Analyzing of Stray Current Interference on Buried Gas Pipeline from Shanghai Urban Rail Transit

With the fast development of urban transit system and natural gas industry, the Stray Current Corrosion (SCC) for buried gas pipeline has become more frequent in china. In this study, principle and characteristic of Stray Current (SC) resulting from rail transit system were introduced. Presently available SC testing methods, equipment and determination standards in china were summarized. For an underground gas pipeline located in the neighboring area and parallel to the rail transit in Shanghai, pipe-to-soil potential, potential gradient of soil, current within pipeline were measured during different operation time of rail transit with a self-made SC monitoring system based upon virtual instrument. Result shows that pipe-to-soil potential fluctuation of the tested gas pipeline is 200 mV, current within pipeline and potential gradient of soil is 100 mA and 62 mV/m, respectively, which is consistent with the operation of rail transit, serious corrosion of the buried gas pipeline may occur. Through theoretical Analysis, several protective measures were introduced.