel pipeline; Under-protection is based on the ground potential of the field test tube and is evaluated by reference to the standards for corrosion and protection investigation methods for steel pipelines and storage tanks.
As an indispensable component of pipeline anti-corrosion maintenance system, cathodic protection is mainly to provide cathodic protection current to the pipeline section with poor insulation of the anticorrosive layer, so as to polarize it and slow down the corrosion of the pipeline. The grounding system of each cathodic protection station is normal, the potential of the junction is high, and the output current and potential load of the potentiostat are large. By further increasing the given potential at the confluence point to improve the level of cathodic protection technology, the operability to extend the protection distance is poor.
Distribution situation of pressure equalization lines Pressure equalization lines with different densities are set between the stations in the parallel section to ensure the electrical connectivity of the pipelines laid in parallel in each test section. The corrosion protection technology level is uneven. The quality of the corrosion protection pipelines a and b in each parallel section varies greatly, and most of the cathodic protection current is bound to be consumed on the pipeline with poor insulation performance, and the remaining part is consumed. On another pipe. Because the output of the potentiostat is limited by the position of the junction point of the cathodic protection system and the control potential and loop resistance, the pipes a and b cannot be fully polarized to achieve complete protection.
Therefore, the density of the voltage equalization line is different, but the number of loops of the cathodic protection current in this section is increased, so that the protection potential distribution is more likely to maintain a uniform distribution, and the impact on the current and potential output of the cathodic protection system is minimal. It is further confirmed that there is no corresponding relationship between the number of equalizing lines existing in each test section and the level of corrosion protection technology. On the other hand, even if all existing voltage equalization lines are completely removed, when each pipeline is separately cathodic protected, there is also the problem of current shielding or interference with each other due to the short distance of the parallel pipelines. In short, the existence of the pressure equalization line is not the reason why the pipeline anticorrosion system cannot fully work.
Due to the continuous overhaul of the anti-corrosion layer, the quality of the anti-corrosion layer has been significantly improved. However, because the equalizing line is not completely removed, the two pipelines are still jointly protected in the parallel section. The cathodic protection current in the anti-corrosion system is mainly concentrated on the pipeline b that has almost never been overhauled. Therefore, unilaterally improving the insulation level of the anticorrosion layer of pipeline a, but not simultaneously carrying out overhaul and maintenance of the anticorrosion layer of pipeline b, will result in an unbalanced technical level of anticorrosion maintenance between parallel pipelines, and it is impossible to fundamentally change the status of pipeline leakage accidents .
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