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The West-East natural gas pipeline project adopts the cathodic protection technology combined with " forced current method + sacrificial anode method ". Aiming at the high corrosion risks (such as soil resistivity difference, DC/AC interference, etc.) of the long distance gas pipeline (the total length of nearly 3900km), it can ensure the safe operation life of for more than 30 years in complex environment. The technology covers the whole pipeline external anti-corrosion layer and cathodic protection system combined protection, and introduces solar power supply system for the no-power area to ensure the stable output of protection current .
forced current cathodic protection.
There are cathodic protection stations equipped with potentiostatic devices and auxiliary anodes. High silicon cast iron anodes or flexible anodes are selected according to the environmental requirements. The minimum protection current density is 4μA/m², and the protection potential ranges from -0.85V to -1.25v (CSE) .
In no-power areas (such as Gansu and Shaanxi sections), solar photovoltaic power supply system is adopted to replace the traditional power supply. Combined with TEG (thermoelectric generator) and CCVT (capacitance-coupled voltage transformer) technology, the cathodic protection system in remote areas can continue to operate .
sacrificial anode assisted protection
In the sections with high soil resistivity or interference risk (such as crossing rivers and railway sections), the magnesium alloy sacrificial anodes are installed, the ground resistance is reduced by filling coke powder with coating material, and the anodes are corroded preferously to protect the pipelines. The anode spacing is designed as 3-5m.
Anti-corrosion layer joint protection
The exterior wall of the pipeline is designed with different anti-corrosion layers: PE three-layer structural covering layer is used in sections with harsh natural environment, double-layer fused epoxy powder (FBE) is used in areas with strong corrosion resistance, and FBE enhanced grade covering layer is used in other sections to effectively isolate the corrosive medium .
Material and process optimization
flexible anode (conductive plastic material) is introduced to meet the requirements of bending laying of long-distance pipeline, reduce anode consumption rate and simplify the installation process .
controlled rolling and controlled cooling process steel (such as X70 steel) is adopted to improve the strength and toughness of pipelines and weldability, and reduce carbon equivalent to extend the life of basic materials .
Intelligent monitoring and maintenance
The in-situ corrosion monitoring system was deployed to collect pipeline potential, current density and other parameters in real time, and dynamically adjust protection parameters combined with the central control platform. The effectiveness of the system was verified by power failure test .
For old equipment (such as potential transmitters and potentiostat that have been in operation for 20 years), carry out renovation projects, replace the failed reference electrodes and restore the remote transmission function to ensure the accuracy of monitoring data .
project results
The coverage rate of cathodic protection system exceeds 98%, the corrosion rate of pipeline is reduced below the safety threshold, and the service life of gas pipeline is significantly prolonged.
The solar power supply system has been successfully applied in the western regions without electricity, reducing carbon emissions and improving energy efficiency .
Ecological protection measures
When crossing ecologically sensitive areas (such as Anxi Extreme Dry Desert Reserve in Gansu Province), vegetation damage can be reduced by scientific route selection, green construction and ecological restoration , and project promotion and environmental protection can be achieved simultaneously at .
The project is the benchmark of China's long-distance pipeline anti-corrosion technology, and its " joint protection + intelligent operation and maintenance " model provides an important reference for the global energy artery project .
