To improve the insulation of the anti-corrosion layer, the old pipeline is laid in parallel. The cathodic protection current is mainly consumed in the aging part of the anti-corrosion layer. In the formed protection circuit, the protection current can only be distributed in this area and its adjacent parts, so that the remote end of the pipeline Insufficient protection, therefore, when overhauling the anticorrosion layer, try to maintain the consistency of the insulation performance of the parallel pipeline anticorrosion layer, arrange and implement the overhaul plan synchronously, improve the insulation level of the overall anticorrosion layer of the parallel pipeline, so that the cathodic protection current The parallel pipelines are evenly distributed, and the measured protection potentials represent the respective true potentials of the parallel pipelines as much as possible, so as to facilitate the later anti-corrosion maintenance of the pipelines.
Reforming the cathodic protection system In the cathodic protection system, the relative position and distribution of the cathode and anode determine the distribution of the protection potential along the pipeline. Therefore, in the anti-corrosion maintenance of parallel pipelines, the anodes should be distributed as uniformly as possible to avoid mutual interference between the anodes, so that the protection current distribution is more uniform and the pipeline protection distance is longer.
In comparison, improving the insulation of the anti-corrosion layer is the key to improving the anti-corrosion maintenance effect of laying old pipelines in parallel. Only by improving the quality of the anti-corrosion layer of the system, the leakage current of the cathodic protection can be reduced, the cathodic protection system can play a more full role, and the cost of anti-corrosion maintenance can be greatly reduced in the later period. Otherwise, as the anti-corrosion layer ages, the modified cathodic protection system will still provide insufficient cathodic protection for parallel pipelines, and there will also be situations where maintenance is unfavorable and leads to hidden corrosion. Therefore, it is recommended to improve the anti-corrosion technical level of parallel pipelines mainly by improving the insulation of the pipeline anticorrosion layer and supplementing the measures of the cathodic protection system. In summary,
(1) Due to the inevitable difference in the level of anti-corrosion technology of laying old pipelines in parallel, there is a hidden danger of corrosion. The key to improving the technical level of anti-corrosion maintenance is to increase the insulation level of the pipeline anti-corrosion layer, and then carry out the transformation of the cathodic protection system.
(2) The number of parallel connection of old pipelines using equalizing lines only affects the number of cathodic protection current loops in the cathodic protection system, equalizes the voltage drop generated by the current in the pipeline, and does not fundamentally change the level of anti-corrosion technology. In the later maintenance, the method of removing the equalizing line is difficult to achieve the purpose of improving the level of corrosion prevention technology.
(3) After the parallel pipelines are incorporated into the same cathodic protection system, the mutual differences between the pipeline anti-corrosion materials and the quality of the anti-corrosion layer should be minimized. When carrying out post-maintenance of pipeline anti-corrosion system, it is necessary to take into account the status of the anti-corrosion layer of each pipeline in the parallel section, minimize the difference between the quality of the anti-corrosion layer, and reasonably arrange and implement the anti-corrosion layer overhaul.
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