Cong Wu, Zhiguang Chen, Chaokui Qin and Yibin Wu
Presented to The 7th International Symposium on Innovation & Sustainability of Modern Railway (ISMR 2020) October 23-25, 2020, Nanchang, China
Keywords: Casing, carrier pipe, insulating joint, magnesium anode, pipe-to-soil potential
Since the beginning of the 21st century, the total mileage of China's railway operations has continued to rise, and the coverage of the rail network has been expanding. However, due to the existence of the huge rail network, buried gas pipelines are often laid in such a way that they cross the railway tracks, which becomes a major security issue. In this case, the casing technology has been widely applied as a safe method in the buried gas pipeline construction engineering. The cathodic protection system of the gas pipeline will be affected by the shielding and space medium of the casing, and its effectiveness needs to be tested and analysed. In this paper, a field test system has been established based on a gas pipeline reconstruction project with external casing in Shanghai, and the pipe-to-soil potential, current in pipe, and the protection potential/current of sacrificial anode have been monitored. The corrosion of the buried casing and carrier pipe has been experimentally studied with different connection position of magnesium anode and different on-off condition of insulating joints. The protective effectiveness of insulating joints, and best connection method of magnesium anodes and the winding zinc ribbon have also been discussed by the analysis of the pipe-to-soil potential change and the current balance.
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