Study On On - Line Detection And Maintenance Of Gas Transmission Pipeline

Natural gas pipeline will be damaged or destroyed during its operation because of the factors such as geographical location, sabotage and contingencies. Some of these problems of damage and destruction are potential, so the online inspection appears necessary to detect the defects and to adopt related rehabilitation measures such as rehabilitating the defects, plugging the micro-leakage, blocking and repairing the burst pipeline rapidly. These relevant measures ensure the safety and reliability of pipeline operations and avoid enormous loss of personnel and property.In view of the problems of gas pipeline aging, defects, micro-leakage and bursts in southwestern China, the characteristics and adaptability of magnetic leakage detection, acoustic detection and metal magnetic memory detection technology are analyzed and compared in this paper. The leakage magnetic detection technology was applied to the on-line inspection of the Duzhou-Lianglu gas pipeline, and the defect level was evaluated. The advantages and disadvantages of welding, epoxy sleeve and composite reinforcement technologies were analyzed comparatively. Later the composite materials with superior performance were employed in the reinforcement for the Wolonghe-Lianglu, Naxi-Fujiaomiao and Fujiaomiao-Yuexi gas pipelines, and the effectiveness was substantiated by excavation. Six polymer materials were evaluated and screened, and their plugging performance was tested. The shutdown and in-service pipeline plugging and rehabilitation technologies were studied, and the dependability was testified through practical application.According to the results,28581metal loss characteristics on the Duzhou-Lianglu gas pipeline were detected through magnetic flux leakage testing. The deepest of all the defects reaches66%depth of the wall thickness. Most of these were caused by external corrosion and there are25most seriously-corroded defects. The color of reinforcing layers on fibrous composites is uniform, without cracking, hollowing, or delaminating phenomena, and with closely-bound pressure sides and landing edges, reinforcing layer thickness greater than the reference value, qualified impact resistance, peel strength greater than165N/cm, and metallic luster on the pipe surface after delamination. Polymer sealing material FastSteel (rapid steel) has high viscosity, high strength, excellent pressure-bearing capacity, short curing time, remarkable durability and workability thus more suitable for micro-leakage treatments. At the11threaded leaking points in3valve chambers of Liangfo pipeline and2valve ones of Lianglu pipeline, FastSteel was successfully applied and satisfactory plugging effects were achieved; in-service plugging was also successfully actualized in the rerouting of Danling-Jiajiang-Emei gas pipeline.