In our country, the protection method of buried gas pipeline in the early stage is only a single method of petroleum asphalt and glass fiber cloth external anti-corrosion coating, most of which are in the field operation, so it is difficult to guarantee the quality of rust removal and coating process. In recent years, with the development of coal tar enamel, epoxy powder, three-layer PE and other excellent coating materials and technologies, the protection life of pipeline is greatly prolonged. However, even if the steel pipeline has a good external anti-corrosion coating, the coating is damaged due to various reasons during transportation and on-site construction, and the coating itself has porous defects. These weak parts are often the source of pipeline early corrosion perforation.
With the development of urban modernization, the crowding degree of underground structures is becoming more and more serious. The gas pipeline and water pipeline, sewer pipeline, heat pipe network, power cable, communication cable and other pipe networks are laid or crossed in a very narrow underground space. In addition, with the construction and development of underground Railway Engineering, the underground environment is more and more complex Once leakage occurs, the consequences are obvious. Therefore, the requirements for the protection level and safety and reliability of urban gas pipeline network are higher and higher.
The quality of external anti-corrosion coating varies with the years of construction. With the passage of time, the quality of anti-corrosion coating gradually decreases, such as the increase of iron leakage point and the decrease of adhesion. Sometimes the pipe surface appears to be in good condition, but its insulation resistance has decreased. The scope of urban gas pipeline laying is increasing with the expansion of the city, and the environmental corrosivity of the gas pipeline is also different. After the gas pipeline enters the courtyard, the situation is more complicated. In addition to continuing to interweave with a variety of pipe networks, the buried pipelines are relatively shallow, there are more elbows and tee joints, the quality of anticorrosive coating is not as good as that of urban pipelines, and the probability of random excavation in the courtyard is much greater than that of urban pipelines.
As there are many valve wells and expansion joints in the gas pipeline, the resistance of flange gasket at the joint increases, which hinders the flow of cathodic protection current. However, some pipelines pass through the concrete and overlap with the steel bars in the concrete or the gas pipeline enters the user's home, and the user winds iron wire between the natural gas pipeline and the water pipe at will, which makes the natural gas pipeline and the water pipeline electrically connected. When the cathodic protection is implemented, a large amount of protection current will be lost, which also increases the difficulty of cathodic protection.
Due to the development of the city, the usable area of the city is less and less. The shallow buried anode ground bed covers a large area of the surface, which requires harsh conditions for the distribution of other underground metal structures, and the current distribution is uneven, which is easy to cause interference and shielding; the application of sacrificial anode is limited due to the limited protection distance, especially for the old pipelines, the short interval distance and the difficulties in municipal road excavation. These particularities of urban gas pipeline network increase the difficulty of pipeline cathodic protection.
Shandong Linyi Bosi conductive materials Co., Ltd. is a high-tech enterprise specializing in the production of MMO flexible anode, conductive polymer flexible anode and titanium coated anode, mainly providing cathodic protection technology, engineering design, installation and technical services. Tel: 0539 3712117, 15588026668.